Sazuna/UAT_keywords huggingface dataset:
Direct Imaging Discovery of a Young Brown Dwarf Companion to an A2V Star. We present the discovery and spectroscopy of HIP 75056Ab, a companion directly imaged at a very small separation of 0"125 to an A2V star in the Scorpius-Centaurus OB2 association. Our observations utilized Very Large Telescope/Spectro-Polarimetric High-contrast Exoplanet Research Experiment between 2015 and 2019, enabling low-resolution spectroscopy (0.95-1.65 μm), dual-band imaging (2.1-2.25 μm), and relative astrometry over a four-year baseline. HIP 75056Ab is consistent with spectral types in the range of M6-L2 and Teff ∼ 2000-2600 K. A comparison of the companion's brightness to evolutionary tracks suggests a mass of ∼20-30 MJup. The astrometric measurements are consistent with an orbital semimajor axis of ∼15-45 au and an inclination close to face-on (i ≲ 35°). In this range of mass and orbital separation, HIP 75056Ab is likely at the low-mass end of the distribution of companions formed via disk instability, although a formation of the companion via core accretion cannot be excluded. The orbital constraints are consistent with the modest eccentricity values predicted by disk instability, a scenario that can be confirmed by further astrometric monitoring. HIP 75056Ab may be utilized as a low-mass atmospheric comparison to older, higher-mass brown dwarfs, and also to young giant planets. Finally, the detection of HIP 75056Ab at 0"125 represents a milestone in detecting low-mass companions at separations corresponding to the habitable zones of nearby Sun-like stars.

Keywords: Brown dwarfs, Direct imaging, Exoplanets
Discovery of Ground-state Absorption Line Polarization and Sub-Gauss Magnetic Field in the Post-AGB Binary System 89 Her. We report the polarization of ground-state absorption lines from the post-asymptotic giant branch (post-AGB) binary star system 89 Herculis (89 Her). Two ground-state neutral iron lines are found to have counterintuitive high-amplitude polarizations and an unchanged polarization direction through the orbital period. This is contrary to the pattern of polarization of absorption lines from excited states, which are synchronized with the orbital phase due to optical pumping. This can be explained by magnetic realignment of the ground state, whereby the 3D mean magnetic field is separated from the degree and direction of the polarizations of the two iron lines. The field strength is also constrained to be ≲100 mG. Our result improves the accuracy by orders of magnitude compared to the previous 10 G upper limit set by non-detection of the Zeeman effect.

Keywords: Spectropolarimetry, Stellar properties, Astrophysical magnetism, Stellar magnetic fields, Starlight polarization, Stellar photospheres, Stellar spectral lines
Helium-rich Superluminous Supernovae from the Zwicky Transient Facility. Helium is expected to be present in the massive ejecta of some hydrogen-poor superluminous supernovae (SLSN-I). However, until now only one event has been identified with He features in its photospheric spectra (PTF10hgi). We present the discovery of a new He-rich SLSN-I, ZTF19aawfbtg (SN2019hge), at z = 0.0866. This event has more than 10 optical spectra at phases from -41 to +103 days relative to the peak, most of which match well with that of PTF10hgi. Confirmation comes from a near-IR spectrum taken at +34 days, revealing He I features with P-Cygni profiles at 1.083 and 2.058 μm. Using the optical spectra of PTF10hgi and SN2019hge as templates, we examined 70 other SLSNe-I discovered by Zwicky Transient Facility in the first two years of operation and found five additional SLSNe-I with distinct He-features. The excitation of He I atoms in normal core-collapse supernovae requires nonthermal radiation, as proposed by previous studies. These He-rich events cannot be explained by the traditional 56Ni mixing model because of their blue spectra, high peak luminosities, and long rise timescales. Magnetar models offer a possible solution since pulsar winds naturally generate high-energy particles, potential sources of nonthermal excitation. An alternative model is the interaction between the ejecta and dense H-poor circumstellar material, which may be supported by observed undulations in the light curves. These six SLSNe-Ib have relatively low-peak luminosities (rest frame Mg = -20.06 ± 0.16).

Keywords: Type Ib supernovae, Supernovae
An Earth-like Stellar Wind Environment for Proxima Centauri c. A new planet has been recently discovered around Proxima Centauri. With an orbital separation of ∼1.44 au and a minimum mass of about $7\,{M}_{\oplus }$ , Proxima c is a prime direct imaging target for atmospheric characterization. The latter can only be performed with a good understanding of the space environment of the planet, as multiple processes can have profound effects on the atmospheric structure and evolution. Here, we take one step in this direction by generating physically realistic numerical simulations of Proxima's stellar wind, coupled to a magnetosphere and ionosphere model around Proxima c. We evaluate their expected variation due to the magnetic cycle of the host star, as well as for plausible inclination angles for the exoplanet orbit. Our results indicate stellar wind dynamic pressures comparable to present-day Earth, with a slight increase (by a factor of 2) during high-activity periods of the star. A relatively weak interplanetary magnetic field at the distance of Proxima c leads to negligible stellar wind Joule heating of the upper atmosphere (about 10% of the solar wind contribution on Earth) for an Earth-like planetary magnetic field (0.3 G). Finally, we provide an assessment of the likely extreme conditions experienced by the exoplanet candidate Proxima d, tentatively located at 0.029 au with a minimum mass of 0.29 M⊕.

Keywords: Exoplanets, Super Earths, Stellar magnetic fields, Stellar mass loss, Stellar activity, Stellar winds, Interplanetary magnetic fields, Planetary magnetospheres
Waterworlds May Have Better Climate Buffering Capacities than Their Continental Counterparts. The long-term habitability of a planet is often assumed to be controlled by its ability to cycle carbon between the solid planetary interior and atmosphere. This process allows the planet to respond to external forcings (i.e., changes in insolation, changes in volcanic outgassing rates, etc.) and regulate its surface temperature through negative feedbacks on atmospheric CO2 involved in silicate weathering. Continental weathering and seafloor weathering rates have different, non-linear dependencies on pCO2 and will respond differently to changes in external forcings. Because waterworlds (planets with only seafloor weathering) have a weaker pCO2 dependence than continental worlds (such as modern Earth), we find that waterworlds are better at resisting changes in surface temperature resulting from perturbations in insolation than their continental counterparts, and may be more habitable in this respect.

Keywords: Extrasolar rocky planets, Ocean planets, Exoplanets, Carbon dioxide, Habitable planets
Multimessenger Constraints on Intergalactic Magnetic Fields from the Flare of TXS 0506+056. The origin of magnetic fields in the universe is an open problem. Seed magnetic fields possibly produced in early times may have survived up to the present day close to their original form, providing an untapped window to the primeval universe. The recent observations of high-energy neutrinos from the blazar TXS 0506+056 in association with an electromagnetic counterpart in a broad range of wavelengths can be used to probe intergalactic magnetic fields via the time delay between the neutrinos and gamma-rays as well as the time dependence of the gamma-ray fluxes. Using extensive three-dimensional Monte Carlo simulations, we constrain both the magnetic-field strength and, for the first time, its coherence length, considering six orders of magnitude for each.

Keywords: Primordial magnetic fields, High-energy cosmic radiation, High energy astrophysics, Neutrino astronomy, Active galactic nuclei, Magnetic fields, Gamma-rays, Extragalactic magnetic fields
Characterizing Astrophysical Binary Neutron Stars with Gravitational Waves. Merging binary neutron stars are thought to be formed predominantly via isolated binary evolution. In this standard formation scenario, the first-born neutron star goes through a recycling process and might be rapidly spinning during the final inspiral, whereas the second-born star is expected to have effectively zero spin at merger. Based on this feature, we propose a new framework for the astrophysical characterization of binary neutron stars observed from their gravitational wave emission. We further propose a prior for the dimensionless spins of recycled neutron stars, given by a gamma distribution with a shape parameter of 2 and a scale parameter of 0.012, extrapolated from radio pulsar observations of Galactic binary neutron stars. Interpreting GW170817 and GW190425 in the context of the standard formation scenario and adopting the gamma-distribution prior, we find positive support (with a Bayes factor of 6, over the nonspinning hypothesis) for a spinning recycled neutron star in GW190425, whereas the spin of the recycled neutron star in GW170817 is small and consistent with our prior. We measure the masses of the recycled (slow) neutron stars in GW170817 and GW190425 to be ${1.34}_{-0.09}^{+0.12}$ $({1.38}_{-0.11}^{+0.11}){M}_{\odot }$ and ${1.64}_{-0.11}^{+0.13}$ $({1.66}_{-0.12}^{+0.12}){M}_{\odot }$ , with 68% credibility, respectively. We discuss implications for the astrophysical origins of these two events and outline future prospects of studying binary neutron stars using our framework.

Keywords: Neutron stars, Binary pulsars, Gravitational waves
The Two Emission States of PSR B1534+12. We have observed PSR B1534+12 (J1537+1155), a pulsar with a neutron star companion, using the Five-hundred-meter Aperture Spherical radio Telescope. We found that this pulsar shows two distinct emission states: a weak state with a wide pulse profile and a burst state with a narrow pulse profile. The weak state is always present. We cannot, with our current data, determine whether the pulse energy of the weak state follows a normal or a log-normal distribution. The burst state energy distribution follows a power law. The amplitude of the single-pulse emission in the burst state varies significantly; the peak flux intensity of the brightest pulse is 334 times stronger than that of the average pulse. We also examined the timing precision achievable using only bright pulses, which showed no demonstrable improvement because of pulse jitter and therefore quantified the jitter noise level for this pulsar.

Keywords: Astronomy data analysis, Radio pulsars, Millisecond pulsars
Increasing Activity in T CrB Suggests Nova Eruption Is Impending. Estimates of the accretion rate in symbiotic recurrent novae (RNe) often fall short of theoretical expectations by orders of magnitude. This apparent discrepancy can be resolved if the accumulation of mass by the white dwarf (WD) is highly sporadic, and most observations are performed during low states. Here we use a re-analysis of archival data from the Digital Access to a Sky Century @Harvard survey to argue that the most recent nova eruption in symbiotic RN T CrB, in 1946, occurred during—and was therefore triggered by—a transient accretion high state. Based on similarities in the optical light curve around 1946 and the time of the prior eruption, in 1866, we suggest that the WD in T CrB accumulates most of the fuel needed to ignite the thermonuclear runaways (TNRs) during accretion high states. A natural origin for such states is dwarf-nova like accretion-disk instabilities, which are expected in the presumably large disks in symbiotic binaries. The timing of the TNRs in symbiotic RNe could thus be set by the stability properties of their accretion disks. T CrB is in the midst of an accretion high state like the ones we posit led to the past two nova eruptions. Combined with the approach of the time at which a TNR would be expected based on the 80 yr interval between the prior two novae (2026 ± 3), the current accretion high state increases the likelihood of a TNR occurring in T CrB in the next few years.

Keywords: Accretion, Symbiotic binary stars, Recurrent novae
Long-term Evolution of the Sun's Magnetic Field during Cycles 15-19 Based on Their Proxies from Kodaikanal Solar Observatory. The regular observation of the solar magnetic field is available only for about the last five cycles. Thus, to understand the origin of the variation of the solar magnetic field, it is essential to reconstruct the magnetic field for the past cycles, utilizing other data sets. Long-term uniform observations for the past 100 yr as recorded at the Kodaikanal Solar Observatory (KoSO) provide such an opportunity. We develop a method for the reconstruction of the solar magnetic field using the synoptic observations of the Sun's emission in the Ca II K and Hα lines from KoSO for the first time. The reconstruction method is based on the fact that the Ca II K intensity correlates well with the unsigned magnetic flux, while the sign of the flux is derived from the corresponding Hα map that provides the information of the dominant polarities. Based on this reconstructed magnetic map, we study the evolution of the magnetic field in Cycles 15-19. We also study bipolar magnetic regions (BMRs) and their remnant flux surges in their causal relation. Time-latitude analysis of the reconstructed magnetic flux provides an overall view of magnetic field evolution: emergent magnetic flux, its further transformations with the formation of unipolar magnetic regions (UMRs), and remnant flux surges. We identify the reversals of the polar field and critical surges of following and leading polarities. We found that the poleward transport of opposite polarities led to multiple changes of the dominant magnetic polarities in poles. Furthermore, the remnant flux surges that occur between adjacent 11 yr cycles reveal physical connections between them.

Keywords: H alpha photometry, Sunspot cycle, Solar magnetic fields, Solar chromosphere
The MOSDEF Survey: Neon as a Probe of ISM Physical Conditions at High Redshift. We present results on the properties of neon emission in z ∼ 2 star-forming galaxies drawn from the MOSFIRE Deep Evolution Field (MOSDEF) survey. Doubly ionized neon ([Ne III]λ3869) is detected at ≥3σ in 61 galaxies, representing ∼25% of the MOSDEF sample with Hα, Hβ, and [O III]λ5007 detections at similar redshifts. We consider the neon emission-line properties of both individual galaxies with [Ne III]λ3869 detections and composite z ∼ 2 spectra binned by stellar mass. With no requirement of [Ne III]λ3869 detection, the latter provide a more representative picture of neon emission-line properties in the MOSDEF sample. The [Ne III]λ3869/[O II]λ3727 ratio (Ne3O2) is anticorrelated with stellar mass in z ∼ 2 galaxies, as expected based on the mass-metallicity relation. It is also positively correlated with the [O III]λ5007/[O II]λ3727 ratio (O32), but z ∼ 2 line ratios are offset toward higher Ne3O2 at fixed O32, compared with both local star-forming galaxies and individual H II regions. Despite the offset toward higher Ne3O2 at fixed O32 at z ∼ 2, biases in inferred Ne3O2-based metallicity are small. Accordingly, Ne3O2 may serve as an important metallicity indicator deep into the reionization epoch. Analyzing additional rest-optical line ratios including [Ne III]λ3869/[O III]λ5007 (Ne3O3) and [O III]λ5007/Hβ (O3Hβ), we conclude that the nebular emission-line ratios of z ∼ 2 star-forming galaxies suggest a harder ionizing spectrum (lower stellar metallicity, i.e., Fe/H) at fixed gas-phase oxygen abundance, compared to systems at z ∼ 0. These new results based on neon lend support to the physical picture painted by oxygen, nitrogen, hydrogen, and sulfur emission of an ionized interstellar medium in high-redshift star-forming galaxies irradiated by chemically young, α-enhanced massive stars. * Based on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration, and was made possible by the generous financial support of the W.M. Keck Foundation.

Keywords: High-redshift galaxies, Galaxy evolution, Interstellar medium
FRB 121102 Bursts at a Constant Rate per Log Time. Despite many searches for periodicity in the repeating fast radio burst FRB 121102, the underlying pattern of bursts does not appear to be a periodic one. We report a logarithmic repetition pattern in FRB 121102 in the sense that the rate falls off inversely with time for each set of bursts. This result implies that repeating fast radio burst sources are not necessarily associated with a pulsar, but rather could be caused by a different type of phenomenon that involves an equal amount of energy output per log time.

Keywords: Radio transient sources
Crepuscular Rays from the Highly Inclined Active Galactic Nucleus in IC 5063. On Earth near sunset, the Sun may cast "crepuscular rays" such that clouds near the horizon obscure the origin of light scattered in bright rays. In principle, active galactic nuclei (AGN) should be able to produce similar effects. Using new Hubble Space Telescope (HST) near-infrared and optical observations, we show that the active galaxy IC 5063 contains broad radial rays extending to ≳11 kpc from the nucleus. We argue that the bright rays may arise from dusty scattering of continuum emission from the active nucleus, while the dark rays are due to shadowing near the nucleus, possibly by a warped torus. We also consider alternative AGN-related and stellar origins for the extended light. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. These observations are associated with programs #15444 and #15609.

Keywords: AGN host galaxies, Interstellar dust, Galaxy classification systems, Galaxy winds, Galaxy mergers, Interstellar scattering
Into the UV: The Atmosphere of the Hot Jupiter HAT-P-41b Revealed. For solar system objects, ultraviolet spectroscopy has been critical in identifying sources of stratospheric heating and measuring the abundances of a variety of hydrocarbon and sulfur-bearing species, produced via photochemical mechanisms, as well as oxygen and ozone. To date, fewer than 20 exoplanets have been probed in this critical wavelength range (0.2-0.4 μm). Here we use data from Hubble's newly implemented WFC3 UVIS G280 grism to probe the atmosphere of the hot Jupiter HAT-P-41b in the ultraviolet through optical in combination with observations at infrared wavelengths. We analyze and interpret HAT-P-41b's 0.2-5.0 μm transmission spectrum using a broad range of methodologies including multiple treatments of data systematics as well as comparisons with atmospheric forward, cloud microphysical, and multiple atmospheric retrieval models. Although some analysis and interpretation methods favor the presence of clouds or potentially a combination of Na, VO, AlO, and CrH to explain the ultraviolet through optical portions of HAT-P-41b's transmission spectrum, we find that the presence of a significant H- opacity provides the most robust explanation. We obtain a constraint for the abundance of H-, $\mathrm{log}({{\rm{H}}}^{-})=-8.65\pm 0.62$ , in HAT-P-41b's atmosphere, which is several orders of magnitude larger than predictions from equilibrium chemistry for a ∼1700-1950 K hot Jupiter. We show that a combination of photochemical and collisional processes on hot hydrogen-dominated exoplanets can readily supply the necessary amount of H- and suggest that such processes are at work in HAT-P-41b and the atmospheres of many other hot Jupiters.

Keywords: Observational astronomy, Exoplanet atmospheric composition , Exoplanet atmospheres, Spectroscopy
Application of Orbital Stability and Tidal Migration Constraints for Exomoon Candidates. Satellites of extrasolar planets, or exomoons, are on the frontier of detectability using current technologies and theoretical constraints should be considered in their search. In this Letter, we apply theoretical constraints of orbital stability and tidal migration to the six candidate Kepler Object of Interest (KOI) systems proposed by Fox &amp; Wiegert to identify whether these systems can potentially host exomoons. The host planets orbit close to their respective stars and the orbital stability extent of exomoons is limited to only ∼40% of the host planet's Hill radius (∼20 Rp). Using plausible tidal parameters from the solar system, we find that four out of six systems would either tidally disrupt their exomoons or lose them to outward migration within the system lifetimes. The remaining two systems (KOI 268.01 and KOI 1888.01) could host exomoons that are within 25 Rp and less than ∼3% of the host planet's mass. However, a recent independent transit timing analysis by Kipping found that these systems fail rigorous statistical tests to validate them as candidates. Overall, we find the presence of exomoons in these systems that are large enough for transit timing variation signatures to be unlikely given the combined constraints of observational modeling, tidal migration, and orbital stability. Software to reproduce our results is available in the GitHub repository: Multiversario/satcand.

Keywords: Exoplanet dynamics, Exoplanet tides, Exoplanet systems, Natural satellites (Extrasolar)
Gravitational-wave Constraints on the Equatorial Ellipticity of Millisecond Pulsars. We present a search for continuous gravitational waves from five radio pulsars, comprising three recycled pulsars (PSR J0437-4715, PSR J0711-6830, and PSR J0737-3039A) and two young pulsars: the Crab pulsar (J0534+2200) and the Vela pulsar (J0835-4510). We use data from the third observing run of Advanced LIGO and Virgo combined with data from their first and second observing runs. For the first time, we are able to match (for PSR J0437-4715) or surpass (for PSR J0711-6830) the indirect limits on gravitational-wave emission from recycled pulsars inferred from their observed spin-downs, and constrain their equatorial ellipticities to be less than 10-8. For each of the five pulsars, we perform targeted searches that assume a tight coupling between the gravitational-wave and electromagnetic signal phase evolution. We also present constraints on PSR J0711-6830, the Crab pulsar, and the Vela pulsar from a search that relaxes this assumption, allowing the gravitational-wave signal to vary from the electromagnetic expectation within a narrow band of frequencies and frequency derivatives.

Keywords: Neutron stars, Gravitational waves, Gravitational wave sources, Pulsars