Papers for Wednesday, Aug 14 2024

UW Coronae Borealis (UW CrB) is a low mass X-ray binary that shows both Type 1 X-ray and optical bursts, which typically last for 20 s. The system has a binary period of close to 2 hours and is thought to have a relatively high inclination due to the presence of an eclipse in the optical light curve. There is also evidence that an asymmetric disc is present in the system, which precesses every 5.5 days based on changes in the depth of the eclipse. In this paper, we present optical photometry and spectroscopy of UW CrB taken over 2 years. We update the orbital ephemeris using observed optical eclipses and refine the orbital period to 110.97680(1) min. A total of 17 new optical bursts are presented, with 10 of these bursts being resolved temporally. The average $e$-folding time of $19\pm3$s for the bursts is consistent with the previously found value. Optical bursts are observed during a previously identified gap in orbital phase centred on $\phi=0.967$, meaning the reprocessing site is not eclipsed as previously thought. Finally, we find that the apparent P-Cygni profiles present in some of the atomic lines in the optical spectra are due to transient absorption.

We present the application of the $n$-th order Eulerian Perturbation Theory ($n$EPT) for modeling the matter bispectrum in real space as an advancement over the Standard Perturbation Theory (SPT). The $n$EPT method, detailed in Wang et al. (2023) \cite{Wang2023nEPT}, sums up the density perturbations up to the $n$-th order before computing summary statistics such as bispectrum. Taking advantage of grid-based calculation of SPT (GridSPT), we make a realization-based comparison of the analytical nonlinear bispectrum predictions from $n$EPT and SPT against a suite of $N$-body simulations. Using a spherical-bispectrum visualization scheme, we show that $n$EPT bispectrum matches better than SPT bispectrum over a wide range of scales in general $w$CDM cosmologies. Like the power spectrum case, we find that $n$EPT bispectrum modeling accuracy is controlled by $\sigma_8(z) \equiv \sigma_8 D(z)$, where $D(z)$ is the linear growth factor at a redshift $z$. Notably, the 6EPT doubles the bispectrum model's validity range compared to the one-loop SPT for $\sigma_8(z) < 0.5$, corresponding to redshifts $z\ge1$ for the best-fitting Planck-2018 cosmology. For $n\ge5$, however, $n$EPT bispectrum depends sensitively on the cut-off scale or the grid resolution. The percent-level modeling accuracy achieved for the spherical bispectrum (where we average over all triangular configurations) becomes much degraded when fixing configurations. Thus, we show that the validity range of the field-level cosmological inferences must be different from that derived from averaged summary statistics such as $n$-point correlation functions.

Stellar streams in the Milky Way are promising detectors of low-mass dark matter (DM) subhalos predicted by $\Lambda$CDM. Passing subhalos induce perturbations in streams that indicate the presence of the subhalos. Understanding how known DM-dominated satellites impact streams is a crucial step towards using stream perturbations to constrain the properties of dark perturbers. Here, we cross-match a $\textit{Gaia}$ EDR3 and SEGUE member catalog of the Cetus-Palca stream (CPS) with H3 for additional radial velocity measurements and fit the orbit of the CPS using this 6-D data. We demonstrate for the first time that the ultra-faint dwarf Segue 2 had a recent (77$\pm$5 Myr ago) close flyby (within the stream's 2$\sigma$ width) with the CPS. This interaction enables constraints on Segue 2's mass and density profile at larger radii ($\mathcal{O}(1)$ kpc) than are probed by its stars ($\mathcal{O}(10)$ pc). While Segue 2 is not expected to strongly affect the portion of the stream covered by our 6-D data, we predict that if Segue 2's mass within $\sim 6$ kpc is $5\times 10^9\,M_\odot$, the CPS's velocity dispersion will be $\sim 40$ km/s larger ahead of the impact site than behind it. If no such heating is detected, Segue 2's mass cannot exceed $10^9\,M_\odot$ within $\sim 6$ kpc. The proper motion distribution of the CPS near the impact site is mildly sensitive to the shape of Segue 2's density profile. This study presents a critical test for frameworks designed to constrain properties of dark subhalos from stream perturbations.

Molecular clouds (MCs) are the birthplaces of new stars in galaxies. A key component of MCs are photodissociation regions (PDRs), where far-ultraviolet radiation plays a crucial role in determining the gas's physical and chemical state. Traditional PDR models assume chemical steady state (CSS), where the rates of H$_2$ formation and photodissociation are balanced. However, real MCs are dynamic and can be out of CSS. In this study, we demonstrate that combining H$_2$ emission lines observed in the far-ultraviolet or infrared with column density observations can be used to derive the rates of H$_2$ formation and photodissociation. We derive analytical formulae that relate these rates to observable quantities, which we validate using synthetic H$_2$ line emission maps derived from the SILCC-Zoom hydrodynamical simulation. Our method estimates integrated H$_2$ formation and dissociation rates to within 29\% accuracy. Our simulations cover a wide dynamic range in H$_2$ formation and photodissociation rates, showing significant deviations from CSS, with 74\% of the MC's mass deviating from CSS by a factor greater than 2. Our analytical formulae can effectively distinguish between regions in and out of CSS. When applied to actual H$_2$ line observations, our method can assess the chemical state of MCs, providing insights into their evolutionary stages and lifetimes.

Detecting exoplanet transits at X-ray wavelengths would provide a window into the effects of high energy irradiation on the upper atmospheres of planets. However, stars are relatively dim in the X-ray, making exoplanet transit detections difficult with current X-ray telescopes. To date, only one exoplanet (HD~189733~b) has an X-ray transit detection. In this study, we investigate the capability of future X-ray observatories to detect more exoplanet transits, focusing on both the NewAthena-WFI instrument and the proposed Advanced X-ray Imaging Satellite (AXIS), which provide more light-collecting power than current instruments. We examined all the transiting exoplanet systems in the NASA Exoplanet Archive and gathered X-ray flux measurements or estimates for each host star. We then predicted the stellar count rates for both AXIS and NewAthena and simulated light curves, using null-hypothesis testing to identify the top 15 transiting planets ranked by potential detection significance. We also evaluate transit detection probabilities when the apparent X-ray radius is enlarged due to atmospheric escape, finding that $\geq 5$ of these planetary systems may be detectable on the $>4\sigma$ level in this scenario. Finally, we note that the assumed host star coronal temperature, which affects the shape of an X-ray transit, can also significantly affect our ability to detect the planet.

Solar energetic events are caused by the release of magnetic energy accumulated in the solar atmosphere. To understand their initiating physical mechanisms, the dynamics of the coronal magnetic fields must be studied. Unfortunately, the dominant mechanisms are still unclear due to lack of direct measurements. Numerical simulations based on magnetohydrodynamics (MHD) can reproduce the dynamical evolution of solar coronal magnetic field providing a useful tool to explore flare initiation. Data-driven MHD simulations, in which the time-series observational data of the photospheric magnetic field is used as the simulation boundary condition, can explore different mechanisms. To investigate the accumulation of free magnetic energy through to a solar eruption, we simulated the first of several large flares in NOAA Active Region 11283. We used a data-driven model (Kaneko et al 2021) that was governed by zero-beta MHD, focusing on the free magnetic energy accumulation prior to the M5.3 flare (September 6, 01:59 UT, 2011). We reproduced the flare-associated eruption following the formation of twisted magnetic fields, or a magnetic flux rope (MFR), formed by photospheric motions at its footpoints. We found that the eruption was first triggered by the growth of the torus instability. The erupting MFR caused magnetic reconnections with neighboring magnetic field lines located along the direction of the eruption. Using the simulation results and an axial-radial decay index centered on the MFR, we find a natural explanation for the inclination of the eruption and a possible approach to predict the direction of solar eruptive events.

We present a population-level analysis of the dayside thermal emission spectra of 19 planets observed with Hubble WFC3 and Spitzer IRAC 3.6 and 4.5 microns, spanning equilibrium temperatures 1200-2700 K and 0.7-10.5 Jupiter masses. We use grids of planet-specific 1D, cloud-free, radiative-convective-thermochemical equilibrium models (1D-RCTE) combined with a Bayesian inference framework to estimate atmospheric metallicity, the carbon-to-oxygen ratio, and day-to-night heat redistribution. In general, we find that the secondary eclipse data cannot reject the physics encapsulated within the 1D-RCTE assumption parameterized with these three variables. We find a large degree of scatter in atmospheric metallicities, with no apparent trend, and carbon-to-oxygen ratios that are mainly consistent with solar or subsolar values but do not exhibit population agreement. Together, these indicate either (1) formation pathways vary over the hot and ultra-hot Jupiter population and/or (2) more accurate composition measurements are needed to identify trends. We also find a broad scatter in derived dayside temperatures that do not demonstrate a trend with equilibrium temperature. Like with composition estimates, this suggests either significant variability in climate drivers over the population and/or more precise dayside temperature measurements are needed to identify a trend. We anticipate that 1D-RCTE models will continue to provide valuable insights into the nature of exoplanet atmospheres in the era of JWST.

We review the evolution of our understanding of the planetary nebulae phenomenon and their place in the scheme of stellar evolution. The historical steps leading to our current understanding of central star evolution and nebular formation are discussed. Recent optical imaging, X-ray, ultraviolet, infrared, millimeter wave, radio observations have led to a much more complex picture of the structure of planetary nebulae. The optically bright regions have multiple shell structures (rims, shells, crowns, and haloes), which can be understood within the interacting winds framework. However, the physical mechanism responsible for bipolar and multipolar structures that emerged during the proto-planetary nebulae phase is yet to be identified. Our morphological classifications of planetary nebulae are hampered by the effects of sensitivity, orientation, and field-of-view coverage, and the fraction of bipolar or multipolar nebulae may be much higher than commonly assumed. The optically bright bipolar lobes may represent low-density, ionization-bounded cavities carved out of a neutral envelope by collimated fast winds. Planetary nebulae are sites of active synthesis of complex organic compounds, suggesting that planetary nebulae play a major role in the chemical enrichment of the Galaxy. Possible avenues of future advancement are discussed.

In this paper, we evaluate the viability of CubeSats as an attractive platform for lightweight instrumentation by describing a proof of concept CubeSat that houses an astrophotonic chip for transit spectroscopy-based exoplanet atmosphere gas sensing. The Twin Earth SEnsoR Astrophotonic CubesaT (TESERACT) was designed to house a correlation spectroscopy chip along with an electrical and optical system for operation. We investigate design challenges and considerations in incorporating astrophotonic instrumentation such as component integration, thermal management and optical alignment. This work aims to be a pathfinder for demonstrating that astrophotonic-based CubeSat missions can perform leading edge, targeted science in lower-cost CubeSat platforms.

Long baseline optical interferometry and aperture synthesis using ground-based telescopes can enable unprecedented angular resolution astronomy in the optical domain. However, atmospheric turbulence leads to large, dynamic phase errors between participating apertures that limit fringe visibility using telescopes arrays or subaperture configurations in a single large telescope. Diffraction limited optics or adaptive optics can be used to ensure coherence at each aperture, but correlating the phase between apertures requires high speed, high stroke phase correction and recombination that is extremely challenging and costly. As a solution, we show an alternative phase correction and beam combination method using a centimeter-scale silicon astrophotonic chip optimized for H-band operation. The 4.7x10mm silicon photonic chip is fabricated using electron beam lithography with devices with 2 up to 32 independent channels. Light is coupled into the chip using single mode fiber ribbons. An array of microheaters is used to individually tune the effective index of each spiral delay waveguides. Narrowband spectral splitters at each spatial channel divert a modulated digital reference signal from an artificial guide star off-chip for phase measurement. Science light from other wavelengths is coherently combined using on-chip beam combiners and outputted to a single waveguide. We described the role, design, fabrication and characterization of the photonic chip. This photonic phase control scheme can be applied in astronomical interferometry or optical satellite communications.

The Santa Cruz Extreme AO Lab (SEAL) testbed is an optical bench meant to design and develop new wavefront control techniques for high-contrast imaging for segmented telescopes. These techniques allow for astronomical efficiency in exoplanet imaging and characterization. SEAL consists of several wavefront sensors (WFS) and deformable mirrors (DM) that are currently performing techniques like predictive control or non-linear reconstruction. In this paper, we present the implementation and characterization of a new coronagraphic branch on SEAL and assess the contrast limitations in the testbed. For our coronagraphic branch, we used a vector vortex coronagraph which has high contrast performance. The W. M. Keck Observatory also uses a vortex coronagraph, allowing us to compare the limitations with our own coronagraph. We relied on the testbed and simulations of the vortex coronagraph to compare performance with expected ones. To create a more reliable simulation, we also injected in our numerical model data collected by a Zernike Wavefront sensor (ZWFS) used to perform fine wavefront sensing on the bench. Now that the coronagraphic branch is aligned on SEAL, we will be able to use contrast as a metric for the performance of wavefront control methods on the bench.

Radio-frequency interference (RFI) is becoming an increasingly significant problem for most radio telescopes. Working with Green Bank Telescope data from PSR J1730+0747 in the form of complex-valued channelized voltages and their respective high-resolution power spectral densities, we evaluate a variety of statistical measures to characterize RFI. As a baseline for performance comparison, we use median absolute deviation (MAD) in complex channelized voltage data and spectral kurtosis (SK) in power spectral density data to characterize and filter out RFI. From a new perspective, we implement the Shapiro-Wilks (SW) test for normality and two information theoretical measures, spectral entropy (SE) and spectral relative entropy (SRE), and apply them to mitigate RFI. The baseline RFI mitigation algorithms are compared against our novel RFI detection algorithms to determine how effective and robust the performance is. Except for MAD, we find significant improvements in signal-to-noise ratio through the application of SE, symmetrical SRE, asymmetrical SRE, SK, and SW. These algorithms also do a good job of characterizing broadband RFI. Time- and frequency-variable RFI signals are best detected by SK and SW tests.

Electromagnetic follow-up observations of gravitational wave events offer critical insights and provide significant scientific gain from this new class of astrophysical transients. Accurate identification of gravitational wave candidates and rapid release of sky localization information are crucial for the success of these electromagnetic follow-up observations. However, searches for gravitational wave candidates in real time suffer a non-negligible false alarm rate. By leveraging the sky localization information and other metadata associated with gravitational wave candidates, GWSkyNet, a machine learning classifier developed by Cabero et al. (2020), demonstrated promising accuracy for the identification of the origin of event candidates. We improve the performance of the classifier for LIGO-Virgo-KAGRA's fourth observing run by reviewing and updating the architecture and features used as inputs by the algorithm. We also retrain and fine-tune the classifier with data from the third observing run. To improve the prospect of electromagnetic follow-up observations, we incorporate GWSkyNet into LIGO-Virgo-KAGRA's low-latency infrastructure as an automatic pipeline for the evaluation of gravitational wave alerts in real time. We test the readiness of the algorithm on a LIGO-Virgo-KAGRA mock data challenge campaign. The results show that by thresholding on the GWSkyNet score, noise masquerading as astrophysical sources can be rejected efficiently and the majority of true astrophysical signals correctly identified.

Primordial black holes (PBHs), possibly constituting a non-negligible fraction of dark matter (DM), might be responsible for a number of gravitational wave events detected by LIGO/Virgo/KAGRA. In this paper, we simulate the evolution of PBH binaries in DM halos and calculate their merger rate up to redshift of 10. We assume that DM halos are made entirely by a combination of single PBHs and PBH binaries. We present the resulting merger rates from the two main channels that lead to merging PBH binaries: two-body captures and binary-single interactions. We account for alternative assumptions on the dark matter halo mass-concentration relationship versus redshift. We also study what impact the PBH mass distribution, centered in the stellar-mass range, has on the PBH merger rate that the ground-based gravitational-wave observatories can probe. We find that under reasonable assumptions on the abundance of PBH binaries relative to single PBHs, the binary-single interaction rates can be dominant over the two-body capture channel. Our work studies in detail the dynamics of PBHs inside DM halos, advancing our understanding on how the current gravitational-wave events constrain the properties of PBHs. Moreover, we make predictions in a redshift range to be probed by future observatories.

RX Pup is a symbiotic binary which experienced a nova outburst in the 1970's. Here we report a discovery of a ~1300 year old nova shell around the system and a possible detection of a ~7000 year old nova shell. Together with the nova shell ejected in the 1970's this makes RX Pup the first system with three nova shells observed. This triad of eruptions suggests a change in the nova recurrence time. The most likely explanation is an alteration in the mass transfer rate attributed to evolutionary changes of the mass-donor in the system. Notably, comparative analyses with theoretical models indicate an increase in the average mass transfer rate by a factor of three over the past 10,000 years. This makes RX Pup a unique system, which allows us to probe millenium-scale evolution of mass transfer rates in binary systems.

Due to the nonseparability of the post-Newtonian (PN) Hamiltonian systems of compact objects, the symplectic methods that admit the linear error growth and the near preservation of first integrals are always implicit as explicit symplectic methods have not been currently found for general nonseparable Hamiltonian systems. Since the PN Hamiltonian has a particular formulation that includes a dominant Newtonian part and a perturbation PN part, we present the generalized flow-composed Runge--Kutta (GFCRK) method with a free parameter $\lambda$ to PN Hamiltonian systems. It is shown that the GFCRK method is symplectic once the underlying RK method is symplectic, and it is symmetric once the underlying RK method is symmetric under the setting $\lambda=1/2$. Numerical experiments with the 2PN Hamiltonian of spinning compact binaries demonstrate the higher accuracy and efficiency of the symplectic GFCRK method than the underlying symplectic RK. Meanwhile, the numerical results also support higher efficiency of the symplectic GFCRK method than the semi-explicit mixed symplectic method of the same order.

Gamma-ray bursts (GRBs), both from merger of binary compact objects (short GRBs) and collapse of massive stars (long GRBs), are expected to occur in the dense environments, e.g., the accretion disk of active galactic nuclei (AGN). The propagating of GRB jets in such dense environment will result in multiband transients. Investigating the properties of these transients plays important roles in their identification, understanding the jet structure and constraining population of the star and compact object in AGN disks. In this work, we intend to study the propagation and emission of a two-component GRB jet (a fast narrow component and wide slow one) in the AGN disk. We consider the influence of wind from the short and long GRB progenitors, which would reconstruct the surrounding density distribution and form a cavity in the AGN disk. We find that the long GRB jets will be chocked, the dynamcis and the emission are resemble to the case without cavity. The narrow and wide cocoon breakout emission can be detected by EP and HXMT, respectively. For short GRBs, we expect a non-thermal afterglow emission from the wide jet and a cocoon breakout emission from the chocked narrow jet, which can be monitored by EP and HXMT, respectively. Therefore, the joint observations by EP and HXMT might be helpful to distinguish the type of GRBs in the AGN disk and the jet components.

Filament eruptions and coronal mass ejections are physical phenomena related to magnetic flux ropes carrying electric current. A magnetic flux rope is a key structure for solar eruptions, and when it carries a southward magnetic field component when propagating to the Earth. It is the primary driver of strong geomagnetic storms. As a result, developing a numerical model capable of capturing the entire progression of a flux rope, from its inception to its eruptive phase, is crucial for forecasting adverse space weather. The existence of such flux ropes is revealed by the presence of sigmoids in active regions or hot channels by observations from space and ground instruments. After proposing cartoons in 2D, potential, linear, non-linear-force-free-field (NLFFF) and non-force-free-field (NFFF) magnetic extrapolations, 3D numerical magnetohydrodynamic (MHD) simulation models were developed, first in a static configuration and later dynamic data-driven MHD models using high resolution observed vector magnetograms. This paper reviews a few recent developments in data-driven mode, such as the time-dependent magneto-frictional (TMF) and thermodynamic magnetohydrodynamic (MHD) models. Hereafter, to demonstrate the capacity of these models to reveal the physics of observations, we present the results for three events explored in our group: 1. the eruptive X1.0 flare on 28 October 2021; 2. the filament eruption on 18 August 2022; and 3. the confined X2.2 flare on 6 September 2017. These case studies validate the ability of data-driven models to retrieve observations, including the formation and eruption of flux ropes, 3D magnetic reconnection, CME three-part structures and the failed eruption. Based on these results, we provide some arguments for the formation mechanisms of flux ropes, the physical nature of the CME leading front, and the constraints of failed eruptions.

The First Large Absorption Survey in HI (FLASH) is a large-area radio survey for neutral hydrogen in the redshift range 0.4<z<1.0, using the 21cm HI absorption line as a probe of cold neutral gas. FLASH uses the ASKAP radio telescope and is the first large 21cm absorption survey to be carried out without any optical preselection of targets. We use an automated Bayesian line-finding tool to search through large datasets and assign a statistical significance to potential line detections. The survey aims to explore the neutral gas content of galaxies at a cosmic epoch where almost no HI data are currently available, and to investigate the role of neutral gas in AGN fuelling and feedback. Two Pilot Surveys, covering around 3000 deg$^2$ of sky, were carried out in 2019-22 to test and verify the strategy for the full FLASH survey. The processed data from these Pilot Surveys (spectral-line cubes, continuum images, and catalogues) are available online. Here, we describe the FLASH spectral-line and continuum data and discuss the quality of the HI spectra and the completeness of our automated line search. Finally, we present a set of 30 new HI absorption lines that were robustly detected in the Pilot Surveys. These lines span a wide range in HI optical depth, including three lines with a peak optical depth $\tau>1$, and appear to be a mixture of intervening and associated systems. The overall detection rate for HI absorption lines in the Pilot Surveys (0.3 to 0.5 lines per ASKAP field) is a factor of two below the expected value. There are several possible reasons for this, but one likely factor is the presence of a range of spectral-line artefacts in the Pilot Survey data that have now been mitigated and are not expected to recur in the full FLASH survey. A future paper will discuss the host galaxies of the HI absorption systems identified here.

We present a multi-frequency polarimetric study for the quasar 1604+159. The source was observed at the $L$ band with the American Very Long Baseline Array (VLBA) and the $L$, $X$, and $U$ bands with the Very Large Array (VLA). These observations provide different resolutions from mas to arcsec, enabling us to probe the morphology and magnetic field from tens of parsec to hundreds of kilo-parsec scale. We detect a symmetrical Fanaroff-Riley-Class-I-like structure. The source has several lobes and bulges, forming a cocoon shape. The polarization is normal to the edges of the structure with high fractional polarization up to $\sim 60\%$. Two hotspots are observed at the eastern and western sides of the source, located symmetrically relative to the core. The flux density ratio ($>1.5$) between the two hotspots suggests the Doppler beaming effect exists at a large scale. The polarized emission in the hotspots also shows a symmetrical structure with an oblique direction from the jet direction. In general, the jet propagates in a collimating structure with several bends. Polarization is also detected perpendicular to the local jet from $\sim$100 mas to $\sim$ 1 arcsec. The jet shows strong polarized intensity and high fractional polarization at the bending edges. We discuss the possible origins of the observed structure and magnetic field.

Foreground removal presents a significant obstacle in both current and forthcoming intensity mapping surveys. While numerous techniques have been developed that show promise in simulated datasets, their efficacy often diminishes when applied to real-world data. A primary issue is the frequency-dependent variations in the instrumental response. In this paper, we propose a novel approach utilizing the internal cross-correlation among different frequencies to calibrate the beam's frequency fluctuations. Using a simulated dataset that incorporates frequency-dependent random fluctuations into the beam model, we illustrate that our method can achieve considerable improvements over traditional techniques. Our results represent a step forward in enhancing the precision and reliability of foreground removal in intensity mapping surveys.

The standard external shock model in the thin-shell scenario predicts an onset bump in the early optical afterglow light curves of gamma-ray bursts (GRBs). We collect such a textbook-version light curve sample of $30$ GRBs, and derive the jet properties from our joint fit to their X-ray and optical afterglow light curves. It is found that the distributions of the isotropic initial Lorentz factors ($\Gamma_0$), the deceleration radii ($R_{\rm dec}$), and the magnetic field strength ($B_0$) are log-normal, but the distributions of the isotropic kinetic energy ($E_{\rm k, iso}$), medium density ($n_{0}$), and the magnetization parameter ($\sigma_{B}\equiv\epsilon_B/\epsilon_e$) are tentatively bimodal. A tight $R_{\rm dec}\mbox{-}B_{0}\mbox{-}\sigma_{B}$ relation is found. It infers a universal $\epsilon_e E_{\rm k,iso}$ among bursts, plausibly supporting the previous argument of a universal GRB radiation energy among GRBs. A jet break is required for modeling the light curves of $26$ GRBs. The distributions of the jet opening angles and the jet-corrected kinetic energies log-normally center at $\log \theta_{\rm j,c}/{\rm rad}=-1.51$ (standard deviation $\sigma=0.27$) and $\log (E_{\rm k, j,c}/{\rm erg})=51.78$ ($\sigma=0.54$), respectively. Those GRBs ($19$ GRBs), whose prompt gamma-ray emission is well estimated with broad energy-band observations, satisfy the previously discovered $L_{\rm \gamma, p, iso}-E_{\rm p,z}-\Gamma_{0}$ relation, and their gamma-ray radiation efficiencies log-normally distribute in the range from $0.04\%$ to $10\%$ with a central value of $0.42\%$. Such a low efficiency favors the baryonic fireball model, and the distribution of their baryon mass loading in the GRB ejecta log-normally centers at $\log (M_{\rm fb,c}/M_{\rm sun})=-5$ ($\sigma=0.75$).

It has been suggested that under solar coronal conditions, drift waves may contribute to coronal heating. Specific properties of the drift waves to be expected in the solar corona have, however, not yet been determined using more advanced numerical models. We investigate the linear properties of density-gradient-driven drift waves in the solar coronal plasma using gyrokinetic ion-electron simulations with the gyrokinetic code GENE, solving the Vlasov-Maxwell equations in five dimensions assuming a simple slab geometry. We determine the frequencies and growth rates of the coronal density gradient-driven drift waves with changing plasma parameters, such as the electron \b{eta} , the density gradient, the magnetic shear and additional temperature gradients. To investigate the influence of the finite Larmor radius effect on the growth and structure of the modes, we also compare the gyrokinetic simulation results to those obtained from drift-kinetics. In most of the investigated conditions, the drift wave has positive growth rates that increase with increasing density gradient and decreasing \b{eta} . In the case of increasing magnetic shear, we find that from a certain point, the growth rate reaches a plateau. Depending on the considered reference environment, the frequencies and growth rates of these waves lie on the order of 0.1 mHz to 1 Hz. These values correspond to the observed solar wind density fluctuations near the Sun detected by WISPR, currently of unexplained origin. As a next step, nonlinear simulations are required to determine the expected fluctuation amplitudes and the plasma heating resulting from this mechanism.

The early-type star ASASSN-21js started to fade in 2021, as was detected by the All Sky Automated Survey for Supernovae, undergoing a multi-year eclipse that is still underway. We interpret this event as being due to a structured disc of material transiting in front of the star. The disc is in orbit around a substellar object with the mass and luminosity of a brown dwarf or smaller. We want to determine the expected duration and ending date of the eclipse. We modelled a tilted and inclined azimuthally symmetric ring system around an unseen companion and calculated the resulting time-varying light curve as the object transited in front of the star. We made an initial estimate of the ring parameters and used these as inputs to an MCMC algorithm to determine the geometric properties of the rings with associated uncertainties. The model most consistent with the light curve to date is a two-ring system at high inclination with respect to the line of sight that has a semi-major axis of 71.6 stellar radii. With an estimate of the stellar radius, the transverse velocity is around 0.7 km/s, which if bound to the star is an orbit with a semi-major axis of around 13000 au, placing it in the Oort cloud of the parent star. The transit is ongoing and will finish around MJD 61526 (May 1 2027). We encourage the community to continue observing this object in order to understand its properties.

Recently, the detection of a coherent radio flash associated with short GRB 201006A, occurring 76.6 minutes after the burst, has attracted great attention. However, the physical origin of the coherent radio flash remains in debate. By reanalyzing its data observed by Fermi and Swift, we find that an early radio afterglow as the physical origin of the radio flash can be ruled out, but the coherent radio emission seems to be consistent with the hypothesis of a supramassive magnetar as the central engine collapsing into a black hole. Within this scenario, the derived magnetar surface magnetic field ($B_{\rm p}$) and the initial spin period ($P_{\rm 0}$) fall into a reasonable range, but require to prefer a low value of $\eta_{\rm R} = 10^{-7}$ or $10^{-6}$. Moreover, the calculated low-$\varepsilon$ value and $E_{\rm \gamma,iso}-E_{\rm p}$ correlation of GRB 201006A also support to the progenitor from merger of compact stars. No detected the kilonova emission associated with GRB 201006A to compare with the upper limits of optical observations is also discussed.

Dwarf galaxy star formation histories are theoretically expected to be bursty, potentially leaving distinct imprints on their chemical evolution. We propose that episodic starbursts with quiescent periods longer than $\sim$100 Myr should lead to discontinuous tracks in a dwarf galaxy's [$\alpha$/Fe]-[Fe/H] chemical abundance plane, with metallicity gaps as large as 0.3-0.5 dex at [Fe/H] = -2. This occurs due to continued Fe production by Type Ia supernovae during quiescent periods. We demonstrate that Gaussian mixture models can statistically distinguish discontinuous and continuous tracks based on the Akaike Information Criterion. Applying this method to APOGEE observations of the Sculptor dSph galaxy suggests an episodic star formation history with $\sim$300 Myr quiescent periods. While current dwarf galaxy datasets are limited by small spectroscopic sample sizes, future surveys and extremely large telescopes will enable determining large numbers of precise chemical abundances, opening up the investigation of very short timescales in early dwarf galaxy formation. This unprecedentedly high time resolution of dwarf galaxy formation in the early Universe has important implications for understanding both reionization in the early Universe and the episodic star formation cycle of dwarf galaxies.

Massive star-forming regions (MSFRs) are commonly associated with hub-filament systems (HFSs) and sites of cloud-cloud collision (CCC). Recent observational studies of some MSFRs suggest a possible connection between CCC and the formation of HFSs. To understand this connection, we analyzed the magneto-hydrodynamic simulation data from Inoue et al. (2018). This simulation involves the collision of a spherical turbulent molecular cloud with a plane-parallel sea of dense molecular gas at a relative velocity of about 10 km/s. Following the collision, the turbulent and non-uniform cloud undergoes shock compression, rapidly developing filamentary structures within the compressed layer. We found that CCC can lead to the formation of HFSs, which is a combined effect of turbulence, shock compression, magnetic field, and gravity. The collision between the cloud components shapes the filaments into a cone and drives inward flows among them. These inward flows merge at the vertex of the cone, rapidly accumulating high-density gas, which can lead to the formation of massive star(s). The cone acts as a mass-collecting machine, involving a non-gravitational early process of filament formation, followed by gravitational gas attraction to finalize the HFS. The gas distribution in the position-velocity (PV) and position-position spaces highlights the challenges in detecting two cloud components and confirming their complementary distribution if the colliding clouds have a large size difference. However, such CCC events can be confirmed by the PV diagrams presenting gas flow toward the vertex of the cone, which hosts gravitationally collapsing high-density objects, and by the magnetic field morphology curved toward the direction of the collision.

We present the first X-ray polarization measurements of GX 339-4. IXPE observed this source twice during its 2023-2024 outburst, once in the soft-intermediate state and again during a soft state. The observation taken during the intermediate state shows significant ($4\sigma$) polarization degree P = $1.3\% \pm 0.3\%$ and polarization angle $\theta$ = -74\degree $\pm$ 7\degree only in the 3 - 8 keV band. FORS2 at VLT observed the source simultaneously detecting optical polarization in the B, V, R, I bands (between $0.1%$ and $0.7\%$), all roughly aligned with the X-ray polarization. We also detect a discrete jet knot from radio observations taken later in time; this knot would have been ejected from the system around the same time as the hard-to-soft X-ray state transition and a bright radio flare occurred $\sim$3 months earlier. The proper motion of the jet knot provides a direct measurement of the jet orientation angle on the plane of the sky at the time of the ejection. We find that both the X-ray and optical polarization angles are aligned with the direction of the ballistic jet.

In 2012, Brazil began the studies to send its first deep space exploration mission, ASTER, which would be the first mission to orbit a triple asteroid system, 2001 SN263. We aim to contribute to the ASTER mission by defining the parameters of a multispectral camera system that will be used to study the asteroid system 2001 SN263, through software simulations that should help planning the data collection. We inserted the shape model of the objects in the software POV-Ray and modeled two cameras, a Wide Angle (WAC) and a Narrow Angle (NAC). We inserted the asteroid's parameters and simulated the satellite position. We created various scenes so we could obtain a good view of the asteroid. Alpha is entirely visible only in the WAC images, while the NAC is expected to reveal surface details. Beta seems relatively small in the WAC images, whereas we obtain a broad view from the NAC at 100 km distance. Gamma, smaller than Beta, should provide more detailed images through the NAC, whereas the WAC images should be able to show its inclined orbit around Alpha. To see Gamma behind Alpha in its revolution movement, we would have to elevate the camera's orbit. The method employed to simulate images generated by satellite cameras can be applied to other scenarios where the target requires imaging, extending beyond the field of planetary geology.

We present a comprehensive study of the X-ray spectral properties of the accreting millisecond pulsar IGR J17498$-$2921 during its 2023 outburst. Similar to other accreting millisecond pulsars, the broad-band spectral emission observed quasi-simultaneously by NICER and NuSTAR is well described by an absorbed Comptonized emission with an electron temperature of $\sim$17 keV plus a disk reflection component. The broadening of the disk reflection spectral features, such as a prominent iron emission line at 6.4-6.7 keV, is consistent with the relativistic motion of matter in a disk truncated at $\sim$$21 \, \mathrm{R_g}$ from the source, near the Keplerian co-rotation radius. From the high-cadence monitoring data obtained with NICER, we observe that the evolution of the photon index and the temperature of seed photons tracks variations in the X-ray flux. This is particularly evident close to a sudden $\sim$-0.25 cycles jump in the pulse phase, which occurs immediately following an X-ray flux flare and a drop in the pulse amplitude below the $3\sigma$ detection threshold. We also report on the non-detection of optical pulsations with TNG/SiFAP2 from the highly absorbed optical counterpart.

Precise space-based photometry from the Transiting Exoplanet Survey Satellite results in a huge number of exoplanetary candidates. However, the masses of these objects are unknown and must be determined by ground-based spectroscopic follow-up observations, frequently revealing the companions to be low-mass stars rather than exoplanets. We present the first orbital and stellar parameter solutions for five such eclipsing binary-star systems using radial-velocity follow-up measurements together with spectral-energy-distribution solutions. TOI-416 and TOI-1143 are totally eclipsing F+M star systems with well-determined secondary masses, radii, and temperatures. TOI-416 is a circular system with an F6 primary and a secondary with a mass of $M_2={0.131(8)}{M_\odot}$. TOI-1143 consists of an F6 primary with an $M_2={0.142(3)}{M_\odot}$ secondary on an eccentric orbit with a third companion. With respect to the other systems, TOI-1153 shows ellipsoidal variations, TOI-1615 contains a pulsating primary, and TOI-1788 has a spotted primary, while all have moderate mass ratios of 0.2-0.4. However, these systems are in a grazing configuration, which limits their full description. The parameters of TOI-416B and TOI-1143B are suitable for the calibration of the radius-mass relation for dwarf stars.

New ground-based and space-based photometric data have been obtained and archival spectroscopic measurements were used in this study of three detached early-type and southern-hemisphere eccentric eclipsing binaries GM Nor (P = 1.88 d, e = 0.05), V397 Pup (3.00, 0.30), and PT Vel (1.80, 0.12). Their TESS observations in several sectors have also been included and the corresponding light curves were solved using the Phoebe code. As a result, new accurate photoelectric times of minimum light have been obtained. The newly completed O-C diagrams were analyzed using all reliable timings found in the literature and calculated using the TESS light curves. New or improved values for the elements of apsidal motion were obtained. Using ESO archive spectroscopy, for V397 Pup, the precise absolute parameters were newly derived: M1 = 3.076(35) M$\odot$, M2 = 2.306(35) M$\odot$, and R1 = 2.711(55) R$\odot$, R2 = 1.680(55) R$\odot$. For PT Vel the absolute dimensions were improved: M1 = 2.204(25) M$\odot$, M2 = 1.638(25) M$\odot$, and R1 = 2.108(30) R$\odot$, R2 = 1.605(30) R$\odot$. For GM Nor, the less accurate absolute parameters based on the light curve analysis were evaluated: M1 = 1.94(15) M$\odot$, M2 = 1.84(14) M$\odot$, and R1 = 2.27(20) R$\odot$, R2 = 2.25(20) R$\odot$. We found more precise and relatively short periods of apsidal motion of about 80, 335, and 160 years, along with the corresponding internal structure constants, log k2, -2.524, -2.361, and -2.563, for GM Nor, V397 Pup, and PT Vel, respectively. Relativistic effects are small but not negligible, making up to 10\% of the total apsidal motion rate in all systems. No marks of the presence of the third body were revealed in the light curves, on the O-C diagrams, or in the reduced spectra of the eccentric systems studied here.

In this study, we report the likely GeV {\gamma}-ray emissions originating from the pulsar PSR J1849-0001's pulsar wind nebula (PWN) G32.64+0.53. Our analysis covers approximately 14.7 years of data from the Fermi Large Area Telescope (Fermi-LAT) Pass 8. The position of the source and its spectrum matches those in X-ray and TeV energy bands, so we propose that the GeV {\gamma}-ray source is indicative of PWN G32.64+0.53. We interpret the broadband spectral energy distribution (SED) using a time-dependent one-zone model, which assumes that the multi-band non-thermal emission of the target source can be generated by synchrotron radiation and inverse Compton scattering (ICS) of the electrons/positrons. Our findings demonstrate that the model substantially elucidates the observed SED. These results lend support to the hypothesis that the {\gamma}-ray source originates from the PWN G32.64+0.53 powered by PSR J1849-0001. Furthermore, the {\gamma}-rays in TeV bands are likely generated by electrons/positrons within the nebula through Inverse Compton Scattering.

We present a parameter estimation algorithm on kilonova light curves using likelihood-free inference. Our inference is optimized through a pre-trained embedding network that marginalizes the time of arrival and the luminosity distance of the signal. We find that parameter inference utilizing a pre-trained embedding outperforms the use of likelihood-free inference alone, reducing training time and offering the capability to marginalize over certain nuisance parameters. The model is capable of retrieving the intrinsic parameters of the kilonova light curves with a comparable accuracy and precision to nested sampling methods while taking significantly less computational time. This framework has been integrated into the publicly available Nuclear Multi-Messenger Astronomy codebase so users can leverage the model for their inference purposes. This algorithm is broadly applicable to parameterized or simulated light curves of other transient objects.

Epsilon Eridani ($\epsilon$ Eri) is one of the first debris disk systems detected by the Infrared Astronomical Satellite (IRAS). However, the system has thus far eluded detection in scattered light with no components having been directly imaged. Its similarity to a relatively young Solar System combined with its proximity makes it an excellent candidate to further our understanding of planetary system evolution. We present a set of coronagraphic images taken using the Space Telescope Imaging Spectrograph (STIS) coronagraph on the Hubble space telescope at a small inner working angle to detect a predicted warm inner debris disk inside 1". We used three different post-processing approaches; Non-negative Matrix Factorization (NMF), Karhunen-Lo`eve Image Processing (KLIP), and Classical reference differential imaging (RDI), to best optimize reference star subtraction, and find that NMF performed the best overall while KLIP produced the absolute best contrast inside 1". We present limits on scattered light from warm dust, with constraints on surface brightness at 6 mJy/as$^2$ at our inner working angle of 0.6". We also place a constraint of 0.5 mJy/as$^2$ outside 1", which gives us an upper limit on the brightness for outer disks and substellar companions. Finally, we calculated an upper limit on the dust albedo at $\omega <$ 0.487.

With the commissioning of the refurbished adaptive secondary mirror (ASM) for the 6.5-meter MMT Observatory under way, special consideration had to be made to properly calibrate the mirror response functions to generate an interaction matrix (IM). The commissioning of the ASM is part of the MMT Adaptive optics exoPlanet characterization System (MAPS) upgrade the observatory's legacy adaptive optics (AO) system. Unlike most AO systems, MAPS employs a convex ASM which prevents the introduction of a calibration source capable of simultaneously illuminating its ASM and wavefront sensor (WFS). This makes calibration of the AO system a significant hurdle in commissioning. To address this, we have employed a hybrid calibration strategy we call the Efficient Synthesis of Calibrations for Adaptive Optics through Pseudo-synthetic and Empirical methods (ESCAPE). ESCAPE combines the DO-CRIME on-sky calibration method with the SPRINT method for computing pseudo-synthetic calibration matrices. To monitor quasi-static system change, the ESCAPE methodology rapidly and continuously generates pseudo-synthetic calibration matrices using continual empirical feedback in either open or closed-loop. In addition, by measuring the current IM in the background while in close-loop, we are also able to measure the optical gains for pyramid wavefront sensor (PyWFS) systems. In this paper, we will provide the mathematical foundation of the ESCAPE calibration strategy and on-sky results from its application in calibrating the MMT Observatory's ASM. Additionally, we will showcase the validation of our approach from our AO testbed and share preliminary on-sky results from MMT.

We present a catalog of dust clouds at high Galactic latitude based on the Planck 857 GHz dust emission data. Using a clustering hierarchical algorithm, 315 dust cloud at high Galactic latitudes are identified. Additionally, using the optical and ultraviolet extinction of 4 million and 1 million stars, respectively, provided by Sun et al., we derive the distances and physical properties for 190 high Galactic latitude dust clouds and the ultraviolet excess ratios for 165 of them. Through the study of color excess ratios, this work confirms that molecular clouds with large Galactic distances and low extinction likely have a higher proportion of small-sized dust grains. In addition, clouds with well-defined distances in the catalog are used to trace the local bubble, showing good consistency with the boundary of the local bubble from the literature.

The $\epsilon$ Lupi A (HD 136504) system stands out among magnetic massive binaries as the only short-period binary system in which both components have detectable magnetic fields. The proximity of the magnetospheres of the components leads to magnetospheric interactions, which are revealed as periodic pulses in the radio light curve of this system. In this work, we aim to investigate the magnetospheric interaction phenomenon in the X-ray domain. We observed this system with the XMM-Newton telescope, covering its orbital period. We observe variable X-ray emission with maximum flux near periastron, showing similarity with radio observations. The X-ray spectra show significantly elevated hard X-ray flux during periastron. We attribute the soft X-ray emission to individual magnetospheres, while the hard X-ray emission is explained by magnetospheric interaction, particularly due to magnetic reconnection. However, unlike in the radio, we do not find any significant short-term X-ray bursts. This exotic system can be an ideal target to study magnetospheric interactions in close binaries with organized magnetospheres.

We present the Ultracool Dwarf Companion Catalogue of 278 multiple systems, 32 of which are newly discovered, each with at least one spectroscopically confirmed Ultracool Dwarf, within a 100 pc volume-limited sample. This catalogue is compiled using the Gaia Catalogue of Nearby Stars for stellar primaries and the Gaia Ultracool Dwarf Sample for low-mass companions and includes 241 doubles, 33 triples, and 4 higher-order systems established from positional, proper motion, and parallax constraints. The catalogue seeks to identify probable benchmark systems within 100 pc to obtain model-independent astrophysical parameters of Ultracool Dwarfs. Chance alignment probabilities are calculated to evaluate the physical nature of each system. Astrometric and photometric data from Gaia Data Release 3 and the Two Micron All Sky Survey are included for all objects. We identify potential unseen companions using a combination of the Renormalised Unit Weight Error, Image Parameter Determination statistics, Non-Single Star solutions, and photometric blending as provided by Gaia, identifying hierarchical Ultracool triple systems. Our catalogue includes 17 White Dwarf - Ultracool Dwarf systems, whose ages are determined using cooling models. We also use the Gaia FLAME results and the BANYAN $\Sigma$ procedures to age 40 and 34 systems respectively, and derive mass estimates from evolutionary models.

We introduce a new, non-parametric method to infer deprojected 3D mass profiles $M(r)$ of galaxy clusters from weak gravitational lensing observations. The method assumes spherical symmetry and a moderately small convergence, $\kappa \lesssim 1$. The assumption of spherical symmetry is an important restriction, which is, however, quite common in practice, for example in methods that fit lensing data to an NFW profile. Unlike other methods, our method relies on spherical symmetry only at radii larger than the radius $r$ at which the mass $M$ is inferred. That is, the method works even if there is a non-symmetric inner region. We provide an efficient implementation in Julia code that runs in a few milliseconds per galaxy cluster. We explicitly demonstrate the method by using data from KiDS DR4 to infer mass profiles for two example clusters, Abell 1835 and Abell 2744, finding results consistent with existing literature.

[Abridged] Over the years, several compact group catalogues have been built using different methods, but most of them are not deep enough to go beyond the very local universe with a high level of redshift completeness. We build statistically reliable samples of compact groups to study the influence of their inner extreme environment at intermediate redshifts. We adopted the GAMA redshift survey as a parent catalogue, complemented with galaxies from the SDSS, to identify compact groups using Hickson-like criteria. We explored the parameter space to perform several identifications: we reduced the maximum galaxy separation in the line-of-sight to 500 km/s and we implemented different magnitude ranges to define membership. For comparison, we used control samples extracted from a catalogue of loose groups to contrast properties with the compact groups. We build five considerably large compact group samples, ranging from more than 400 up to ~2400 systems, and maximum redshifts from 0.2 to 0.4. The overall properties of each sample are in agreement with previous findings. Compact groups tend to have a larger fraction of quenched galaxies than control loose groups, mainly for low stellar mass galaxies in compact groups with small crossing times. In addition, ~45% of compact groups are embedded in loose galaxy systems and display the highest compactness, lowest crossing times and brightest first-ranked galaxies compared to compact groups considered non-embedded or isolated. There is almost no evolution of compact group properties with redshift. Our results confirm previous findings that postulate compact groups as one of the suitable places to study the suppression of the star formation rate in galaxies primarily due to galaxy interactions. These new samples will be valuable to deepen the analysis of these peculiar galaxy systems in a redshift regime poorly explored so far.

This study presents a systematic approach to optimize the scheduling of exoplanet observations using the James Webb Space Telescope (JWST), focusing on targets discovered by the Transiting Exoplanet Survey Satellite (TESS). We developed a methodology to refine transit timing predictions for JWST's Cycle 3 Guest Observer program, specifically for the NIRISS/SOSS and NIRSpec/BOTS observation modes. Our process involved data collection from JWST proposal documents, cross-matching with TESS data, and applying the Transit Least Squares (TLS) algorithm for transit detection and characterization. We created comprehensive timelines for instrument usage and individual proposals, providing a visual representation of the observation schedule from July 2024 to September 2025. This approach demonstrates the potential for improved efficiency in JWST time allocation and sets a foundation for future refinements in astronomical observation planning.

The emergence of magnetic flux, its transition to complex configurations, and the pre-eruptive state of active regions are probed using photospheric magnetograms. We aim to pinpoint different evolutionary stages in active regions, explore their differences and produce parameters that could advance flare prediction, using color-coded maps of the photospheric magnetic field. The three components of the photospheric magnetic field vector are combined in color-coded magnetograms (COCOMAGs). From these, the areas occupied by different colors are extracted, creating appropriate time series (color curves). The COCOMAGs and color curves are used as proxies of the active region evolution and complexity. The COCOMAGs morphology reflects typical features of active regions, such as sunspots, plages, and sheared polarity inversion lines. The color curves represent the area occupied by photospheric magnetic field of different orientation and contain information relevant to the evolutionary stages of active regions. During emergence, most of the area is dominated by horizontal or highly inclined magnetic field, which gradually gives its place to more vertical magnetic field. In complex regions, large parts are covered by highly inclined magnetic fields, appearing as abrupt color changes. Active region decay is signified by a domination of vertical magnetic field, indicating a gradual relaxation of the magnetic field configuration. The color curves exhibit varying degree of correlation with active region complexity. The red and magenta color curves, which represent strong, purely horizontal magnetic field, are good indicators of future flaring. Color-coded magnetograms facilitate a comprehensive view of the evolution of active regions and their complexity. They offer a framework for the treatment of complex observations and can be used in pattern recognition, feature extraction and flare prediction.

Cosmological collider signals of primordial non-Gaussianity arise at tree level when an extra scalar has Hubble mass during inflation. We critically review the formalism finding that a large class of inflationary theories, based on Planck-scale physics, predict a scalar bi-spectrum around the gravitational floor level. This mild signal arises for example in $R^2$ gravity, in the regime where its gravitational scalar has Hubble-scale mass. Signals much above the gravitational floor arise in theories where scalars undergo multiple turns during inflation, thanks to sub-Planckian physics.