bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reinvestigation of the Multiepoch Direct Detections of HD 88133 b and Upsilon Andromedae b
Authors: Buzard Cam , Piskorz Danielle , Lockwood Alexandra C. , Blake Geoffrey , Barman Travis S. , Benneke Björn , Bender Chad F. , Carr John S. 
Published: November 2021

Abstract
We reanalyze the multiepoch direct detections of HD 88133 b and ups And b that were published in Piskorz et al. (2016) and Piskorz et al. (2017), respectively. Using simulations to attempt to reproduce the detections, we find that with the six and seven L-band Keck/NIRSPEC epochs analyzed in the original works, the planets would not have been detectable unless they had unreasonably large radii. HD88133 and ups And both have fairly large stellar radii, which contributed to the difficulty in detecting the planets. We take this opportunity to consider how these planets may have been detectable with the small number of epochs originally presented by running simulations both with the upgraded NIRSPEC instrument and with near-zero primary velocities, as recommended by Buzard et al. (2021). While seven L-band NIRSPEC2.0 epochs with near-zero primary velocities would have allowed a strong (10.8σ) detection of ups And b, many more than six L-band epochs would have been required for a strong detection of HD88133b, which could be due in part to both this system’s large stellar radius and low stellar temperature. This work stresses the importance of careful analytic procedures and the usefulness of simulations in understanding the expected sensitivity of high-resolution spectroscopic data.
The Magnetic Mechanism for Hotspot Reversals in Hot Jupiter Atmospheres
Authors: Hindle A. W. , Bushby P. J. , Rogers T. M. 
Published: November 2021

Abstract
Magnetically driven hotspot variations (which are tied to atmospheric wind variations) in hot Jupiters are studied using nonlinear numerical simulations of a shallow-water magnetohydrodynamic (SWMHD) system and a linear analysis of equatorial SWMHD waves. In hydrodynamic models, mid-to-high-latitude geostrophic circulations are known to cause a net west-to-east equatorial thermal energy transfer, which drives hotspot offsets eastward. We find that a strong toroidal magnetic field can obstruct these energy transporting circulations. This results in winds aligning with the magnetic field and generates westward Lorentz force accelerations in hotspot regions, ultimately causing westward hotspot offsets. In the subsequent linear analysis we find that this reversal mechanism has an equatorial wave analogy in terms of the planetary-scale equatorial magneto-Rossby waves. We compare our findings to three-dimensional MHD simulations, both quantitatively and qualitatively, identifying the link between the mechanics of magnetically driven hotspot and wind reversals. We use the developed theory to identify physically motivated reversal criteria, which can be used to place constraints on the magnetic fields of ultra-hot Jupiters with observed westward hotspots.
Forced Linear Shear Flows with Rotation: Rotating Couette–Poiseuille Flow, Its Stability, and Astrophysical Implications
Authors: Ghosh Subham , Mukhopadhyay Banibrata 
Published: November 2021

Abstract
We explore the effect of forcing on the linear shear flow or plane Couette flow, which is also the background flow in the very small region of the Keplerian accretion disk. We show that depending on the strength of forcing and boundary conditions suitable for the systems under consideration, the background plane shear flow, and hence the accretion disk velocity profile, is modified into parabolic flow, which is a plane Poiseuille flow or Couette–Poiseuille flow, depending on the frame of reference. In the presence of rotation, the plane Poiseuille flow becomes unstable at a smaller Reynolds number under pure vertical as well as three-dimensional perturbations. Hence, while rotation stabilizes the plane Couette flow, the same destabilizes the plane Poiseuille flow faster and hence the forced local accretion disk. Depending on the various factors, when the local linear shear flow becomes a Poiseuille flow in the shearing box due to the presence of extra force, the flow becomes unstable even for Keplerian rotation, and hence turbulence will ensue. This helps to resolve the long-standing problem of subcritical transition to turbulence in hydrodynamic accretion disks and the laboratory plane Couette flow.
A Catalog of Host Galaxies for WISE-selected AGN: Connecting Host Properties with Nuclear Activity and Identifying Contaminants
Authors: Barrows R. Scott , Comerford Julia M. , Stern Daniel , Assef Roberto J. 
Published: November 2021

Abstract
We present a catalog of physical properties for galaxies hosting active galactic nuclei (AGN) detected by the Wide-field Infrared Survey Explorer (WISE). By fitting broadband spectral energy distributions of sources in the WISE AGN Catalog with empirical galaxy and AGN templates, we derive photometric redshifts, AGN bolometric luminosities, measures of AGN obscuration, host galaxy stellar masses, and host galaxy star formation rates (SFRs) for 695,273 WISE AGN. The wide-area nature of this catalog significantly augments the known number of obscured AGN out to redshifts z ∼ 3 and will be useful for studies focused on AGN or their host galaxy physical properties. We first show that the most likely non-AGN contaminants are galaxies at redshifts z = 0.2–0.3, with relatively blue W1–W2 colors, and with high specific SFRs for which the dust continuum emission is elevated in the W2 filter. Toward increasingly lower redshifts, WISE AGN host galaxies have systematically lower specific SFRs relative to those of normal star-forming galaxies, likely due to decreased cold gas fractions and the time delay between global star formation and AGN triggering. Finally, WISE AGN obscuration is not strongly correlated with AGN bolometric luminosity but shows a significant negative correlation with the Eddington ratio. This result is consistent with a version of the receding torus model in which the obscuring material is located within the supermassive black hole gravitational sphere of influence and the dust inner radius increases due to radiation pressure.
Characterizing Extreme Emission-line Galaxies. I. A Four-zone Ionization Model for Very High-ionization Emission*
Authors: Berg Danielle A. , Chisholm John , Erb Dawn K. , Skillman Evan D. , Pogge Richard W. , Olivier Grace M. 
Published: November 2021

Abstract
Stellar population models produce radiation fields that ionize oxygen up to O+2, defining the limit of standard H ii region models (<54.9 eV). Yet, some extreme emission-line galaxies, or EELGs, have surprisingly strong emission originating from much higher ionization potentials. We present UV HST/COS and optical LBT/MODS spectra of two nearby EELGs that have very high-ionization emission lines (e.g., He ii
λλ1640,4686 C iv
λλ1548,1550, [Fe v]λ4227, [Ar iv]λλ4711,4740). We define a four-zone ionization model that is augmented by a very high-ionization zone, as characterized by He+2 (>54.4 eV). The four-zone model has little to no effect on the measured total nebular abundances, but does change the interpretation of other EELG properties: we measure steeper central ionization gradients; higher volume-averaged ionization parameters; and higher central T

e
, n

e
, and log U values. Traditional three-zone estimates of the ionization parameter can underestimate the average log U by up to 0.5 dex. Additionally, we find a model-independent dichotomy in the abundance patterns, where the α/H abundances are consistent but N/H, C/H, and Fe/H are relatively deficient, suggesting these EELGs are α/Fe-enriched by more than three times. However, there still is a high-energy ionizing photon production problem (HEIP3). Even for such α/Fe enrichment and very high log U s, photoionization models cannot reproduce the very high-ionization emission lines observed in EELGs.
Testing Evolutionary Models with Red Supergiant and Wolf–Rayet Populations
Authors: Massey Philip , Neugent Kathryn F. , Dorn-Wallenstein Trevor Z. , Eldridge J. J. , Stanway E. R. , Levesque Emily M. 
Published: November 2021

Abstract
Despite the many successes that modern massive star evolutionary theory has enjoyed, reproducing the apparent trend in the relative number of red supergiants (RSGs) and Wolf–Rayet (WR) stars has remained elusive. Previous estimates show the RSG/WR ratio decreasing strongly with increasing metallicity. However, the evolutionary models have always predicted a relatively flat distribution for the RSG/WR ratio. In this paper we reexamine this issue, drawing on recent surveys for RSGs and WRs in the Magellanic Clouds, M31, and M33. The RSG surveys have used Gaia astrometry to eliminate foreground contamination and have separated RSGs from asymptotic giant branch stars using near-infrared colors. The surveys for WRs have utilized interference-filter imaging, photometry, and image subtraction techniques to identify candidates, which have then been confirmed spectroscopically. After carefully matching the observational criteria to the models, we now find good agreement in both the single-star Geneva and binary BPASS models with the new observations. The agreement is better when we shift the RSG effective temperatures derived from J − Ks photometry downwards by 200 K in order to agree with the Levesque TiO effective temperature scale. In an appendix we also present a source list of RSGs for the SMC which includes effective temperatures and luminosities derived from near-infrared 2MASS photometry, in the same manner as used for the other galaxies.
Daily Variations of Plasma Density in the Solar Streamer Belt
Authors: Morgan Huw 
Published: November 2021

Abstract
Improved space weather diagnostics depend critically on improving our understanding of the evolution of the slow solar wind in the streamer belts near the Sun. Recent innovations in tomography techniques are opening a new window on this complex environment. In this work, a new time-dependent technique is applied to COR2A/Solar Terrestrial Relations Observatory observations from a period near solar minimum (2018 November 11) for heliocentric distances of 4–8 R
⊙. For the first time, we find density variations of large amplitude throughout the quiescent streamer belt, ranging between 50% and 150% of the mean density, on timescales of tens of hours to days. Good agreement is found with Parker Solar Probe measurements at perihelion; thus, the variations revealed by tomography must form a major component of the slow solar wind variability, distinct from coronal mass ejections or smaller transients. A comparison of time series at different heights reveals a consistent time lag, so that changes at 4 R
⊙ occur later at increasing height, corresponding to an outward propagation speed of around 100 km s−1. This speed may correspond to either the plasma sound speed or the bulk outflow speed depending on an important question: are the density variations caused by the spatial movement of a narrow streamer belt (moving magnetic field, constant plasma density), or changes in plasma density within a nonmoving streamer belt (rigid magnetic field, variable density), or a combination of both?
Coherent Emission in Pulsars, Magnetars, and Fast Radio Bursts: Reconnection-driven Free Electron Laser
Authors: Lyutikov Maxim 
Published: November 2021

Abstract
We develop a model of the generation of coherent radio emission in the Crab pulsar, magnetars, and fast radio bursts (FRBs). Emission is produced by a reconnection-generated beam of particles via a variant of the free electron laser mechanism, operating in a weakly turbulent, guide field-dominated plasma. We first consider nonlinear Thomson scattering in a guide field-dominated regime, and apply it to explain emission bands observed in Crab pulsar and in FRBs. We consider particle motion in a combined field of the electromagnetic wave and the electromagnetic (Alfvénic) wiggler. Charge bunches, created via a ponderomotive force, Compton/Raman scatter the wiggler field coherently. The model is both robust to the underlying plasma parameters and succeeds in reproducing a number of subtle observed features: (i) emission frequencies depend mostly on the scale λ

t
of turbulent fluctuations and the Lorentz factor of the reconnection-generated beam,

ω
∼

γ

b

2

(
c

/

λ

t

)

—it is independent of the absolute value of the underlying magnetic field. (ii) The model explains both broadband emission and the presence of emission stripes, including multiple stripes observed in the high frequency interpulse of the Crab pulsar. (iii) The model reproduces correlated polarization properties: the presence of narrow emission bands in the spectrum favors linear polarization, while broadband emission can have an arbitrary polarization. (iv) The mechanism is robust to the momentum spread of the particle in the beam. We also discuss a model of wigglers as nonlinear force-free Alfvén solitons (light darts).
Partial, Zombie, and Full Tidal Disruption of Stars by Supermassive Black Holes
Authors: Nixon C. J. , Coughlin Eric R. , Miles Patrick R. 
Published: November 2021

Abstract
We present long-duration numerical simulations of the tidal disruption of stars modeled with accurate stellar structures and spanning a range of pericenter distances, corresponding to cases where the stars are partially and completely disrupted. We substantiate the prediction that the late-time power-law index of the fallback rate n
∞ ≃ −5/3 for full disruptions, while for partial disruptions—in which the central part of the star survives the tidal encounter intact—we show that n
∞ ≃ −9/4. For the subset of simulations where the pericenter distance is close to that which delineates full from partial disruption, we find that a stellar core can reform after the star has been completely destroyed; for these events the energy of the zombie core is slightly positive, which results in late-time evolution from n ≃ −9/4 to n ≃ −5/3. We find that self-gravity can generate an n(t) that deviates from n
∞ by a small but significant amount for several years post-disruption. In one specific case with the stellar pericenter near the critical value, we find that self-gravity also drives the recollapse of the central regions of the debris stream into a collection of several cores while the rest of the stream remains relatively smooth. We also show that it is possible for the surviving stellar core in a partial disruption to acquire a circumstellar disk that is shed from the rapidly rotating core. Finally, we provide a novel analytical fitting function for the fallback rates that may also be useful in a range of contexts beyond tidal disruption events.
Modeling the Unresolved NIR–MIR SEDs of Local (z < 0.1) QSOs
Authors: Martínez-Paredes M. , González-Martín O. , HyeongHan K. , Geier S. , García-Bernete I. , Ramos Almeida C. , Alonso-Herrero A. , Aretxaga I. , Kim M. , Sohn B. W. , Masegosa J. 
Published: November 2021

Abstract
To study the nuclear (≲1 kpc) dust of nearby (z < 0.1) quasi-stellar objects (QSOs), we obtained new near-infrared (NIR) high angular resolution (∼0.″3) photometry in the H and Ks bands for 13 QSOs with available mid-infrared (MIR) high angular resolution spectroscopy (∼7.5–13.5 μm). We find that in most QSOs, the NIR emission is unresolved. We subtract the contribution from the accretion disk, which decreases from NIR (∼35%) to MIR (∼2.4%). We also estimate these percentages assuming a bluer accretion disk and find that the contribution in the MIR is nearly seven times larger. We find that the majority of objects (64%, 9/13) are better fitted by the disk+wind H17 model, while others can be fitted by the smooth F06 (14%, 2/13), clumpy N08 (7%, 1/13), clumpy H10 (7%, 1/13), and two-phase media S16 (7%, 1/13) models. However, if we assume the bluer accretion disk, the models fit only 2/13 objects. We measured two NIR-to-MIR spectral indexes, α
NIR−MIR(1.6–8.7 μm) and α
NIR−MIR(2.2–8.7 μm), and two MIR spectral indexes, α
MIR(7.8–9.8 μm) and α
MIR(9.8–11.7 μm), from models and observations. From observations, we find that the NIR-to-MIR spectral indexes are ∼−1.1, and the MIR spectral indexes are ∼−0.3. Comparing the synthetic and observed values, we find that none of the models simultaneously match the measured NIR-to-MIR and 7.8–9.8 μm slopes. However, we note that measuring α
MIR(7.8–9.8 μm) on the starburst-subtracted Spitzer/IRS spectrum gives values of the slopes (∼−2) that are similar to the synthetic values obtained from the models.
Physical Drivers of Emission-line Diversity of SDSS Seyfert 2s and LINERs after Removal of Contributions from Star Formation
Authors: Agostino Christopher J. , Salim Samir , Faber S. M. , Juneau Stéphanie , Koo David C. , Tang Yimeng , Luo Yifei , Quiros Sofia , Zhao Pin-Song 
Published: November 2021

Abstract
Ionization sources other than H ii regions give rise to the right-hand branch in the standard ([N ii]) BPT diagram, populated by Seyfert 2s and LINERs. However, because the majority of Seyfert/LINER hosts are star-forming (SF), H ii regions contaminate the observed lines to some extent, making it unclear if the position along the branch is merely due to various degrees of mixing between pure Seyferts/LINERs and SF, or whether it reflects the intrinsic diversity of Seyfert/LINER ionizing sources. In this study, we empirically remove SF contributions in ∼100,000 Seyferts/LINERs from SDSS using the doppelganger method. We find that mixing is not the principal cause of the extended morphology of the observed branch. Rather, Seyferts/LINERs intrinsically have a wide range of line ratios. Variations in ionization parameter and metallicity can account for much of the diversity of Seyfert/LINER line ratios, but the hardness of the ionization field also varies significantly. Furthermore, our k-means classification on seven decontaminated emission lines reveals that LINERs are made up of two populations, which we call soft and hard LINERs. The Seyfert 2s differ from both types of LINERs primarily by higher ionization parameter, whereas the two LINER types mainly differ from each other (and from star-forming regions) in the hardness of the radiation field. We confirm that the [N ii] BPT diagram more efficiently identifies LINERs than [S ii] and [O i] diagnostics, because in the latter many LINERs, especially soft ones, occupy the same location as pure starformers, even after the SF has been removed from LINER emission.
Formation of Phosphorus Monoxide (PO) in the Interstellar Medium: Insights from Quantum-chemical and Kinetic Calculations
Authors: García de la Concepción Juan , Puzzarini Cristina , Barone Vincenzo , Jiménez-Serra Izaskun , Roncero Octavio 
Published: November 2021

Abstract
In recent years, phosphorus monoxide (PO), an important molecule for prebiotic chemistry, has been detected in star-forming regions and in the comet 67P/Churyumov-Gerasimenko. These studies have revealed that, in the interstellar medium (ISM), PO is systematically the most abundant P-bearing species, with abundances that are about one to three times greater than those derived for phosphorus nitride (PN), the second-most abundant P-containing molecule. The reason why PO is more abundant than PN remains still unclear. Experimental studies with phosphorus in the gas phase are not available, probably because of the difficulties in dealing with its compounds. Therefore, the reactivity of atomic phosphorus needs to be investigated using reliable computational tools. To this end, state-of-the-art quantum-chemical computations have been employed to evaluate accurate reaction rates and branching ratios for the P + OH → PO + H and P + H2O → PO + H2 reactions in the framework of a master equation approach based on ab initio transition state theory. The hypothesis that OH and H2O can be potential oxidizing agents of atomic phosphorus is based on the ubiquitous presence of H2O in the ISM. Its destruction then produces OH, which is another very abundant species. While the reaction of atomic phosphorus in its ground state with water is not a relevant source of PO because of emerged energy barriers, the P + OH reaction represents an important formation route of PO in the ISM. Our kinetic results show that this reaction follows an Arrhenius–Kooij behavior, and thus its rate coefficients (α = 2.28 × 10−10 cm3 molecule−1 s−1, β = 0.16 and γ = 0.37 K) increase by increasing the temperature.
First HETDEX Spectroscopic Determinations of Lyα and UV Luminosity Functions at z = 2–3: Bridging a Gap between Faint AGNs and Bright Galaxies
Authors: Zhang Yechi , Ouchi Masami , Gebhardt Karl , Mentuch Cooper Erin , Liu Chenxu , Davis Dustin , Jeong Donghui , Farrow Daniel J. , Finkelstein Steven L. , Gawiser Eric , Hill Gary J. , Harikane Yuichi , Kakuma Ryota , Acquaviva Viviana , Casey Caitlin M. , Fabricius Maximilian , Hopp Ulrich , Jarvis Matt J. , Landriau Martin , Mawatari Ken , Mukae Shiro , Ono Yoshiaki , Sakai Nao , Schneider Donald P. 
Published: November 2021

Abstract
We present Lyα and ultraviolet (UV)-continuum luminosity functions (LFs) of galaxies and active galactic nuclei (AGNs) at z = 2.0–3.5 determined by the untargeted optical spectroscopic survey of the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). We combine deep Subaru imaging with HETDEX spectra resulting in 11.4 deg2 of fiber spectra sky coverage, obtaining 18,320 galaxies spectroscopically identified with Lyα emission, 2126 of which host type 1 AGNs showing broad (FWHM > 1000 km s−1) Lyα emission lines. We derive the Lyα (UV) LF over 2 orders of magnitude covering bright galaxies and AGNs in

log

L

Ly
α

/

[
erg

s

−
1

]
=
43.3
–
45.5

(−27 < M
UV < −20) by the 1/V
max estimator. Our results reveal that the bright-end hump of the Lyα LF is composed of type 1 AGNs. In conjunction with previous spectroscopic results at the faint end, we measure a slope of the best-fit Schechter function to be

α

Sch

=
−

1.70

−
0.14

+
0.13

, which indicates that α
Sch steepens from z = 2–3 toward high redshift. Our UV LF agrees well with previous AGN UV LFs and extends to faint-AGN and bright-galaxy regimes. The number fraction of Lyα-emitting objects (X
LAE) increases from

M

UV

*

∼
−
21

to bright magnitude due to the contribution of type 1 AGNs, while previous studies claim that X
Lyα
decreases from faint magnitudes to

M

UV

*

, suggesting a valley in the X
Lyα
–magnitude relation at

M

UV

*

. Comparing our UV LF of type 1 AGNs at z = 2–3 with those at z = 0, we find that the number density of faint (M
UV > −21) type 1 AGNs increases from z ∼ 2 to 0, as opposed to the evolution of bright (M
UV < −21) type 1 AGNs, suggesting AGN downsizing in the rest-frame UV luminosity.
Compton-Thick AGN in the NuSTAR ERA VII. A joint NuSTAR, Chandra, and XMM-Newton Analysis of Two Nearby, Heavily Obscured Sources
Authors: Traina A. , Marchesi S. , Vignali C. , Torres-Albà N. , Ajello M. , Pizzetti A. , Silver R. , Zhao X. , Ananna T. , Baloković M. , Boorman P. , Gandhi P. , Gilli R. , Lanzuisi G. 
Published: November 2021

Abstract
We present the joint Chandra, XMM-Newton, and NuSTAR analysis of two nearby Seyfert galaxies, NGC 3081 and ESO 565-G019. These are the only two having Chandra data in a larger sample of 10 low-redshift (z ≤ 0.05), candidates Compton-thick (CT) Active Galactic Nuclei selected in the 15–150 keV band with Swift-BAT that were still lacking NuSTAR data. Our spectral analysis, performed using physically motivated models, provides an estimate of both the line-of-sight (l.o.s.) and average (N
H,S
) column densities of the two torii. NGC 3081 has a Compton-thin l.o.s. column density N
H,z
= [0.58–0.62] × 1024 cm−2, but the N
H,S
, beyond the CT threshold (N
H,S
= [1.41–1.78] × 1024 cm−2), suggests a “patchy” scenario for the distribution of the circumnuclear matter. ESO 565-G019 has both CT l.o.s. and N
H,S
column densities (N
H,z
> 2.31 × 1024 cm−2 and N
H,S
> 2.57 × 1024 cm−2, respectively). The use of physically motivated models, coupled with the broad energy range covered by the data (0.6–70 keV and 0.6–40 keV, for NGC 3081 and ESO 565-G019, respectively) allows us to constrain the covering factor of the obscuring material, which is C
TOR = [0.63–0.82] for NGC 3081, and C
TOR = [0.39–0.65] for ESO 565-G019.