adsabs/SciX_UAT_keywords huggingface dataset:
The Herschel Orion Protostar Survey: Far-infrared Photometry and Colors of Protostars and Their Variations across Orion A and B

The degree to which the properties of protostars are affected by environment remains an open question. To investigate this, we look at the Orion A and B molecular clouds, home to most of the protostars within 500 pc. At ∼400 pc, Orion is close enough to distinguish individual protostars across a range of environments in terms of both the stellar and gas projected densities. As part of the Herschel Orion Protostar Survey (HOPS), we used the Photodetector Array Camera and Spectrometer to map 108 partially overlapping square fields with edge lengths of 5' or 8' and measure the 70 and 160 μm flux densities of 338 protostars within them. In this paper we examine how these flux densities and their ratio depend on evolutionary state and environment within the Orion complex. We show that Class 0 protostars occupy a region of the 70 μm flux density versus 160 μm/70 μm flux density ratio diagram that is distinct from their more evolved counterparts. We then present evidence that the Integral-Shaped Filament (ISF) and Orion B contain protostars with more massive inner envelopes than those in the more sparsely populated LDN 1641 region. This can be interpreted as evidence for increasing star formation rates in the ISF and Orion B or as a tendency for more massive inner envelopes to be inherited from denser birth environments. We also provide technical details about the mapmaking and photometric procedures used in the HOPS program. * Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

Keywords: protostars; star formation; infrared sources
The Physical Properties of Low-redshift FeLoBAL Quasars. IV. Optical–Near-IR Spectral Energy Distributions and Near-IR Variability Properties

We present the optical–near-infrared spectral energy distributions (SED) and near-infrared variability properties of 30 low-redshift iron low-ionization Broad Absorption Line quasars (FeLoBALQs) and matched samples of LoBALQs and unabsorbed quasars. Significant correlations between the SED properties and accretion rate indicators found among the unabsorbed comparison sample objects suggest an intrinsic origin for SED differences. A range of reddening likely mutes these correlations among the FeLoBAL quasars. The rest-frame optical-band reddening is correlated with the location of the outflow, suggesting a link between the outflows and the presence of dust. We analyzed the WISE variability and provide a correction for photometry uncertainties in an appendix. We found an anticorrelation between the variability amplitude and inferred continuum emission region size, and we suggest that as the origin of the anticorrelation between variability amplitude and luminosity typically observed in quasars. We found that the LoBALQ Optical Emission-line and other parameters are more similar to those of the unabsorbed continuum sample objects than the FeLoBALQs. Thus, FeLoBAL quasars are a special population of objects. We interpret the results using an accretion-rate scenario for FeLoBAL quasars. The high-accretion-rate FeLoBAL quasars are radiating powerfully enough to drive a thick, high-velocity outflow. Quasars with intermediate accretion rates may have an outflow, but it is not sufficiently thick to include Fe II absorption. Low-accretion-rate FeLoBAL outflows originate in absorption in a failing torus, no longer optically thick enough to reprocess radiation into the near-IR.

Keywords: quasars; spectral energy distribution
A Universal Cloud Composition on the Nightsides of Hot Jupiters

The day and nightside temperatures of hot Jupiters are diagnostics of heat transport processes in their atmospheres. Recent observations have shown that the nightsides of hot Jupiters are a nearly constant 1100 K for a wide range of equilibrium temperatures (Teq), lower than those predicted by 3D global circulation models. Here we investigate the impact of nightside clouds on the observed nightside temperatures of hot Jupiters using an aerosol microphysics model. We find that silicates dominate the cloud composition, forming an optically thick cloud deck on the nightsides of all hot Jupiters with Teq ≤ 2100 K. The observed nightside temperature is thus controlled by the optical depth profile of the silicate cloud with respect to the temperature-pressure profile. As nightside temperatures increase with Teq, the silicate cloud is pushed upward, forcing observations to probe cooler altitudes. The cloud vertical extent remains fairly constant due to competing impacts of increasing vertical mixing strength with Teq and higher rates of sedimentation at higher altitudes. These effects, combined with the intrinsically subtle increase of the nightside temperature with Teq due to decreasing radiative timescale at higher instellation levels, lead to low, constant nightside photospheric temperatures consistent with observations. Our results suggest a drastic reduction in the day-night temperature contrast when nightside clouds dissipate, with the nightside emission spectra transitioning from featureless to feature-rich. We also predict that cloud absorption features in the nightside emission spectra of hot Jupiters should reach ≥100 ppm, potentially observable with the James Webb Space Telescope.

Keywords: exoplanet atmospheres; atmospheric clouds; planetary atmospheres; exoplanet atmospheric composition; hot jupiters
Primordial Helium-3 Redux: The Helium Isotope Ratio of the Orion Nebula

We report the first direct measurement of the helium isotope ratio, 3He/4He, outside of the Local Interstellar Cloud, as part of science-verification observations with the upgraded CRyogenic InfraRed Echelle Spectrograph. Our determination of 3He/4He is based on metastable He I* absorption along the line of sight toward Θ2A Ori in the Orion Nebula. We measure a value 3He/4He = (1.77 ± 0.13) × 10-4, which is just ~40% above the primordial relative abundance of these isotopes, assuming the Standard Model of particle physics and cosmology, (3He/4He)p = (1.257 ± 0.017) × 10-4. We calculate a suite of galactic chemical evolution simulations to study the Galactic build up of these isotopes, using the yields from Limongi & Chieffi for stars in the mass range M = 8-100 M ⊙ and Lagarde et al. for M = 0.8-8 M ⊙. We find that these simulations simultaneously reproduce the Orion and protosolar 3He/4He values if the calculations are initialized with a primordial ratio ${\left({}^{3}\mathrm{He}{/}^{4}\mathrm{He}\right)}_{{\rm{p}}}=(1.043\pm 0.089)\times {10}^{-4}$ . Even though the quoted error does not include the model uncertainty, this determination agrees with the Standard Model value to within ~2σ. We also use the present-day Galactic abundance of deuterium (D/H), helium (He/H), and 3He/4He to infer an empirical limit on the primordial 3He abundance, ${\left({}^{3}\mathrm{He}/{\rm{H}}\right)}_{{\rm{p}}}\leqslant (1.09\pm 0.18)\times {10}^{-5}$ , which also agrees with the Standard Model value. We point out that it is becoming increasingly difficult to explain the discrepant primordial 7Li/H abundance with nonstandard physics, without breaking the remarkable simultaneous agreement of three primordial element ratios (D/H, 4He/H, and 3He/4He) with the Standard Model values. *Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO program(s) 107.22U1.001, 194.C-0833.

Keywords: interstellar medium; interstellar absorption; cosmology; big bang nucleosynthesis; interstellar line absorption; cosmochemistry; astrochemistry; galaxy chemical evolution; quasar absorption line spectroscopy; astronomical techniques; spectroscopy; astronomy data analysis
Time-varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains

Observations toward type Ia supernovae (SNe Ia) frequently report an unusually low total-to-selective extinction ratio (RV < 2) and a small peak wavelength of polarization (λmax < 0.4 μm). Hoang et al. proposed that the dominance of small grains near SNe Ia due to RAdiative Torque Disruption (RATD) can explain the puzzle. To test this scenario, we model the dust extinction and polarization of SNe Ia, accounting for grain disruption and alignment by radiative torques and different grain tensile strengths from ${S}_{\max }={10}^{7}\mbox{--}{10}^{10}\,\mathrm{erg}\,{\mathrm{cm}}^{-3}$ . We find that RV decreases from ∼3.1 to ∼1.5 after disruption time tdisr < 40 days for clouds at a distance d < 4 pc from SNe Ia. We then calculate the observed lightcurves of SNe Ia and find that their colors change with time, due to varying dust extinction. The peak wavelength λmax also decreases from ∼0.55 to ∼0.15 μm over an alignment time of talign < 10 days, due to the enhanced alignment of small grains. By fitting the theoretical polarization with the Serkowski law characterized by the K and λmax parameters, we find that K increases when large grains are disrupted by RATD, which is consistent with the unusual K versus λmax relationship of SNe Ia. Nevertheless, an accurate measurement of K and λmax is challenging, due to atmospheric effects and potential contamination of polarization by Rayleigh scattering by circumstellar matter. Our results demonstrate the importance of RATD for time-dependent extinction, polarization, and colors of SNe Ia.

Keywords: astrosphere interstellar medium interactions; interstellar dust; interstellar dust extinction; interstellar dust processes; type ia supernovae; supernovae; core-collapse supernovae; starlight polarization
Extreme-ultraviolet Late Phase of Solar Flares

A second peak in the extreme ultraviolet sometimes appears during the gradual phase of solar flares, which is known as the EUV late phase (ELP). Stereotypically ELP is associated with two separated sets of flaring loops with distinct sizes, and it has been debated whether ELP is caused by additional heating or extended plasma cooling in the longer loop system. Here we carry out a survey of 55 M-and-above GOES-class flares with ELP during 2010-2014. Based on the flare-ribbon morphology, these flares are categorized as circular-ribbon (19 events), two-ribbon (23 events), and complex-ribbon (13 events) flares. Among them, 22 events (40%) are associated with coronal mass ejections, while the rest are confined. An extreme ELP, with the late-phase peak exceeding the main-phase peak, is found in 48% of two-ribbon flares, 37% of circular-ribbon flares, and 31% of complex-ribbon flares, suggesting that additional heating is more likely present during ELP in two-ribbon than in circular-ribbon flares. Overall, cooling may be the dominant factor causing the delay of the ELP peak relative to the main-phase peak, because the loop system responsible for the ELP emission is generally larger than, and well separated from, that responsible for the main-phase emission. All but one of the circular-ribbon flares can be well explained by a composite "dome-plate" quasi-separatrix layer (QSL). Only half of these show a magnetic null point, with its fan and spine embedded in the dome and plate, respectively. The dome-plate QSL, therefore, is a general and robust structure characterizing circular-ribbon flares.

Keywords: active sun; solar flares; solar extreme ultraviolet emission; active solar corona; solar active region magnetic fields; solar active regions; solar activity; solar physics
Birthplaces of Extreme Ultraviolet Waves Driven by Impingement of Solar Jets upon Coronal Loops

Solar extreme ultraviolet (EUV) waves are large-scale propagating disturbances in the corona. It is generally believed that a vital key to the formation of EUV waves is the rapid expansion of the loops that overlie erupting cores in solar eruptions, such as coronal mass ejections (CMEs) and solar jets. However, the details of the interaction between the erupting cores and overlying loops are not clear because the overlying loops always instantly open after energetic eruptions. Here, we present three typical jet-driven EUV waves without CMEs to study the interaction between the jets and the overlying loops that remained closed during the events. All three jets emanated from magnetic flux cancellation sites in the source regions. Interestingly, after the interactions between the jets and overlying loops, three EUV waves respectively formed ahead of the top, the near end (close to the jet source), and the far (another) end of the overlying loops. According to the magnetic field distribution of the loops extrapolated through the potential field source surface method, it is confirmed that the birthplaces of three jet-driven EUV waves were around the parts of the overlying loops with the weakest magnetic field strengths. We suggest that the jet-driven EUV waves preferentially occur at the weakest part of the overlying loops, and the location can be subject to the magnetic field intensity around the ends of the loops.

Keywords: solar activity; beta cephei variable stars; solar magnetic fields; solar coronal waves
Velocity Dispersions of Brightest Cluster Galaxies and Their Host Clusters

We explore connections between brightest cluster galaxies (BCGs) and their host clusters. We first construct a HeCS-omnibus cluster sample including 227 galaxy clusters within 0.02 < z < 0.30; the total number of spectroscopic members from MMT/Hectospec and SDSS observations is 52325. Taking advantage of the large spectroscopic sample, we compute physical properties of the clusters including the dynamical mass and cluster velocity dispersion (σcl). We also measure the central stellar velocity dispersion of the BCGs (σ*,BCGs) to examine the relation between BCG velocity dispersion and cluster velocity dispersion for the first time. The observed relation between BCG velocity dispersion and the cluster velocity dispersion is remarkably tight. Interestingly, the σ*,BCG/σcl ratio decreases as a function of σcl unlike the prediction from the numerical simulation of Dolag et al. The trend in σ*,BCG/σcl suggests that BCG formation is more efficient in lower mass halos.

Keywords: brightest cluster galaxies; galaxy clusters; galaxy dark matter halos; redshift surveys
First Detection of an Overmassive Black Hole Galaxy UHZ1: Evidence for Heavy Black Hole Seed Formation from Direct Collapse

The recent Chandra-JWST discovery of a quasar in the z ≈ 10.1 galaxy UHZ1 reveals that accreting supermassive black holes were already in place 470 million years after the Big Bang. The Chandra X-ray source detected in UHZ1 is a Compton-thick quasar with a bolometric luminosity of L bol ~ 5 × 1045 erg s-1, which corresponds to an estimated black hole (BH) mass of ~4 × 107 M ⊙, assuming accretion at the Eddington rate. JWST NIRCAM and NIRSpec data yield a stellar mass estimate for UHZ1 comparable to its BH mass. These characteristics are in excellent agreement with prior theoretical predictions for a unique class of transient, high-redshift objects, overmassive black hole galaxies (OBGs) by Natarajan et al., that harbor a heavy initial black hole seed that likely formed from the direct collapse of the gas. Given the excellent agreement between the observed multiwavelength properties of UHZ1 and theoretical model template predictions, we suggest that UHZ1 is the first detected OBG candidate. Our assertion rests on multiple lines of concordant evidence between model predictions and the following observed properties of UHZ1: its X-ray detection and the estimated ratio of the X-ray flux to the IR flux, which is consistent with theoretical expectations for a heavy initial BH seed; its high measured redshift of z ≈ 10.1, as predicted for the transient OBG stage (9 < z < 12); the amplitude and shape of the detected JWST spectral energy distribution (SED) between 1 and 5 μm, which is in very good agreement with simulated template SEDs for OBGs; and the extended JWST morphology of UHZ1, which is suggestive of a recent merge and is also expected for the formation of transient OBGs. As the first OBG candidate, UHZ1 provides compelling evidence for the formation of heavy initial seeds from direct collapse in the early Universe.

Keywords: black holes; quasars; astrophysical black holes; supermassive black holes
Connection between Subsurface Layers and Surface Magnetic Activity over Multiple Solar Cycles Using GONG Observations

We investigate the spatiotemporal evolution of high-degree acoustic-mode frequencies of the Sun and surface magnetic activity over the course of multiple solar cycles, to improve our understanding of the connection between the solar interior and atmosphere. We focus on high-degree p-modes due to their ability to characterize conditions in the shear layer just below the solar surface, and analyze 22 yr of oscillation frequencies obtained from the Global Oscillation Network Group. Considering 10.7 cm radio flux measurements, the sunspot number, and the local magnetic activity index as solar-activity proxies, we find strong correlation between the mode frequencies and each activity index. We further investigate the hemispheric asymmetry associated with oscillation frequencies and magnetic activity proxies, and find that both were dominant in the southern hemisphere during the descending phase of cycle 23, while in cycle 24 these quantities fluctuated between northern and southern hemispheres. Analyzing the frequencies at different latitudes with the progression of solar cycles, we observe that the variations at midlatitudes were dominant in the southern hemisphere during the maximum-activity period of cycle 24, but the values overlap as the cycle advances toward the minimum phase. The mode frequencies at the beginning of cycle 25 are found to be dominant in the southern hemisphere following the pattern of magnetic activity. The analysis provides added evidence that the variability in oscillation frequencies is caused by both strong and weak magnetic fields.

Keywords: solar interior; helioseismology; solar activity; solar cycle; solar oscillations
SCExAO and Keck Direct Imaging Discovery of a Low-mass Companion Around the Accelerating F5 Star HIP 5319

We present the direct imaging discovery of a low-mass companion to the nearby accelerating F star, HIP 5319, using SCExAO coupled with the CHARIS, VAMPIRES, and MEC instruments in addition to Keck/NIRC2 imaging. CHARIS JHK (1.1-2.4 μm) spectroscopic data combined with VAMPIRES 750 nm, MEC Y, and NIRC2 L p photometry is best matched by an M3-M7 object with an effective temperature of T = 3200 K and surface gravity log(g) = 5.5. Using the relative astrometry for HIP 5319 B from CHARIS and NIRC2, and absolute astrometry for the primary from Gaia and Hipparcos, and adopting a log-normal prior assumption for the companion mass, we measure a dynamical mass for HIP 5319 B of ${31}_{-11}^{+35}{M}_{{\rm{J}}}$ , a semimajor axis of ${18.6}_{-4.1}^{+10}$ au, an inclination of ${69.4}_{-15}^{+5.6}$ degrees, and an eccentricity of ${0.42}_{-0.29}^{+0.39}$ . However, using an alternate prior for our dynamical model yields a much higher mass of ${128}_{-88}^{+127}{M}_{{\rm{J}}}$ . Using data taken with the LCOGT NRES instrument we also show that the primary HIP 5319 A is a single star in contrast to previous characterizations of the system as a spectroscopic binary. This work underscores the importance of assumed priors in dynamical models for companions detected with imaging and astrometry, and the need to have an updated inventory of system measurements. *Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Some of the data presented herein were 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. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT).

Keywords: direct imaging; low mass stars; radial velocity; exoplanet astronomy
Study of Advective Energy Transport in the Inflow and Outflow of Super-Eddington Accretion Flows

Photon trapping is believed to be an important mechanism in super-Eddington accretion, which greatly reduces the radiative efficiency as photons are swallowed by the central black hole before they can escape from the accretion flow. This effect is interpreted as the radial advection of energy in one-dimensional height-integrated models, such as the slim-disk model. However, when multidimensional effects are considered, the conventional understanding may no longer hold. In this paper, we study the advective energy transport in super-Eddington accretion based on a new two-dimensional inflow-outflow solution with radial self-similarity, in which the advective factor is calculated self-consistently by incorporating the calculation of radiative flux instead of being set as an input parameter. We found that radial advection is actually a heating mechanism in the inflow due to compression, and the energy balance in the inflow is maintained by cooling via radiation and vertical (θ-direction) advection, which transports entropy upward to be radiated closer to the surface or carried away by the outflow. As a result, fewer photons are advected inward, and more photons are released from the surface, so that the mean advective factor is smaller and the emergent flux is higher than the fluxes predicted by the slim-disk model. The radiative efficiency of super-Eddington accretion thus should be higher than that of the slim-disk model, which agrees with the results of some recent numerical simulations.

Keywords: accretion; hydrodynamics; high energy astrophysics
Stars on the Verge: From Days to Decades, Studying the Photometric Variations of the Red Supergiant W Persei

W Persei is a massive, luminous and large red supergiant located relatively nearby. W Persei is a probable SN-II progenitor. We analyzed ~120 yr of photometry from the AAVSO database. The analysis was conducted in the period analysis software Peranso where the CLEANest power spectrum and WWZ-wavelet programs were utilized. Two dominant periods of P = 532 ± 68 days and P = 2922 ± 140 days are found. Intermediate and transitory periods are also uncovered along with period events such as a significant increase in the long-period, period-merging and period-splitting. Using Transiting Exoplanet Survey Satellite observations, stochastic ~0.3-0.8 mmag light variability on timescales of ~0.3 day appears present. The physical causes of these variations is discussed.

Keywords: red supergiant stars
Classical OBe Stars as Post-supernova Runaways: Confirming Binary Origins

Massive binaries play an important role in fields ranging from gravitational-wave astronomy to stellar evolution. We provide several lines of evidence that classical OBe stars in the Small Magellanic Cloud (SMC) obtain their rapid rotation from mass and angular momentum transfer in massive binaries, which predicts that the subsequent supernovae should often eject OBe stars into the field. We find that (1) OBe stars have a higher field frequency than OB stars; (2) our cumulative distribution function (CDF) of stellar distances from O stars shows that OBe stars are indeed much more isolated than ordinary OB stars of corresponding spectral types; (3) the CDFs of OBe stars approach that of high-mass X-ray binaries (HMXBs), which are confirmed post-supernova objects; and (4) Oe stars are as isolated from clusters as Be stars, implying that their final masses are relatively independent of their initial masses, consistent with major mass transfer. Lastly, we also find that the spatial distribution of supergiant OBe stars differs from that of classical OBe stars, consistent with the different mechanisms responsible for their emission-line spectra.

Keywords: be stars; oe stars; core-collapse supernovae; stellar evolutionary models; high mass x-ray binary stars; circumstellar disks; interacting binary stars; multiple star evolution; compact objects; star clusters; small magellanic cloud; runaway stars