adsabs/SciX_UAT_keywords huggingface dataset:
Exploring High-energy Emission from the BL Lacertae Object S5 0716+714 with the Fermi Large Area Telescope

We present the results of an extensive γ-ray data analysis of the emission from the blazar S5 0716+714 with the primary motivation to study its temporal and spectral variability behavior. In this work, we extract a 10 days binned γ-ray light curve from 2008 August 4 to 2016 April 27 in the energy range of 0.1-300 GeV and identify six outburst periods with peak flux of >4 × 10-7 ph cm-2 s-1 from this highly variable source. The brightest flares are identified by zooming in these outburst periods to 1 day binning and using the Bayesian Blocks algorithm. The fastest variability timescale is found to be 1.5 ± 0.3 hr at MJD 57128.01 ± 0.01 with a peak flux above 100 MeV of (26.8 ± 6.9) × 10-7 ph cm-2 s-1. No hint of periodic modulations has been detected for the light curve of S5 0716+714. During the outburst phases, the γ-ray spectrum shows an obvious spectral break with a break energy between 0.93 and 6.90 GeV energies, which may be caused by an intrinsic break in the energy distribution of radiating particles. The five highest-energy photons, with E > 100 GeV, imply that the high-energy emission from this source may originate from a moving emission region in a helical path upstream in the jet. The spectral behavior and temporal characteristics of the individual flares indicate that the location of the emission region lies in the sub-parsec scale (rγ < 0.85 pc).

Keywords: blazars; bl lacertae objects; relativistic jets
White Dwarf Photospheric Abundances in Cataclysmic Variables-II. White Dwarfs with and without a Mask

Taking advantage of the now-available Gaia EDR3 parallaxes, we carry out an archival Hubble Space Telescope (HST) far-ultraviolet spectroscopic analysis of 10 cataclysmic variable systems, including five carefully selected eclipsing systems. We obtain accurate white dwarf (WD) masses and temperatures, in excellent agreement with the masses for four of the eclipsing systems. For three systems in our sample, BD Pav, HS 2214, and TT Crt, we report the first robust masses for their WDs. We modeled the absorption lines to derive the WD chemical abundances and rotational velocities for each of the 10 systems. As expected, for five higher-inclination (i ≳ 75°) systems, the model fits are improved with the inclusion of a cold absorbing slab (a curtain masking the WD) with N H ≈ 1020-1022 cm-2. Modeling of the metal lines in the HST spectra reveals that seven of the 10 systems have significant subsolar carbon abundance, and six have subsolar silicon abundance, thereby providing further evidence that CV WDs exhibit subsolar abundances of carbon and silicon. We suggest that strong aluminum absorption lines (and iron absorption features) in the spectra of some CV WDs (such as IR Com) may be due to the presence of a thin iron curtain (N H ≈ 1019 cm-2) rather than to suprasolar aluminum and iron abundances in the WD photosphere. The derived WD (projected) rotational velocities all fall in the range ≈100-400 km s-1, all sub-Keplerian similar to the values obtained in earlier studies.

Keywords: white dwarf stars; cataclysmic variable stars
SOFIA/HAWC+ Far-infrared Polarimetric Large Area CMZ Exploration Survey. II. Detection of a Magnetized Dust Ring in the Galactic Center

We present the detection of a magnetized dust ring (M0.8–0.2) in the central molecular zone (CMZ) of the Galactic center. The results presented in this paper utilize the first data release of the Far-Infrared Polarimetric Large Area CMZ Emission (FIREPLACE) survey (i.e., Paper I of this series). The FIREPLACE survey is a 214 μm polarimetric survey of the Galactic center using the SOFIA/HAWC+ telescope. The M0.8–0.2 ring is a region of gas and dust that has a circular morphology with a central depression. The dust polarization in the M0.8–0.2 ring implies a curved magnetic field that traces the ring-like structure of the cloud. We posit an interpretation in which an expanding shell compresses and concentrates the ambient gas and magnetic field. We argue that this compression results in strengthening of the magnetic field, as we infer from the observations toward the interior of the ring.

Keywords: dust continuum emission; galactic center; polarimetry; interstellar medium
The Presupernova Core Mass-Radius Relation of Massive Stars: Understanding Its Formation and Evolution

We present a fine grid of solar metallicity models of massive stars (320 in the range 12 ≤ M( ${M}_{\odot }$ ) ≤ 27.95), extending from the main sequence up to the onset of the collapse, in order to quantitatively determine how their compactness ξ2.5, defined by O'Connor & Ott, scales with the carbon-oxygen core mass at the beginning of core collapse. We find a well defined, nonmonotonic (but not scattered) trend of the compactness with the carbon-oxygen core mass that is strictly (and mainly) correlated to the behavior, I.e., birth, growth, and disappearance, of the various carbon convective episodes that follow one another during the advanced evolutionary phases. Though both the mass size of the carbon-oxygen core and the amount of 12C left by the central He burning play a major role in sculpting the final mass-radius relation, it is the abundance of 12C that is ultimately responsible for the final degree of compactness of a star, because it controls the ability of the carbon-burning shell to advance in mass before the final collapse.

Keywords: massive stars; stellar evolution; stellar interiors; core-collapse supernovae
Can Cosmological Simulations Reproduce the Spectroscopically Confirmed Galaxies Seen at z ≥ 10?

Recent photometric detections of extreme (z > 10) redshift galaxies from the JWST have been shown to be in strong tension with existing simulation models for galaxy formation and in the most acute case, in tension with ΛCDM itself. These results, however, all rest on the confirmation of these distances by spectroscopy. Recently, the JADES survey has detected the most distant galaxies with spectroscopically confirmed redshifts, with four galaxies found with redshifts between z = 10.38 and z = 13.2. In this Letter, we compare simulation predictions from four large cosmological volumes and two zoom-in protoclusters with the JADES observations to determine whether these spectroscopically confirmed galaxy detections are in tension with existing models for galaxy formation or with ΛCDM more broadly. We find that existing models for cosmological galaxy formation can generally reproduce the observations for JADES in terms of galaxy stellar masses, star formation rates, and the number density of galaxies at z > 10.

Keywords: astronomical simulations; hydrodynamical simulations; cosmology; galaxy formation; protogalaxies
The Peculiar Variable X-Ray Spectrum of the Active Galactic Nucleus PKS 2005-489

PKS 2005-489 is a well-known, bright southern BL Lac object that has been detected up to TeV energies. In a low-flux state it exhibits the expected multiwavelength double-peaked spectrum in the radio-γ-ray band. The high-flux state shows extreme flux variations in the X-ray band with a hardening as well as a peculiar curved feature in the spectrum. Thus far, PKS 2005-489 is the only source to exhibit such a feature. To study the X-ray variability further, we obtained the first hard X-ray spectrum of the source with the Nuclear Spectroscopic Telescope Array. We compare quasi-simultaneous radio, optical, UV, soft and hard X-ray, and γ-ray data of PKS 2005-489 to archival data in order to study its broadband behavior. We find a very consistent quiet state in the spectral energy distribution, with little variation in spectral shape or flux between the 2012 and 2020 data. A possible explanation for the peculiar X-ray spectrum in the flaring state is an additional component in the jet, possibly accelerated via magnetic reconnection, that is not co-spatial to the low-flux state emission region.

Keywords: active galaxies; active galactic nuclei; bl lacertae objects; jets; radio jets; high energy astrophysics; blazars; x-ray active galactic nuclei
The Physical Properties of Luminous z ≳ 8 Galaxies and Implications for the Cosmic Star Formation Rate Density from 0.35 deg2 of (Pure-)Parallel HST Observations

We present the largest systematic, Hubble Space Telescope (HST)-based search to date for luminous z ≳ 8 galaxy candidates using ~1267 arcmin2 of (pure-)parallel observations from a compilation of 288 random sightlines with Advanced Camera for Surveys and Wide Field Camera 3 observations, derived from the (Super)Brightest of Reionizing Galaxies (SuperBoRG) data set and together representing a factor ~1.12× larger than existing space-based data sets. Using near-infrared (NIR) color cuts and careful photo-z analyses, we find 31 z ≳ 8 galaxy candidates over 29 unique sightlines, and derive global galaxy properties such as UV magnitudes and continuum slopes, sizes, and rest-frame optical properties (e.g., star formation rates (SFRs), stellar masses, A v). Taking advantage of the (pure-)parallel nature of our data set-making it one of the most representative thus far-and derived SFRs, we evaluate the cosmic SFR density for the bright end of the UV luminosity function (LF) at z ~ 8-10 and test the validity of luminosity-function-derived results using a conversion factor. We find that our method yields comparable results to those derived with LFs. Furthermore, we present follow-up observations of five (Super)BoRG targets with the Keck Multi-Object Spectrometer For Infra-Red Exploration (MOSFIRE) instrument, finding no evidence of Lyα in >3 hr of Y-band observations in either, consistent with a largely neutral medium at z ~ 8. Our results offer a definitive HST legacy on the bright end of the LF and provide a valuable benchmark as well as targets for follow-up with the James Webb Space Telescope. *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.

Keywords: early universe; high-redshift galaxies; reionization; star formation
A New Method to Estimate Halo CME Mass Using Synthetic CMEs Based on a Full Ice Cream Cone Model

In this study, we suggest a new method to estimate the mass of a halo coronal mass ejection (CME) using synthetic CMEs. For this, we generate synthetic CMEs based on two assumptions: (1) the CME structure is a full ice cream cone, and (2) the CME electron number density follows a power-law distribution (ρcme = ρ0r-n). The power-law exponent n is obtained by minimizing the rms error between the electron number density distributions of an observed CME and the corresponding synthetic CME at a position angle of the CME leading edge. By applying this methodology to 56 halo CMEs, we estimate two kinds of synthetic CME masses. One is a synthetic CME mass that considers only the observed CME region (Mcme1), the other is a synthetic CME mass that includes both the observed CME region and the occulted area (Mcme2). From these two cases, we derive conversion factors that are the ratio of a synthetic CME mass to an observed CME mass. The conversion factor for Mcme1 ranges from 1.4 to 3.0 and its average is 2.0. For Mcme2, the factor ranges from 1.8 to 5.0 with an average of 3.0. These results imply that the observed halo CME mass can be underestimated by about 2 times when we consider the observed CME region, and about 3 times when we consider the region including the occulted area. Interestingly these conversion factors have a very strong negative correlation with angular widths of halo CMEs.

Keywords: solar coronal mass ejections; solar corona
A Massive, Dusty, HI Absorption-Selected Galaxy at z ≈ 2.46 Identified in a CO Emission Survey

We report a NOrthern Extended Millimeter Array (NOEMA) and Atacama Large Millimeter/submillimeter Array search for redshifted CO emission from the galaxies associated with seven high-metallicity ([M/H] ≥ -1.03) damped Lyα absorbers (DLAs) at z ≈ 1.64-2.51. Our observations yielded one new detection of CO(3-2) emission from a galaxy at z = 2.4604 using NOEMA, associated with the z = 2.4628 DLA toward QSO B0201+365. Including previous searches, our search results in detection rates of CO emission of $\approx {56}_{-24}^{+38}$ % and $\approx {11}_{-9}^{+26}$ %, respectively, in the fields of DLAs with [M/H] > -0.3 and [M/H] < -0.3. Further, the HI-selected galaxies associated with five DLAs with [M/H] > -0.3 all have high molecular gas masses, ≳5 × 1010 M ⊙. This indicates that the highest-metallicity DLAs at z ≈ 2 are associated with the most massive galaxies. The newly identified z ≈ 2.4604 HI-selected galaxy, DLA0201+365g, has an impact parameter of ≈7 kpc to the QSO sightline, and an implied molecular gas mass of (5.04 ± 0.78) × 1010 × (α CO/4.36) × (r 31/0.55) M ⊙. Archival Hubble Space Telescope Wide Field and Planetary Camera 2 imaging covering the rest-frame near-ultraviolet (NUV) and far-ultraviolet (FUV) emission from this galaxy yield nondetections of rest-frame NUV and FUV emission, and a 5σ upper limit of 2.3 M ⊙ yr-1 on the unobscured star formation rate (SFR). The low NUV-based SFR estimate, despite the very high molecular gas mass, indicates that DLA0201+365g either is a very dusty galaxy, or has a molecular gas depletion time that is around 2 orders of magnitude larger than that of star-forming galaxies at similar redshifts.

Keywords: high-redshift galaxies; damped lyman-alpha systems; co line emission
Evidence that 1I/2017 U1 ('Oumuamua) was Composed of Molecular Hydrogen Ice

'Oumuamua (I1 2017) was the first macroscopic (l ∼ 100 m) body observed to traverse the inner solar system on an unbound hyperbolic orbit. Its light curve displayed strong periodic variation, and it showed no hint of a coma or emission from molecular outgassing. Astrometric measurements indicate that 'Oumuamua experienced nongravitational acceleration on its outbound trajectory, but energy balance arguments indicate this acceleration is inconsistent with a water ice sublimation-driven jet of the type exhibited by solar system comets. We show that all of 'Oumaumua's observed properties can be explained if it contained a significant fraction of molecular hydrogen (H2) ice. H2 sublimation at a rate proportional to the incident solar flux generates a surface-covering jet that reproduces the observed acceleration. Mass wasting from sublimation leads to monotonic increase in the body axis ratio, explaining 'Oumuamua's shape. Back-tracing 'Oumuamua's trajectory through the solar system permits calculation of its mass and aspect ratio prior to encountering the Sun. We show that H2-rich bodies plausibly form in the coldest dense cores of giant molecular clouds, where number densities are of order n ∼ 105, and temperatures approach the T = 3 K background. Post-formation exposure to galactic cosmic rays implies a τ ∼ 100 Myr age, explaining the kinematics of 'Oumuamua's inbound trajectory.

Keywords: interstellar medium; small solar system bodies
Large-scale Effect of an Accretion Burst in the High-Mass Young Stellar Object G358.93-0.03-MM1

The high-mass young stellar object G358.93-0.03-MM1 underwent a rapid accretion burst event from 2019 January to June, resulting in flares observed in most class II methanol maser transitions starting in mid-January. In contrast, the 22.235 GHz water maser flare started in mid-April. To investigate the physical origin of this significant difference, we made the Karl G. Jansky Very Large Array observations toward the G358.93-0.03 region on 2019 March 23 and April 4 and obtained the intensity and spatial distribution images of the water maser as well as the continuum emissions at Ku and K bands on the epoch close to the water maser flare. A comparative analysis, incorporating previously reported detections in February (pre-water maser flare) and June (post-water maser flare), reveals the time lag between the accretion burst and water maser flare. These observations confirm the variations of the propagation speed of a heatwave induced by the accretion burst in different directions: the heatwave is decelerated in dense regions (e.g., the disk and jet), whereas in directions from G358-MM1 to water maser components, the heatwave speed is supposed to be close to the speed of light. Variations in flux density and spatial positions were detected for water masers and continuum emissions, indicating that the accretion burst event originating from G358-MM1 affects not only the immediate environment within a dense structure of 0.″2 (1400 au at a source distance of 6.75 kpc) around MM1 itself, but also exerts influence on broader-scale regions extending up to approximately 3″ (21,000 au).

Keywords: star forming regions; astrophysical masers; accretion; burst astrophysics
Re-evaluation of Cosmogenic 10Be Dating of the Ferromanganese Crust VA13/2 Archiving Interstellar Radionuclides on Earth

Interstellar radionuclides, such as 60Fe, are produced in massive stars, ejected by supernovae and can be recovered in geological archives on Earth. Ferromanganese encrustations on the bottom of Earth's major oceans represent one important geological archive with a time-record of interstellar radionuclides. The paper of Segl et al. provided the first cosmogenic 10Be dating of the ferromanganese crust VA13/2 in which interstellar 60Fe was discovered. After re-evaluation and comparison with other published and recently acquired data of the same crust, we conclude that the calculated 10Be/9Be data set is wrong by a factor of 9 due to a mathematical lapse. In addition, the ordinate of the corresponding 10Be/9Be graph is in discrepancy with the given data. The updated data set is now in agreement with recently published and acquired data.

Keywords: cosmic ray nucleosynthesis
Measuring the Metallicity of Early-type Galaxies. I. Composite Region

We present the data of 9739 early-type galaxies (ETGs), cross-matching Galaxy Zoo 1 with our sample selected from the catalog of the Sloan Digital Sky Survey Data Release 7 of MPA-JHU emission-line measurements. We first investigate the divisor between ETGs with and without star formation (SF), and find the best separator of W2-W3 = 2.0 is added. We explore the ETG sample by refusing a variety of ionization sources, and derive 5376 ETGs with SF by utilizing a diagnostic tool of the division line of W2-W3 = 2.0. We measure their metallicities with four abundance calibrators. We find that our composite ETG sample has similar distributions of M* and star formation rate as star-forming galaxies (SFGs) do, that most of them lie on the "main sequence," and that our fit is a slightly steeper slope than that derived in Renzini & Peng. Compared with the distributions between different metallicities calibrated by four abundance indicators, we find that the Curti17 method is the most accurate calibrator for composite ETGs among the four abundance indicators. We present a weak positive correlation of SFR and metallicity only when the metallicity is calibrated by the PP04, Curti17, and T04 indicators. The correlation is not consistent with the negative correlation of both parameters in SFGs. We suggest that the weak correlation is due to the dilution effect of gas inflow driven by minor mergers.

Keywords: early-type galaxies; galaxy abundances; galaxy evolution
Investigating the Narrow-line Region Dynamics in Nearby Active Galaxies

We present dynamical models of the narrow-line region (NLR) outflows in the nearby Seyfert galaxies Mrk 3, Mrk 78, NGC 1068, and NGC 4151 using observations from the Hubble Space Telescope and Apache Point Observatory. We employ long-slit spectroscopy to map the spatially resolved outflow and rotational velocities of the ionized gas. We also perform surface brightness decompositions of host galaxy images to constrain the enclosed stellar mass distributions as functions of distance from the supermassive black holes (SMBHs). Assuming that the NLR gas is accelerated by active galactic nuclei (AGN) radiation pressure, and subsequently decelerated by the host galaxy and SMBH gravitational potentials, we derive outflow velocity profiles where the gas is launched in situ at multiple distances from the SMBH. We find a strong correlation between the turnover (from acceleration to deceleration) radii from our models, with the turnovers seen in the observed velocities and spatially resolved mass outflow rates for the AGN with bolometric luminosities > 1044 erg s-1. This consistency indicates that radiation pressure is the dominant driving mechanism behind the NLR outflows in these moderate-luminosity AGNs, with a force multiplier ~500 yielding the best agreement between the modeled and observed turnover radii. However, in Meena et al. we found that this trend may not hold at lower luminosities, where our modeled turnover distance for NGC 4051 is much smaller than in the observed kinematics. This result may indicate that either additional force(s) are responsible for accelerating the NLR outflows in low-luminosity AGNs, or higher spatial resolution observations are required to quantify their turnover radii.

Keywords: active galactic nuclei; agn host galaxies; seyfert galaxies; emission line galaxies; galaxy winds; galaxy kinematics; galaxy mass distribution; galaxy rotation curves; supermassive black holes
Evolution of X-Ray Activity in <25 Myr Old Pre-main Sequence Stars

Measuring the evolution of X-ray emission from pre-main-sequence (PMS) stars gives insight into two issues: the response of magnetic dynamo processes to changes in the interior structure, and the effects of high-energy radiation on protoplanetary disks and primordial planetary atmospheres. We present a sample of 6003 stars with ages 7-25 Myr in 10 nearby open clusters from Chandra X-ray and Gaia-EDR3 surveys. Combined with previous results in large samples of younger (≲5 Myr) stars in MYStIX and SFiNCs star-forming regions, mass-stratified activity-age relations are derived for the early phases of stellar evolution. X-ray luminosity (L X ) is constant during the first few Myr, possibly due to the presence of extended X-ray coronas insensitive to temporal changes in stellar size. L X then decays during the 7-25 Myr period, more rapidly as stellar mass increases. This decay is interpreted as decreasing efficiency of the α 2 dynamo as radiative cores grow and a solar-type αΩ dynamo emerges. For more massive 3.5-7 M ⊙ fully radiative stars, the X-ray emission plummets-indicating the lack of an effective magnetic dynamo. The findings provide improved measurements of high-energy radiation effects on circumstellar material, first for the protoplanetary disk and then for the atmospheres of young planets. The observed X-ray luminosities can be so high that an inner Earth-mass rocky, unmagnetized planet around a solar-mass PMS star might lose its primary and secondary atmospheres within a few (several) million years. PMS X-ray emission may thus have a significant impact on the evolution of early-planetary atmospheres and the conditions promoting the rise of habitability.

Keywords: pre-main sequence stars; planetary atmospheres; protoplanetary disks; stellar x-ray flares; single x-ray stars; x-ray stars