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Papers for Tuesday, Mar 23 2021

Papers with local authors

Harold A. Peña-Herazo, Francesco Massaro, Minfeng Gu, Alessandro Paggi, Marco Landoni, Raffaele D'Abrusco, Federica Ricci, Nicola Masetti, Vahram Chavushyan

16 pages, 2 figures, 4 tables

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Paper 33 — arXiv:2103.10861
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Paper 33 — arXiv:2103.10861

The extragalactic γ-rays sky observed by Fermi-Large Area Telescope (LAT) is dominated by blazars. In the fourth release of the Fermi-LAT Point Source Catalog (4FGL), are sources showing a multifrequency behavior similar to that of blazars but lacking an optical spectroscopic confirmation of their nature known as Blazar Candidate of Uncertain type (BCUs). We aim at confirming the blazar nature of BCUs and test if new optical spectroscopic observations can reveal spectral features, allowing us to get a redshift estimate for known BL Lac objects. We also aim to search for and discover changing-look blazars (i.e., blazars that show a different classification at different epochs). We carried out an extensive search for optical spectra available in the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) Data Release 5 (DR5) archive. We selected sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified or unassociated γ-ray sources, and the multifrequency catalog of blazars: the Roma-BZCAT. We selected a total of 392 spectra. We also compare some of the LAMOST spectra with those available in the literature. We classified 20 BCUs confirming their blazar-like nature. Then we obtained 15 new redshift estimates for known blazars. We discovered 26 transitional (i.e., changing-look) blazars that changed their classification. Finally, we were able to confirm the blazar-like nature of six BL Lac candidates. All remaining sources analyzed agree with previous classifications. BL Lac objects are certainly the most elusive type of blazars in the γ-ray extragalactic sky.

All other papers

P. Pietrukowicz, I. Soszynski, H. Netzel, M. Wrona, A. Udalski, M.K. Szymanski, R. Poleski, S. Kozlowski, J. Skowron, K. Ulaczyk, D.M. Skowron, P. Mroz, K. Rybicki, P. Iwanek, M. Gromadzki

23 pages, 19 figures, 2 tables

We present a collection of 10 111 genuine delta Sct-type pulsating variable stars detected in the OGLE-IV Galactic bulge fields. In this sample, 9835 variables are new discoveries. For most of the stars photometric data cover the whole decade 2010-2019. We illustrate a huge variety of light curve shapes of delta Sct variables. Long-term observations have allowed us to spot objects with evident period, amplitude, and mean brightness variations. Our analysis indicates that about 28% of the stars are single-mode pulsators. Fourteen delta Sct stars show additional eclipsing or ellipsoidal binary modulation. We report significant attenuation or even disappearance of the pulsation signal in six sources. The whole set of variables is a mix of objects representing various Milky Way's populations, with the majority of stars from the Galactic bulge. There are also representatives of the Sagittarius Dwarf Spheroidal Galaxy. Some of the newly detected variables could be SX Phe-type stars residing in globular clusters. The collection, including full V- and I-band time-series data, is available to the astronomical community from the OGLE On-line Data Archive.

L. Costantin, P. G. Pérez-González, J. Méndez-Abreu, M. Huertas-Company, P. Dimauro, B. Alcalde-Pampliega, F. Buitrago, D. Ceverino, E. Daddi, H. Domínguez-Sánchez, N. Espino-Briones, A. Hernán-Caballero, A. M. Koekemoer, G. Rodighiero

Accepted for publication in ApJ. 27 pages, 18 figures

Studying the resolved stellar populations of the different structural components which build massive galaxies directly unveils their assembly history. We aim at characterizing the stellar population properties of a representative sample of bulges and pure spheroids in massive galaxies (M>1010 M) in the GOODS-N field. We take advantage of the spectral and spatial information provided by SHARDS and HST data to perform the multi-image spectro-photometrical decoupling of the galaxy light. We derive the spectral energy distribution separately for bulges and disks in the redshift range 0.14<z1 with spectral resolution R50. Analyzing these SEDs, we find evidences of a bimodal distribution of bulge formation redshifts. We find that 33% of them present old mass-weighted ages, implying a median formation redshift zform=6.2+1.51.7. They are relics of the early Universe embedded in disk galaxies. A second wave, dominant in number, accounts for bulges formed at median redshift zform=1.3+0.60.6. The oldest (1st-wave) bulges are more compact than the youngest. Virtually all pure spheroids (i.e., those without any disk) are coetaneous with the 2nd-wave bulges, presenting a median redshift of formation zform=1.1+0.30.3. The two waves of bulge formation are not only distinguishable in terms of stellar ages, but also in star formation mode. All 1st-wave bulges formed fast at z6, with typical timescales around 200 Myr. A significant fraction of the 2nd-wave bulges assembled more slowly, with star formation timescales as long as 1 Gyr. The results of this work suggest that the centers of massive disk-like galaxies actually harbor the oldest spheroids formed in the Universe.

Hamidreza Mahani, Akram Hasani Zonoozi, Hosein Haghi, Tereza Jerabkova, Pavel Kroupa, Steffen Mieske

Accepted for publication in MNRAS. 16 pages, 11 figures, 1 table

Some ultra-compact dwarf galaxies (UCDs) have elevated observed dynamical V-band mass-to-light (M/LV) ratios with respect to what is expected from their stellar populations assuming a canonical initial mass function (IMF). Observations have also revealed the presence of a compact dark object in the centers of several UCDs, having a mass of a few to 15\% of the present-day stellar mass of the UCD. This central mass concentration has typically been interpreted as a super-massive black hole, but can in principle also be a sub-cluster of stellar remnants. We explore the following two formation scenarios of UCDs, i) monolithic collapse and ii) mergers of star clusters in cluster complexes as are observed in massively star-bursting regions. We explore the physical properties of the UCDs at different evolutionary stages assuming different initial stellar masses of the UCDs and the IMF being either universal or changing systematically with metallicity and density according to the Integrated Galactic IMF (IGIMF) theory. While the observed elevated M/LV ratios of the UCDs cannot be reproduced if the IMF is invariant and universal, the empirically derived IMF which varies systematically with density and metallicity shows agreement with the observations. Incorporating the UCD-mass-dependent retention fraction of dark remnants improves this agreement. In addition we apply the results of N-body simulations to young UCDs and show that the same initial conditions describing the observed M/LV ratios reproduce the observed relation between the half-mass radii and the present-day masses of the UCDs. The findings thus suggest that the majority of UCDs that have elevated M/LV ratios could have formed monolithically with significant remnant-mass components that are centrally concentrated, while those with small M/LV values may be merged star-cluster complexes.

Eugenio Carretta (INAF - Osservatorio di Astrofisica e Scienza dello Spazio di Bologna)

13 pages, 12 figures, 3 tables; accepted for publication on Astronomy and Astrophysics

NGC 4833 is a metal-poor Galactic globular cluster (GC) whose multiple stellar populations present an extreme chemical composition. The Na-O anti-correlation is quite extended, which is in agreement with the long tail on the blue horizontal branch, and the large star-to-star variations in the [Mg/Fe] ratio span more than 0.5 dex. Recently, significant excesses of Ca and Sc with respect to field stars of a similar metallicity were also found, signaling the production of species forged in H-burning at a very high temperature in the polluters of the first generation in this cluster. Since an enhancement of potassium is also expected under these conditions, we tested this scenario by analysing intermediate resolution spectra of 59 cluster stars including the K I resonance line at 7698.98 A. We found a wide spread of K abundances, anti-correlated to Mg and O abundances, as previously also observed in NGC 2808. The abundances of K are found to be correlated to those of Na, Ca, and Sc. Overall, this chemical pattern confirms that NGC 4833 is one of the relatively few GCs where the self-enrichment from first generation polluters occurred at such high temperatures that proton-capture reactions were able to proceed up to heavier species such as K and possibly Ca. The spread in K observed in GCs appears to be a function of a linear combination of cluster total luminosity and metallicity, as other chemical signatures of multiple stellar populations in GCs.

J. S. den Brok, D. Chatzigiannakis, F. Bigiel, J. Puschnig, A. T. Barnes, A. K. Leroy, M. J. Jiménez-Donaire, A. Usero, E. Schinnerer, E. Rosolowsky, C. M. Faesi, K. Grasha, A. Hughes, J. M. D. Kruijssen, D. Liu, L. Neumann, J. Pety, M. Querejeta, T. Saito, A. Schruba, S. Stuber

27 pages, 18 figures, 5 tables; accepted for publication in MNRAS

Both the CO(2-1) and CO(1-0) lines are used to trace the mass of molecular gas in galaxies. Translating the molecular gas mass estimates between studies using different lines requires a good understanding of the behaviour of the CO(2-1)-to-CO(1-0) ratio, R21. We compare new, high quality CO(1-0) data from the IRAM 30-m EMPIRE survey to the latest available CO(2-1) maps from HERACLES, PHANGS-ALMA, and a new IRAM 30-m M51 Large Program. This allows us to measure R21 across the full star-forming disc of nine nearby, massive, star-forming spiral galaxies at 27" (12 kpc) resolution. We find an average R21=0.64±0.09 when we take the luminosity-weighted mean of all individual galaxies. This result is consistent with the mean ratio for disc galaxies that we derive from single-pointing measurements in the literature, R21,lit = 0.59+0.180.09. The ratio shows weak radial variations compared to the point-to-point scatter in the data. In six out of nine targets the central enhancement in R21 with respect to the galaxy-wide mean is of order 1020%. We estimate an azimuthal scatter of 20% in R21 at fixed galactocentric radius but this measurement is limited by our comparatively coarse resolution of 1.5 kpc. We find mild correlations between R21 and CO brightness temperature, IR intensity, 70-to-160μm ratio, and IR-to-CO ratio. All correlations indicate that R21 increases with gas surface density, star formation rate surface density, and the interstellar radiation field.

Philip F. Hopkins (Caltech), Jonathan Squire (Otago), Iryna S. Butsky (Washington)

17 pages, 2 figures. Readers not interested in the detailed derivations can skip to Appendix A, which simply summarizes the key equations derived

We derive a consistent set of moments equations for CR-magnetohydrodynamics, assuming a gyrotropic distribution function (DF). Unlike previous efforts we derive a closure, akin to the M1 closure in radiation hydrodynamics (RHD), that is valid in both the nearly-isotropic-DF and/or strong-scattering regimes, and the arbitrarily-anisotropic DF or free-streaming regimes, as well as allowing for anisotropic scattering and transport/magnetic field structure. We present the appropriate two-moment closure and equations for various choices of evolved variables, including the CR phase space distribution function, number density, total energy, kinetic energy, and their fluxes or higher moments, and the appropriate coupling terms to the gas. We show that this naturally includes and generalizes a variety of terms including convection/fluid motion, anisotropic CR pressure, streaming, diffusion, gyro-resonant/streaming losses, and re-acceleration. We discuss how this extends previous treatments of CR transport including diffusion and moments methods and popular forms of the Fokker-Planck equation, as well as how this differs from the analogous M1-RHD equations. We also present two different methods for incorporating a reduced speed of light (RSOL) to reduce timestep limitations: in both we carefully address where the RSOL (versus true c) must appear for the correct behavior to be recovered in all interesting limits, and show how current implementations of CRs with a RSOL neglect some additional terms.

Philip F. Hopkins (Caltech), Sarah Wellons (Northwestern), Daniel Angles-Alcazar (UConn), Claude-Andre Faucher-Giguere (Northwestern), Michael Y. Grudic (Northwestern)

8 pages, 3 figures, submitted to MNRAS. Comments welcome

Previous studies of fueling black holes (BHs) in galactic nuclei have argued (on scales ~0.01-1000pc) accretion is dynamical with inflow rates ˙MηMgas/tdyn in terms of gas mass Mgas, dynamical time tdyn, and some η. But these models generally neglected expulsion of gas by stellar feedback, or considered extremely high densities where expulsion is inefficient. Studies of star formation, however, have shown on sub-kpc scales the expulsion efficiency fwind=Mejected/Mtotal scales with the gravitational acceleration as (1fwind)/fwindˉagrav/˙p/mΣeff/Σcrit where ˉagravGMtot(<r)/r2 and ˙p/m is the momentum injection rate from young stars. Adopting this as the simplest correction for stellar feedback, ηη(1fwind), we show this provides a more accurate description of simulations with stellar feedback at low densities. This has immediate consequences, predicting e.g. the slope and normalization of the Mσ and MMbulge relation, LAGNSFR relations, and explanations for outliers in compact Es. Most strikingly, because star formation simulations show expulsion is efficient (fwind1) below total-mass surface density Mtot/πr2<Σcrit3×109Mkpc2 (where Σcrit=˙p/m/(πG)), BH mass is predicted to specifically trace host galaxy properties above a critical surface brightness Σcrit (B-band μcritB19magarcsec2). This naturally explains why BH masses preferentially reflect bulge properties or central surface-densities (Σ1kpc), not 'total' galaxy properties.

K.Boutsia, A.Grazian, F. Fontanot, E. Giallongo, N. Menci, G. Calderone, S. Cristiani, V. D'Odorico, G. Cupani, F. Guarneri, A. Omizzolo

Accepted for publication in ApJ, 15 pages, 5 figures, 4 tables

Based on results by recent surveys, the number of bright quasars at redshifts z>3 is being constantly revised upwards. Current consensus is that at bright magnitudes (M145027) the number densities of such sources could have been underestimated by a factor of 30-40%. In the framework of the QUBRICS survey, we identified 58 bright QSOs at 3.6z4.2, with magnitudes ipsf18, in an area of 12400deg2. The uniqueness of our survey is underlined by the fact that it allows us, for the first time, to extend the sampled absolute magnitude range up to M1450=29.5. We derived a bright-end slope of β=4.025 and a space density at <M1450>=28.75 of 2.61×1010Mpc3 comoving, after taking into account the estimated incompleteness of our observations. Taking into account the results of fainter surveys, AGN brighter than M1450=23 could produce at least half of the ionizing emissivity at z4. Considering a mean escape fraction of 0.7 for the QSO and AGN population, combined with a mean free path of 41.3 proper Mpc at z=3.9, we derive a photoionization rate of Log(Γ[s1])=12.17+0.130.07, produced by AGN at M1450<18, i.e. ~100% of the measured ionizing background at z~4.

Giacomo Fragione, Sambaran Banerjee

5 pages, 5 figures. arXiv admin note: text overlap with arXiv:2006.06702

Several astrophysical scenarios have been proposed to explain the origin of the of the population of binary black hole (BBH) mergers detected in gravitational waves (GWs) by the LIGO-Virgo Collaboration. Among them, BBH mergers assembled dynamically in young massive and open clusters have been shown to produce merger rate densities consistent with LIGO/Virgo estimated rates. We use the results of a suite of direct, high-precision N-body evolutionary models of young massive and open clusters and build the population of BBH mergers, by accounting for both a cosmologically-motivated model for the formation of young massive and open clusters and the detection probability of LIGO/Virgo. We show that our models produce dynamically-paired BBH mergers that are well consistent with the observed masses, mass ratios, effective spin parameters, and final spins of the second Gravitational Wave Transient Catalog (GWTC-2).

S.K. Yerli, N. Aksaker, M. Bayazit, Z. Kurt, A. Aktay, M.A. Erdoğan

15 pages, 7 figures and 4 tables, Accepted for publication in Astrophysics and Space Science

Artificial Light pollution (AL) in Turkey and in Turkish observatories between 2012--2020 have been studied using the archival data of Visible Infrared Imaging Radiometer Suite (VIIRS) instrument. The astroGIS database has been used in processing the data (\href{https://www.astrogis.org}{astrogis.org}) \cite{2020MNRAS.493.1204A}. The total energy released to space from Turkey increased by 80\% in 2019 with respect to 2012. In the span of the dataset, a steady and continuous increase has been observed throughout all cities of the country. On the other hand, Dark Sky Park locations, East and Southeast Anatolian regions and mostly rural areas around the cities kept their AL level constant. Four demographic parameters have been studied and they were found to be correlated very well with AL: Population (R0.90); GDP (R0.87); Total Power Consumption (R0.66) and Outdoor Lightening (R0.67). Contrary to countries acting to prevent AL increases, Turkey seems to be at the beginning of an era where AL will arithmetically increase throughout the country and enormous amount of energy will continuously escape to space and therefore will be wasted. Therefore, a preventive legislation, especially for invaluable astronomical site locations such as TURAG, TUG, DAG and \c{C}AAM where each is counted as a truly dark site due to their SQM values, has to be enacted in Turkey, in very near future.

E. Pérez-Montero, R. Amorín, J. Sánchez Almeida, J. M. Vílchez, R. García-Benito, C. Kehrig

16 pages, 13 figures. Accepted for publication by MNRAS

Local star-forming galaxies show properties that are thought to differ from galaxies in the early Universe. Among them, the ionizing stellar populations and the gas geometry make the recipes designed to derive chemical abundances from nebular emission lines to differ from those calibrated in the Local Universe. A sample of 1969 Extreme Emission Line Galaxies (EELGs) at a redshift 0 < z < 0.49, selected from the Sloan Digital Sky Survey (SDSS) to be local analogues of high-redshift galaxies, was used to analyze their most prominent emission lines and to derive total oxygen abundances and nitrogen-to-oxygen ratios following the direct method in the ranges 7.7 < 12+log(O/H) < 8.6 and -1.8 < log(N/O) < -0.8. They allow us to obtain new empirically calibrated strong-line methods and to evaluate other recipes based on photoionization models that can be later used for a chemical analysis of actively star-forming galaxies in very early stages of galaxy evolution. Our new relations are in agreement with others found for smaller samples of objects at higher redshifts. When compared with other relations calibrated in the local Universe, they differ when the employed strong-line ratio depends on the hardness of the ionizing radiation, such as O32 or Ne3O2, but they do not when the main dependence is on the ionization parameter, such as S23. In the case of strong-line ratios depending on [NII] lines, the derivation of O/H becomes very uncertain due to the very high N/O values derived in this sample, above all in the low-metallicity regime. Finally, we adapt the bayesian-like code HII-Chi-mistry for the conditions found in this kind of galaxies and we prove that it can be used to derive within errors both O/H and N/O, in consistency with the direct method .

P. Pinilla, N. T. Kurtovic, M. Benisty, C. F. Manara, A. Natta, E. Sanchis, M. Tazzari, S. M. Stammler, L. Ricci, L. Testi

Accepted for publication in A&A

Observations of protoplanetary disks around very low mass stars and Brown Dwarfs remain challenging and little is known about the properties of these disks. The disk around CIDA 1 (0.1-0.2 M) is one of the very few known disks that hosts a large cavity (20 au radius in size) around a very low mass star. We present new ALMA observations at Band 7 (0.9 mm) and Band 4 (2.1 mm) of CIDA 1 with a resolution of 0.05. These new ALMA observations reveal a very bright and unresolved inner disk, a shallow spectral index of the dust emission (\sim2), and a complex morphology of a ring located at 20 au. We also present X-Shooter (VLT) observations that confirm a high value of the accretion rate of CIDA 1 of \dot{M}_{\rm acc} = 1.4 ~\times~10^{-8} M_\odot/yr. This high value of \dot{M}_{\rm acc}, the observed inner disk, and the large cavity of 20 au exclude models of photo-evaporation as potential origin of the observed cavity. When comparing these observations with models that combine planet-disk interaction, dust evolution, and radiative transfer, we exclude planets more massive than 0.5 M_{\rm{Jup}} as the potential origin of the large cavity because otherwise it is difficult to maintain a long-lived and bright inner disk. Even in this planet mass regime, an additional physical process may be needed to stop the particles to migrate inwards and maintain a bright inner disk at million-years timescales. Such mechanisms include a trap formed by a very close-in extra planet or the inner edge of a dead zone. The low spectral index of the disk around CIDA 1 is difficult to explain and challenges our current dust evolution models, in particular processes like fragmentation, growth, and diffusion of particles inside pressure bumps.

L. D. Anderson, Matteo Luisi, Bin Liu, Trey V. Wenger, Dana. S. Balser, T. M. Bania, L. M. Haffner, Dylan J. Linville, J. L. Mascoop

Accepted for publication by ApJS. Data may be downloaded here: this http URL

The Green Bank Telescope (GBT) Diffuse Ionized Gas Survey (GDIGS) traces ionized gas in the Galactic midplane by measuring 4-8GHz radio recombination line (RRL) emission. The nominal survey zone is 32.3^{\circ}> l >-5^{\circ}, |b|<0.5^{\circ}, but coverage extends above and below the plane in select fields, and additionally includes the areas around W47 (l \simeq 37.5^{\circ}) and W49 (l \simeq 43^{\circ}). GDIGS simultaneously observes 22 Hn\alpha (15 usable), 25 Hn\beta (18 usable), and 8 Hn\gamma RRLs (all usable), as well as multiple molecular line transitions (including of H_2^{13}CO, H_2CO, and CH_3OH). Here, we describe the GDIGS survey parameters and characterize the RRL data, focusing primarily on the Hn\alpha data. We produce sensitive data cubes by averaging the usable RRLs, after first smoothing to a common spectral resolution of 0.5km/s and a spatial resolution of 2.65' for Hn\alpha, 2.62' for Hn\beta, and 2.09' for Hn\gamma. The average spectral noise per spaxel in the \hna\ data cubes is \sim\!10mK (\sim\!5mJy/beam). This sensitivity allows GDIGS to detect RRLs from plasma throughout the inner Galaxy. The GDIGS Hn\alpha data are sensitive to emission measures EM \gtrsim 1100cm^{-6}pc, which corresponds to a mean electron density \langle n_e \rangle \gtrsim 30cm^{-3} for a 1pc path length or \langle n_e \rangle \gtrsim 1cm^{-3} for a 1kpc path length.

Jake A. McCoy

Ph.D. thesis in Astronomy & Astrophysics (373 total pages; 312 pages of chapters & appendices with 113 figures & 19 tables), The Pennsylvania State University, Advisor: Randall L. McEntaffer. Defended 12/18/2020

Measuring the diffuse, highly-ionized baryonic content in galactic halos and the intergalactic medium through soft x-ray absorption spectroscopy of active galactic nuclei is a main scientific objective of the Lynx X-ray Observatory mission concept that can only be accomplished with a next-generation grating spectrometer. Realizing such an instrument using reflection grating technology requires thousands of custom blazed gratings that each perform with high diffraction efficiency to be manufactured and aligned to intercept radiation coming to a focus in a Wolter-I telescope. The aim of this thesis is to implement two recently-developed techniques in nanofabrication for this task, with an emphasis on beamline diffraction-efficiency testing for characterizing spectral sensitivity. In particular, thermally-activated selective topography equilibration (TASTE) is pursued as a means for fabricating a master grating with the key advantage that it enables blazed groove facets to be patterned in polymeric electron-beam resist over a non-parallel groove layout not limited by substrate crystal structure. Additionally, substrate-conformal imprint lithography (SCIL) is studied as a method for mass manufacturing high-fidelity grating replicas in a silica sol-gel resist while avoiding many of the detriments associated with large-area patterning in other nanoimprint techniques. Diffraction-efficiency testing of sub-micron grating prototypes coated with gold shows that TASTE is capable of meeting Lynx requirements for spectral sensitivity, with room for improvement at small groove periods, and that while SCIL offers a promising avenue for Lynx grating production, imprints suffer a small blaze-angle reduction due to resist shrinkage. Accompanying this dissertation are appendices that outline physics fundamentals for x-ray spectral lines, x-ray optics, and diffraction gratings.

M. Barnard

PhD thesis supervised by C. Venter and A. K. Harding and accepted by the North-West University (Potchefstroom) South Africa in February 2021, 114 pages, 50 figures. Abstract abridged

The Fermi Large Area Telescope has revolutionised the \gamma-ray pulsar field, increasing the population to over 250 detected pulsars. The majority display spectra with exponential cutoffs in a narrow range around a few GeV. Models predicted cutoffs up to 100 GeV; it was therefore not expected that pulsars would be visible in the very-high-energy (>100 GeV) regime. Subsequent surprise discoveries by ground-based telescopes of pulsed emission from four pulsars above tens of GeV have marked the beginning of a new era, raising important questions about the electrodynamics and local environment of pulsar magnetospheres. Detection of the Vela pulsar by H.E.S.S. (20-120 GeV) and Fermi provides evidence for a curved spectrum. We posit this to result from curvature radiation via primary particles in the pulsar magnetosphere and current sheet. We present energy-dependent light curves using an extended slot gap and current sheet model and invoking a two-step accelerating E-field as motivated by kinetic simulations. I include a refined calculation of the curvature radius of particle trajectories, impacting the particle transport, predicted light curves, and spectra. The model reproduces the decrease of flux of the first light-curve peak relative to the second one, evolution of the bridge emission, near constant phase positions of peaks, and narrowing of pulses with increasing energy. We can fundamentally explain the first of these trends, since I found that the curvature radii of the particle trajectories in regions where the second \gamma-ray light curve peak originates are systematically larger than those associated with the first peak, implying a correspondingly larger cutoff for the second peak. An unknown azimuthal dependence of the E-field as well as uncertainty in the precise emission locale preclude a simplistic discrimination of emission mechanisms.

Annaliese Miller, Marina Kounkel, Chase Boggio, Kevin Covey, Adrian M. Price-Whelan

11 pages, 6 figures, accepted for publication to PASP

We calculated physical and orbital properties for 2M06464003+0109157, a 1.06 day eclipsing double lined spectroscopic binary. We modelled the system's ASAS-SN and TESS light curves, measuring the system's inclination and radii of each component. Extracting radial velocities for each component from 6 SDSS/APOGEE spectra, we measured the system's mass ratio and performed a full orbital fit. Our analysis indicates that 2M06464003+0109157 has components with nearly equal masses (m_1/m_2 =0.99 \pm 0.01; M_1{_,}{_2} = 0.57 \pm 0.015 M_\odot) and comparable radii (R_1 = 0.66 \pm 0.05 R_\odot, R_2 = 0.57 \pm 0.06 R_\odot). The solution required two star spots to incorporate the out of eclipse variation that is seen in the light curve. We report our full characterization of this system, and prospects for similar analyses using survey data to measure precise physical and orbital properties for EBs.

The calculation results of the evolution of the cluster of primordial black holes based on the Fokker-Planck equation with neglecting of the gas accretion onto black holes are presented. In addition, we consider how a massive black hole located within the cluster center affects on its evolution. Despite it creates an additional potential in the central region of the cluster and might capture surrounding black holes, a negligible growth rate of a central black hole was shown for 1 Gyr. Furthermore, we find a significant (approximately tenfold) expansion of the cluster.

Karl Fiteni, Joseph Caruana, João A. S. Amarante, Victor P. Debattista, Leandro Beraldo e Silva

The presence of stars on retrograde orbits in disc galaxies is usually attributed to accretion events, both via direct accretion, as well as through the heating of the disc stars. Recent studies have shown that retrograde orbits can also be produced via scattering by dense clumps, which are often present in the early stages of a galaxy's evolution. However, so far it has been unclear whether other internally-driven mechanisms, such as bars, are also capable of driving retrograde motion. Therefore, in this paper, we investigate the efficiencies with which bars and clumps produce retrograde orbits in disc galaxies. We do this by comparing the retrograde fractions and the spatial distributions of the retrograde populations in four N-body+smooth particle hydrodynamics (SPH) simulations of isolated disc galaxies spanning a range of evolutionary behaviours. We find that both bars and clumps are capable of generating significant retrograde populations of order \sim 10\% of all stars. We also find that while clump-driven retrograde stars may be found at large galactocentric radii, bar-driven retrograde stars remain in the vicinity of the bar, even if the bar dissolves. Consequently, we find that retrograde stars in the Solar Neighbourhood in the clumpy models are exclusively clump-driven, but this is a trace population, constituting 0.01-0.04\% of the total stellar population in this region. Finally, we find that neither bars (including dissolving ones) nor clumps in the models are able to produce rotationally supported counter-rotating discs.

Jeffrey M. Gerber, Eileen D. Friel, Enrico Vesperini

We present results from a study of 94 red giant stars in the globular cluster M53. We use low-resolution spectra to measure the strength of CN and CH features at \sim3800 and 4300 \r{A}, respectively. The strengths of these features are used to classify stars into a CN-enhanced and CN-normal population and to measure C and N abundances in all 94 stars. We find the red giant branch stars to be evenly split between the two populations identified, and observe the presence of CN-enhanced stars on the asymptotic giant branch. In addition, we identify 5 CH star candidates based on the strength of their CN and CH band features, and the presence of a P-branch in their CH band. We compare our identification of multiple populations to those based on the Na-O anti-correlation and pseudo-color indices in HST UV photometry, and find general agreement between all three methods. Our large sample size also allows us to study the radial distribution of each population, and we find that the CN-enhanced population is more centrally concentrated. We use our C and N measurements to compare the evolutionary changes in these elements as a function of magnitude between the two populations, and show that both populations experience similar evolutionary changes to the surface abundances of C and N. Finally, we calculate C+N+O abundances for each population and compare them to similar measurements made in M10; we find that in both clusters CN-enhanced stars have a slightly enhanced C+N+O (\Delta(C+N+O) \sim 0.2 dex).

Candice M. Stauffer, Raffaella Margutti, Justin D. Linford, Laura Chomiuk, Deanne L. Coppejans, Lindsay Demarchi, Wynn Jacobson-Galan, Joe Bright, Ryan J. Foley, Assaf Horesh, Adriano Baldeschi

Submitted to MNRAS, 9 pages and 7 figures

We present X-ray and radio observations of what may be the closest type Iax supernova (SN) to date, SN 2014dt (d=12.3-19.3 Mpc) and provide tight constraints on the radio and X-ray emission. We infer a specific radio luminosity of < (1.0-2.4)E25 erg/s/Hz at a frequency of 7.5 GHz and a X-ray luminosity < 1.4E38 erg/s (0.3-10 keV) at ~38-48 days post-explosion. We interpret these limits in the context of Inverse Compton (IC) emission and synchrotron emission from a population of electrons accelerated at the forward shock of the explosion in a power-law distribution N_e(\gamma_e)\propto \gamma_e^{-p} with p=3. Our analysis constrains the progenitor system mass-loss rate to be smaller than 5E-6 solar masses per year at distances where r <= 1E16 cm for an assumed wind velocity v=100 km/s, and a fraction of post-shock energy into magnetic fields and relativistic electrons of epsilon_B=0.01 and epsilon_e=0.1, respectively. This result rules out some of the parameter space of symbiotic giant star companions, and it is consistent with the low mass-loss rates expected from He-star companions. Our calculations also show that the improved sensitivity of the next generation Very Large Array (ngVLA) is needed to probe the very low-density media characteristic of He stars that are the leading model for binary stellar companions of white dwarfs giving origin to type Iax SNe.

K. K. Gupta, C. Ricci, A. Tortosa, Y. Ueda, T. Kawamuro, M. Koss, B. Trakhtenbrot, K. Oh, F. E. Bauer, F. Ricci, G. C. Privon, L. Zappacosta, D. Stern, D. Kakkad, E. Piconcelli, S. Veilleux, R. Mushotzky, T. Caglar, K. Ichikawa, A. Elagali, M. C. Powell, C. M. Urry, F. Harrison

Accepted for publication in MNRAS, 18 pages, 9 figures, 2 tables, 1 equation

Accreting supermassive black holes (SMBHs), also known as active galactic nuclei (AGN), are generally surrounded by large amounts of gas and dust. This surrounding material reprocesses the primary X-ray emission produced close to the SMBH and gives rise to several components in the broadband X-ray spectra of AGN, including a power-law possibly associated with Thomson-scattered radiation. In this work, we study the properties of this scattered component for a sample of 386 hard-X-ray-selected, nearby (z \sim 0.03) obscured AGN from the 70-month Swift/BAT catalog. We investigate how the fraction of Thomson-scattered radiation correlates with different physical properties of AGN, such as line-of-sight column density, X-ray luminosity, black hole mass, and Eddington ratio. We find a significant negative correlation between the scattering fraction and the column density. Based on a large number of spectral simulations, we exclude the possibility that this anti-correlation is due to degeneracies between the parameters. The negative correlation also persists when considering different ranges of luminosity, black hole mass, and Eddington ratio. We discuss how this correlation might be either due to the angle dependence of the Thomson cross-section or to more obscured sources having a higher covering factor of the torus. We also find a positive correlation between the scattering fraction and the ratio of [OIII] \lambda5007 to X-ray luminosity. This result is consistent with previous studies and suggests that the Thomson-scattered component is associated with the narrow-line region.

Anisotropic outgassing from comets exerts a torque sufficient to rapidly change the angular momentum of the nucleus, potentially leading to rotational instability. Here, we use empirical measures of spin changes in a sample of comets to characterize the torques and to compare them with expectations from a simple model. Both the data and the model show that the characteristic spin-up timescale, \tau_s, is a strong function of nucleus radius, r_n. Empirically, we find that the timescale for comets (most with perihelion 1 to 2 AU and eccentricity \sim0.5) varies as \tau_s \sim 100 r_n^{2}, where r_n is expressed in kilometers and \tau_s is in years. The fraction of the nucleus surface that is active varies as f_A \sim 0.1 r_n^{-2}. We find that the median value of the dimensionless moment arm of the torque is k_T = 0.007 (i.e. \sim0.7\% of the escaping momentum torques the nucleus), with weak (<3\sigma) evidence for a size dependence k_T \sim 10^{-3} r_n^2. Sub-kilometer nuclei have spin-up timescales comparable to their orbital periods, confirming that outgassing torques are quickly capable of driving small nuclei towards rotational disruption. Torque-induced rotational instability likely accounts for the paucity of sub-kilometer short-period cometary nuclei, and for the pre-perihelion destruction of sungrazing comets. Torques from sustained outgassing on small active asteroids can rival YORP torques, even for very small (\lesssim1 g s^{-1}) mass loss rates. Finally, we highlight the important role played by observational biases in the measured distributions of \tau_s, f_A and k_T.

We study the effects of passages of compact objects such as stars, star clusters, and black holes through molecular clouds, and propose that the gravitational interaction between the compact object and the ambient gas can lead to the formation of thin and collimated features made of dense gas, which we call "molecular contrails". Supercritical contrails can collapse further leading to triggered star formation. The width of a molecular contrail is determined by the mass and velocity of the compact object and the velocity dispersion of the ambient molecular medium. Under typical conditions in the Milky Way, passages of stellar-mass objects lead to the formation of width d\gtrsim 0.01\;\rm {parsec} contrails, and passages of star clusters lead to the formation of d\gtrsim 1\;\rm {parsec} contrails. We present a few molecular contrail candidates from both categories identified from ALMA 1.3mm continuum observations of star-forming regions and the ^{13}CO(1-0) map from the Galactic Ring Survey respectively. The contrails represent an overlooked channel where stars and gas in the Galactic disk interact to for structures. They also present a potential way of detecting dark compact objects in the Milky Way.

Sedighe Sajadian, Sohrab Rahvar, Fatemeh Kazemian

10 pages, 3 Tables, 9 Figures; Submitted to ApJ; Comments are welcome

Thanks to the Gaia archived data, we find a correlation between the stellar types (with different average mass) and the scale parameters of the Maxwell-Boltzmann (MB) distribution of their dispersion velocities, by averaging over their age range. As expected, the late-type stars and brown dwarfs have wider velocity (MB) distributions with larger scale parameters than early-type ones. According to this correlation, we conclude that the dispersion velocities of brown dwarfs should have an MB profile with the scale parameter a\simeq 111.9~\rm{km/s}. This mass-velocity dispersion relation confirms the known age-velocity relation and additionally reveals the dependence of the stellar dispersion velocity to mass in the given average age. By considering this correlation as well as a brown dwarf population, we simulate microlensing events detectable by MOA-II toward the Galactic bulge fields gb5 and gb9 which were intensively observed during that observation. From this simulation, the average values of the events' duration are 18.72 and 18.68~days, which are close to the observational amounts, i.e., 17.4 and 22.2~days. In the simulation, we do not consider any extra free-floating exoplanet population. A population of speedy brown dwarfs with the corrected dispersion velocity profile generates the observational results of MOA-II and there is no need to include free-floating exoplanets.

Pulsars are rapidly spinning highly magnetised neutron stars. Their spin period is observed to decrease with time. An early analytical model for this process was the vacuum retarded dipole (VRD) by Deutsch in his 1955 paper "The Electromagnetic Field of an Idealized Star in Rigid Rotation in Vacuo" (D55). This model assumes an idealised star and it finds that the energy is radiated away by the electromagnetic fields. This model has been superseded by more realistic numerical simulations that account for the non-vacuum like surroundings of the neutron star. However, the VRD still provides a reasonable approximation and is a useful limiting case that can provide some qualitative understanding. We provide a detailed derivation of the spin down and related field equations of the VRD. We also correct a typo found in the general field equations in D55.

Mikhail Denissenya, Bruce Grossan, Eric V. Linder

10 pages, 9 figures

Astrophysical burst events such as fast radio bursts and some gamma ray events can repeat -- periodically, without a clear pattern, clustered in time, or with activity occurring in periodic windows. We focus here on periodic windowed behavior, demonstrating methods for identifying it and characterizing it. Predictability of activity offers the opportunity to observe counterpart emission in other wavelengths and learn about the burst astrophysics. An important aspect is accounting for the "curious incident of the dog in the night time" -- lack of bursts carries information. We analyze six years of data from the soft gamma repeater SGR1935+2154 as a worked example, deriving a period of 231 days and 55\% duty cycle.

We identify 225 filaments from an H_2 column density map constructed using simultaneous ^{12}CO, ^{13}CO, and C^{18}O (J=1-0) observations carried out as a part of the MWISP project. We select 46 long filaments with lengths above 1.2 pc to analyze the filament column density profiles. We divide the selected filaments into 397 segments and calculate the column density profiles for each segment. The symmetries of the profiles are investigated. The proportion of intrinsically asymmetrical segments is 65.3\%, and that of intrinsically symmetrical ones is 21.4\%. The typical full width at half maximum (FWHM) of the intrinsically symmetrical filament segments is \sim 0.67 pc with the Plummer-like fitting, and \sim 0.50 pc with the Gaussian fitting, respectively. The median FWHM widths derived from the second-moment method for intrinsically symmetrical and asymmetrical profiles are \sim 0.44 and 0.46 pc, respectively. Close association exists between the filamentary structures and the YSOs in the region.

Toshiya Namikawa, Atsushi Naruko, Ryo Saito, Atsushi Taruya, Daisuke Yamauchi

47 pages, 12 figures

We develop a systematic and unified approach to estimate all possible secondary (i.e. non-primordial) nonlinear effects to the cosmic microwave background (CMB) polarization, named curve-of-sight integration approach. In this approach, the Boltzmann equation for polarized photons is rewritten in a line-of-sight integral along an exact geodesic in the perturbed universe, rather than a geodesic in the background universe used in the linear-order CMB calculation. This approach resolves the difficulty to solve the Boltzmann hierarchy with the nonlinear gravitational effects in the photon free-streaming regime and thus unifies the standard remapping approach for CMB lensing into the direct approach solving the Boltzmann equation for the nonlinear collisional effects. In this paper, we derive formulae that: (i) include all the nonlinear effects; (ii) can treat extended sources such as the contributions after the reionization. It offers a solid framework to discuss possible systematics in the standard estimation of CMB lensing by the remapping approach. As an explicit demonstration, we estimate the secondary B-mode power spectrum induced by all foreground gravitational effects: lensing, redshift, time-delay, emission-angle, and polarization-rotation effects. We define these effects properly so that they do not have any overlap, also without overlooking any effect. Then, we show that these effects only give corrections of the order of 0.001-0.01% to the standard lensing-induced B-mode power spectrum in the concordance \Lambda cold dark matter model. Our result confirms the reliability of using the remapping approach in upcoming CMB experiments aiming to detect the primordial gravitational waves with the tensor-to-scalar ratio of r \sim 10^{-3}.

D. N. Kosenko, S. A. Balashev, P. Noterdaeme, J.-K. Krogager, R. Srianand, C. Ledoux

40 pages, 51 figures, submitted to MNRAS

We present a systematic study of deuterated molecular hydrogen (HD) at high redshift, detected in absorption in the spectra of quasars. We present four new identifications of HD lines associated with known \rm H_2-bearing Damped Lyman-\alpha systems. In addition, we measure upper limits on the \rm HD column density in twelve recently identified \rm H_2-bearing DLAs. We find that the new \rm HD detections have similar N({\rm HD})/N(\rm H_2) ratios as previously found, further strengthening a marked difference with measurements through the Galaxy. This is likely due to differences in physical conditions and metallicity between the local and the high-redshift interstellar media. Using the measured N({\rm HD})/N({\rm H_2}) ratios together with priors on the UV flux (\chi) and number densities (n), obtained from analysis of \rm H_2 and associated CI lines, we are able to constrain the cosmic-ray ionization rate (CRIR, \zeta) for the new \rm HD detections and for eight known HD-bearing systems where priors on n and \chi are available. We find significant dispersion in \zeta, from a few \times 10^{-18} s^{-1} to a few \times 10^{-15} s^{-1}. We also find that \zeta strongly correlates with \chi -- showing almost quadratic dependence, slightly correlates with Z, and does not correlate with n, which probably reflects a physical connection between cosmic rays and star-forming regions.

Hong-Fei Liu, Chuan He, Jin Wang, Peng Jiang, Sheng-Wang Wang, Yang Wu, Hang Zhang, Jin-You Song, Xiang-Wei Shi, Ming-Lei Guo

There are 20 pages and 24 figures

This paper presents an ultra-low noise L-band radio astronomical cryogenic receiver for FAST telescope. The development of key low noise microwave parts of Coupling-LNA and conical quad-ridge OMT and reasonable system integration achieve outstanding performance of receiver.It covers the frequency range of 1.2 GHz to 1.8 GHz. Novel cryogenic Coupling-LNAs with low noise, large return loss, high dynamic range and the function of coupling calibration signals are developed for the proposed receiver.Amplification and coupling function circuits are integrated as a single Coupling-LNA with full noise temperature of 4 K at the physical temperature of 15 K. And its return loss is more than 18 dB, and output 1 dB compression power is +5 dBm. A cryogenic dewar is fabricated to provide 55 K and 15 K cryogenic environment for OMT and Coupling-LNAs, respectively. The receiver's system noise temperature is below 9 K referred to feed aperture plane. Benefiting from optimal design and precise mechanical treatment, good scattering performance of OMT and equalized radiation patterns of horn are achieved with an antenna efficiency above 75%.

S. Alan Stern, Brian Keeney, Kelsi Singer, Oliver White, Jason D. Hofgartner, Will Grundy, The New Horizons Team

19 Pages 08 Figures 01 Tables

One of the most striking and curious features of the small Kuiper Belt Object (KB), Arrokoth, explored by New Horizons, is the bright, annular neck it exhibits at the junction between its two lobes. Here we summarize past reported findings regarding the properties of this feature and report new findings regarding its dimensions, reflectivity and color, shape profile, and its lack of identifiable craters. We conclude by enumerating possible origin scenarios for this unusual feature. New results include a new measurement of the observed neck area of 8+/-1.5 km2, a total neck surface area of 32 km2, a 12.5:1 ratio of neck circumference to height, a normal reflectance histogram of the observed neck, and the fact that no significant (i.e., >2 sigma) color units were identified, meaning the neck's color is generally spatially uniform at the 1.5 km/pixel scale of the best color images. Although several origin hypotheses for the bright material in the neck are briefly discussed, none can be conclusively demonstrated to be the actual origin mechanism at this time; some future tests are identified.

Andreas Schrimpf, Frank Verbunt

18 pages, 6 figures, in "Applied and computational historical astronomy", ed. G. Wolfschmidt, Nuncius Hamburgensis, Beitr\"age zur Geschichte der Naturwissenschaften, vol 51

Near the end of the 16th century Wilhelm IV, Landgraf von Hessen-Kassel, set up an observatory with the main goal to increase the accuracy of stellar positions primarily for use in astrology and for calendar purposes. A new star catalogue was compiled from measurements of altitudes and angles between stars and a print ready version was prepared listing measurements as well as equatorial and ecliptic coordinates of stellar positions. Unfortunately, this catalogue appeared in print not before 1666, long after the dissemination of Brahe's catalogue. With the data given in the manuscript we are able to analyze the accuracy of measurements and computations. The measurements and the computations are very accurate, thanks to the instrument maker and mathematician Jost B\"urgi. The star catalogue is more accurate by a factor two than the later catalogue of Tycho Brahe.

Alexey A. Kuznetsov, Dmitrii Y. Kolotkov

Accepted to ApJ; 20 pages, 11 figures, 4 tables

Solar and stellar flares are powerful events which produce intense radiation across the electromagnetic spectrum. Multiwavelength observations are highly important for understanding the nature of flares, because different flare-related processes reveal themselves in different spectral ranges. To study the correlation between thermal and nonthermal processes in stellar flares, we have searched the databases of Kepler (optical observations) and XMM-Newton (soft X-rays) for the flares observed simultaneously with both instruments; nine distinctive flares (with energies exceeding 10^{33} erg) on three stars (of K-M spectral classes) have been found. We have analyzed and compared the flare parameters in the optical and X-ray spectral ranges; we have also compared the obtained results with similar observations of solar flares. Most of the studied stellar flares released more energy in the optical range than in X-rays. In one flare, X-ray emission strongly dominated, which could be caused either by soft spectrum of energetic electrons or by a near-limb position of this flare. The X-ray flares were typically delayed with respect to and shorter than their optical counterparts, which is partially consistent with the Neupert effect. Using the scaling laws based on the magnetic reconnection theory, we have estimated the characteristic magnetic field strengths in the stellar active regions and the sizes of these active regions as about 25-70 G and 250\,000-500\,000 km, respectively. The observed stellar superflares appear to be scaled-up versions of solar flares, with a similar underlying mechanism and nearly the same characteristic magnetic field values, but with much larger active region sizes.

Simone Dall'Osso, Luigi Stella

31 pages, 3 figures, Preprint of a chapter of the book 'Millisecond Pulsars', of the Astrophysics and Space Science Library (ASSL) series edited by Sudip Bhattacharyya, Alessandro Papitto and Dipankar Bhattacharya

Two classes of X-ray/\gamma-ray sources, the Soft Gamma Repeaters and the Anomalous X-ray Pulsars have been identified with isolated, slowly spinning magnetars, neutron stars whose emission draws energy from their extremely strong magnetic field (\sim 10^{15}-10^{16} G). Magnetars are believed to form with millisecond spin period and to represent an important fraction of the whole population of young neutron stars. Newborn magnetars can convert very quickly their rotational energy into electromagnetic and/or gravitational waves, by virtue of their strong magnetic fields and fast spins. This chapter provides a brief summary of astrophysical problems and scenarios in which millisecond magnetars are believed to play a key role: these include Gamma Ray Bursts, Supernovae, Gravitational Wave events and Fast Radio Bursts.

Claudio Llinares

37 pages. Published as part of the IJMPD special issue "Modified Gravity: Progresses and Outlook of Theories, Numerical Techniques and Observational Tests" edited by Baojiu Li and Kazuya Koyama. Submitted to arXiv after end of embargo period

The standard paradigm of cosmology assumes General Relativity (GR) is a valid theory for gravity at scales in which it has not been properly tested. Developing novel tests of GR and its alternatives is crucial if we want to give strength to the model or find departures from GR in the data. Since alternatives to GR are usually defined through nonlinear equations, designing new tests for these theories implies a jump in complexity and thus, a need for refining the simulation techniques. We summarize existing techniques for dealing with modified gravity (MG) in the context of cosmological simulations. N-body codes for MG are usually based on standard gravity codes. We describe the required extensions, classifying the models not according to their original motivation, but by the numerical challenges that must be faced by numericists. MG models usually give rise to elliptic equations, for which multigrid techniques are well suited. Thus, we devote a large fraction of this review to describing this particular technique. Contrary to other reviews on multigrid methods, we focus on the specific techniques that are required to solve MG equations and describe useful tricks. Finally, we describe extensions for going beyond the static approximation and dealing with baryons.

Louise Breuval, Pierre Kervella, Piotr Wielgórski, Wolfgang Gieren, Dariusz Graczyk, Boris Trahin, Grzegorz Pietrzyński, Frédéric Arenou, Behnam Javanmardi, Bartlomiej Zgirski

26 pages, 9 figures. Accepted for publication in the Astrophysical Journal

The Cepheid Period-Luminosity (PL) relation is the key tool for measuring astronomical distances and for establishing the extragalactic distance scale. In particular, the local value of the Hubble constant (H_0) strongly depends on Cepheid distance measurements. The recent Gaia Data Releases and other parallax measurements from the Hubble Space Telescope (HST) already enabled to improve the accuracy of the slope (\alpha) and intercept (\beta) of the PL relation. However, the dependence of this law on metallicity is still largely debated. In this paper, we combine three samples of Cepheids in the Milky Way (MW), the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC) in order to derive the metallicity term (hereafter \gamma) of the PL relation. The recent publication of extremely precise LMC and SMC distances based on late-type detached eclipsing binary systems (DEBs) provides a solid anchor for the Magellanic Clouds. In the MW, we adopt Cepheid parallaxes from the early third Gaia Data Release. We derive the metallicity effect in V, I, J, H, K_S, W_{VI} and W_{JK}. In the K_S band we report a metallicity effect of -0.221 \pm 0.051 mag/dex, the negative sign meaning that more metal-rich Cepheids are intrinsically brighter than their more metal-poor counterparts of the same pulsation period.

Edward W. Kolb, Andrew J. Long, Evan McDonough

6 pages, 2 figures

We extend the swampland from effective field theories (EFTs) inconsistent with quantum gravity to EFTs inconsistent with quantum supergravity. This enlarges the swampland to include EFTs that become inconsistent when the gravitino is quantized. We propose the Gravitino Swampland Conjecture: the gravitino sound speed must be non-vanishing in all EFTs that are low energy limits of quantum supergravity. This seemingly simple statement has important consequences for both theories and observations. The conjecture is consistent with and supported by the KKLT and LVS scenarios for moduli stabilization in string theory.

Two exact lens equations have been recently shown to be equivalent to each other, being consistent with the gravitational deflection angle of light from a source to an observer, both of which can be within a finite distance from a lens object [Phys. Rev. D 102, 064060 (2020)]. We examine methods for iterative solutions of the gravitational lens equations in the strong deflection limit. It has been so far unclear whether a convergent series expansion can be provided by a known method for obtaining approximate solutions in the strong deflection limit in terms of a small offset angle in earlier publications. By using the ratio of the lens mass to the lens distance, we discuss a slightly different method for iterative solutions and behavior of the convergence. Finite distance effects begin at the third order in the iterative method. The iterative solutions in the strong deflection limit are applied to Sgr A^{*} and M87. These results suggest that only the linear order solution can be relevant with current observations, while the finite distance effects at the third order may be negligible in the Schwarzschild lens model for these astronomical objects.

It has been two decades since the cosmic-ray-driven electron-induced reaction (CRE) mechanism for the formation of the ozone hole was proposed. The derived CRE equation with stratospheric equivalent chlorine level and CR intensity as only two variables has well reproduced all observed data of stratospheric O3 and temperatures over the past 40 years. The CRE predictions of 11-year cyclic variations of the Antarctic O3 hole and associated stratospheric cooling are also well confirmed. Measured altitude profiles of O3 and temperatures in the Antarctic O3 hole provide convincing fingerprints of the CRE mechanism. A quantitative estimate indicates that the CRE-produced Cl atoms could completely deplete or even over-kill O3 in the CR-peak polar stratospheric region, consistent with observed data. These results have provided strong evidence of the CRE mechanism.

Newly discovered descriptions about the great aurora observed in March 1582 are presented in this work. These records were made by Portuguese observers from Lisbon. Both records described the aurora like a great fire in the northern part of the sky. It was observed during three consecutive nights, according to one of the sources. Thus, we present a discussion of these auroral records in order to complement other works that studied the aurora sighted in March 1582.