bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for Two Distinct Broad-line Regions from Reverberation Mapping of PG 0026+129
Authors: Hu Chen , Li Sha-Sha , Guo Wei-Jian , Yang Sen , Yang Zi-Xu , Bao Dong-Wei , Jiang Bo-Wei , Du Pu , Li Yan-Rong , Xiao Ming , Songsheng Yu-Yang , Yu Zhe , Bai Jin-Ming , Ho Luis C. , Bian Wei-Hao , Brotherton Michael S. , Yuan Ye-Fei , Aceituno Jesús , Winkler Hartmut , Wang Jian-Min ,   (SEAMBH collaboration)
Published: December 2020

Abstract
We report on the results of a new spectroscopic monitoring campaign of the quasar PG 0026+129 at the Calar Alto Observatory 2.2 m telescope from 2017 July to 2020 February. Significant variations in the fluxes of the continuum and broad emission lines, including Hβ and He ii, were observed in the first and third years, and clear time lags between them are measured. The broad Hβ line profile consists of two Gaussian components: an intermediate-width H

with an FWHM of 1964 ± 18

and another very broad H

with an FWHM of 7570 ± 83

. H

has long time lags of ∼40–60 days in the rest frame, while H

shows nearly zero time delay with respect to the optical continuum at 5100 Å. The velocity-resolved delays show consistent results: lags of ∼30–50 days at the core of the broad Hβ line and roughly zero lags at the wings. H

has a redshift of ∼400

, which seems to be stable for nearly 30 yr by comparing with archived spectra, and may originate from an infall. The rms spectrum of H

shows a double-peaked profile with brighter blue peak and extended red wing in the first year, which matches the signature of a thin disk. Both the double-peaked profile and the near-zero lag suggest that H

comes from a region associated with the part of the accretion disk that emits the optical continuum. Adopting the FWHM (in the rms spectrum) and the time lag measured for the total Hβ line, and a virial factor of 1.5, we obtain a virial mass of

for the central black hole in this quasar.
Biconical-dominated Accretion Flow onto Seed Black Holes in a Hyperaccretion Regime
Authors: Park KwangHo , Wise John H. , Bogdanović Tamara , Ricotti Massimo 
Published: December 2020

Abstract
Hyperaccretion occurs when the gas inflow rate onto a black hole (BH) is so high that the radiative feedback cannot reverse the accretion flow. This extreme process is a promising mechanism for the rapid growth of seed BHs in the early universe, which can explain high-redshift quasars powered by billion solar mass BHs. In theoretical models, spherical symmetry is commonly adopted for hyperaccretion flows; however, the sustainability of such structures on timescales corresponding to the BH growth has not been addressed yet. Here we show that stochastic interactions between the ionizing radiation from the BH and nonuniform accretion flow can lead to the formation of a rotating gas disk around the BH. Once the disk forms, the supply of gas to the BH preferentially occurs via biconical-dominated accretion flow perpendicular to the disk, avoiding the centrifugal barrier of the disk. Biconical dominated accretion flows from opposite directions collide in the vicinity of the BH supplying high-density, low angular momentum gas to the BH, whereas most of the gas with nonnegligible angular momentum is deflected to the rotationally supported outflowing decretion disk. The disk becomes reinforced progressively as more mass from the biconical flow transfers to the disk and some of the outflowing gas from the disk is redirected to the biconical accretion funnels through a meridional structure. This axisymmetric hydrodynamic structure of a biconical-dominated accretion flow and decretion disk continues to provide uninterrupted flow of high-density gas to the BH.
ZTF20aajnksq (AT 2020blt): A Fast Optical Transient at z ≈ 2.9 with No Detected Gamma-Ray Burst Counterpart
Authors: Ho Anna Y. Q. , Perley Daniel A. , Beniamini Paz , Cenko S. Bradley , Kulkarni S. R. , Andreoni Igor , Singer Leo P. , De Kishalay , Kasliwal Mansi M. , Fremling Christoffer , Bellm Eric C. , Dekany Richard , Delacroix Alexandre , Duev Dmitry A. , Goldstein Daniel A. , Golkhou V. Zach , Goobar Ariel , Graham Matthew J. , Hale David , Kupfer Thomas , Laher Russ R. , Masci Frank J. , Miller Adam A. , Neill James D. , Riddle Reed , Rusholme Ben , Shupe David L. , Smith Roger , Sollerman Jesper , van Roestel Jan 
Published: December 2020

Abstract
We present ZTF20aajnksq (AT 2020blt), a fast-fading (Δr = 2.3 mag in Δt = 1.3 days) red (g − r ≈ 0.6 mag) and luminous (M
1626 Å = −25.9 mag) optical transient at z = 2.9 discovered by the Zwicky Transient Facility (ZTF). AT 2020blt shares several features in common with afterglows to long-duration gamma-ray bursts (GRBs): (1) an optical light curve well-described by a broken power law with a break at t
j = 1 d (observer frame); (2) a luminous (L
0.3–10 KeV = 1046 erg s−1) X-ray counterpart; and (3) luminous (L
10 GHz = 4 × 1031 erg s−1 Hz−1) radio emission. However, no GRB was detected in the 0.74 days between the last ZTF nondetection (r > 21.36 mag) and the first ZTF detection (r = 19.60 mag), with an upper limit on the isotropic-equivalent gamma-ray energy release of E

γ,iso < 7 × 1052 erg. AT 2020blt is thus the third afterglow-like transient discovered without a detected GRB counterpart (after PTF11agg and ZTF19abvizsw) and the second (after ZTF19abvizsw) with a redshift measurement. We conclude that the properties of AT 2020blt are consistent with a classical (initial Lorentz factor Γ0 ≳ 100) on-axis GRB that was missed by high-energy satellites. Furthermore, by estimating the rate of transients with light curves similar to that of AT 2020blt in ZTF high-cadence data, we agree with previous results that there is no evidence for an afterglow-like phenomenon that is significantly more common than classical GRBs, such as dirty fireballs. We conclude by discussing the status and future of fast-transient searches in wide-field high-cadence optical surveys.
Study Turbulence and Probe Magnetic Fields Using the Gradient Technique: Application to H i-to-H2 Transition Regions
Authors: Hu Yue , Lazarian A. , Bialy Shmuel 
Published: December 2020

Abstract
The atomic-to-molecular (H i-to-H2) transition in photodissociation regions (PDRs) has been investigated over the past several decades through analytic and numerical modeling. However, classical PDR models typically assume a uniform-density gas, ignoring the turbulent nature of the interstellar medium. Recently, Bialy et al. have presented a theoretical framework for studying the H i-to-H2 transition in a realistic turbulent medium with a nonhomogeneous density structure. Here we extend these turbulent-chemical models to explore the possibility of tracing the magnetic field direction in turbulent PDRs using the gradient technique. We utilize both subsonic and supersonic magnetohydrodynamic numerical simulations for chemical H i/H2 balance calculations. We confirm that the density fluctuations induced by turbulence can disperse the distribution of the H2 and H i fractions. We find that the energy spectrum of moment maps gets shallower when the sonic Mach number M
S increases. We explore the ability in magnetic field tracing of gradients of higher-order velocity centroids and compare their performance with that of traditional velocity centroid gradients (VCGs) and with intensity gradients (IGs). We find that the velocity gradients of the second-order centroids (VC2Gs) are more accurate than VCGs and IGs in probing the magnetic field orientation.
The Betelgeuse Project. III. Merger Characteristics
Authors: Sullivan J. M. , Nance S. , Wheeler J. Craig 
Published: December 2020

Abstract
We previously proposed that Betelgeuse might have been spun up by accreting a companion of about 1 M
⊙. Here we explore in more detail the possible systematics of such a merger and a larger range of accreted masses. We use the stellar evolutionary code mesa to add angular momentum to a primary star in core helium burning, core carbon burning, or shell carbon burning. Our models provide a reasonable “natural” explanation for why Betelgeuse has a large, but sub-Keplerian equatorial velocity. They eject sufficient mass and angular momentum in rotationally induced mass loss to reproduce the observed ratio of the equatorial velocity to escape velocity of Betelgeuse, ≈0.23, within a factor of 3 nearly independent of the primary mass, the secondary mass, and the epoch at which merger occurs. Our models suggest that merger of a primary of somewhat less than 15 M
⊙ with secondaries from 1 to 10 M
⊙ during core helium burning or core carbon burning could yield the equatorial rotational velocity of ∼15 km s−1 attributed to Betelgeuse. For accreting models, a wave of angular momentum is halted at the composition boundary at the edge of the helium core. The inner core is thus not affected by the accretion of the companion in these simulations. Accretion has relatively little effect on the production of magnetic fields in the inner core. Our results do not prove, but do not negate, that Betelgeuse might have ingested a companion of several M
⊙.
Long-term Orbital Evolution of Galactic Satellites and the Effects on Their Star Formation Histories
Authors: Miyoshi Takahiro , Chiba Masashi 
Published: December 2020

Abstract
We investigate the orbital motions of dwarf spheroidal galaxies (dSphs) in the halo of the Milky Way (MW) to understand their possible effects on the diversity of the star formation histories seen in these MW satellites. In this work, we explicitly consider a time-varying gravitational potential due to the growth of the MW’s dark halo mass to calculate the long-term orbital evolutions of the dSphs, guided with Gaia DR2 proper motions, over the past 13.5 billion years. We find that the infall time of a satellite, defined as when the galaxy first crosses within the growing virial radius of the MW’s halo, coincides well with the time when the star formation rate (SFR) is peaked for the sample of classical dSphs. On the other hand, ultra-faint dSphs already finished their SF activity prior to their infall times as already suggested in previous works, but there is a signature that their earlier SF histories are affected by interaction with the growing MW’s halo to some extent. We also find, for classical dSphs, that the relative fraction of stars formed after the peak of the SFR to the current stellar mass is smaller for the smaller pericentric radius of the galaxy at its first infall. These results suggest that the infalling properties of the dSphs into the MW and the resultant environmental effects, such as ram pressure stripping and/or tidal disturbance in the MW’s dark halo containing hot gas, play important roles in their star formation histories.
The Pairing Probability of Massive Black Holes in Merger Galaxies in the Presence of Radiative Feedback
Authors: Li Kunyang , Bogdanović Tamara , Ballantyne David R. 
Published: December 2020

Abstract
Dynamical friction (DF) against stars and gas is thought to be an important mechanism for orbital evolution of massive black holes (MBHs) in merger remnant galaxies. Recent theoretical investigations, however, show that DF does not always lead to MBH inspiral. For MBHs evolving in gas-rich backgrounds, the ionizing radiation that emerges from the innermost parts of their accretion flow can affect the surrounding gas in such a way to cause the MBHs to accelerate and gain orbital energy. This effect was dubbed “negative DF.” We use a semianalytic model to study the impact of negative DF on pairs of MBHs in merger remnant galaxies evolving under the combined influence of stellar and gaseous DF. Our results show that for a wide range of merger galaxy and MBH properties negative DF reduces the MBH pairing probability by ∼46%. The suppression of MBH pairing is most severe in galaxies with one or more of these properties: (1) a gas fraction of f

g
≥ 0.1; (2) a galactic gas disk rotating close to the circular velocity; (3) MBH pairs in prograde, low eccentricity orbits; and (4) MBH pairs with mass <108
M
⊙. The last point is of importance because MBH pairs in this mass range are direct progenitors of merging binaries targeted by the future space-based gravitational wave observatory the Laser Interferometer Space Antenna (LISA).
A Framework for Relative Biosignature Yields from Future Direct Imaging Missions
Authors: Tuchow Noah W. , Wright Jason T. 
Published: December 2020

Abstract
Future exoplanet direct imaging missions, such as HabEx and LUVOIR, will select target stars to maximize the number of Earth-like exoplanets that can have their atmospheric compositions characterized. Because one of these missions’ aims is to detect biosignatures, they should also consider the expected biosignature yield of planets around these stars. In this work, we develop a method of computing relative biosignature yields among potential target stars, given a model of habitability and biosignature genesis, and using a star’s habitability history. As an illustration and first application of this method, we use MESA stellar models to calculate the time evolution of the habitable zone and examine three simple models for biosignature genesis to calculate the relative biosignature yield for different stars. We find that the relative merits of K stars versus F stars depend sensitively on model choice. In particular, use of the present-day habitable zone as a proxy for biosignature detectability favors young, luminous stars lacking the potential for long-term habitability. Biosignature yields are also sensitive to whether life can arise on Cold Start exoplanets that enter the habitable zone after formation, an open question deserving of more attention. Using the case study of biosignature yields calculated for θ Cygni and 55 Cancri, we find that robust mission design and target selection for HabEx and LUVOIR depend on choosing a specific model of biosignature appearance with time, the terrestrial planet occurrence rate as a function of orbital separation, precise knowledge of stellar properties, and accurate stellar evolutionary histories.
Physical Conditions of Gas Components in Debris Disks of 49 Ceti and HD 21997
Authors: Higuchi Aya E. , Kóspál Ágnes , Moór Attila , Nomura Hideko , Yamamoto Satoshi 
Published: December 2020

Abstract
Characterization of the gas component in debris disks is of fundamental importance for understanding their origin. To address this goal, we have conducted non-LTE (local thermodynamic equilibrium) analyses of the rotational spectral lines of CO including those of rare isotopologues (13CO and C18O) that have been observed toward the gaseous debris disks of 49 Ceti and HD 21997 with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Compact Array (ACA). The analyses have been carried out for a wide range of H2 density, and the observed line intensities are found to be reproduced as long as the H2 density is higher than 103 cm−3. The CO column density and the gas temperature are evaluated to be (1.8–5.9) × 1017 cm−2 and 8–11 K for 49 Ceti and (2.6–15) × 1017 cm−2 and 8–12 K for HD 21997, respectively, where the H2 collision is assumed for the rotational excitation of CO. The results do not change significantly even if electron collision is considered. Thus, CO molecules can be excited under environments containing no H2 or a small number of H2 molecules, even where collisions with CO, C, O, and C+ would make an important contribution to the CO excitation in addition to H2. Meanwhile, our result does not rule out the case of abundant H2 molecules. The low gas temperature observed in the debris disks is discussed in terms of inefficient heating by interstellar and stellar UV radiation.
Flare Rates, Rotation Periods, and Spectroscopic Activity Indicators of a Volume-complete Sample of Mid- to Late-M Dwarfs within 15 pc
Authors: Medina Amber A. , Winters Jennifer G. , Irwin Jonathan M. , Charbonneau David 
Published: December 2020

Abstract
We present a study of flare rates, rotation periods, and spectroscopic activity indicators of 125 single stars within 15 parsecs and with masses between 0.1 and 0.3 M
⊙ observed during the first year of the TESS mission, with the goal of elucidating the relationship between these various magnetically connected phenomena. We gathered multiepoch high-resolution spectra of each target, and we measured equivalent widths of the activity indicators helium I D3, Hα, and the calcium infrared triplet line at 8542.09 Å. We present 18 new rotation periods from MEarth photometry and 19 new rotation periods from TESS photometry. We present a catalog of 1392 flares. After correcting for sensitivity, we find the slope of the flare frequency distribution for all stars to have a standard value of α = 1.98 ± 0.02. We determine R
31.5, the rate of flares per day with energies above E = 3.16 × 1031 ergs in the TESS bandpass. We find that below a critical value of Hα EW = −0.71 Å, log R
31.5 increases linearly with increasing Hα emission; above this value, log R
31.5 declines rapidly. The stars divide into two groups: 26% have Hα in emission, high flare rates with typical values of log R
31.5 = −1.30 ± 0.08, and have Rossby numbers <0.50. The remaining 74% show little to no Hα in emission and exhibit log R
31.5 < −3.86, with the majority of these stars not showing a single flare during the TESS observations.
SuperRAENN: A Semisupervised Supernova Photometric Classification Pipeline Trained on Pan-STARRS1 Medium-Deep Survey Supernovae
Authors: Villar V. Ashley , Hosseinzadeh Griffin , Berger Edo , Ntampaka Michelle , Jones David O. , Challis Peter , Chornock Ryan , Drout Maria R. , Foley Ryan J. , Kirshner Robert P. , Lunnan Ragnhild , Margutti Raffaella , Milisavljevic Dan , Sanders Nathan , Pan Yen-Chen , Rest Armin , Scolnic Daniel M. , Magnier Eugene , Metcalfe Nigel , Wainscoat Richard , Waters Christopher 
Published: December 2020

Abstract
Automated classification of supernovae (SNe) based on optical photometric light-curve information is essential in the upcoming era of wide-field time domain surveys, such as the Legacy Survey of Space and Time (LSST) conducted by the Rubin Observatory. Photometric classification can enable real-time identification of interesting events for extended multiwavelength follow-up, as well as archival population studies. Here we present the complete sample of 5243 “SN-like” light curves (in g
P1
r
P1
i
P1
z
P1) from the Pan-STARRS1 Medium-Deep Survey (PS1-MDS). The PS1-MDS is similar to the planned LSST Wide-Fast-Deep survey in terms of cadence, filters, and depth, making this a useful training set for the community. Using this data set, we train a novel semisupervised machine learning algorithm to photometrically classify 2315 new SN-like light curves with host galaxy spectroscopic redshifts. Our algorithm consists of an RF supervised classification step and a novel unsupervised step in which we introduce a recurrent autoencoder neural network (RAENN). Our final pipeline, dubbed SuperRAENN, has an accuracy of 87% across five SN classes (Type Ia, Ibc, II, IIn, SLSN-I) and macro-averaged purity and completeness of 66% and 69%, respectively. We find the highest accuracy rates for SNe Ia and SLSNe and the lowest for SNe Ibc. Our complete spectroscopically and photometrically classified samples break down into 62.0% Type Ia (1839 objects), 19.8% Type II (553 objects), 4.8% Type IIn (136 objects), 11.7% Type Ibc (291 objects), and 1.6% Type I SLSNe (54 objects).
The Herschel Orion Protostar Survey: Far-infrared Photometry and Colors of Protostars and Their Variations across Orion A and B*
Authors: Fischer William J. , Megeath S. Thomas , Furlan E. , Stutz Amelia M. , Stanke Thomas , Tobin John J. , Osorio Mayra , Manoj P. , Di Francesco James , Allen Lori E. , Watson Dan M. , Wilson T. L. , Henning Thomas 
Published: December 2020

Abstract
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.
Outflows in the Presence of Cosmic Rays and Waves
Authors: Ramzan B. , Ko C. M. , Chernyshov D. O. 
Published: December 2020

Abstract
Plasma outflow or wind against a gravitational potential under the influence of cosmic rays is studied in the context of hydrodynamics. Cosmic rays interact with the plasma via hydromagnetic fluctuations. In the process, cosmic rays advect and diffuse through the plasma. We adopt a multi-fluid model in which, besides thermal plasma, cosmic rays and self-excited Alfvén waves are also treated as fluids. We seek possible, physically allowable steady-state solutions of three-fluid (one Alfvén wave) and four-fluid (two Alfvén waves) models with given boundary conditions at the base of the potential well. Generally speaking, there are two classes of outflows—subsonic and supersonic (with respect to a suitably defined sound speed). A three-fluid model without cosmic-ray diffusion can be studied in the same way as the classic stellar wind problem, and is taken as a reference model. When cosmic-ray diffusion is included, there are two categories of solutions. One of them resembles the three-fluid model without diffusion, and the other behaves like thermal wind at large distances when the waves wither and cosmic rays are decoupled from the plasma. We also examine the effect of wave damping mechanisms (such as nonlinear Landau damping). Roughly speaking, the effect is much smaller in supersonic outflow than in subsonic outflow.
O Fenômeno da Contemplação em Contextos de Consumo de Luxo
Authors: Aureliano-Silva Leonardo , Strehlau Suzane 
Published: December 2020

O objetivo desse artigo é apresentar o fenômeno da contemplação e propor uma reflexão de sua aplicação no campo do marketing. A contemplação é um fenômeno psicológico e cognitivo no qual o indivíduo manifesta grande admiração por algo (MAY, 1982). Compreender esse fenômeno no campo do marketing traz contribuições teóricas para a área, sobretudo, no entendimento do desejo do consumidor por marcas de luxo. Ainda possibilita que gestores de marketing reflitam sobre estratégias de marketing que têm sido utilizadas com o objetivo de posicionar essas marcas para um grupo seleto de consumidores, que de fato, contemplam tais produtos.
Palavras-chave: contemplação, marcas de luxo, consumo, marketing, status