adsabs/SciX_UAT_keywords huggingface dataset:
Hubble Space Telescope Images of SN 1987A: Evolution of the Ejecta and the Equatorial Ring from 2009 to 2022

Supernova (SN) 1987A offers a unique opportunity to study how a spatially resolved SN evolves into a young SN remnant. We present and analyze Hubble Space Telescope (HST) imaging observations of SN 1987A obtained in 2022 and compare them with HST observations from 2009 to 2021. These observations allow us to follow the evolution of the equatorial ring (ER), the rapidly expanding ejecta, and emission from the center over a wide range in wavelength from 2000 to 11,000 Å. The ER has continued to fade since it reached its maximum ∼8200 days after the explosion. In contrast, the ejecta brightened until day ∼11,000 before their emission levelled off; the west side brightened more than the east side, which we attribute to the stronger X-ray emission by the ER on that side. The asymmetric ejecta expand homologously in all filters, which are dominated by various emission lines from hydrogen, calcium, and iron. From this overall similarity, we infer the ejecta are chemically well mixed on large scales. The exception is the diffuse morphology observed in the UV filters dominated by emission from the Mg II resonance lines that get scattered before escaping. The 2022 observations do not show any sign of the compact object that was inferred from highly ionized emission near the remnant's center observed with JWST. We determine an upper limit on the flux from a compact central source in the [O III] HST image. The nondetection of this line indicates that the S and Ar lines observed with JWST originate from the O free inner Si–S–Ar-rich zone and/or that the observed [O III] flux is strongly affected by dust scattering.

Keywords: core-collapse supernovae; supernova remnants; circumstellar matter; shocks; ejecta
ALMA Observations of Two Massive and Dense MALT90 Clumps

We report Atacama Large Millimeter Array observations of 3 mm dust continuum emission and line emission, in HCO+, H13CO+, N2H+, and CH3CN, toward two massive and dense clumps (MDCs) in early but distinct evolutionary phases (prestellar and protostellar), made with the goal of investigating their fragmentation characteristics at angular scales of ∼1″. Toward the prestellar clump we detected 10 compact structures (cores), with radii from 1200-4500 au and masses from 1.6-20 M⊙. Half of these cores exhibit inverse P Cygni profiles in HCO+ and are subvirialized indicating that they are undergoing collapse. Toward the protostellar clump we detected a massive (119 M⊙) central core, with a strong mass infall rate, and nine less massive cores, with masses from 1.7-27 M⊙ and radii from 1000-4300 au. CH3CN rotational temperatures were derived for eight cores in the protostellar clump and three cores in the prestellar clump. Cores within the prestellar clump have smaller line widths and lower temperatures than cores within the protostellar clump. The fraction of total mass in cores to clump mass is smaller in the prestellar clump (∼6%) than in the protostellar clump (∼23%). We conclude that we are witnessing the evolution of the dense gas in globally collapsing MDCs; the prestellar clump illustrating the initial stage of fragmentation, harboring cores that are individually collapsing, and the protostellar clump reflecting a later stage in which a considerable fraction of the gas has been gravitationally focused into the central region.

Keywords: interstellar medium; star formation; massive stars; collapsing clouds
Beyond the Detector Horizon: Forecasting Gravitational-Wave Strong Lensing

When gravitational waves pass near massive astrophysical objects, they can be gravitationally lensed. The lensing can split them into multiple wave fronts, magnify them, or imprint beating patterns on the waves. Here we focus on the multiple images produced by strong lensing. In particular, we investigate strong lensing forecasts, the rate of lensing, and the role of lensing statistics in strong lensing searches. Overall, we find a reasonable rate of lensed detections for double, triple, and quadruple images at the LIGO-Virgo-KAGRA design sensitivity. We also report the rates for A+ and LIGO Voyager and briefly comment on potential improvements due to the inclusion of subthreshold triggers. We find that most galaxy-lensed events originate from redshifts z ~ 1-4 and report the expected distribution of lensing parameters for the observed events. Besides forecasts, we investigate the role of lensing forecasts in strong lensing searches, which explore repeated event pairs. One problem associated with the searches is the rising number of event pairs, which leads to a rapidly increasing false alarm probability. We show how knowledge of the expected galaxy-lensing time delays in our searches allow us to tackle this problem. Once the time delays are included, the false alarm probability increases linearly (similar to nonlensed searches) instead of quadratically with time, significantly improving the search. For galaxy cluster lenses, the improvement is less significant. The main uncertainty associated with these forecasts are the merger-rate density estimates at high redshift, which may be better resolved in the future.

Keywords: gravitational waves; gravitational lensing; general relativity
Verification of Hypervelocity Bulge Red Clump Stars

We verify candidate hypervelocity red clump stars located in the Galactic bulge that were selected based on the VVV and the Gaia DR2 data by Luna et al. To do so, we analyze data from the OGLE-IV survey: difference images and astrometric time series. We have data for 30 stars out of 34 hypervelocity candidates. We confirmed the high proper motion of only one of these stars and find out that it is a nearby one, hence, not a hypervelocity star. To sum up, we do not confirm the candidate stars as hypervelocity ones. Hence, we disprove the production rate of hypervelocity red clump stars by the central supermassive black hole provided by Luna et al.

Keywords: hypervelocity stars; proper motions; galaxy dynamics
The Strength and Structure of the Magnetic Field in the Galactic Outflow of Messier 82

Galactic outflows driven by starbursts can modify the galactic magnetic fields and drive them away from the galactic planes. Here, we quantify how these fields may magnetize the intergalactic medium (IGM). We estimate the strength and structure of the fields in the starburst galaxy M82 using thermal polarized emission observations from the Stratospheric Observatory for Infrared Astronomy/High-resolution Airborne Wideband Camera-plus and a potential field extrapolation commonly used in solar physics. We modified the Davis-Chandrasekhar-Fermi method to account for the large-scale flow and the turbulent field. Results show that the observed magnetic fields arise from the combination of a large-scale ordered potential field associated with the outflow and a small-scale turbulent field associated with bow-shock-like features. Within the central 900 pc radius, the large-scale field accounts for 53 ± 4% of the observed turbulent magnetic energy with a median field strength of 305 ± 15 μG, while small-scale turbulent magnetic fields account for the remaining 40 ± 5% with a median field strength of 222 ± 19 μG. We estimate that the turbulent kinetic and turbulent magnetic energies are in close equipartition up to ~2 kpc (measured), while the turbulent kinetic energy dominates at ~7 kpc (extrapolated). We conclude that the fields are frozen into the ionized outflowing medium and driven away kinetically. The magnetic field lines in the galactic wind of M82 are open, providing a direct channel between the starburst core and the IGM. Our novel approach offers the tools needed to quantify the effects of outflows on galactic magnetic fields as well as their influence on the IGM and evolution of energetic particles.

Keywords: extragalactic magnetic fields; starburst galaxies; polarimetry; solar physics
The Behavior of HgMn Stars in the Far-UV-Paper 10: HD 174933A and HD 35548A

The analysis of low and high resolution spectra of the chemically peculiar stars HR 7113 and HR 1800 recorded by the SWP camera on board the International Ultraviolet Explorer reveals no variations of the far-ultraviolet flux for spectra separated by 4 months and 3 days for HR 7113 and 1 day apart for HR 1800 respectively. The TESS lightcurve of HR 7113 suggests a period close to 6.46 days which is close to the orbital period previously determined. For HR 1800, a clear period is not seen, time intervals between successive maxima range from 5.53 to 5.82 days.

Keywords: chemically peculiar stars
The Mysterious Affair of the H2 in AU Mic

Molecular hydrogen is the most abundant molecule in the galaxy and plays important roles in planets, their circumstellar environments, and many of their host stars. We have confirmed the presence of molecular hydrogen in the AU Mic system using high-resolution FUV spectra from HST-STIS during both quiescence and a flare. AU Mic is a ~23 Myr M dwarf that hosts a debris disk and at least two planets. We estimate the temperature of the gas at 1000-2000 K, consistent with previous detections. Based on the radial velocities and widths of the H2 line profiles and the response of the H2 lines to a stellar flare, the H2 line emission is likely produced in the star, rather than in the disk or the planet. However, the temperature of this gas is significantly below the temperature of the photosphere (~3650 K) and the predicted temperature of its starspots (≳2650 K). We discuss the possibility of colder starspots or a cold layer in the photosphere of a pre-main-sequence M dwarf.

Keywords: exoplanet formation; debris disks; low mass stars; starspots; circumstellar gas; high resolution spectroscopy; exoplanets; pre-main sequence stars; stellar atmospheres
Multiwavelength Properties of the Newly Discovered Dwarf Nova ASASSN-21kt

We report on archival XMM-Newton and post-outburst Swift observations of the newly discovered dwarf nova ASASSN-21kt. Its pre-outburst X-ray emission is consistent with that of a collisionally ionized, thermal plasma with ${kT}={8.1}_{-2.5}^{+10.2}$ keV and LX 0.2-12 keV = 7 × 1032 erg s-1, with no clear modulation. Multiple optical outbursts revealed by Gaia and time evolution of the last one followed by the All-Sky Automated Survey for Supernovae, and X-ray properties presented here support the dwarf nova classification of ASASSN-21kt.

Keywords: cataclysmic variable stars; dwarf novae
Recovery of Returning Halley-type Comet 12P/Pons-Brooks with the Lowell Discovery Telescope

We report the recovery of returning Halley-type comet 12P/Pons-Brooks using the 4.3 m Lowell Discovery Telescope, at a heliocentric distance of 11.89 au. Comparative analysis with a dust model suggests that the comet may have been active since ∼30 au from the Sun. We derive a nuclear radius of 17 ± 6 km from the nucleus photometry, though this number is likely an overestimate due to the contamination from dust and gas. Continuing monitoring is encouraged in anticipation of the comet's forthcoming perihelion in 2024 April.

Keywords: comets; short period comets
Screening Earth Analog Exoplanets on the Basis of a Predicted Nitrogen over Phosphorus Ratio

Since the first discovery in 1995, data for over 5300 exoplanets have been documented in the NASA archive, revealing a vast diversity. Identifying life-enabling analogs of the Earth among this rapidly expanding catalog is of major interest. The stability of liquid water at the planetary surface defining the concept of the habitable zone (HZ) around the host star, may be necessary for the emergence of life as we know it but not sufficient. The practically constant atomic ratio nitrogen:phosphorous = 16:1 in oceanic surface layers of our planet Earth was discovered by Redfield in 1934. It corresponds to phytoplanktonic biomass in suspension and appears optimal to fertilize phytoplankton development and therefore the food pyramid of marine life. Loladze and Elser have shown that it corresponds to a homeostatic protein:RNA ratio and is therefore "rooted in the stoichiometry of the foundational structures of life." I show that according to the recent theory of the chemical differentiation of planets, this optimal ratio is also an intrinsic chemical property of our planet Earth uniquely determined in the solar system by its average orbital radius. On that basis, I propose a criterion of fertility within the HZ of a stellar system, which when applied to screen the public database allows us to sort out an extended list of up to 74 Earth analogs. The latter and its future extensions could provide priority targets for focused detection techniques.

Keywords: astrobiology; biosignatures; astrochemistry; chemical abundances
ENISALA. II. Distinct Star Formation and Active Galactic Nucleus Activity in Merging and Relaxed Galaxy Clusters

The growth of galaxy clusters is energetic and may trigger and/or quench star formation and black hole activity. The ENISALA4 project is a collection of multiwavelength observations aimed at understanding how large-scale structure drives galaxy and black hole evolution. Here, we introduce optical spectroscopy of over 800 Hα emission-line galaxies, selected in 14 z ∼ 0.15-0.31 galaxy clusters, spanning a range of masses and dynamical states. We investigate the nature of the emission lines in relation to the host galaxy properties, its location within the cluster, and the properties of the parent cluster. We uncover remarkable differences between mergers and relaxed clusters. The majority of Hα emission-line galaxies in merging cluster fields are located within 3 Mpc of their center. A large fraction of these line emitters in merging clusters are powered by star formation irrespective of cluster-centric radius, while the rest are powered by active galactic nuclei (AGNs). Star-forming galaxies are rare within 3 Mpc of relaxed clusters and AGNs are most abundant at their outskirts (∼1.5-3 Mpc). We discover a population of star-forming galaxies with large equivalent widths and blue UV-optical colors found exclusively in the merging clusters in our sample. The widespread emission-line activity in merging clusters is likely supported by triggered activity in recently accreted, gas-rich galaxies. By contrast, our observations for relaxed clusters match established models in which black hole activity is enhanced at the virial radius and star formation is quenched within the infall region. We conclude that emission-line galaxies experience distinct evolutionary paths in merging and relaxed clusters.

Keywords: active galaxies; early-type galaxies; emission line galaxies; galaxy clusters; galaxy evolution; ionization; intracluster medium; spectroscopy; spiral galaxies; star formation; shocks; galaxy environments
TOI 540 b: A Planet Smaller than Earth Orbiting a Nearby Rapidly Rotating Low-mass Star

We present the discovery of TOI 540 b, a hot planet slightly smaller than Earth orbiting the low-mass star 2MASS J05051443-4756154. The planet has an orbital period of P = 1.239149 days (±170 ms) and a radius of $r=0.903\pm 0.052{R}_{\oplus }$ , and is likely terrestrial based on the observed mass-radius distribution of small exoplanets at similar insolations. The star is 14.008 pc away and we estimate its mass and radius to be $M=0.159\pm 0.014$ ${M}_{\odot }$ and $R=0.1895\pm 0.0079{R}_{\odot }$ , respectively. The star is distinctive in its very short rotational period of ${P}_{\mathrm{rot}}=17.4264\pm 0.0094$ hr and correspondingly small Rossby number of 0.007 as well as its high X-ray-to-bolometric luminosity ratio of ${L}_{{\rm{X}}}/{L}_{\mathrm{bol}}=0.0028$ based on a serendipitous XMM-Newton detection during a slew operation. This is consistent with the X-ray emission being observed at a maximum value of ${L}_{{\rm{X}}}/{L}_{\mathrm{bol}}\simeq {10}^{-3}$ as predicted for the most rapidly rotating M dwarfs. TOI 540 b may be an alluring target to study atmospheric erosion due to the strong stellar X-ray emission. It is also among the most accessible targets for transmission and emission spectroscopy and eclipse photometry with the James Webb Space Telescope, and may permit Doppler tomography with high-resolution spectroscopy during transit. This discovery is based on precise photometric data from the Transiting Exoplanet Survey Satellite and ground-based follow-up observations by the MEarth team.

Keywords: transit photometry; exoplanets; extrasolar rocky planets; stellar rotation
Fermi-LAT Observations of Sagittarius A*: Imaging Analysis

Sagittarius A* (Sgr A*)-the supermassive black hole (SMBH) in the center of our galaxy-has been observed in most of the electromagnetic spectrum, from radio to X-rays. Diffuse γ-ray emission has been observed around Sgr A* and a γ-ray point source has been detected coinciding with the SMBH's position, although there is no definitive association between the two. In this work, we have used ~11 yr of Fermi Large Area Telescope observations of the point source 4FGL J1745.6-2859 and performed a detailed imaging analysis across four energy bands. Our goal is to elucidate the nature of the γ-ray emission at the Galactic Center (GC) and whether it is associated with the SMBH. We find that the centroid of the emission approaches Sgr A*'s location as the energy increases. Assuming that the γ-ray point source is located at the GC, we estimate a luminosity of 2.61 × 1036 erg s-1 in the 100 MeV to 500 GeV energy range. This is consistent with Sgr A*'s bolometric luminosity. Based on the point source properties, we ruled out several potential candidates for its nature and favor a cosmic-ray origin either from protons, electrons, or both, accelerated by-or in the vicinity of-the SMBH. Our results indicate that the point source at the GC is indeed the γ-ray counterpart of Sgr A* in the GeV range.

Keywords: galactic center; gamma-ray astronomy; supermassive black holes; gamma-ray sources
Hubble Frontier Field Clusters and Their Parallel Fields: Photometric and Photometric Redshift Catalogs

We present a multiband analysis of the six Hubble Frontier Field clusters and their parallel fields, producing catalogs with measurements of source photometry and photometric redshifts. We release these catalogs to the public along with maps of intracluster light and models for the brightest galaxies in each field. This rich data set covers a wavelength range from 0.2 to 8 μm, utilizing data from the Hubble Space Telescope, Keck Observatories, Very Large Telescope array, and Spitzer Space Telescope. We validate our products by injecting into our fields and recovering a population of synthetic objects with similar characteristics to those in real extragalactic surveys. The photometric catalogs contain a total of over 32,000 entries, with 50% completeness at a threshold of magAB ~ 29.1 for unblended sources and magAB ~ 29 for blended ones, in the IR-weighted detection band. Photometric redshifts were obtained by means of template fitting and have an average outlier fraction of 10.3% and scatter σ = 0.067 when compared to spectroscopic estimates. The software we devised, after being tested in the present work, will be applied to new data sets from ongoing and future surveys.

Keywords: hst photometry; galaxy clusters; intracluster medium
Axisymmetric High Spot Coverage on Exoplanet Host HD 189733 A

Transmission spectroscopy is a powerful tool to study exoplanet atmospheres, which can be affected by the ability of stellar photospheric heterogeneity to mimic or mask exoplanetary spectral signatures. The canonical HD 189733 system provides a textbook example of this spectroscopic discrepancy with features that have been variously interpreted as signatures of scattering by haze in the planetary atmosphere or unocculted spots on the stellar disk. Here, we leverage three archival data sets from the Hubble Space Telescope to directly infer the covering fraction of HD 189733 A and explore the evidence for photospheric heterogeneity in the out-of-transit spectra. We model the stellar spectrum using one to three spectral components in a nested-sampling framework, finding that the two-component model (photosphere and spot) is preferred for all data sets. We find photospheric and spot temperatures of $5295{\pm }_{41}^{43}$ and $3222{\pm }_{116}^{100}$ K, respectively, which are consistent across data sets. The spot covering fraction is large and varies between 38% ± 4% and 47% ± 3%. Combined with time-domain insights from Transiting Exoplanet Survey Satellite data revealing HD 189733 A's 1.4% peak-to-peak variability, our findings imply that the majority of the spots must be distributed axisymmetrically, e.g., in a densely filled latitudinal band or at the poles. More work with complementary data sets is necessary to investigate those possible arrangements.

Keywords: starspots; stellar activity; exoplanet atmospheres; planet hosting stars
ALMA Reveals the Molecular Gas Properties of Five Star-forming Galaxies across the Main Sequence at 3

We present the detection of CO (5-4) with signal-to-noise ratio (S/N) > 7-13 and a lower CO transition with S/N > 3 (CO (4-3) for four galaxies, and CO (3-2) for one) with the Atacama Large Millimeter/submillimeter Array in bands 3 and 4 in five main-sequence (MS) star-forming galaxies with stellar masses (3-6) × 1010M⊙ at 3 < z < 3.5. We find a good correlation between the total far-infrared luminosity LFIR and the luminosity of the CO (5-4) transition L_{CO(5-4)}^{'}, where L_{CO(5-4)^{'} increases with star formation rate (SFR), indicating that CO (5-4) is a good tracer of the obscured SFR in these galaxies. The two galaxies that lie closer to the star-forming MS have CO spectral line energy distribution (SLED) slopes that are comparable to other star-forming populations, such as local submillimeter galaxies and BzK star-forming galaxies; the three objects with higher specific star formation rates have far steeper CO SLEDs, which possibly indicates a more concentrated episode of star formation. By exploiting the CO SLED slopes to extrapolate the luminosity of the CO (1-0) transition and using a classical conversion factor for MS galaxies of α_{CO}=3.8 M_{⊙}(K km s01 pc-2)-1, we find that these galaxies are very gas-rich, with molecular gas fractions between 60% and 80% and quite long depletion times, between 0.2 and 1 Gyr. Finally, we obtain dynamical masses that are comparable to the sum of stellar and gas mass (at least for four out of five galaxies), allowing us to put a first constraint on the αCO parameter for MS galaxies at an unprecedented redshift.

Keywords: star formation; interstellar medium
Resonant Chains of Exoplanets: Libration Centers for Three-body Angles

Resonant planetary systems contain at least one planet pair with orbital periods librating at a near-integer ratio (2/1, 3/2, 4/3, etc.) and are a natural outcome of standard planetary formation theories. Systems with multiple adjacent resonant pairs are known as resonant chains and can exhibit three-body resonances—characterized by a critical three-body angle. Here we study three-body angles as a diagnostic of resonant chains through tidally damped N-body integrations. For each combination of the 2:1, 3:2, 4:3, and 5:4 mean motion resonances (the most common resonances in the known resonant chains), we characterize the three-body angle equilibria for several mass schemes, migration timescales, and initial separations. We find that under our formulation of the three-body angle, which does not reduce coefficients, 180° is the preferred libration center, and libration centers shifted away from 180° are associated with nonadjacent resonances. We then relate these angles to observables, by applying our general results to two transiting systems: Kepler-60 and Kepler-223. For these systems, we compare N-body models of the three-body angle to the zeroth order in e approximation accessible via transit phases, used in previous publications. In both cases, we find the three-body angle during the Kepler observing window is not necessarily indicative of the long-term oscillations and stress the role of dynamical models in investigating three-body angles. We anticipate our results will provide a useful diagnostic in the analysis of resonant chains.

Keywords: exoplanets; exoplanet evolution; exoplanet dynamics; exoplanet tides