Papers for Wednesday, Aug 09 2023

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass $M>70$ $M_\odot$) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities $0 < e \leq 0.3$ at $0.33$ Gpc$^{-3}$ yr$^{-1}$ at 90\% confidence level.

Low-frequency gravitational wave experiments such as the Laser Interferometer Space Antenna and pulsar timing arrays are expected to detect individual massive black hole (MBH) binaries and mergers. However, secure methods of identifying the exact host galaxy of each MBH merger amongst the large number of galaxies in the gravitational wave localization region are currently lacking. We investigate the distinct morphological signatures of MBH merger host galaxies, using the Romulus25 cosmological simulation. We produce mock telescope images of 201 simulated galaxies in Romulus25 hosting recent MBH mergers, through stellar population synthesis and dust radiative transfer. Based on comparisons to mass- and redshift-matched control samples, we show that combining multiple morphological statistics via a linear discriminant analysis enables identification of the host galaxies of MBH mergers, with accuracies that increase with chirp mass and mass ratio. For mergers with high chirp masses (>10^8.2 Msun) and high mass ratios (>0.5), the accuracy of this approach reaches >80%, and does not decline for at least >1 Gyr after numerical merger. We argue that these trends arise because the most distinctive morphological characteristics of MBH merger and binary host galaxies are prominent classical bulges, rather than relatively short-lived morphological disturbances from their preceding galaxy mergers. Since these bulges are formed though major mergers of massive galaxies, they lead to (and become permanent signposts for) MBH binaries and mergers that have high chirp masses and mass ratios. Our results suggest that galaxy morphology can aid in identifying the host galaxies of future MBH binaries and mergers.

The presence of short-lived radioisotopes (SLRs) 26-Al and 60-Fe in the Solar system places constraints on the initial conditions of our planetary system. Most theories posit that the origin of 26-Al and 60-Fe is in the interiors of massive stars, and they are either delivered directly to the protosolar disc from the winds and supernovae of the massive stars, or indirectly via a sequential star formation event. However, massive stars that produce SLRs also emit photoionising far and extreme ultraviolet radiation, which can destroy the gas component of protoplanetary discs, possibly precluding the formation of gas giant planets like Jupiter and Saturn. Here, we perfom N-body simulations of star-forming regions and determine whether discs that are enriched in SLRs can retain enough gas to form Jovian planets. We find that discs are enriched and survive the photoionising radiation only when the dust radius of the disc is fixed and not allowed to move inwards due to the photoevaporation, or outwards due to viscous spreading. Even in this optimal scenario, not enough discs survive until the supernovae of the massive stars and so have zero or very little enrichment in 60-Fe. We therefore suggest that the delivery of SLRs to the Solar system may not come from the winds and supernovae of massive stars.

New physics in the early Universe could lead to parity-violation in the late Universe, sourcing statistics whose sign changes under point reflection. The best constraints on such phenomena have come from the Planck temperature fluctuations; however, this is already cosmic-variance-limited down to relatively small scales, thus only small improvements are expected in the future. Here, we search for signatures of parity-violation in the polarized CMB, using the Planck PR4 $T$- and $E$-mode data. We perform both a simulation-based blind test for any parity-violating signal at $\ell<518$, and a targeted search for primordial $U(1)$ gauge fields (and the amplitudes of a generic collapsed model) at $\ell<2000$. In all cases, we find no evidence for new physics, with the model-independent test finding consistency with the FFP10/NPIPE simulation suite at $(-)0.4\sigma$, and the gauge field test constraining the fractional amplitude of gauge fields during inflation to be below $6\times 10^{-19}$ at $95\%$ confidence level for a fiducial model. The addition of polarization data can significantly improve the constraints, depending on the particular model of primordial physics, and the bounds will tighten significantly with the inclusion of smaller-scale information.

It has been widely accepted that Type Ia supernovae (SNe Ia) are thermonuclear explosions of a CO white dwarf. However, the natures of the progenitor system(s) and explosion mechanism(s) are still unclarified. Thanks to the recent development of transient observations, they are now frequently discovered shortly after the explosion, followed by rapid spectroscopic observations. In this study, by modeling very early-phase spectra of SNe Ia, we try to constrain the explosion models of SNe Ia. By using the Monte Carlo radiation transfer code, TARDIS, we estimate the properties of their outermost ejecta. We find that the photospheric velocity of normal-velocity supernovae (NV SNe) in the first week is $\sim$15000 km s$^{-1}$. The outer velocity, to which the carbon burning extends, spans the range between $\sim$20000 and 25000 km s$^{-1}$. The ejecta density of NV SNe also shows a large diversity. For high-velocity supernovae (HV SNe) and 1999aa-like SNe, the photospheric velocity is higher, $\sim$20000 km s$^{-1}$. They are different in the photospheric density, with HV SNe having higher density than 1999aa-like SNe. For all these types, we show that the outermost composition is closely related to the outermost ejecta density; the carbon burning layer and the unburnt carbon layer are found in the higher-density and lower-density objects, respectively. This finding suggests that there might be two sequences, the high-density and carbon-poor group (HV SNe and some NV SNe) and the low-density and carbon-rich group (1999aa-like and other NV SNe), which may be associated with different progenitor channels.

The recent discovery of a 4 $\times$ 10$^7$ M$_{\odot}$ black hole (BH) in UHZ1 at $z =$ 10.3, just 450 Myr after the big bang, suggests that the seeds of the first quasars may have been direct-collapse black holes (DCBHs) from the collapse of supermassive primordial stars at $z \sim$ 20. This object was identified in James Webb Space Telescope (JWST) NIRcam and Chandra X-ray data, but recent studies suggest that radio emission from such a BH should also be visible to the Square Kilometer Array (SKA) and the next-generation Very Large Array (ngVLA). Here, we present estimates of radio flux for UHZ1 from 0.1 - 10 GHz, and find that SKA and ngVLA could detect it with integration times of 10 - 100 hr and just 1 - 10 hr, respectively. It may be possible to see this object with VLA now with longer integration times. The detection of radio emission from UHZ1 would be a first test of exciting new synergies between near infrared (NIR) and radio observatories that could open the era of $z \sim$ 5 - 15 quasar astronomy in the coming decade.

Over the past 2 decades, wide-field photometric surveys in optical and infrared domains reached a nearly all-sky coverage thanks to numerous observational facilities operating in both hemispheres. However, subtle differences among exact realizations of Johnson and SDSS photometric systems require one to convert photometric measurements into the same system prior to analysis of composite datasets originating from multiple surveys. It turns out that the published photometric transformations lead to substantial biases when applied to integrated photometry of galaxies from the corresponding catalogs. Here we present photometric transformations based on piece-wise linear approximations of integrated photometry of galaxies in the optical surveys SDSS, DECaLS, BASS, MzLS, DES, DELVE, KiDS, VST ATLAS, and the near-infrared surveys UKIDSS, UHS, VHS, and VIKING. We validate our transformations by constructing k-corrected color-magnitude diagrams of non-active galaxies and measuring the position and tightness of the "red sequence". We also provide transformations for aperture magnitudes and show how they are affected by the image quality difference among the surveys. We present the implementation of the derived transformations in Python and IDL and also a web-based color transformation calculator for galaxies. By comparing DECaLS and DES, we identified systematic issues in DECaLS photometry for extended galaxies, which we attribute to the photometric software package used by DECaLS. As an application of our method, we compiled two multi-wavelength photometric catalogs for over 200,000 low- and intermediate-redshift galaxies originating from CfA FAST and Hectospec spectral archives.

Collapsing massive stars lead to a broad range of astrophysical transients, whose multi-wavelength emission is powered by a variety of processes including radioactive decay, activity of the central engine, and interaction of the outflows with a dense circumstellar medium. These transients are also candidate factories of neutrinos with energy up to hundreds of PeV. We review the energy released by such astrophysical objects across the electromagnetic wavebands as well as neutrinos, in order to outline a strategy to optimize multi-messenger follow-up programs. We find that, while a significant fraction of the explosion energy can be emitted in the infrared-optical-ultraviolet (UVOIR) band, the optical signal alone is not optimal for neutrino searches. Rather, the neutrino emission is strongly correlated with the one in the radio band, if a dense circumstellar medium surrounds the transient, and with X-rays tracking the activity of the central engine. Joint observations of transients in radio, X-rays, and neutrinos will crucially complement those in the UVOIR band, breaking degeneracies in the transient parameter space. Our findings call for heightened surveys in the radio and X-ray bands to warrant multi-messenger detections.

The cold dark matter (CDM) paradigm provides a remarkably good description of the Universe's large-scale structure. However, some discrepancies exist between its predictions and observations at very small sub-galactic scales. To address these issues, the consideration of a strong interaction between dark matter particles and dark radiation emerges as an intriguing alternative. In this study, we explore the constraints on those models using joint observations of Cosmic Microwave Background (CMB) and Quasars with our previously built parameter estimation package CosmoReionMC. At 2-$\sigma$ confidence limits, this analysis rules out all strongly interacting Dark Matter - Dark Radiation models proposed to date, representing the most stringent constraint on those models to the best of our knowledge. Future research using a 21-cm experiment holds the potential to reveal stronger constraints or uncover hidden interactions within the dark sector.

We present an analysis of the degree of energy equipartition in a sample of 101 Monte Carlo numerical simulations of globular clusters (GCs) hosting either a system of stellar-mass black holes (BHS), an intermediate-mass black hole (IMBH) or neither of them. For the first time, we systematically explore the signatures that the presence of BHS or IMBHs produces on the degree of energy equipartition and if these signatures could be found in current observations. We show that a BHS can halt the evolution towards energy equipartition in the cluster centre. We also show that this effect grows stronger with the number of stellar-mass black holes in the GC. The signatures introduced by IMBHs depend on how dominant their masses are to the GCs and for how long the IMBH has co-evolved with its host GCs. IMBHs with a mass fraction below 2% of the cluster mass produce a similar dynamical effect to BHS, halting the energy equipartition evolution. IMBHs with a mass fraction larger than 2% can produce an inversion of the observed mass-dependency of the velocity dispersion, where the velocity dispersion grows with mass. We compare our results with observations of Galactic GCs and show that the observed range of the degree of energy equipartition in real clusters is consistent with that found in our analysis. In particular, we show that some Galactic GCs fall within the anomalous behaviour expected for systems hosting a BHS or an IMBH and are promising candidates for further dynamical analysis.

IceCube real-time alerts allow for rapid follow-up observations of likely astrophysical neutrino events, enabling searches for multi-messenger counterparts. The Enhanced Starting Track Real-time Stream (ESTReS) is a real-time extension of the Enhanced Starting Track Event Selection (ESTES), a high astrophysical purity muon-neutrino sample recently used by IceCube to measure the astrophysical diffuse flux. A set of computationally cheap cuts allows us to run a fast filter in seconds. This online filter selects about 100 events per day to be sent to Madison, WI via satellite where the full ESTES event selection is applied within minutes. Events that pass the final set of cuts (ESTReS + ESTES) will be sent out as real-time alerts to the broader astrophysical community. ESTReS's unique contribution to the current real-time alerts will be events in the southern sky in the 5 TeV - 100 TeV range. We expect about 10.3 events per year which average 50% astrophysical purity. In this talk I will report the status of the ESTReS alert stream in the context of the IceCube real-time program.

Widefield surveys of the sky probe many clustered scalar fields -- such as galaxy counts, lensing potential, gas pressure, etc. -- that are sensitive to different cosmological and astrophysical processes. Our ability to constrain such processes from these fields depends crucially on the statistics chosen to summarize the field. In this work, we explore the cumulative distribution function (CDF) at multiple scales as a summary of the galaxy lensing convergence field. Using a suite of N-body lightcone simulations, we show the CDFs' constraining power is modestly better than that of the 2nd and 3rd moments of the field, as they approximately capture the information from all moments of the field in a concise data vector. We then study the practical aspects of applying the CDFs to observational data, using the first three years of the Dark Energy Survey (DES Y3) data as an example, and compute the impact of different systematics on the CDFs. The contributions from the point spread function are 2-3 orders of magnitude below the cosmological signal, while those from reduced shear approximation contribute $\lesssim 1\%$ to the signal. Source clustering effects and baryon imprints contribute $1-10\%$. Enforcing scale cuts to limit systematics-driven biases in parameter constraints degrades these constraints a noticeable amount, and this degradation is similar for the CDFs and the moments. We also detect correlations between the observed convergence field and the shape noise field at $13\sigma$. We find that the non-Gaussian correlations in the noise field must be modeled accurately to use the CDFs, or other statistics sensitive to all moments, as a rigorous cosmology tool.

Estimating a reliable covariance matrix for correlation functions of galaxies is a crucial task to obtain accurate cosmological constraints from galaxy surveys. We generate 2,000 independent lightcone mock luminous red galaxy (LRGs) catalogues at $0.3 \leq z \leq 1.25$, designed to cover CAMIRA LRGs observed by the Subaru Hyper Suprime-Cam Subaru Strategic Programme (HSC SSP). We first produce full-sky lightcone halo catalogues using a COmoving Lagrangian Acceleration (COLA) technique, and then trim them to match the footprints of the HSC SSP S20A Wide layers. The mock LRGs are subsequently populated onto the trimmed halo catalogues according to the halo occupation distribution model constrained by the observed CAMIRA LRGs. The stellar mass ($M_{\star}$) is assigned to each LRG by the subhalo abundance-matching technique using the observed stellar-mass functions of CAMIRA LRGs. We evaluate photometric redshifts (photo-$z$) of mock LRGs by incorporating the photo-$z$ scatter, which is derived from the observed $M_{\star}$--photo-$z$-scatter relations of the CAMIRA LRGs. We validate the constructed full-sky halo and lightcone LRG mock catalogues by comparing their angular clustering statistics (i.e., power spectra and correlation functions) with those measured from the halo catalogues of full $N$-body simulations and the CAMIRA LRG catalogues from the HSC SSP, respectively. We detect clear signatures of baryon acoustic oscillations (BAOs) from our mock LRGs, whose angular scales are well consistent with theoretical predictions. These results demonstrate that our mock LRGs can be used to evaluate covariance matrices at large scales and provide predictions for the BAO detectability and cosmological constraints.

Hydrodynamical simulations solve the governing equations on a discrete grid of space and time. This discretization causes numerical diffusion similar to a physical viscous diffusion, whose magnitude is often unknown or poorly constrained. With the current trend of simulating accretion disks with no or very low prescribed physical viscosity, it becomes essential to understand and quantify this inherent numerical diffusion, in the form of a numerical viscosity. We study the behavior of the viscous spreading ring and the spiral instability that develops in it. We then use this setup to quantify the numerical viscosity in Cartesian grids and study its properties. We simulate the viscous spreading ring and the related instability on a two-dimensional polar grid using PLUTO as well as FARGO, and ensure convergence of our results with a resolution study. We then repeat our models on a Cartesian grid and measure the numerical viscosity by comparing results to the known analytical solution, using PLUTO and Athena++. We find that the numerical viscosity in a Cartesian grid scales with resolution as approximately $\nu_{num}\propto\Delta x^2$ and is equivalent to an effective $\alpha\sim10^{-4}$ for a common numerical setup. We also show that the spiral instability manifests as a single leading spiral throughout the whole domain on polar grids. This is contrary to previous results and indicates that sufficient resolution is necessary in order to correctly resolve the instability. Our results are relevant in the context of models where the origin should be included in the computational domain, or when polar grids cannot be used. Examples of such cases include models of disk accretion onto a central binary and inherently Cartesian codes.

Context: Increasingly, Oort Cloud comets are being discovered at great distances from the Sun and tracked over ever wider ranges of heliocentric distances as observational equipment improves. Aims: To investigate in detail how the original semimajor axis for near-parabolic comets depends on the selected data arc and the assumed form of the non-gravitational (NG) acceleration. Methods: Among currently known Oort Cloud comets with large perihelion distances ($q > 3$ au), we selected 32 objects observed over the widest ranges of heliocentric distances in orbital legs before and after perihelion. For each of them, we determined a series of orbits using at least three basic types of data sets selected from available positional data (pre- and post-perihelion data and the entire data set), and a few forms of NG acceleration representing water ice or CO sublimation. Results: We found that the motion of comets is often measurably affected by NG forces at heliocentric distances beyond 5 au from the Sun. The most spectacular example is C/2010 U3 (Boattini), whose perihelion distance is 8.44 au. NG effects are detectable for 19 of the 32 comets within the positional data. For five comets, we found asymmetric effects of NG forces - in three cases significantly greater before perihelion than afterward (C/2017 M4, C/2000 SV$_{75}$, and C/2015 O1), and in two others the opposite (C/1997 BA$_6$ and C/2006 S3). We also find that the well-known systematic effect of finding more tightly bound original orbits when including the NG acceleration than in purely gravitational solutions may be related to the specific form of the standard $g(r)$ function describing the sublimation of ices.

We present photometric and morphological analyses of nuclear star clusters (NSCs) -- very dense, massive star clusters present in the central regions of most galaxies -- in a sample of 33 massive disk galaxies within 20 Mpc, part of the "Composite Bulges Survey." We use data from the Hubble Space Telescope including optical (F475W and F814W) and near-IR (F160W) images from the Wide Field Camera 3. We fit the images in 2D to take into account the full complexity of the inner regions of these galaxies (including the contributions of nuclear disks and bars), isolating the nuclear star cluster and bulge components. We derive NSC radii and magnitudes in all 3 bands, which we then use to estimate NSC masses. Our sample significantly expands the sample of massive late-type galaxies with measured NSC properties. We clearly identify nuclear star clusters in nearly 80% of our galaxies, putting a lower limit on the nucleation fraction in these galaxies that is higher than previous estimates. We find that the NSCs in our massive disk galaxies are consistent with previous NSC mass-NSC radius and Galaxy Mass-NSC Mass relations. However, we also find a large spread in NSC masses, with a handful of galaxies hosting very low-mass, compact clusters. Our NSCs are aligned in PA with their host galaxy disks but are less flattened. They show no correlations with bar or bulge properties. Finally, we find the ratio of NSC to BH mass in our massive disk galaxy sample spans a factor of $\sim$300.

Eclipsing X-ray binaries make an ideal condition to study reprocessed X-rays, as the X-rays detected during eclipse are purely reprocessed while the much brighter primary X-rays are blocked by the companion star. We carried out a comprehensive study of X-ray reprocessing with four eclipsing Low Mass X-ray Binary (LMXB) systems by comparing X-ray spectra during and outside eclipse with \textit{XMM-Newton} EPIC pn observations. The 17 observations of MXB 1659$-$298, AX J1745.6$-$2901, EXO 0748$-$676 and XTE J1710$-$281 give unique features of the systems. For example, X-ray reprocessing characteristics in AX J1745.6$-$2901 is found to be nearly same irrespective of the intensity state; there is an indication of different types of variable warp structures in the inner accretion disk in EXO 0748$-$676, a high out-of-eclipse to eclipse flux ratio in XTE J1710$-$281 inspite of a large size of the accretion disk perhaps indicates low scale height of the accretion disk. The eclipse spectra for some of the LMXB sources are reported for the first time. We have derived the fractional visible area of the accretion disk during maximum eclipse phase for various obscuration geometries. The out-of-eclipse to eclipse flux ratio in LMXBs observed to be smaller compared to that found in High Mass X-ray Binaries. This indicates greater reprocessing in LMXBs despite having less dense, less extended stellar wind from the companion. The X-ray reprocessing efficiencies observed in LMXBs indicate large dependencies of X-ray reprocessing on the scale height of the accretion disk, relative size of the disk compared to the companion and some other unknown factors.

Zirconium monoxide (ZrO) absorption lines define rare S-type stars and are currently being sought on exoplanets. Successful detection is dependent on an accurate and comprehensive line list, with existing data not ideal for many applications. Specifically, the Plez \etal{} line list is near-complete but has insufficient accuracy for high-resolution cross-correlation, while the Sorensen \& Bernath data has high accuracy but only considers a small number of spectral bands. This article presents a novel spectroscopic model, variational line list and trihybrid line list for the main \ZrO{} isotopologue, as well as isotopologue-extrapolated hybrid line lists for the \isoa{}, \isob{}, \isoc{}, \isod{}~and \isoe{} isotopologues. These were constructed using \DUO{} based on icMRCI-SD/CASSCF~\abinitio{} electronic data calculated using \MOLPRO{}, experimental energies obtained from a previous \Marvel{} data compilation and perturbative energies from Sorensen \& Bernath. The new \ZrO{} \EXOMOL{}-style trihybrid line list, \LLname{}, comprises \noenergies{} energies (\noMaenergies{} experimental) and \notransitions{} transitions up to 30,000~\cm{} (333~nm) between ten low-lying electronic states (\ZrOX{}, \ZrOaa{}, \ZrOA{}, \ZrObb{}, \ZrOB{}, \ZrOC{}, \ZrOdd{}, \ZrOee{}, \ZrOff{} and \ZrOF{}). The inclusion of experimental energy levels in \LLname{} means ZrO will be much easier to detect using high-resolution ground-based telescopes in the 12,500 -- 17,500~\cm{} (571 -- 800~nm) spectral region. The inclusion of variational energy levels means that the ZorrO line list has very high completeness and can accurately model molecular absorption cross-sections even at high temperatures. The \LLname{} data will hopefully facilitate the first detection of ZrO in the atmosphere of a hot Jupiter exoplanet, or alternatively more conclusively exclude its presence.

To enforce incumbent protection through a spectrum access system (SAS) or future centralized shared spectrum system, dynamic protection area (DPA) neighborhood distances are employed. These distances are distance radii, in which citizen broadband radio service devices (CBSDs) are considered as potential interferers for the incumbent spectrum users. The goal of this paper is to create an algorithm to define DPA neighborhood distances for radio astronomy (RA) facilities with the intent to incorporate those distances into existing SASs and to adopt for future frameworks to increase national spectrum sharing. This paper first describes an algorithm to calculate sufficient neighborhood distances. Verifying this algorithm by recalculating previously calculated and currently used neighborhood distances for existing DPAs then proves its viability for extension to radio astronomy facilities. Applying the algorithm to the Hat Creek Radio Observatory (HCRO) with customized parameters results in distance recommendations, 112 kilometers for category A (devices with 30 dBm/10 MHz max EIRP) and 144 kilometers for category B (devices with 47 dBm/10MHz max EIRP), for HCRO's inclusion into a SAS and shows that the algorithm can be applied to RA facilities in general. Calculating these distances identifies currently used but likely out-of-date metrics and assumptions that should be revisited for the benefit of spectrum sharing.

A new molecular line list for lithium hydroxide ($^{7}$Li$^{16}$O$^{1}$H) covering wavelengths $\lambda > 1 \mu$m (the 0-10000 cm$^{-1}$ range) is presented. The OYT7 line list contains over 331 million transitions between rotation-vibration energy levels with total angular momentum up to $J=95$ and is applicable for temperatures up to $T\approx 3500$ K. Line list calculations are based on a previously published, high-level \textit{ab initio} potential energy surface and a newly computed dipole moment surface of the ground $\tilde{X}\,^1\Sigma^+$ electronic state. Lithium-containing molecules are important in a variety of stellar objects and there is potential for LiOH to be observed in the atmospheres of exoplanets. This work provides the first, comprehensive line list of LiOH and will facilitate its future molecular detection. The OYT7 line list along with the associated temperature- and pressure-dependent opacities can be downloaded from the ExoMol database at www.exomol.com and the CDS astronomical database.

We present, for the first time, recoil velocity estimates for binary neutron star mergers using data from numerical relativity simulations. We find that binary neutron star merger remnants can have recoil velocity of the order of a few tens of km/s and as high as $150$ km/s in our dataset. These recoils are attained due to equivalent contributions from the anisotropic gravitational wave emission as well as the asymmetric ejection of dynamical matter during the merger. We provide fits for net recoil velocity as well as its ejecta component as a function of the amount of ejected matter, which may be useful when constraints on the ejected matter are obtained through electromagnetic observations. We also estimate the mass and spin of the remnants and find them to be in the range $[2.34, 3.38] M_{\odot}$ and $[0.63, 0.82]$ respectively, for our dataset.

Neutrinos are known to play important roles in many astrophysical scenarios from the early period of the big bang to current stellar evolution being a unique messenger of the fusion reactions occurring in the center of our sun. In particular, neutrinos are crucial in determining the dynamics and the composition evolution in explosive events such as core-collapse supernovae and the merger of two neutron stars. In this paper, we review the current understanding of supernovae and binary neutron star mergers by focusing on the role of neutrinos therein. Several recent improvements on the theoretical modeling of neutrino interaction rates in nuclear matter as well as their impact on the heavy element nucleosynthesis in the supernova neutrino-driven wind are discussed, including the neutrino-nucleon opacity at the mean field level taking into account the relativistic kinematics of nucleons, the effect due to the nucleon-nucleon correlation, and the nucleon-nucleon bremsstrahlung. We also review the framework used to compute the neutrino-nucleus interactions and the up-to-date yield prediction for isotopes from neutrino nucleosynthesis occurring in the outer envelope of the supernova progenitor star during the explosion. Here improved predictions of energy spectra of supernova neutrinos of all flavors have had significant impact on the nucleosynthesis yields. Rapid progresses in modeling the flavor oscillations of neutrinos in these environments, including several novel mechanisms for collective neutrino oscillations and their potential impacts on various nucleosynthesis processes are summarized.

The Second Gamma-ray Burst Catalog (2FLGC) was announced by the Fermi Large Area Telescope (Fermi-LAT) Collaboration. It includes 29 bursts with photon energy higher than 10 GeV. Gamma-ray burst (GRB) afterglow observations have been adequately explained by the classic synchrotron forward-shock model, however, photon energies greater than 10 GeV from these transient events are challenging, if not impossible, to characterize using this afterglow model. Recently, the closure relations (CRs) of the synchrotron self-Compton (SSC) forward-shock model evolving in a stellar wind and homogeneous medium was presented to analyze the evolution of the spectral and temporal indexes of those bursts reported in 2FLGC. In this work, we provide the CRs of the same afterglow model, but evolving in an intermediate density profile ($\propto {\rm r^{-k}}$) with ${\rm 0\leq k \leq2.5}$, taking into account the adiabatic/radiative regime and with/without energy injection for any value of the electron spectral index. The results show that the current model accounts for a considerable subset of GRBs that cannot be interpreted in either stellar-wind or homogeneous afterglow SSC model. The analysis indicates that the best-stratified scenario is most consistent with ${\rm k=0.5}$ for no-energy injection and ${\rm k=2.5}$ for energy injection.

The origin of most astrophysical neutrinos is unknown, but extragalactic neutrino sources may follow the spatial distribution of the large-scale structure of the universe. Galaxies also follow the same large scale distribution, so establishing a correlation between galaxies and IceCube neutrinos could help identify the origins of the diffuse neutrinos observed by IceCube. Following a preliminary study based on the WISE and 2MASS catalogs, we will investigate an updated galaxy catalog with improved redshift measurements and reduced stellar contamination. Our IceCube data sample consists of track-like muon neutrinos selected from the Northern sky. The excellent angular resolution of track-like events and low contamination with atmospheric muons is necessary for the sensitivity of the analysis. Unlike a point source stacking analysis, the calculation of the cross correlation does not scale with the number of entries in the catalog, making the work tractable for catalogs with millions of objects. We present the development and performance of a two-point cross correlation of IceCube neutrinos with a tracer of the large scale structure.

The so-called "unidentified infrared emission" (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 micron ubiquitously seen in a wide variety of astrophysical regions are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Astronomical PAHs often have an aliphatic component (e.g., aliphatic sidegroups like methyl --CH3 may be attached as functional groups to PAHs) as revealed by the detection in many UIE sources of the aliphatic C--H stretching feature at 3.4 micron. With its unprecedented sensitivity, unprecedented spatial resolution and high spectral resolution, the James Webb Space Telescope (JWST) holds great promise for evolutionizing the studies of aliphatics and aromatics in the universe. To facilitate analyzing JWST observations, we present a theoretical framework for determining the aliphatic fractions (\eta_ali) of PAHs, the fractions of C atoms in aliphatic units, from the emission intensity ratios of the 3.4 micron feature to the 3.3 micron feature. To demonstrate the effectiveness of this framework, we compile the 3.3 and 3.4 micron UIE data obtained in the pre-JWST era for an as complete as possible sample, and then apply the framework to these pre-JWST data. We derive a median aliphatic fraction of <\eta_ali>=5.4\% and find that the aliphatic fractions are the highest in protoplanetary nebulae illuminated by cool stars lacking ultraviolet radiation. Nevertheless, the "hardness" of stellar photons is not the only factor affecting the PAH aliphaticity, other factors such as the starlight intensity may also play an important role.

Blue metal-poor (BMP) stars are the main-sequence stars that appear bluer and more luminous than normal turn-off stars of metal-poor globular clusters. They are believed to be either field blue straggler stars (FBSS) formed via post-mass transfer mechanism or accreted from dwarf satellite galaxies of the Milky Way. A significant fraction of BMP stars are discovered to be potential binaries. We observed 27 BMP stars using UVIT/\textit{AstroSat} in two FUV filters, F148W and F169M. We report the discovery of white dwarf (WD) companions of 12 BMP stars for the first time. The WD companions have estimated temperatures T$_{eff}$ $\sim$10500 $-$ 18250 K, and masses 0.17 M$_{\odot}$ $-$ 0.8 M$_{\odot}$. Based on [Fe/H] and space velocity, we group the 12 BMP/FBSS stars as the thick disk (5) and halo (5), whereas two stars appear to be in-between. All the 5 thick disk BMP/FBSS have extremely low-mass (M $<$ 0.2 M$_{\odot}$) WDs as companions, whereas the 5 halo BMP/FBSS have low (0.2 M$_{\odot}$ $<$ M $<$ 0.4 M$_{\odot}$), normal (0.4 M$_{\odot}$ $<$ M $<$ 0.6M$_{\odot}$), and high mass (M $>$ 0.6 M$_{\odot}$) WD companions. Our analysis suggests that at least $\sim$44 $\%$ of BMP stars are FBSS, and these stars hold the key to understand the details of mass transfer, binary properties, and chemical enrichment among the FBSS.

The most striking characteristics of the mysterious 2175 Angstrom extinction bump, the strongest spectroscopic absorption feature seen on the interstellar extinction curve, are the invariant central wavelength and variable bandwidth: its peak position at 2175 Angstrom is remarkably constant while its bandwidth varies from one line of sight to another. However, recent studies of the lines of sight toward a number of Herbig Ae/Be stars have revealed that the extinction bump exhibits substantial shifts from the canonical wavelength of 2175 Angstrom. In this work we revisit these lines of sight and take a physical approach to determine the ultraviolet (UV) extinction curve for each line of sight. It is found that the wavelengths of the derived UV extinction bumps are around 2200 Angstrom and the scatters are considerably smaller than that of the previous study based on the same set of Herbig Ae/Be stars, consistent with the conventional wisdom. Nevertheless, the scatters are still appreciably larger than that associated with the nominal bump position of 2175 Angstrom. This is discussed in the context that Herbig Ae/Be stars are not well-suited for interstellar extinction studies.

We explore the environment of a combined set of $367$ grand-design and $619$ flocculent spiral galaxies. We introduce a novel estimator called the \textit{local geometric index} to quantify the morphology of the local environment of these $986$ spirals. The local geometric index allows us to classify the environment of galaxies into voids, sheets, filaments, and clusters. We find that grand-designs are mostly located in dense environments like clusters and filaments ($\sim 78\%$), whereas the fraction of the flocculents lying in sparse environments like voids and sheets is significantly higher ($ > 10\%$) than that of the grand-designs. A $p$-value $<$ $10 ^{-3}$ from a Kolmogorov-Smirnov test indicates that our results are statistically significant at $99.9\%$ confidence level. Further, we note that dense environments with large tidal flows are dominated by the grand-designs. On the other hand, low-density environments such as sheets and voids favor the growth of flocculents.

The exact nature of the 2175 Angstrom extinction bump, the strongest spectroscopic absorption feature superimposed on the interstellar extinction curve, remains unknown ever since its discovery in 1965. Popular candidate carriers for the extinction bump include nano-sized graphitic grains and polycyclic aromatic hydrocarbon (PAH) molecules. To quantitatively evaluate PAHs as a possible carrier, we perform quantum chemical computations for the electronic transitions of 30 compact, pericondensed PAH molecules and their cations as well as anions with a wide range of sizes from 16 to 96 C atoms and a mean size of 43 C atoms. It is found that a mixture of such PAHs, which individually exhibit sharp absorption features, show a smooth and broad absorption band that resembles the 2175 Angstrom interstellar extinction bump. Arising from $\pi^*\leftarrow\pi$ transitions, the width and intensity of the absorption bump for otherwise randomly-selected and uniformly-weighted PAH mixtures, do not vary much with PAH sizes and charge states, whereas the position shifts to longer wavelengths as PAH size increases. While the computed bump position, with the computational uncertainty taken into account, appears to agree with that of the interstellar extinction bump, the computed width is considerably broader than the interstellar bump which remains unaccounted for as far as the PAH mixtures considered here are concerned. It appears that, to account for the observed bump width, one has to resort to PAH species of specific sizes and structures.

Deuterium (D) was exclusively generated in the Big Bang and the standard Big Bang Nucleosynthesis (BBN) model predicts a primordial abundance of D/H~26ppm. As the Galaxy evolves, D/H gradually decreases because of astration. The Galactic chemical evolution (GCE) model predicts a present-day abundance of D/H~20ppm. However, observations of the local interstellar medium (ISM) have revealed that the gas-phase interstellar D/H varies considerably from one region to another and has a median abundance of D/H~13ppm, substantially lower than predicted from the BBN and GCE models. It has been suggested that the missing D atoms of D/H~7ppm could have been locked up in deuterated polycyclic aromatic hydrocarbon (PAH) molecules. However, we have previously demonstrated that PAHs with aromatic C--D units are insufficient to account for the missing D. Here we explore if PAHs with aliphatic C--D units could be a reservoir of D. We perform quantum chemical computations of the vibrational spectra of "superdeuterated" PAHs (in which one D and one H share an C atom) and PAHs attached with D-substituted methyl group, and derive the band strengths of the aliphatic C--D stretch (A_4.65). By applying the computationally derived A_4.65 to the observed aliphatic C--D emission at ~4.6--4.8 micron, we find that PAHs with aliphatic C--D units could have tied up a substantial amount of D/H and marginally account for the missing D. The possible routes to generate PAHs with aliphatic C--D units are also discussed.

Pre-outburst signal (a decrease of the optical brightness) just before the outburst is clearly detected in the observations of the T CrB obtained before and during the 1946 outburst. A similar decrease is also visible in the light curve of RS Oph during the 2021 outburst. We suppose that this is due to formation of a thick, dense envelope around the white dwarf, and we estimate its size (1000 - 2000 km), mass (5.10$^{-8}$ - 6.10$^{-7}$ M$_\odot$) and average density (5 - 16 g cm$^{-3}$).

We present an analysis of the gas kinematics in NGC 2992, based on VLT/MUSE, ALMA and VLA data, aimed at characterising the disk, the wind and their interplay in the cold molecular and warm ionised phases. CO(2-1) and H$\rm \alpha~$ arise from a multiphase disk with inclination 80 deg and radii 1.5 and 1.8 kpc, respectively. We find that the velocity dispersion of the cold molecular phase is consistent with that of star forming galaxies at the same redshift, except in the inner 600 pc region, and in the region between the cone walls and the disk. This suggests that a disk-wind interaction locally boosts the gas turbulence. We detect a clumpy ionised wind distributed in two wide opening angle ionisation cones reaching scales of 7 kpc. The [O III] wind expands with velocity exceeding -1000 km/s in the inner 600 pc, a factor of 5 larger than the previously reported wind velocity. Based on spatially resolved electron density and ionisation parameter maps, we infer an ionised outflow mass of $M_{\rm of,ion} = (3.2 \pm 0.3) \times \, 10^7 \, M_{\odot}$, and a total ionised outflow rate of $\dot M_{\rm of,ion}=13.5\pm1$ \sfr. We detected clumps of cold molecular gas located above and below the disk reaching maximum projected distances and velocities of 1.7 kpc and 200 km/s, respectively. On these scales, the wind is multiphase, with a fast ionised component and a slower molecular one, and a total mass of $M_{\rm of, ion+mol}= 5.8 \times 10^7 \, M_{\odot}$, of which the molecular component carries the bulk of the mass. The dusty molecular outflowing clumps and the turbulent ionised gas are located at the edges of the radio bubbles, suggesting that the bubbles interact with the surrounding medium through shocks. We detect a dust reservoir co-spatial with the molecular disk, with a cold dust mass $M_{\rm dust} = (4.04 \pm 0.03) \times \, 10^{6} \, M_{\odot}$.

Comprehensive and accurate rovibronic line lists for the X $^{1}\Sigma^{+}$ and A $^{1}\Pi$ states of $^{12}$C$^{1}$H$^{+}$ and $^{13}$C$^{1}$H$^{+}$ which should be applicable up to temperatures of 5000 K are presented. Available empirical potential energy curves and high-level ab initio dipole and transition dipole moment curves are used with the program LEVEL to compute rovibronic energy levels and Einstein $A$ coefficients. $\Lambda$-doubling is incorporated into the energy levels and $A$-coefficients involving the A $^{1}\Pi$ state using an empirical method. For $^{12}$C$^{1}$H$^{+}$, line positions are improved by using both laboratory and astronomical observational spectra as input to the MARVEL procedure. The $^{12}$C$^{1}$H$^{+}$ line list contains 1505 states and 34194 transitions over the frequency range of 0 - 33010 cm$^{-1}$ ($\lambda > 300$ nm). Comparisons with observed astronomical and laboratory spectra give very good agreement. The PYT CH$^{+}$ line lists and partition functions are available from the ExoMol database at www.exomol.com.

Empirical line lists for the open shell molecule $^{89}$Y$^{16}$O (yttrium oxide) and its isotopologues are presented. The line list covers the 6 lowest electronic states: $X {}^{2}\Sigma^{+}$, $A {}^{2}\Pi$, $A' {}^{2}\Delta$, $B {}^{2}\Sigma^{+}$, $C {}^{2}\Pi$ and $D {}^{2}\Sigma^{+}$ up to 60000 cm$^{-1}$ ($<0.167$ $\mu$m) for rotational excitation up to $J = 400.5$. An \textit{ab initio} spectroscopic model consisting of potential energy curves (PECs), spin-orbit and electronic angular momentum couplings is refined by fitting to experimentally determined energies of YO, derived from published YO experimental transition frequency data. The model is complemented by empirical spin-rotation and $\Lambda$-doubling curves and \textit{ab initio} dipole moment and transition dipole moment curves computed using MRCI. The \textit{ab initio} PECs computed using the complete basis set limit extrapolation and the CCSD(T) method with its higher quality provide an excellent initial approximation for the refinement. Non-adiabatic coupling curves for two pairs of states of the same symmetry $A$/$C$ and $B$/$D$ are computed using a state-averaged CASSCF and used to built diabatic representations for the $A {}^{2}\Pi$, $C {}^{2}\Pi$, $B {}^{2}\Sigma^{+}$ and $D {}^{2}\Sigma^{+}$ curves. Calculated lifetimes of YO are tuned to agree well with the experiment, where available. The BRYTS YO line lists for are included into the ExoMol data base (www.exomol.com).

N-body numerical simulations code for the orbital motion of asteroids/planetesimals within the asteroid belt under the gravitational influence of the sun and the accreting planets has been developed. The aim is to make qualitative, and to an extent a semi-quantitative argument, regarding the possible extent of radial mixing and homogenization of planetesimal reservoirs of the two observed distinct spectral types , viz., the S-type and C-type, across the heliocentric distances due to their dynamical orbital evolution, thereby, eventually leading to the possible accretion of asteroids having chemically diverse constituents. The spectral S-type and C-type asteroids are broadly considered as the parent bodies of the two observed major meteoritic dichotomy classes, namely, the non-carbonaceous (NC) and carbonaceous (CC) meteorites, respectively. The present analysis is performed to understand the evolution of the observed dichotomy and its implications due to the nebula and early planetary processes during the initial 10 Myrs (Million years). The homogenization across the two classes is studied in context to the accretion timescales of the planetesimals with respect to the half-life of the potent planetary heat source, 26Al. The accretion over a timescale of ~1.5 Myr. possibly resulted in the planetary-scale differentiation of planetesimals to produce CC and NC achondrites and iron meteorite parent bodies, whereas, the prolonged accretion over a timescale of 2-5 Myrs. resulted in the formation of CC and NC chondrites. Our simulation results indicate a significant role of the initial eccentricities and the masses of the accreting giant planets, specifically, Jupiter and Saturn, in triggering the eccentricity churning of the planetesimals across the radial distances......

One of the greatest challenge facing current space weather monitoring operations is forecasting the arrival of coronal mass ejections (CMEs) and Solar Energetic Particles (SEPs) within their Earth-Sun propagation timescales. Current campaigns mainly rely on extreme ultra-violet and white light observations to create forecasts, missing out many potential events that may be hazardous to Earth's infrastructure undetectable at these wavelengths. Here we introduce the SURROUND mission, a constellation of CubeSats each with identical radio spectrometers, and the results of the initial Phase-0 study for the concept. The main goal of SURROUND is to monitor and track solar radio bursts (SRBs), widely utilised as a useful diagnostic for space weather activity, and revolutionise current forecasting capabilities. The Phase-0 study concludes that SURROUND can achieve its mission objectives using 3 - 5 spacecraft using current technologies with feasible SEP and CME forecasting potential: a first for heliospheric monitors.

The spectroscopic observations of two novae namely V1065 CEN and V1280 SCO were made by 45 cm Cassegrain telescope in high resolution ($\lambda/\delta\lambda$=22000) at H$\alpha$ (6563 \r{A}) region. V1065 CEN is He/N-type spectra which characterize a broad (Gaussian FWHM 49 \r{A}), saddle shaped and asymmetric H$\alpha$ emission line without prominent P-Cyg absorption component. Completely different H$\alpha$ profile of V1280 SCO shows prominent P-Cyg absorption and narrow emission line (Gaussian FWHM 26 \r{A}) which can be classified as Fe II type nova. The expansion velocities of these two systems measured from the minima of the P-Cyg profiles are close to 2300 km/s for V1065 CEN, and 716 km/s for V1280 SCO. Based on the photometric analysis, the Nova V1065 CEN can be classified as fast (11$<$t${_2}$$<$25) nova. The derived absolute magnitudes at maximum for nova V1065 CEN to be M$_{o,V}$ = -7.58$\pm$0.18 and M$_{o,B}$= -7.75$\pm$0.25 correspond to a distance 8.51$\pm$0.33 kpc. The parameters t$_{2V}$=12 days and t$_{3V}$=14 days of nova V1280 SCO determine that the nova is in between very fast and fast nova. The mean absolute magnitude at maximum is calculated to be M$_{o,V}$=-8.7$\pm$0.1 and the estimated distance to the nova V1280 SCO is 3.2$\pm$0.2 kpc.

It is natural to wonder how far the flat pattern in the distribution of galaxies and clusters of galaxies around the de Vaucoueurs Local Supercluster extends, and whether there are other similarly extended flat patterns in cosmic structure. I present evidence of two extended flat sheet-like patterns in the distributions of galaxies and clusters detected at redshifts less than 0.021. Sheet A contains our position and is tilted 11 degrees from the supergalactic pole, meaning the Local Supercluster is a moderately bent part of the more extended Sheet A. The continuation of this sheet is detected in the disjoint samples of galaxies at redshifts 0.021 to 0.041 and of galaxies and clusters of galaxies at redshifts 0.042 to 0.085. Sheet B is 15 Mpc from us at its closest point. It is detected at redshift less than 0.021 and at redshift 0.021 to 0.041. These results make a serious case for the reality of signatures of close to flat extended sheet-like patterns.

The Kepler space telescope leaves a legacy of tens of thousands of stellar rotation period measurements. While many of these stars show strong periodicity, there exists an even bigger fraction of stars with irregular variability for which rotation periods are unknown. As a consequence, many stellar activity studies might be strongly biased toward the behavior of more active stars with measured rotation periods. To at least partially lift this bias, we apply a new method based on the Gradient of the Power Spectrum (GPS). The maximum of the gradient corresponds to the position of the inflection point (IP). It was shown previously that the stellar rotation period $P_{rot}$ is linked to the inflection point period $P_{IP}$ by the simple equation $P_{rot} = P_{IP}/\alpha$, where $\alpha$ is a calibration factor. The GPS method is superior to classical methods (such as auto-correlation functions (ACF)) because it does not require a repeatable variability pattern in the time series. From the initial sample of 142,168 stars with effective temperature $T_{eff}\leq6500K$ and surface gravity $log g\geq4.0$ in the Kepler archive, we could measure rotation periods for 67,163 stars by combining the GPS and the ACF method. We further report the first determination of a rotation period for 20,397 stars. The GPS periods show good agreement with previous period measurements using classical methods, where these are available. Furthermore, we show that the scaling factor $\alpha$ increases for very cool stars with effective temperatures below 4000K, which we interpret as spots located at higher latitudes. We conclude that new techniques (such as the GPS method) must be applied to detect rotation periods of stars with small and more irregular variabilities. Ignoring these stars will distort the overall picture of stellar activity and, in particular, solar-stellar comparison studies.

We conduct a methodological study for statistically comparing the sensitivities of two periodograms for weak signal planet detection in transit surveys: the widely used Box-Least Squares (BLS) algorithm following light curve detrending and the Transit Comb Filter (TCF) algorithm following autoregressive ARIMA modeling. Small depth transits are injected into light curves with different simulated noise characteristics. Two measures of spectral peak significance are examined: the periodogram signal-to-noise ratio (SNR) and a False Alarm Probability (FAP) based on the generalized extreme value distribution. The relative performance of the BLS and TCF algorithms for small planet detection is examined for a range of light curve characteristics, including orbital period, transit duration, depth, number of transits, and type of noise. The TCF periodogram applied to ARIMA fit residuals with the SNR detection metric is preferred when short-memory autocorrelation is present in the detrended light curve and even when the light curve noise had white Gaussian noise. BLS is more sensitive to small planets only under limited circumstances with the FAP metric. BLS periodogram characteristics are inferior when autocorrelated noise is present. Application of these methods to TESS light curves with small exoplanets confirms our simulation results. The study ends with a decision tree that advises transit survey scientists on procedures to detect small planets most efficiently. The use of ARIMA detrending and TCF periodograms can significantly improve the sensitivity of any transit survey with regularly spaced cadence.

As more Fast Radio Bursts (FRBs) are being localised, we are learning that some fraction have persistent radio sources (PRSs). Such a discovery motivates an improvement in our understanding of the nature of those counterparts, the relation to the bursts themselves and why only some FRBs have PRSs. We report on observations made of FRB 20121102A with the MeerKAT radio telescope. Across five epochs, we detect the PRS associated with FRB 20121102A. Our observations are split into a cluster of four epochs (MJD 58732 - 58764) and a separate single epoch about 1000days later. The measured flux density is constant across the first four observations but then decays by more than one-third in the final observation. Our observations on MJD 58736 coincided with the detections of 11 bursts from FRB 20121102A by the MeerTRAP backend, seven of which we detected in the image plane. We discuss the importance of image plane detections when considering the commensal transient searches being performed with MeerKAT and other radio facilities. We find that MeerKAT is so sensitive that within a two-second image, we can detect any FRB with a flux density above 2.4mJy at 1.3GHz and so could localise every FRB that has been detected by CHIME to date.

In recent years, evidence has accumulated that some high-energy cosmic neutrinos can be associated with blazars. The strongest evidence for an individual association was found in the case of the blazar TXS 0506+056 in 2017. In July 2019, another track-like neutrino event (IC190730A) was found spatially coincident with the well-known bright flat-spectrum radio quasar PKS 1502+106. PKS 1502+106 was not found to be in a particularly elevated gamma-ray state, but exhibited a remarkably bright radio outburst at the time of the neutrino detection, similar to TXS 0506+056. We have performed a multi-frequency VLBI study from 15 GHz up to 86 GHz on TXS 0506+056, PKS 1502+106 and one additional neutrino-candidate blazar (PKS 0215+015) to study the radio structure of neutrino candidate blazars in response to their neutrino association. We have obtained target of opportunity observations with the VLBA for all three sources within $\sim$1 month from their associated neutrino events and are performing multi-epoch studies of the jet kinematics at 15 GHz as part of the MOJAVE program. Here, we present first results on TXS 0506+056 at 86 GHz and one additional 43 GHz image obtained 27 days after IC170922A, closer in time to the neutrino event than previously published images. We also give an overview about our recent work on PKS 1502+106 and PKS 0215+015.

I estimate the frequencies of gravitational waves from jittering jets that explode core collapse supernovae (CCSNe) to crudely be 5-30 Hz, and with strains that might allow detection of Galactic CCSNe. The jittering jets explosion mechanism (JJEM) asserts that most CCSNe are exploded by jittering jets that the newly born neutron star (NS) launches within few seconds. According to the JJEM, instabilities in the accreted gas lead to the formation of intermittent accretion disks that launch the jittering jets. Earlier studies that did not include jets calculated the gravitational frequencies that instabilities around the NS emit to have a peak in the crude frequency range of 100-2000 Hz. Based on a recent study, I take the source of the gravitational waves of jittering jets to be the turbulent bubbles (cocoons) that the jets inflate as they interact with the outer layers of the core of the star at thousands of kilometres from the NS. The lower frequencies and larger strain than those of gravitational waves from instabilities in CCSNe allow future, and maybe present, detectors to identify the gravitational wave signals of jittering jets. Detection of gravitational waves from local CCSNe might distinguish between the neutrino-driven explosion mechanism and the JJEM.

Protoplanetary disk are the foundation of planet formation. Lightning can have a profound impact on the chemistry of planetary atmospheres. The emergence of lightning in a similar manner in protoplanetary disks, would substantially alter the chemistry of protoplanetary disks. We aim to study under which conditions lightning could emerge within protoplanetary disks. We employ the ProDiMo code to make 2D thermo-chemical models of protoplanetary disks. We included a new way of how the code handles dust grains, which allows the consideration of dust grains of different sizes. We investigate the chemical composition, dust charging behaviour and charge balance of these models, to determine which regions could be most sufficient for lightning. We identify 6 regions within the disks where the charge balance is dominated by different radiation processes and find that the emergence of lightning is most probable in the lower and warmer regions of the midplane. This is due to the low electron abundance ($n_{\rm e}/n_{\rm\langle H \rangle}<10^{-15}$) in these regions and dust grains being the most abundant negative charge carriers ($ n_{\rm Z}/n_{\rm\langle H \rangle}> 10^{-13}$). We find that $\rm NH4^+$ is the most abundant positive charge carrier in those regions at the same abundances as the dust grains. We then develop a method of inducing electric fields via turbulence within this mix of dust grains and $\rm NH_4^+$. The electric fields generated with this mechanism are however several orders of magnitude weaker than required to overcome the critical electric field.

IceCube has reported evidence for neutrino emission from the Seyfert-II galaxy NGC 1068 and the blazar TXS 0506+056. The former was identified in a time-integrated search, and the latter using time-dependent and multi-messenger methods. A natural question is: are sources identified in time-integrated searches consistent with a steady neutrino source? We present a non-parametric method, TAUNTON, to answer this question. Motivated by the Cram\'er-von Mises test, TAUNTON is an unbinned single-hypothesis method to identify deviations in neutrino data from the steady hypothesis. An advantage of TAUNTON is that it is sensitive to arbitrary deviations from the steady hypothesis. Here we present results of TAUNTON applied to a 8.7 year data-set of muon neutrino track events; the same data used to identify NGC 1068 at 4.2$\sigma$. We use TAUNTON on 51 objects, a subset (with >4 signal neutrinos) of the 110 objects studied in the NGC 1068 publication. We set a threshold of 3$\sigma$ pre-trial to identify sources inconsistent with the steady hypothesis. TAUNTON reports a p-value of 0.9 for NGC 1068, consistent with the steady hypothesis. Using the time integrated fit, data for TXS 0506+056 is consistent with the steady hypothesis at 1.7$\sigma$. Time variability is not identified for TXS 0506+056 because there are few neutrino events.

The main goal of the present lectures is to outline the key particle interactions and energy loss mechanisms in the Galactic medium that high-energy particles are subject to. These interactions are an important ingredient entering the cosmic ray propagation equation, contributing to shape cosmic ray spectra. They also source the so-called secondary species, like gamma rays, neutrinos, "fragile" nuclei not synthesised in stars, and antiparticles, all routinely used as diagnostic tools in a multi-messenger context. These lectures are complementary to Denise Boncioli's ones, focusing instead on processes happening at ultra-high energies in the extragalactic environment. They include propaedeutic material to Felix Aharonian's and, to some extent, Stefano Gabici's and Carmelo Evoli's lectures.

We present \chandra X-ray observations of the dynamically complex galaxy cluster Abell 119 ($z = 0.044$). A119 is host to two NAT radio sources (0053-015 \& 0053-016) whose tails are oriented parallel to each other despite orthogonally oriented jet axes. Imaging and spectral analysis reveal X-ray emission elongated along the NE-SW axis along with the presence of complex structures, including surface brightness discontinuities, which suggest possible merger activity along this axis. From radial profiles of the X-ray surface brightness, temperature, pressure, and density, we identify two surface brightness edges which are found to be cold fronts, possibly associated with large-scale sloshing of ICM gas. We also identify a brightness edge to the south which is found to be a shock front with Mach number $M = 1.21 \pm 0.11$, consistent with a merger shock. In addition, previous optical studies show alignment of optical substructures along the north-south direction. The elongated X-ray emission, orientations of the NAT tails, and alignment of optical substructure all suggest recent or on-going merger activity in the NE-SW direction.

Over the past half century, gas outflows and winds have been observed as asymmetric emission lines in a wide range of astrophysical contexts, including galaxies and early-type stars. While P Cygni lines are modeled and understood with physically-motivated profiles under the Sobolev approximation, asymmetric nebular lines are not. Previous studies of galactic outflows using nebular emission lines have made physically unjustified assumptions about the shape of the line profile. These approaches limit assessment of outflow properties and do not connect observations to the underlying physics. The physical complexity of galactic outflows requires a more robust approach. In response to this need, we present a novel profile for modeling nebular emission lines which is generalized yet physically motivated and provides insight into the underlying mechanisms of galactic outflows. To demonstrate the usefulness of this profile, we fit it to the asymmetric nebular lines observed in the nuclear region of Mrk 462, a starburst-AGN composite galaxy. From analysis of the best-fit profile, we conclude that the observed profile arises from a dusty radiation-pressure-driven outflow with a terminal velocity of 750 km s-1. This outflow, while weak by some standards, is still sufficiently strong to regulate star formation and black hole growth in the host galaxy by removing gas from the inner few kiloparsecs. Outflows like the one we observe and characterize in Mrk 462 are crucial to our understanding of episodic gas-fueled activity in galactic nuclei, which undoubtedly plays a pivotal role in galaxy evolution.

The solar atmosphere is known to contain many different types of wavelike oscillation. Waves and other fluctuations (e.g., turbulent eddies) are believed to be responsible for at least some of the energy transport and dissipation that heats the corona and accelerates the solar wind. Thus, it is important to understand the behavior of magnetohydrodynamic (MHD) waves as they propagate and evolve in different regions of the Sun's atmosphere. In this paper, we investigate how MHD waves can affect the overall plasma state when they reflect and refract at sharp, planar interfaces in density. First, we correct an error in a foundational paper (Stein 1971) that affects the calculation of wave energy-flux conservation. Second, we apply this model to reflection-driven MHD turbulence in the solar wind, where the presence of density fluctuations can enhance the generation of inward-propagating Alfven waves. This model reproduces the time-averaged Elsasser imbalance fraction (i.e., ratio of inward to outward Alfvenic power) from several published numerical simulations. Lastly, we model how the complex magnetic field threading the transition region between the chromosphere and corona helps convert a fraction of upward-propagating Alfven waves into fast-mode and slow-mode MHD waves. These magnetosonic waves dissipate in a narrow region around the transition region and produce a sharp peak in the heating rate. This newly found source of heating sometimes exceeds the expected heating rate from Alfvenic turbulence by an order of magnitude. It may explain why some earlier models seemed to require an additional ad-hoc heat source at this location.

Experimental bounds on the neutrino lifetime depend on the nature of the neutrinos and the details of the potentially new physics responsible for neutrino decay. In the case where the decays involve active neutrinos in the final state, the neutrino masses also qualitatively impact how these manifest themselves experimentally. In order to further understand the impact of nonzero neutrino masses, we explore how observations of solar neutrinos constrain a very simple toy model. We assume that neutrinos are Dirac fermions and there is a new massless scalar that couples to neutrinos such that a heavy neutrino - $\nu_2$ with mass $m_2$ - can decay into a lighter neutrino - $\nu_1$ with mass $m_1$ - and a massless scalar. We find that the constraints on the new physics coupling depend, sometimes significantly, on the ratio of the daughter-to-parent neutrino masses, and that, for large enough values of the new physics coupling, the "dark side" of the solar neutrino parameter space - $\sin^2\theta_{12}\sim 0.7$ - provides a reasonable fit to solar neutrino data. Our results generalize to other neutrino-decay scenarios, including those that mediate $\nu_2\to\nu_1\bar{\nu}_3\nu_3$ when the neutrino mass ordering is inverted mass and $m_2>m_1\gg m_3$, the mass of $\nu_3$.

Over the next decade, third-generation interferometers and the space-based LISA mission will observe binaries in galactic centers involving supermassive black holes with millions of solar masses. More precise measurements of more extreme events that probe stronger gravitational fields can have a tremendous impact on fundamental physics, astrophysics, and cosmology. However, at the galactic scale, accretion disks, dark matter halos, and dense populations of compact objects can interact gravitationally with coalescing bodies. The role these astrophysical structures play in the evolution and gravitational-wave signature of binary systems remains largely unexplored and previous studies have often relied on ad-hoc Newtonian approximations. In this thesis, we aim to improve this picture. We study how tidal deformations of matter surrounding black holes can mask off deviations from General Relativity. We also explore the deep connection between light rings -- closed orbits of massless particles -- and the proper oscillation modes of compact objects. We show that independently of the presence of an environment, the light ring controls the late-time appearance of infalling matter to distant observers and how the final black hole formed in a collision relaxes to stationarity. Finally, we develop the first fully-relativistic framework capable of studying gravitational wave emission in non-vacuum environments. We apply it to galactic black-hole binaries surrounded by a dark matter halo and observe the conversion between matter and gravitational waves. This coupling results in significant changes in the energy flux emitted, which could help constrain the properties of galactic matter distributions.