bluuebunny/crossref_metadata_2025_split huggingface dataset:
PHOTOIONIZATION MODELS OF THE INNER GASEOUS DISK OF THE HERBIG BE STAR BD+65 1637
Authors: Patel P. , Sigut T. A. A. , Landstreet J. D. 
Published: January 2016

ABSTRACT
We attempt to constrain the physical properties of the inner, gaseous disk of the Herbig Be star BD+65 1637 using non-LTE, circumstellar disk codes and observed spectra (3700–10500 Å) from the ESPaDOnS instrument on the Canada–France–Hawaii Telescope. The photoionizing radiation of the central star is assumed to be the sole source of input energy for the disk. We model optical and near-infrared emission lines that are thought to form in this region using standard techniques that have been successful in modeling the spectra of classical Be stars. By comparing synthetic line profiles of hydrogen, helium, iron, and calcium with the observed line profiles, we try to constrain the geometry, density structure, and kinematics of the gaseous disk. Reasonable matches have been found for all line profiles individually; however, no disk density model based on a single power law for the equatorial density was able to simultaneously fit all of the observed emission lines. Among the emission lines, the metal lines, especially the Ca ii IR triplet, seem to require higher disk densities than the other lines. Excluding the Ca ii lines, a model in which the equatorial disk density falls as 10−10 (R
*/R)3 g cm−3 seen at an inclination of 45° for a 50 R
* disk provides reasonable matches to the overall line shapes and strengths. The Ca ii lines seem to require a shallower drop-off as 10−10 (R
*/R)2 g cm−3 to match their strength. More complex disk density models are likely required to refine the match to the BD+65 1637 spectrum.
THE EVOLUTION OF PLANET–DISK SYSTEMS THAT ARE MILDLY INCLINED TO THE ORBIT OF A BINARY COMPANION
Authors: Lubow Stephen H. , Martin Rebecca G. 
Published: January 2016

ABSTRACT
We determine the evolution of a giant planet–disk system that orbits a member of a binary star system and is mildly inclined with respect to the binary orbital plane. The planet orbit and disk are initially mutually coplanar. We analyze the evolution of the planet and the disk by analytic means and hydrodynamic simulations. We generally find that the planet and the disk do not remain coplanar unless the disk mass is very large or the gap that separates the planet from the disk is very small. The relative planet–disk tilt undergoes secular oscillations whose initial amplitudes are typically of the order of the initial disk tilt relative to the binary orbital plane for disk masses ∼1% of the binary mass or less. The effects of a secular resonance and the disk tilt decay enhance the planet–disk misalignment. The secular resonance plays an important role for disk masses greater than the planet mass. At later times, the accretion of disk gas by the planet causes its orbit to evolve toward alignment, if the disk mass is sufficiently large. The results have several implications for the evolution of massive planets in binary systems.
IS THE PALE BLUE DOT UNIQUE? OPTIMIZED PHOTOMETRIC BANDS FOR IDENTIFYING EARTH-LIKE EXOPLANETS
Authors: Krissansen-Totton Joshua , Schwieterman Edward W. , Charnay Benjamin , Arney Giada , Robinson Tyler D. , Meadows Victoria , Catling David C. 
Published: January 2016

ABSTRACT
The next generation of ground- and space-based telescopes will image habitable planets around nearby stars. A growing literature describes how to characterize such planets with spectroscopy, but less consideration has been given to the usefulness of planet colors. Here, we investigate whether potentially Earth-like exoplanets could be identified using UV-visible-to-NIR wavelength broadband photometry (350–1000 nm). Specifically, we calculate optimal photometric bins for identifying an exo-Earth and distinguishing it from uninhabitable planets including both Solar System objects and model exoplanets. The color of some hypothetical exoplanets—particularly icy terrestrial worlds with thick atmospheres—is similar to Earth's because of Rayleigh scattering in the blue region of the spectrum. Nevertheless, subtle features in Earth's reflectance spectrum appear to be unique. In particular, Earth's reflectance spectrum has a “U-shape” unlike all our hypothetical, uninhabitable planets. This shape is partly biogenic because

-rich, oxidizing air is transparent to sunlight, allowing prominent Rayleigh scattering, while ozone absorbs visible light, creating the bottom of the “U.” Whether such uniqueness has practical utility depends on observational noise. If observations are photon limited or dominated by astrophysical sources (zodiacal light or imperfect starlight suppression), then the use of broadband visible wavelength photometry to identify Earth twins has little practical advantage over obtaining detailed spectra. However, if observations are dominated by dark current, then optimized photometry could greatly assist preliminary characterization. We also calculate the optimal photometric bins for identifying extrasolar Archean Earths, and find that the Archean Earth is more difficult to unambiguously identify than a modern Earth twin.
SPECTRAL VARIATIONS OF THE SKY: CONSTRAINTS ON ALTERNATE UNIVERSES
Authors: Chary R. 
Published: January 2016

ABSTRACT
The fine tuning of parameters required to reproduce our present day universe suggests that our universe may simply be a region within an eternally inflating super-region. Many other regions beyond our observable universe would exist with each such region governed by a different set of physical parameters. Collision between these regions, if they occur, should leave signatures of anisotropy in the cosmic microwave background (CMB) but have not been seen. We analyze the spectral properties of masked, foreground-cleaned maps between 100 and 545 GHz constructed from the Planck data set. Four distinct ∼2°–4° regions associated with CMB cold spots show anomalously strong 143 GHz emission but no correspondingly strong emission at either 100 or 217 GHz. The signal to noise of this 143 GHz residual emission is at the ≳6σ level which reduces to 3.2–5.4σ after subtraction of remaining synchrotron/free–free foregrounds. We assess different mechanisms for this residual emission and conclude that although there is a 30% probability that noise fluctuations may cause foregrounds to fall within 3σ of the excess, there is less than a 0.5% probability that foregrounds can explain all the excess. A plausible explanation is that the collision of our universe with an alternate universe whose baryon to photon ratio is a factor of ∼4500 larger than ours, could produce enhanced hydrogen Paschen-series emission at the epoch of recombination. Future spectral mapping and deeper observations at 100 and 217 GHz are needed to mitigate systematics arising from unknown Galactic foregrounds and to confirm this unusual hypothesis.
THE CHANDRA COSMOS LEGACY SURVEY: OPTICAL/IR IDENTIFICATIONS
Authors: Marchesi S. , Civano F. , Elvis M. , Salvato M. , Brusa M. , Comastri A. , Gilli R. , Hasinger G. , Lanzuisi G. , Miyaji T. , Treister E. , Urry C. M. , Vignali C. , Zamorani G. , Allevato V. , Cappelluti N. , Cardamone C. , Finoguenov A. , Griffiths R. E. , Karim A. , Laigle C. , LaMassa S. M. , Jahnke K. , Ranalli P. , Schawinski K. , Schinnerer E. , Silverman J. D. , Smolcic V. , Suh H. , Trakhtenbrot B. 
Published: January 2016

ABSTRACT
We present the catalog of optical and infrared counterparts of the Chandra COSMOS-Legacy Survey, a 4.6 Ms Chandra program on the 2.2 deg2 of the COSMOS field, combination of 56 new overlapping observations obtained in Cycle 14 with the previous C-COSMOS survey. In this Paper we report the i, K, and 3.6 μm identifications of the 2273 X-ray point sources detected in the new Cycle 14 observations. We use the likelihood ratio technique to derive the association of optical/infrared (IR) counterparts for 97% of the X-ray sources. We also update the information for the 1743 sources detected in C-COSMOS, using new K and 3.6 μm information not available when the C-COSMOS analysis was performed. The final catalog contains 4016 X-ray sources, 97% of which have an optical/IR counterpart and a photometric redshift, while ≃54% of the sources have a spectroscopic redshift. The full catalog, including spectroscopic and photometric redshifts and optical and X-ray properties described here in detail, is available online. We study several X-ray to optical (X/O) properties: with our large statistics we put better constraints on the X/O flux ratio locus, finding a shift toward faint optical magnitudes in both soft and hard X-ray band. We confirm the existence of a correlation between X/O and the the 2–10 keV luminosity for Type 2 sources. We extend to low luminosities the analysis of the correlation between the fraction of obscured AGNs and the hard band luminosity, finding a different behavior between the optically and X-ray classified obscured fraction.
VERTICAL STRUCTURE OF MAGNETIZED ACCRETION DISKS AROUND YOUNG STARS
Authors: Lizano S. , Tapia C. , Boehler Y. , D’Alessio P. 
Published: January 2016

ABSTRACT
We model the vertical structure of the magnetized accretion disks that are subject to viscous and resistive heating and irradiation by the central star. We apply our formalism to the radial structure of the magnetized accretion disks that are threaded by the poloidal magnetic field dragged during the process of star formation, which was developed by Shu and coworkers. We consider disks around low-mass protostars, T Tauri, and FU Orionis stars, as well as two levels of disk magnetization:

(strongly magnetized disks) and

(weakly magnetized disks). The rotation rates of strongly magnetized disks have large deviations from Keplerian rotation. In these models, resistive heating dominates the thermal structure for the FU Ori disk, and the T Tauri disk is very thin and cold because it is strongly compressed by magnetic pressure; it may be too thin compared with observations. Instead, in the weakly magnetized disks, rotation velocities are close to Keplerian, and resistive heating is always less than 7% of the viscous heating. In these models, the T Tauri disk has a larger aspect ratio, which is consistent with that inferred from observations. All the disks have spatially extended hot atmospheres where the irradiation flux is absorbed, although most of the mass (∼90%–95%) is in the disk midplane. With the advent of ALMA one expects direct measurements of magnetic fields and their morphology at disk scales. It will then be possible to determine the mass-to-flux ratio of magnetized accretion disks around young stars, an essential parameter for their structure and evolution. Our models contribute to the understanding of the vertical structure and emission of these disks.
UNUSUAL SHOCK-EXCITED OH MASER EMISSION IN A YOUNG PLANETARY NEBULA
Authors: Qiao Hai-Hua , Walsh Andrew J. , Gómez José F. , Imai Hiroshi , Green James A. , Dawson Joanne R. , Shen Zhi-Qiang , Ellingsen Simon P. , Breen Shari L. , Jones Paul A. , Gibson Steven J. , Cunningham Maria R. 
Published: January 2016

ABSTRACT
We report on OH maser emission toward G336.644−0.695 (IRAS 16333−4807), which is a H2O maser-emitting Planetary Nebula (PN). We have detected 1612, 1667, and 1720 MHz OH masers at two epochs using the Australia Telescope Compact Array, hereby confirming it as the seventh known case of an OH-maser-emitting PN. This is only the second known PN showing 1720 MHz OH masers after K 3−35 and the only evolved stellar object with 1720 MHz OH masers as the strongest transition. This PN is one of a group of very young PNe. The 1612 MHz and 1667 MHz masers are at a similar velocity to the 22 GHz H2O masers, whereas the 1720 MHz masers show a variable spectrum, with several components spread over a higher velocity range (up to 36 km s−1). We also detect Zeeman splitting in the 1720 MHz transition at two epochs (with field strengths of ∼2 to ∼10 mG), which suggests the OH emission at 1720 MHz is formed in a magnetized environment. These 1720 MHz OH masers may trace short-lived equatorial ejections during the formation of the PN.
MONITORING SHORT-TERM COSMIC-RAY SPECTRAL VARIATIONS USING NEUTRON MONITOR TIME-DELAY MEASUREMENTS
Authors: Ruffolo D. , Sáiz A. , Mangeard P.-S. , Kamyan N. , Muangha P. , Nutaro T. , Sumran S. , Chaiwattana C. , Gasiprong N. , Channok C. , Wuttiya C. , Rujiwarodom M. , Tooprakai P. , Asavapibhop B. , Bieber J. W. , Clem J. , Evenson P. , Munakata K. 
Published: January 2016

ABSTRACT
Neutron monitors (NMs) are ground-based detectors of cosmic-ray showers that are widely used for high-precision monitoring of changes in the Galactic cosmic-ray (GCR) flux due to solar storms and solar wind variations. In the present work, we show that a single neutron monitor station can also monitor short-term changes in the GCR spectrum, avoiding the systematic uncertainties in comparing data from different stations, by means of NM time-delay histograms. Using data for 2007–2014 from the Princess Sirindhorn Neutron Monitor, a station at Doi Inthanon, Thailand, with the world’s highest vertical geomagnetic cutoff rigidity of 16.8 GV, we have developed an analysis of time-delay histograms that removes the chance coincidences that can dominate conventional measures of multiplicity. We infer the “leader fraction” L of neutron counts that do not follow a previous neutron count in the same counter from the same atmospheric secondary, which is inversely related to the actual multiplicity and increases for increasing GCR spectral index. After correction for atmospheric pressure and water vapor, we find that L indicates substantial short-term GCR spectral hardening during some but not all Forbush decreases in GCR flux due to solar storms. Such spectral data from Doi Inthanon provide information about cosmic-ray energies beyond the Earth’s maximum geomagnetic cutoff, extending the reach of the worldwide NM network and opening a new avenue in the study of short-term GCR decreases.
OBSERVATIONS OF A SERIES OF FLARES AND ASSOCIATED JET-LIKE ERUPTIONS DRIVEN BY THE EMERGENCE OF TWISTED MAGNETIC FIELDS
Authors: Lim Eun-Kyung , Yurchyshyn Vasyl , Park Sung-Hong , Kim Sujin , Cho Kyung-Suk , Kumar Pankaj , Chae Jongchul , Yang Heesu , Cho Kyuhyoun , Song Donguk , Kim Yeon-Han 
Published: January 2016

ABSTRACT
We studied temporal changes of morphological and magnetic properties of a succession of four confined flares followed by an eruptive flare using the high-resolution New Solar Telescope (NST) operating at the Big Bear Solar Observatory (BBSO) and Helioseismic and Magnetic Imager (HMI) magnetograms and Atmospheric Image Assembly (AIA) EUV images provided by the Solar Dynamics Observatory (SDO). From the NST/Hα and the SDO/AIA 304 Å observations we found that each flare developed a jet structure that evolved in a manner similar to evolution of the blowout jet: (1) an inverted-Y-shaped jet appeared and drifted away from its initial position; (2) jets formed a curtain-like structure that consisted of many fine threads accompanied by subsequent brightenings near the footpoints of the fine threads; and finally, (3) the jet showed a twisted structure visible near the flare maximum. Analysis of the HMI data showed that both the negative magnetic flux and the magnetic helicity have been gradually increasing in the positive-polarity region, indicating the continuous injection of magnetic twist before and during the series of flares. Based on these results, we suggest that the continuous emergence of twisted magnetic flux played an important role in producing successive flares and developing a series of blowout jets.
DETERMINING AGES OF APOGEE GIANTS WITH KNOWN DISTANCES
Authors: Feuillet Diane K. , Bovy Jo , Holtzman Jon , Girardi Léo , MacDonald Nick , Majewski Steven R. , Nidever David L. 
Published: January 2016

ABSTRACT
We present a sample of 705 local giant stars observed using the New Mexico State University 1 m telescope with the Sloan Digital Sky Survey-III/Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectrograph, for which we estimate stellar ages and the local star formation history (SFH). The high-resolution (R ∼ 22,500), near infrared (1.51–1.7 μm) APOGEE spectra provide measurements of stellar atmospheric parameters (temperature, surface gravity, [M/H], and [α/M]). Due to the smaller uncertainties in surface gravity possible with high-resolution spectra and accurate Hipparcos distance measurements, we are able to calculate the stellar masses to within 30%. For giants, the relatively rapid evolution up the red giant branch allows the age to be constrained by the mass. We examine methods of estimating age using both the mass–age relation directly and a Bayesian isochrone matching of measured parameters, assuming a constant SFH. To improve the SFH prior, we use a hierarchical modeling approach to constrain the parameters of the model SFH using the age probability distribution functions of the data. The results of an α-dependent Gaussian SFH model show a clear age–[α/M] relation at all ages. Using this SFH model as the prior for an empirical Bayesian analysis, we determine ages for individual stars. The resulting age–metallicity relation is flat, with a slight decrease in [M/H] at the oldest ages and a ∼0.5 dex spread in metallicity across most ages. For stars with ages ≲1 Gyr we find a smaller spread, consistent with radial migration having a smaller effect on these young stars than on the older stars.
HIGH-RESOLUTION SPECTROSCOPY OF EXTREMELY METAL-POOR STARS IN THE LEAST EVOLVED GALAXIES: BOÖTES II*
Authors: Ji Alexander P. , Frebel Anna , Simon Joshua D. , Geha Marla 
Published: January 2016

ABSTRACT
We present high-resolution Magellan/MIKE spectra of the four brightest confirmed red giant stars in the ultra-faint dwarf galaxy Boötes II (Boo II). These stars all inhabit the metal-poor tail of the Boo II metallicity distribution function. The chemical abundance pattern of all detectable elements in these stars is consistent with that of the Galactic halo. However, all four stars have undetectable amounts of neutron-capture elements Sr and Ba, with upper limits comparable to the lowest ever detected in the halo or in other dwarf galaxies. One star exhibits significant radial velocity variations over time, suggesting it to be in a binary system. Its variable velocity has likely increased past determinations of the Boo II velocity dispersion. Our four stars span a limited metallicity range, but their enhanced α-abundances and low neutron-capture abundances are consistent with the interpretation that Boo II has been enriched by very few generations of stars. The chemical abundance pattern in Boo II confirms the emerging trend that the faintest dwarf galaxies have neutron-capture abundances distinct from the halo, suggesting the dominant source of neutron-capture elements in halo stars may be different than in ultra-faint dwarfs.
A RADIAL VELOCITY TEST FOR SUPERMASSIVE BLACK HOLE BINARIES AS AN EXPLANATION FOR BROAD, DOUBLE-PEAKED EMISSION LINES IN ACTIVE GALACTIC NUCLEI
Authors: Liu Jia , Eracleous Michael , Halpern Jules P. 
Published: January 2016

ABSTRACT
One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked Hα emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. and we use much longer time series for the three objects studied in that paper. Although systematic changes in radial velocity can be traced in many of their lines, they are demonstrably not like those of a spectroscopic binary in a circular orbit. Any spectroscopic binary period must therefore be much longer than the span of the monitoring (assuming a circular orbit), which in turn would require black hole masses that exceed by 1–2 orders of magnitude the values obtained for these objects using techniques such as reverberation mapping and stellar velocity dispersion. Moreover, the response of the double-peaked Balmer line profiles to fluctuations of the ionizing continuum and the shape of the Lyα profiles are incompatible with an SMBH binary. The binary broad-line region hypothesis is therefore disfavored. Other processes evidently shape these line profiles and cause the long-term velocity variations of the double peaks.
THE RELATION BETWEEN SOLAR ERUPTION TOPOLOGIES AND OBSERVED FLARE FEATURES. II. DYNAMICAL EVOLUTION
Authors: Savcheva A. , Pariat E. , McKillop S. , McCauley P. , Hanson E. , Su Y. , DeLuca E. E. 
Published: January 2016

ABSTRACT
A long-established goal of solar physics is to build understanding of solar eruptions and develop flare and coronal mass ejection (CME) forecasting models. In this paper, we continue our investigation of nonlinear forces free field (NLFFF) models by comparing topological properties of the solutions to the evolution of the flare ribbons. In particular, we show that data-constrained NLFFF models of three erupting sigmoid regions (SOL2010-04-08, SOL2010-08-07, and SOL2012-05-12) built to reproduce the active region magnetic field in the pre-flare state can be rendered unstable and the subsequent sequence of unstable solutions produces quasi-separatrix layers that match the flare ribbon evolution as observed by SDO/AIA. We begin with a best-fit equilibrium model for the pre-flare active region. We then add axial flux to the flux rope in the model to move it across the stability boundary. At this point, the magnetofrictional code no longer converges to an equilibrium solution. The flux rope rises as the solutions are iterated. We interpret the sequence of magnetofrictional steps as an evolution of the active region as the flare/CME begins. The magnetic field solutions at different steps are compared with the flare ribbons. The results are fully consistent with the three-dimensional extension of the standard flare/CME model. Our ability to capture essential topological features of flaring active regions with a non-dynamic magnetofrictional code strongly suggests that the pre-flare, large-scale topological structures are preserved as the flux rope becomes unstable and lifts off.