bluuebunny/crossref_metadata_2025_split huggingface dataset:
Parallax of Star-forming Region G027.22+0.14
Authors: Bian S. B. , Xu Y. , Li J. J. , Wu Y. W. , Zhang B. , Chen X. , Li Y. J. , Lin Z. H. , Hao C. J. , Liu D. J. 
Published: January 2022

Abstract
Using the Very Long Baseline Array, we measured the trigonometric parallax and proper motions toward a 6.7 GHz methanol maser in the distant high-mass star-forming region G027.22+0.14. The distance of this source is determined to be

6.3

−
0.5

+
0.6

kpc. Combining its Galactic coordinates, radial velocity, and proper motion, we assign G027.22+0.14 to the far portion of the Norma arm. The low peculiar motion and lower luminosity of G027.22+0.14 support the conjecture by Immer et al. that low-luminosity sources tend to have low peculiar motions.
A Semianalytic Afterglow with Thermal Electrons and Synchrotron Self-Compton Emission
Authors: Warren Donald C. , Dainotti Maria , Barkov Maxim V. , Ahlgren Björn , Ito Hirotaka , Nagataki Shigehiro 
Published: January 2022

Abstract
We extend previous work on gamma-ray burst afterglows involving hot thermal electrons at the base of a shock-accelerated tail. Using a physically motivated electron distribution based on first-principles simulations, we compute the broadband emission from radio to TeV gamma rays. For the first time, we present the effects of a thermal distribution of electrons on synchrotron self-Compton emission. The presence of thermal electrons causes temporal and spectral structure across the entire observable afterglow, which is substantively different from models that assume a pure power-law distribution for the electrons. We show that early-time TeV emission is enhanced by more than an order of magnitude for our fiducial parameters, with a time-varying spectral index that does not occur for a pure power law of electrons. We further show that the X-ray closure relations take a very different, also time-dependent, form when thermal electrons are present; the shape traced out by the X-ray afterglows is a qualitative match to observations of the traditional decay phase.
Supersonic Expansion of the Bipolar H ii Region Sh2-106: A 3500 Year Old Explosion?
Authors: Bally John , Chia Zen , Ginsburg Adam , Reipurth Bo , Tanaka Kei E. I , Zinnecker Hans , Faulhaber John 
Published: January 2022

Abstract
Multi-epoch narrowband Hubble Space Telescope images of the bipolar H ii region Sh2-106 reveal highly supersonic nebular proper motions that increase with projected distance from the massive young stellar object S106 IR, reaching over ∼30 mas yr−1 (∼150 km s−1 at D = 1.09 kpc) at a projected separation of ∼1.′4 (0.44 pc) from S106 IR. We propose that S106 IR experienced a ∼1047 erg explosion ∼3500 yr ago. The explosion may be the result of a major accretion burst or a recent encounter with another star, or a consequence of the interaction of a companion with the bloated photosphere of S106 IR as it grew from ∼10 through ∼15 M
⊙ at a high accretion rate. Near-IR images reveal fingers of H2 emission pointing away from S106 IR and an asymmetric photon-dominated region surrounding the ionized nebula. Radio continuum and Brγ emission reveal a C-shaped bend in the plasma, indicating either the motion of S106 IR toward the east, or the deflection of plasma toward the west by the surrounding cloud. The H ii region bends around a ∼1′ diameter dark bay west of S106 IR that may be shielded from direct illumination by a dense molecular clump. Herbig–Haro and Molecular Hydrogen Objects tracing outflows powered by stars in the Sh2-106 protocluster such as the Class 0 source S106 FIR are discussed.
Variable Ion Compositions of Solar Energetic Particle Events in the Inner Heliosphere: A Field Line Braiding Model with Compound Injections
Authors: Guo Fan , Zhao Lulu , Cohen Christina M. S. , Giacalone Joe , Leske R. A. , Wiedenbeck M. E. , Kahler S. W. , Li Xiaocan , Zhang Qile , Ho George C. , Desai Mihir I. 
Published: January 2022

Abstract
We propose a model for interpreting highly variable ion composition ratios in solar energetic particle (SEP) events recently observed by the Parker Solar Probe (PSP) at 0.3–0.45 au. We use numerical simulations to calculate SEP propagation in a turbulent interplanetary magnetic field with a Kolmogorov power spectrum from large scales down to the gyration scale of energetic particles. We show that when the source regions of different species are offset by a distance comparable to the size of the source regions, the observed energetic particle composition He/H can be strongly variable over more than two orders of magnitude, even if the source ratio is at the nominal value. Assuming a 3He/4He source ratio of 10% in impulsive 3He-rich events and the same spatial offset of the source regions, the 3He/4He ratio at observation sites also vary considerably. The variability of the ion composition ratios depends on the radial distance, which can be tested by observations made at different radial locations. We discuss the implications of these results on the variability of ion composition of impulsive events and on further PSP and Solar Orbiter observations close to the Sun.
SN 2015bq: A Luminous Type Ia Supernova with Early Flux Excess
Authors: Li Liping , Zhang Jujia , Dai Benzhong , Li Wenxiong , Wang Xiaofeng , Zhai Qian , Bai Jinming 
Published: January 2022

Abstract
We present optical and ultraviolet (UV) observations of a luminous type Ia supernova (SN Ia) SN 2015bq characterized by early flux excess. This SN reaches a B-band absolute magnitude at M

B
= −19.68 ± 0.41 mag and a peak bolometric luminosity at L = (1.75 ± 0.37) × 1043 erg s−1, with a relatively small post-maximum decline rate [Δm
15(B) = 0.82 ± 0.05 mag]. The flux excess observed in the light curves of SN 2015bq a few days after the explosion, especially seen in the UV bands, might be due to the radioactive decay of 56Ni mixed into the surface. The radiation from the decay of the surface 56Ni heats the outer layer of this SN. It produces blue U − B color followed by monotonically reddening in the early phase, dominated iron-group lines, and weak intermediate-mass element absorption features in the early spectra. The scenario of enhanced 56Ni in the surface is consistent with a large amount of 56Ni (

M

56

Ni

=
0.97
±
0.20

M
☉) synthesized during the explosion. The properties of SN 2015bq are found to locate between SN 1991T and SN 1999aa, suggesting the latter two subclasses of SNe Ia may have a common origin.
Simulation of Plasma Emission in Magnetized Plasmas
Authors: Lee Sang-Yun , Yoon Peter H. , Lee Ensang , Tu Weichao 
Published: January 2022

Abstract
The recent Parker Solar Probe observations of type III radio bursts show that the effects of the finite background magnetic field can be an important factor in the interpretation of data. In the present paper, the effects of the background magnetic field on the plasma-emission process, which is believed to be the main emission mechanism for solar coronal and interplanetary type III radio bursts, are investigated by means of the particle-in-cell simulation method. The effects of the ambient magnetic field are systematically surveyed by varying the ratio of plasma frequency to electron gyrofrequency. The present study shows that for a sufficiently strong ambient magnetic field, the wave–particle interaction processes lead to a highly field-aligned longitudinal mode excitation and anisotropic electron velocity distribution function, accompanied by a significantly enhanced plasma emission at the second-harmonic plasma frequency. For such a case, the polarization of the harmonic emission is almost entirely in the sense of extraordinary mode. On the other hand, for moderate strengths of the ambient magnetic field, the interpretation of the simulation result is less clear. The underlying nonlinear-mode coupling processes indicate that to properly understand and interpret the simulation results requires sophisticated analyses involving interactions among magnetized plasma normal modes, including the two transverse modes of the magneto-active plasma, namely, the extraordinary and ordinary modes, as well as electron-cyclotron-whistler, plasma oscillation, and upper-hybrid modes. At present, a nonlinear theory suitable for quantitatively analyzing such complex-mode coupling processes in magnetized plasmas is incomplete, which calls for further theoretical research, but the present simulation results could provide a guide for future theoretical efforts.
Discovery of a Double Radio Relic in ZwCl1447.2+2619: A Rare Testbed for Shock-acceleration Models with a Peculiar Surface-brightness Ratio
Authors: Lee Wonki , James Jee M. , Finner Kyle , HyeongHan Kim , Kale Ruta , Yoon Hyein , Forman William , Kraft Ralph , Jones Christine , Chung Aeree 
Published: January 2022

Abstract
We report a discovery of a double radio relic in the cluster merger ZwCl1447.2+2619 (z = 0.376) with uGMRT observations at 420 MHz and 700 MHz. The linear sizes of the northern and southern relics are ∼0.3 Mpc and ∼1.2 Mpc, respectively, which is consistent with the theoretical expectation that a larger relic is produced in the less massive subcluster side. However, ZwCl1447.2+2619 is unlike other known double radio relic systems, where the larger relics are much more luminous by several factors. In this merger, the higher surface brightness of the smaller northern relic makes its total radio luminosity comparable to that of the much larger southern relic. The surface brightness ratio ∼0.1 between the two radio relics differs significantly from the relation observed in other double radio relic systems. From our radio spectral analysis, we find that both relics signify similar weak shocks with Mach numbers of 2.9 ± 0.8 and 2.0 ± 0.7 for the northern and southern relics, respectively. Moreover, the northern relic is connected to a discrete radio source with an optical counterpart, which indicates the possible presence of cosmic-ray injection and reacceleration. Therefore, we propose that this atypical surface brightness ratio can be explained with the particle acceleration efficiency precipitously dropping in the weak shock regime and/or with reacceleration of fossil cosmic rays. Our multi-wavelength analysis and numerical simulation suggest that ZwCl1447.2+2619 is a postmerger, which has experienced a near head-on collision ∼0.7 Gyr ago.
Validation of the HERA Phase I Epoch of Reionization 21 cm Power Spectrum Software Pipeline
Authors: Aguirre James E. , Murray Steven G. , Pascua Robert , Martinot Zachary E. , Burba Jacob , Dillon Joshua S. , Jacobs Daniel C. , Kern Nicholas S. , Kittiwisit Piyanat , Kolopanis Matthew , Lanman Adam , Liu Adrian , Whitler Lily , Abdurashidova Zara , Alexander Paul , Ali Zaki S. , Balfour Yanga , Beardsley Adam P. , Bernardi Gianni , Billings Tashalee S. , Bowman Judd D. , Bradley Richard F. , Bull Philip , Carey Steve , Carilli Chris L. , Cheng Carina , DeBoer David R. , Dexter Matt , de Lera Acedo Eloy , Ely John , Ewall-Wice Aaron , Fagnoni Nicolas , Fritz Randall , Furlanetto Steven R. , Gale-Sides Kingsley , Glendenning Brian , Gorthi Deepthi , Greig Bradley , Grobbelaar Jasper , Halday Ziyaad , Hazelton Bryna J. , Hewitt Jacqueline N. , Hickish Jack , Julius Austin , Kerrigan Joshua , Kohn Saul A. , La Plante Paul , Lekalake Telalo , Lewis David , MacMahon David , Malan Lourence , Malgas Cresshim , Maree Matthys , Matsetela Eunice , Mesinger Andrei , Molewa Mathakane , Morales Miguel F. , Mosiane Tshegofalang , Neben Abraham R. , Nikolic Bojan , Parsons Aaron R. , Patra Nipanjana , Pieterse Samantha , Pober Jonathan C. , Razavi-Ghods Nima , Ringuette Jon , Robnett James , Rosie Kathryn , Santos Mario G. , Sims Peter , Singh Saurabh , Smith Craig , Syce Angelo , Thyagarajan Nithyanandan , Williams Peter K. G. , Zheng Haoxuan ,   HERA Collaboration
Published: January 2022

Abstract
We describe the validation of the HERA Phase I software pipeline by a series of modular tests, building up to an end-to-end simulation. The philosophy of this approach is to validate the software and algorithms used in the Phase I upper-limit analysis on wholly synthetic data satisfying the assumptions of that analysis, not addressing whether the actual data meet these assumptions. We discuss the organization of this validation approach, the specific modular tests performed, and the construction of the end-to-end simulations. We explicitly discuss the limitations in scope of the current simulation effort. With mock visibility data generated from a known analytic power spectrum and a wide range of realistic instrumental effects and foregrounds, we demonstrate that the current pipeline produces power spectrum estimates that are consistent with known analytic inputs to within thermal noise levels (at the 2σ level) for k > 0.2h Mpc−1 for both bands and fields considered. Our input spectrum is intentionally amplified to enable a strong “detection” at k ∼ 0.2 h Mpc−1—at the level of ∼25σ—with foregrounds dominating on larger scales and thermal noise dominating at smaller scales. Our pipeline is able to detect this amplified input signal after suppressing foregrounds with a dynamic range (foreground to noise ratio) of ≳107. Our validation test suite uncovered several sources of scale-independent signal loss throughout the pipeline, whose amplitude is well-characterized and accounted for in the final estimates. We conclude with a discussion of the steps required for the next round of data analysis.
A Quasar-based Supermassive Black Hole Binary Population Model: Implications for the Gravitational Wave Background
Authors: Casey-Clyde J. Andrew , Mingarelli Chiara M. F. , Greene Jenny E. , Pardo Kris , Nañez Morgan , Goulding Andy D. 
Published: January 2022

Abstract
The nanohertz gravitational wave background (GWB) is believed to be dominated by GW emission from supermassive black hole binaries (SMBHBs). Observations of several dual-active galactic nuclei (AGN) strongly suggest a link between AGN and SMBHBs, given that these dual-AGN systems will eventually form bound binary pairs. Here we develop an exploratory SMBHB population model based on empirically constrained quasar populations, allowing us to decompose the GWB amplitude into an underlying distribution of SMBH masses, SMBHB number density, and volume enclosing the GWB. Our approach also allows us to self-consistently predict the number of local SMBHB systems from the GWB amplitude. Interestingly, we find the local number density of SMBHBs implied by the common-process signal in the NANOGrav 12.5-yr data set to be roughly five times larger than previously predicted by other models. We also find that at most ∼25% of SMBHBs can be associated with quasars. Furthermore, our quasar-based approach predicts ≳95% of the GWB signal comes from z ≲ 2.5, and that SMBHBs contributing to the GWB have masses ≳108
M
⊙. We also explore how different empirical galaxy–black hole scaling relations affect the local number density of GW sources, and find that relations predicting more massive black holes decrease the local number density of SMBHBs. Overall, our results point to the important role that a measurement of the GWB will play in directly constraining the cosmic population of SMBHBs, as well as their connections to quasars and galaxy mergers.
Late-time Evolution and Modeling of the Off-axis Gamma-Ray Burst Candidate FIRST J141918.9+394036
Authors: Mooley K. P. , Margalit B. , Law C. J. , Perley D. A. , Deller A. T. , Lazio T. J. W. , Bietenholz M. F. , Shimwell T. , Intema H. T. , Gaensler B. M. , Metzger B. D. , Dong D. Z. , Hallinan G. , Ofek E. O. , Sironi L. 
Published: January 2022

Abstract
We present new radio and optical data, including very-long-baseline interferometry, as well as archival data analysis, for the luminous, decades-long radio transient FIRST J141918.9+394036. The radio data reveal a synchrotron self-absorption peak around 0.3 GHz and a radius of around 1.3 mas (0.5 pc) 26 yr post-discovery, indicating a blastwave energy ∼5 × 1050 erg. The optical spectrum shows a broad [O iii]λ4959,5007 emission line that may indicate collisional excitation in the host galaxy, but its association with the transient cannot be ruled out. The properties of the host galaxy are suggestive of a massive stellar progenitor that formed at low metallicity. Based on the radio light curve, blastwave velocity, energetics, nature of the host galaxy and transient rates, we find that the properties of J1419+3940 are most consistent with long gamma-ray burst (LGRB) afterglows. Other classes of (optically discovered) stellar explosions as well as neutron star mergers are disfavored, and invoking any exotic scenario may not be necessary. It is therefore likely that J1419+3940 is an off-axis LGRB afterglow (as suggested by Law et al. and Marcote et al.), and under this premise the inverse beaming fraction is found to be

f

b

−
1

≃

280

−
200

+
700

, corresponding to an average jet half-opening angle

<

θ

j

>
≃

5

−
2

+
4

degrees (68% confidence), consistent with previous estimates. From the volumetric rate we predict that surveys with the Very Large Array, Australian Square Kilometre Array Pathfinder, and MeerKAT will find a handful of J1419+3940-like events over the coming years.
Detection of a 100,000 M
⊙ black hole in M31's Most Massive Globular Cluster: A Tidally Stripped Nucleus
Authors: Pechetti Renuka , Seth Anil , Kamann Sebastian , Caldwell Nelson , Strader Jay , den Brok Mark , Luetzgendorf Nora , Neumayer Nadine , Voggel Karina 
Published: January 2022

Abstract
We investigate the presence of a central black hole (BH) in B023-G078, M31's most massive globular cluster. We present high-resolution, adaptive-optics assisted, integral-field spectroscopic kinematics from Gemini/NIFS that show a strong rotation (∼20 km s−1) and a velocity dispersion rise toward the center (37 km s−1). We combine the kinematic data with a mass model based on a two-component fit to HST ACS/HRC data of the cluster to estimate the mass of a putative BH. Our dynamical modeling suggests a >3σ detection of a BH component of

9.1

−
2.8

+
2.6

×

10

4

M

⊙

(1σ uncertainties). The inferred stellar mass of the cluster is

6.22

−
0.05

+
0.03

×

10

6

M

⊙

, consistent with previous estimates, thus the BH makes up 1.5% of its mass. We examine whether the observed kinematics are caused by a collection of stellar mass BHs by modeling an extended dark mass as a Plummer profile. The upper limit on the size scale of the extended mass is 0.56 pc (95% confidence), which does not rule out an extended mass. There is compelling evidence that B023-G078 is the tidally stripped nucleus of a galaxy with a stellar mass >109
M
⊙, including its high-mass, two-component luminosity profile, color, metallicity gradient, and spread in metallicity. Given the emerging evidence that the central BH occupation fraction of >109
M
⊙ galaxies is high, the most plausible interpretation of the kinematic data is that B023-G078 hosts a central BH. This makes it the strongest BH detection in a lower-mass (<107
M
⊙) stripped nucleus, and one of the few dynamically detected intermediate-mass BHs.
V606 Cen: A Newly Formed Massive Contact Binary in a Hierarchical Triple System
Authors: Li F.-X. , Liao W.-P. , Qian S.-B. , Fernández Lajús E. , Zhang J. , Zhao E.-G. 
Published: January 2022

Abstract
V606 Centauri (V606 Cen) is an early B-type close binary with an orbital period of 1.4950935 days, and its complete light curves are very difficult to observe on the ground. By analyzing the continuous light curve obtained by TESS, we found that it is a marginal contact binary with a very low fill-out factor of about 2%. The O − C diagram of V606 Cen is constructed for the first time based on 118.8 yr of eclipse times. The O − C diagram has been found to show a downward parabolic change together with a cyclic oscillation with a semiamplitude of 0.0545 days and a period of 88.3 yr. The downward parabolic variation reveals a linear period decrease at a rate of dP/dt = −2.08 × 10−7 days yr−1 that can be explained by the mass transfer from the more massive component to the less massive one. Both the marginal contact configuration and the continuous period decrease suggest that V606 Cen is a newly formed contact binary via Case A mass transfer. The cyclic change in the O − C diagram can be explained by the light-travel time effect via the presence of a third body. The lowest mass of the tertiary companion is determined to be M
3 = 4.51 (±0.43) M
⊙ and the tertiary is orbiting around the central eclipsing binary in a nearly circular orbit (e = 0.33). All of the results indicate that V606 Cen is a newly formed massive contact binary in a hierarchical triple system.
The Physical Parameters of Four WC-type Wolf–Rayet Stars in the Large Magellanic Cloud: Evidence of Evolution*
Authors: Aadland Erin , Massey Philip , Hillier D. John , Morrell Nidia 
Published: January 2022

Abstract
We present a spectral analysis of four Large Magellanic Cloud (LMC) WC-type Wolf–Rayet (WR) stars (BAT99-8, BAT99-9, BAT99-11, and BAT99-52) to shed light on two evolutionary questions surrounding massive stars. The first is: are WO-type WR stars more oxygen enriched than WC-type stars, indicating further chemical evolution, or are the strong high-excitation oxygen lines in WO-type stars an indication of higher temperatures. This study will act as a baseline for answering the question of where WO-type stars fall in WR evolution. Each star’s spectrum, extending from 1100 to 25000 Å, was modeled using cmfgen to determine the star’s physical properties such as luminosity, mass-loss rate, and chemical abundances. The oxygen abundance is a key evolutionary diagnostic, and with higher resolution data and an improved stellar atmosphere code, we found the oxygen abundance to be up to a factor of 5 lower than that of previous studies. The second evolutionary question revolves around the formation of WR stars: do they evolve by themselves or is a close companion star necessary for their formation? Using our derived physical parameters, we compared our results to the Geneva single-star evolutionary models and the Binary Population and Spectral Synthesis (BPASS) binary evolutionary models. We found that both the Geneva solar-metallicity models and BPASS LMC-metallicity models are in agreement with the four WC-type stars, while the Geneva LMC-metallicity models are not. Therefore, these four WC4 stars could have been formed either via binary or single-star evolution.
Ultra-high-energy Gamma-Ray Radiation from the Crab Pulsar Wind Nebula
Authors: Nie Lin , Liu Yang , Jiang Zejun , Geng Xiongfei 
Published: January 2022

Abstract
It has been long debated whether the high-energy gamma-ray radiation from the Crab Nebula stems from leptonic or hadronic processes. In this work, we investigate the multiband nonthermal radiation from the Crab pulsar wind nebula with the leptonic and leptonic–hadronic hybrid models, respectively. Then we use the Markov Chain Monte Carlo sampling technology and method of sampling trace to study the stability and reasonability of the model parameters according to the recently observed results and obtain the best-fitting values of parameters. Finally, we calculate different radiative components generated by the electrons and protons in the Crab Nebula. The modeling results indicate that the pure leptonic origin model with the one-zone only can partly agree with some segments of the data from various experiments (including the PeV gamma-ray emission reported by the LHAASO and the other radiation ranging from the radio to very-high-energy gamma-ray wave band), and the contribution of hadronic interaction is hardly constrained. However, we find that the hadronic process may also contribute, especially in the energy range exceeding the PeV. In addition, it can be inferred that the higher energy signals from the Crab Nebula could be observed in the future.