bluuebunny/crossref_metadata_2025_split huggingface dataset:
Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. I. Oscillation Mode Parameters
Authors: Lund Mikkel N. , Aguirre Víctor Silva , Davies Guy R. , Chaplin William J. , Christensen-Dalsgaard Jørgen , Houdek Günter , White Timothy R. , Bedding Timothy R. , Ball Warrick H. , Huber Daniel , Antia H. M. , Lebreton Yveline , Latham David W. , Handberg Rasmus , Verma Kuldeep , Basu Sarbani , Casagrande Luca , Justesen Anders B. , Kjeldsen Hans , Mosumgaard Jakob R. 
Published: January 2017

Abstract
The advent of space-based missions like Kepler has revolutionized the study of solar-type stars, particularly through the measurement and modeling of their resonant modes of oscillation. Here we analyze a sample of 66 Kepler main-sequence stars showing solar-like oscillations as part of the Kepler seismic LEGACY project. We use Kepler short-cadence data, of which each star has at least 12 months, to create frequency-power spectra optimized for asteroseismology. For each star, we identify its modes of oscillation and extract parameters such as frequency, amplitude, and line width using a Bayesian Markov chain Monte Carlo “peak-bagging” approach. We report the extracted mode parameters for all 66 stars, as well as derived quantities such as frequency difference ratios, the large and small separations

and

the behavior of line widths with frequency and line widths at

with

, for which we derive parametrizations; and behavior of mode visibilities. These average properties can be applied in future peak-bagging exercises to better constrain the parameters of the stellar oscillation spectra. The frequencies and frequency ratios can tightly constrain the fundamental parameters of these solar-type stars, and mode line widths and amplitudes can test models of mode damping and excitation.
Standing on the Shoulders of Dwarfs: the Kepler Asteroseismic LEGACY Sample. II. Radii, Masses, and Ages
Authors: Aguirre Víctor Silva , Lund Mikkel N. , Antia H. M. , Ball Warrick H. , Basu Sarbani , Christensen-Dalsgaard Jørgen , Lebreton Yveline , Reese Daniel R. , Verma Kuldeep , Casagrande Luca , Justesen Anders B. , Mosumgaard Jakob R. , Chaplin William J. , Bedding Timothy R. , Davies Guy R. , Handberg Rasmus , Houdek Günter , Huber Daniel , Kjeldsen Hans , Latham David W. , White Timothy R. , Coelho Hugo R. , Miglio Andrea , Rendle Ben 
Published: January 2017

Abstract
We use asteroseismic data from the Kepler satellite to determine fundamental stellar properties of the 66 main-sequence targets observed for at least one full year by the mission. We distributed tens of individual oscillation frequencies extracted from the time series of each star among seven modeling teams who applied different methods to determine radii, masses, and ages for all stars in the sample. Comparisons among the different results reveal a good level of agreement in all stellar properties, which is remarkable considering the variety of codes, input physics, and analysis methods employed by the different teams. Average uncertainties are of the order of ∼2% in radius, ∼4% in mass, and ∼10% in age, making this the best-characterized sample of main-sequence stars available to date. Our predicted initial abundances and mixing-length parameters are checked against inferences from chemical enrichment laws ΔY/ΔZ and predictions from 3D atmospheric simulations. We test the accuracy of the determined stellar properties by comparing them to the Sun, angular diameter measurements, Gaia parallaxes, and binary evolution, finding excellent agreement in all cases and further confirming the robustness of asteroseismically determined physical parameters of stars when individual frequencies of oscillation are available. Baptised as the Kepler dwarfs LEGACY sample, these stars are the solar-like oscillators with the best asteroseismic properties available for at least another decade. All data used in this analysis and the resulting stellar parameters are made publicly available for the community.
The Effect of AGN Heating on the Low-redshift Lyα Forest
Authors: Gurvich Alex , Burkhart Blakesley , Bird Simeon 
Published: January 2017

Abstract
We investigate the effects of AGN heating and the ultraviolet background on the low-redshift Lyα forest column density distribution (CDD) using the Illustris simulation. We show that Illustris reproduces observations at z = 0.1 in the column density range

cm−2, relevant for the “photon underproduction crisis.” We attribute this to the inclusion of AGN feedback, which changes the gas distribution so as to mimic the effect of extra photons, as well as the use of the Faucher-Giguère ultraviolet background, which is more ionizing at z = 0.1 than the Haardt & Madau background previously considered. We show that the difference between simulations run with smoothed particle hydrodynamics and simulations using a moving mesh is small in this column density range but can be more significant at larger column densities. We further consider the effect of supernova feedback, Voigt profile fitting, and finite resolution, all of which we show to have little influence on the CDD. Finally, we identify a discrepancy between our simulations and observations at column densities

cm−2, where Illustris produces too few absorbers, which suggests the AGN feedback model should be further refined. Since the “photon underproduction crisis” primarily affects lower column density systems, we conclude that AGN feedback and standard ionizing background models can resolve the crisis.
The Post-starburst Evolution of Tidal Disruption Event Host Galaxies
Authors: French K. Decker , Arcavi Iair , Zabludoff Ann 
Published: January 2017

Abstract
We constrain the recent star formation histories of the host galaxies of eight optical/UV-detected tidal disruption events (TDEs). Six hosts had quick starbursts of <200 Myr duration that ended 10–1000 Myr ago, indicating that TDEs arise at different times in their hosts’ post-starburst evolution. If the disrupted star formed in the burst or before, the post-burst age constrains its mass, generally excluding O, most B, and highly massive A stars. If the starburst arose from a galaxy merger, the time since the starburst began limits the coalescence timescale and thus the merger mass ratio to more equal than 12:1 in most hosts. This uncommon ratio, if also that of the central supermassive black hole (SMBH) binary, disfavors the scenario in which the TDE rate is boosted by the binary but is insensitive to its mass ratio. The stellar mass fraction created in the burst is 0.5%–10% for most hosts, not enough to explain the observed 30–200× boost in TDE rates, suggesting that the host’s core stellar concentration is more important. TDE hosts have stellar masses 109.4–1010.3 M
☉, consistent with the Sloan Digital Sky Survey volume-corrected, quiescent Balmer-strong comparison sample and implying SMBH masses of 105.5–107.5 M
☉. Subtracting the host absorption line spectrum, we uncover emission lines; at least five hosts have ionization sources inconsistent with star formation that instead may be related to circumnuclear gas, merger shocks, or post-AGB stars.
Properties of Magnetars Mimicking 56Ni-Powered Light Curves in Type IC Superluminous Supernovae
Authors: Moriya Takashi J. , Chen Ting-Wan , Langer Norbert 
Published: January 2017

Abstract
Many Type Ic superluminous supernovae have light-curve decline rates after their luminosity peak, which are close to the nuclear decay rate of

, consistent with the interpretation that they are powered by

and possibly pair-instability supernovae. However, their rise times are typically shorter than those expected from pair-instability supernovae, and Type Ic superluminous supernovae are often suggested to be powered by magnetar spin-down. If magnetar spin-down is actually a major mechanism to power Type Ic superluminous supernovae, it should be able to produce decline rates similar to the

decay rate rather easily. In this study, we investigate the conditions for magnetars under which their spin-down energy input can behave like the

nuclear decay energy input. We find that an initial magnetic field strength within a certain range is sufficient to keep the magnetar energy deposition within a factor of a few of the

decay energy for several hundreds of days. Magnetar spin-down needs to be by almost pure dipole radiation with the braking index close to three to mimic

in a wide parameter range. Not only late-phase

-decay-like light curves, but also rise time and peak luminosity of most

-powered light curves can be reproduced by magnetars. Bolometric light curves for more than 700 days are required to distinguish the two energy sources solely by them. We expect that more slowly declining superluminous supernovae with short rise times should be found if they are mainly powered by magnetar spin-down.
XMM-Newton Observation of the Nearby Pulsar B1133+16
Authors: Szary Andrzej , Gil Janusz , Zhang Bing , Haberl Frank , Melikidze George I. , Geppert Ulrich , Mitra Dipanjan , Xu Ren-Xin 
Published: January 2017

Abstract
We constrain the X-ray properties of the nearby

(
360

pc
)

, old (

5

Myr

) pulsar B1133+16 with

∼
100

ks

effective exposure time by XMM-Newton. The observed pulsar flux in the 0.2–3 keV energy range is

∼

10

−
14

erg

cm

−
2

s

−
1

, which results in the recording of ∼600 source counts with the EPIC pn and MOS detectors. The X-ray radiation is dominated by nonthermal radiation and is well described by both a single power-law model (PL) and a sum of blackbody and power-law emission (BB+PL). The BB+PL model results in a spectral photon index

Γ
=

2.4

−
0.3

+
0.4

and a nonthermal flux in the 0.2–3 keV energy range of

(
7
±
2
)
×

10

−
15

erg

cm

−
2

s

−
1

. The thermal emission is consistent with the blackbody emission from a small hot spot with a radius of

R

pc

≈

14

−
5

+
7

m

and a temperature of

T

s

=

2.9

−
0.4

+
0.6

MK

. Assuming that the hot spot corresponds to the polar cap of the pulsar, we can use the magnetic flux conservation law to estimate the magnetic field at the surface

B

s

≈
3.9
×

10

14

G

. The observations are in good agreement with the predictions of the partially screened gap model, which assumes the existence of small-scale surface magnetic field structures in the polar cap region.
Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultraluminous Infrared Galaxy UGC 5101 with Broadband X-Ray Spectroscopy
Authors: Oda Saeko , Tanimoto Atsushi , Ueda Yoshihiro , Imanishi Masatoshi , Terashima Yuichi , Ricci Claudio 
Published: January 2017

Abstract
We report the broadband X-ray spectra of the ultraluminous infrared galaxy (ULIRG) UGC 5101 in the 0.25–100 keV band observed with the Swift/Burst Alert Telescope (BAT), Nuclear Spectroscopic Telescope Array (NuSTAR), Suzaku, XMM-Newton, and Chandra. A Compton-thick active galactic nucleus (AGN) obscured with a hydrogen column density of

cm−2 is detected above 10 keV. A spectral fit with a numerical torus model favors a large half-opening angle of the torus,

°, suggesting that the covering fraction of material heavily obscuring the X-ray source is moderate. The intrinsic 2–10 keV luminosity is determined to be

erg s−1, which is

times larger than the previous estimate using only data below 10 keV with a simple spectral model. We find that UGC 5101 shows the ratio between the [O iv] 26 μm line and 2–10 keV luminosities similar to those of normal Seyfert galaxies, along with other ULIRGs observed with NuSTAR, indicating that a significant portion of local ULIRGs are not really “X-ray faint” with respect to the flux of forbidden lines originating from the narrow-line region. We propose a possible scenario that (1) the AGN in UGC 5101 is surrounded not only by Compton-thick matter located close to the equatorial plane but also by Compton-thin (

cm−2) matter in the torus-hole region and (2) it is accreting at a high Eddington rate with a steep UV to X-ray spectral energy distribution. Nevertheless, we argue that AGNs in many ULIRGs do not look extraordinary (i.e., extremely X-ray faint), as suggested by recent works, compared with normal Seyferts.
Pruning The ELM Survey: Characterizing Candidate Low-mass White Dwarfs through Photometric Variability
Authors: Bell Keaton J. , Gianninas A. , Hermes J. J. , Winget D. E. , Kilic Mukremin , Montgomery M. H. , Castanheira B. G. , Vanderbosch Z. , Winget K. I. , Brown Warren R. 
Published: January 2017

Abstract
We assess the photometric variability of nine stars with spectroscopic T
eff and log g values from the ELM Survey that locates them near the empirical extremely low-mass (ELM) white dwarf instability strip. We discover three new pulsating stars: SDSS J135512.34+195645.4, SDSS J173521.69+213440.6, and SDSS J213907.42+222708.9. However, these are among the few ELM Survey objects that do not show radial velocity (RV) variations that confirm the binary nature expected of helium-core white dwarfs. The dominant 4.31 hr pulsation in SDSS J135512.34+195645.4 far exceeds the theoretical cut-off for surface reflection in a white dwarf, and this target is likely a high-amplitude δ Scuti pulsator with an overestimated surface gravity. We estimate the probability to be less than 0.0008 that the lack of measured RV variations in four of eight other pulsating candidate ELM white dwarfs could be due to low orbital inclination. Two other targets exhibit variability as photometric binaries. Partial coverage of the 19.342 hr orbit of WD J030818.19+514011.5 reveals deep eclipses that imply a primary radius >0.4 R
⊙—too large to be consistent with an ELM white dwarf. The only object for which our time series photometry adds support to ELM white dwarf classification is SDSS J105435.78−212155.9, which has consistent signatures of Doppler beaming and ellipsoidal variations. We conclude that the ELM Survey contains multiple false positives from another stellar population at T
eff ≲ 9000 K, possibly related to the sdA stars recently reported from SDSS spectra.
Magnetar Central Engine and Possible Gravitational Wave Emission of Nearby Short GRB 160821B
Authors: Lü Hou-Jun , Zhang Hai-Ming , Zhong Shu-Qing , Hou Shu-Jin , Sun Hui , Rice Jared , Liang En-Wei 
Published: January 2017

Abstract
GRB 160821B is a short gamma-ray burst (SGRB) at redshift z = 0.16, with a duration less than 1 s and without any “extended emission” detected up to more than 100 s in both Swift/BAT and Fermi/GBM bands. An X-ray plateau with a sharp drop 180 s after the BAT trigger was observed with Swift/XRT. No supernova or kilo-nova signature was detected. Assuming the central engine of this SGRB is a recently born supra-massive magnetar, we can explain the SGRB as jet radiation and its X-ray plateau as the internal energy dissipation of the pulsar wind as it spins down. We constrain its surface magnetic field to B
p < 3.12 × 1016 G and initial spin period to P
0 < 8.5 × 10−3 s. Its equation of state is consistent with the GM1 model with M
TOV ∼ 2.37 M
⊙ and ellipticity ϵ < 0.07. Its gravitational wave (GW) radiation may be detectable with the future Einstein Telescope, but is much weaker than the current detectability limit of Advanced LIGO. The GW radiation of such an event would be detectable by Advanced LIGO if it occurred at a distance of 100 Mpc (z = 0.023).
Multiband Observations of the Quasar PKS 2326–502 during Active and Quiescent Gamma-Ray States in 2010–2012
Authors: Dutka Michael S. , Carpenter Bryce D. , Ojha Roopesh , Finke Justin D. , D’Ammando Filippo , Kadler Matthias , Edwards Philip G. , Stevens Jamie , Torresi Eleonora , Grandi Paola , Nesci Roberto , Krauß Felicia , Müller Cornelia , Wilms Joern , Gehrels Neil 
Published: January 2017

Abstract
Quasi-simultaneous observations of the Flat Spectrum Radio Quasar PKS 2326−502 were carried out in the γ-ray, X-ray, UV, optical, near-infrared, and radio bands. Using these observations, we are able to characterize the spectral energy distribution (SED) of the source during two flaring and one quiescent γ-ray states. These data were used to constrain one-zone leptonic models of the SEDs of each flare and investigate the physical conditions giving rise to them. While modeling one flare required only changes in the electron spectrum compared to the quiescent state, modeling the other flare required changes in both the electron spectrum and the size of the emitting region. These results are consistent with an emerging pattern of two broad classes of flaring states seen in blazars. Type 1 flares are explained by changes solely in the electron distribution, whereas type 2 flares require a change in an additional parameter. This suggests that different flares, even in the same source, may result from different physical conditions or different regions in the jet.
Testing the Universality of the Stellar IMF with Chandra and HST
Authors: Coulter D. A. , Lehmer B. D. , Eufrasio R. T. , Kundu A. , Maccarone T. , Peacock M. , Hornschemeier A. E. , Basu-Zych A. , Gonzalez A. H. , Maraston C. , Zepf S. E. 
Published: January 2017

Abstract
The stellar initial mass function (IMF), which is often assumed to be universal across unresolved stellar populations, has recently been suggested to be “bottom-heavy” for massive ellipticals. In these galaxies, the prevalence of gravity-sensitive absorption lines (e.g., Na i and Ca ii) in their near-IR spectra implies an excess of low-mass (

) stars over that expected from a canonical IMF observed in low-mass ellipticals. A direct extrapolation of such a bottom-heavy IMF to high stellar masses (

) would lead to a corresponding deficit of neutron stars and black holes, and therefore of low-mass X-ray binaries (LMXBs), per unit near-IR luminosity in these galaxies. Peacock et al. searched for evidence of this trend and found that the observed number of LMXBs per unit K-band luminosity (

) was nearly constant. We extend this work using new and archival Chandra X-ray Observatory and Hubble Space Telescope observations of seven low-mass ellipticals where

is expected to be the largest and compare these data with a variety of IMF models to test which are consistent with the observed

. We reproduce the result of Peacock et al., strengthening the constraint that the slope of the IMF at

must be consistent with a Kroupa-like IMF. We construct an IMF model that is a linear combination of a Milky Way-like IMF and a broken power-law IMF, with a steep slope (

) for stars <0.5

(as suggested by near-IR indices), and that flattens out (

) for stars >0.5

, and discuss its wider ramifications and limitations.
The Relation Between Globular Cluster Systems and Supermassive Black Holes in Spiral Galaxies: The Case Study of NGC 4258
Authors: González-Lópezlira Rosa A. , Lomelí-Núñez Luis , Álamo-Martínez Karla , Órdenes-Briceño Yasna , Loinard Laurent , Georgiev Iskren Y. , Muñoz Roberto P. , Puzia Thomas H. , Bruzual A. Gustavo , Gwyn Stephen 
Published: January 2017

Abstract
We aim to explore the relationship between globular cluster total number,

N

GC

, and central black hole mass, M
•, in spiral galaxies, and compare it with that recently reported for ellipticals. We present results for the Sbc galaxy NGC 4258, from Canada–France–Hawaii Telescope data. Thanks to water masers with Keplerian rotation in a circumnuclear disk, NGC 4258 has the most precisely measured extragalactic distance and supermassive black hole mass to date. The globular cluster (GC) candidate selection is based on the (

u

*

−

i

′

) versus (

i

′

−

K

s

) diagram, which is a superb tool to distinguish GCs from foreground stars, background galaxies, and young stellar clusters, and hence can provide the best number counts of GCs from photometry alone, virtually free of contamination, even if the galaxy is not completely edge-on. The mean optical and optical-near-infrared colors of the clusters are consistent with those of the Milky Way and M 31, after extinction is taken into account. We directly identify 39 GC candidates; after completeness correction, GC luminosity function extrapolation, and correction for spatial coverage, we calculate a total

N

GC

=
144
±

31

−
36

+
38

(random and systematic uncertainties, respectively). We have thus increased to six the sample of spiral galaxies with measurements of both M
• and

N

GC

. NGC 4258 has a specific frequency

S

N

=
0.4
±
0.1

(random uncertainty), and is consistent within 2σ with the

N

GC

versus M
• correlation followed by elliptical galaxies. The Milky Way continues to be the only spiral that deviates significantly from the relation.
Similarity of PSR J1906+0746 to PSR J0737–3039: a Candidate of a New Double Pulsar System?
Authors: Yang Yi-Yan , Zhang Cheng-Min , Li Di , Wang De-Hua , Pan Yuan-Yue , Lingfu Rong-Feng , Zhou Zhu-Wen 
Published: January 2017

Abstract
PSR J1906+0746 is a nonrecycled strong magnetic field neutron star (NS), sharing the properties of the secondary-formed NS PSR J0737–3039B in the double pulsar system PSR J0737–3039AB. By comparing the orbital parameters of PSR J1906+0746 with those of PSR J0737–3039AB, we conclude that both systems have a similar origin and evolution history, involving an e-capture process for forming the second-born NS, like in the case of PSR J0737–3039B. We expect the companion of PSR J1906+0746 to be a long-lived recycled pulsar with radio beams that currently cannot be observed from Earth. We suggest possible ways to detect its presence. To compare PSR J1906+0746 with PSR J0737–3039, we also present the mass distribution of eight pairs of double NSs and find that in double NSs the mass of the recycled pulsar is usually larger than that of the nonrecycled one, which may be the result of accretion.
Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets
Authors: Tan Xianyu , Showman Adam P. 
Published: January 2017

Abstract
The growing number of observations of brown dwarfs (BDs) has provided evidence for strong atmospheric circulation on these objects. Directly imaged planets share similar observations and can be viewed as low-gravity versions of BDs. Vigorous condensate cycles of chemical species in their atmospheres are inferred by observations and theoretical studies, and latent heating associated with condensation is expected to be important in shaping atmospheric circulation and influencing cloud patchiness. We present a qualitative description of the mechanisms by which condensational latent heating influences circulation, and then illustrate them using an idealized general circulation model that includes a condensation cycle of silicates with latent heating and molecular weight effect due to the rainout of the condensate. Simulations with conditions appropriate for typical T dwarfs exhibit the development of localized storms and east–west jets. The storms are spatially inhomogeneous, evolving on a timescale of hours to days and extending vertically from the condensation level to the tropopause. The fractional area of the BD covered by active storms is small. Based on a simple analytic model, we quantitatively explain the area fraction of moist plumes and show its dependence on the radiative timescale and convective available potential energy (CAPE). We predict that if latent heating dominates cloud formation processes, the fractional coverage area of clouds decreases as the spectral type goes through the L/T transition from high to lower effective temperature. This is a natural consequence of the variation of the radiative timescale and CAPE with the spectral type.