bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spectral Evolution of a New X-Ray Transient MAXI J0556−332 Observed by MAXI, Swift, and RXTE
Authors: Sugizaki Mutsumi , Yamaoka Kazutaka , Matsuoka Masaru , Kennea Jamie A. , Mihara Tatehiro , Hiroi Kazuo , Ishikawa Masaki , Isobe Naoki , Kawai Nobuyuki , Kimura Masashi , Kitayama Hiroki , Kohama Mitsuhiro , Matsumura Takanori , Morii Mikio , Nakagawa Yujin E. , Nakahira Satoshi , Nakajima Motoki , Negoro Hitoshi , Serino Motoko , Shidatsu Megumi , Sootome Tetsuya , Sugimori Kousuke , Suwa Fumitoshi , Toizumi Takahiro , Tomida Hiroshi , Tsuboi Yoko , Tsunemi Hiroshi , Ueda Yoshihiro , Ueno Shiro , Usui Ryuichi , Yamamoto Takayuki , Yamauchi Makoto , Yamazaki Kyohei , Yoshida Atsumasa 
Published: March 2014

Abstract
We report on the spectral evolution of a new X-ray transient, MAXI J0556$-$ 332, observed by MAXI, Swift, and RXTE. The source was discovered on 2011 January 11 (MJD $ =$ 55572) by the MAXI Gas Slit Camera all-sky survey at ($ l$, $ b$) $ =$ (238.$ ^{\!\!\!\circ}$ 9, $-$ 25.$ ^{\!\!\!\circ}$ 2), relatively away from the Galactic plane. Swift/XRT follow-up observations identified it with a previously uncatalogued bright X-ray source, which led to optical identification. For more than one year since its appearance, MAXI J0556$-$ 332 has been X-ray active, with a 2–10 keV intensity above 30 mCrab. The MAXI/GSC data revealed rapid X-ray brightening in the first five days, and a hard-to-soft transition in the meantime. For the following $ \sim$ 70 days, the 0.5–30 keV spectra, obtained by the Swift/XRT and the RXTE/PCA on an almost daily basis, show a gradual hardening, with large flux variability. These spectra are approximated by a cutoff power-law with a photon index of 0.4–1 and a high-energy exponential cutoff at 1.5–5 keV, throughout the initial 10 months where the spectral evolution is mainly represented by a change of the cutoff energy. To be more physical, the spectra are consistently explained by thermal emission from an accretion disk plus Comptonized emission from a boundary layer around a neutron star. This supports the source identification as being a neutron-star X-ray binary. The obtained spectral parameters agree with those of neutron-star X-ray binaries in the soft state, whose luminosity is higher than 1.8 $ \times$ 10$ ^{37}$ erg s$ ^{-1}$. This suggests a source distance of $ &gt;$ 17 kpc.
Gravitational-Wave Memory from the Relativistic Jet of Gamma-Ray Bursts
Authors: Akiba Shota , Nakada Megumi , Yamaguchi Chiyo , Iwamoto Koichi 
Published: March 2014

Abstract
The gravitational-wave (GW) memory from a radiating and decelerating point mass is studied in detail. It is found that for isotropic photon emission the memory generated from the photons is essentially the same as the memory from the point mass that radiated the photons, so that it is anti-beamed. On the other hand, for anisotropic emission the memory from the photons may have a non-vanishing amplitude, even if it is seen at small viewing angles. In the decelerating phases of gamma-ray burst (GRB) jets the kinetic energy of the jet is converted into the energy of gamma-ray photons. It would then be possible to observe a variation in the GW memory associated with GRB jets on the timescale of the gamma-ray emission if the emission is partially anisotropic. Such anisotropy in gamma-ray emission has been suggested by polarizations detected in recent observations of GRBs. The GW memory from GRB jets would provide clues for clarifying the geometry of the jets and the emission mechanism in GRBs. Thus, it will be an interesting target for the next-generation detectors of GWs.
Multicolor Photometry of an Outburst of a New WZ Sge-Type Dwarf Nova, OT J012059.6+325545
Authors: Nakagawa Shinichi , Noguchi Ryo , Iino Eriko , Ogura Kazuyuki , Matsumoto Katsura , Arai Akira , Isogai Mizuki , Uemura Makoto 
Published: March 2014

Abstract
We present our photometric studies of a newly discovered optical transient, OT J012059.6$ +$ 325545, which underwent a large outburst during the period between 2010 November and 2011 January. The amplitude of the outburst was $ \sim$ 8 mag. We performed simultaneous multicolor photometry using g$ '$-, $ R_{\rm C}$-, and $ i'$-band filters from the early stage of the outburst. Time-resolved photometry during its early stage revealed periodic variations with double-peaked profiles, which are referred to as early superhumps, with amplitudes of $ \sim$ 0.08 mag. After rapid fading in the main outburst, we found rebrightening phenomena, which occurred at least nine times. The large amplitude of the outburst, early superhumps, and rebrightening phenomena are typical features of WZ Sge-type dwarf novae. We detected color variations within early superhump modulations, which established this objects as the second system of WZ Sge-type dwarf nova, next to V445 And. We carried out numerical calculations of the accretion disk to explain both of the modulations and the color variations of the early superhump. This modeling of the disk height supports the idea that height variations within the outer disk can produce early-superhump modulations, though we cannot rule out an idea that temperature asymmetry may also play a role.
Active Galactic Nucleus and Extended Starbursts in a Midstage Merger VV 114
Authors: Iono Daisuke , Saito Toshiki , Yun Min S. , Kawabe Ryohei , Espada Daniel , Hagiwara Yoshiaki , Imanishi Masatoshi , Izumi Takuma , Kohno Kotaro , Motohara Kentaro , nakanishi Kouichiro , Sugai Hajime , Tateuchi Ken , Tamura Yoichi , Ueda Junko , Yoshii Yuzuru 
Published: March 2014

Abstract
High-resolution ($ \sim$ 0$ .\!\!\!''$ 4) Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 0 observations of HCO$ ^+$ (4–3) and HCN (4–3) toward a midstage infrared bright merger, VV 114, have revealed a compact nuclear ($ &lt;$ 200 pc) and extended ($ \sim$ 3–4 kpc) dense gas distribution across the eastern part of the galaxy pair. We have found a significant enhancement of HCN (4–3) emission in an unresolved compact and broad (290 km s$ ^{-1}$ ) component found in the eastern nucleus of VV 114, and suggest dense gas associated with the surrounding material around an Active Galactic Nucleus (AGN), with a mass upper limit of $ \lesssim$ 4 $ \times$ 10$ ^{8}$ $ M_{\odot}$ . The extended dense gas is distributed along a filamentary structure with resolved dense gas concentrations ($ \sim$ 230 pc; $ \sim$ 10$ ^{6}$ $ M_{\odot}$ ) separated by a mean projected distance of $ \sim$ 600 pc, many of which are generally consistent with the location of star formation traced in Pa$ \alpha$ emission. Radiative-transfer calculations suggest moderately dense ($ n_{\rm H_2}$ $ =$ 10$ ^{5}$ –10$ ^{6}$ cm$ ^{-3}$ ) gas averaged over the entire emission region. These new ALMA observations demonstrate the strength of the dense gas tracers for identifying both the AGN and the star-formation activity in a galaxy merger, even in the most dust-enshrouded environment in the local universe.
Quasars with Anomalous Hβ Profiles. I. Demographics
Authors: Steinhardt Charles L. , Silverman John D. 
Published: March 2014

Abstract
The H$\beta$ emission line in a typical Type I quasar is composed of a broad base and a narrow core, with the core velocity characteristic of narrow-line region emission, and line-fitting routines typically assume this picture. We test the effects of removing this constraint, and find a substantial group of Type I quasars in the Sloan Digital Sky Survey catalog with H$\beta$ emission line cores broader than 1200 km s$^{-1}$, above the velocity believed possible for gas in the quasar narrow-line region. We identify this group of “anomalous H$\beta$ quasars” (AHQs) as a distinct population because of a variety of spectral and photometric signatures common to these AHQs but atypical of other quasars. These features are similar to some aspects of narrow-line Seyfert 1s and correlations identified by Eigenvector 1, but also contain distinct features that make it difficult to classify AHQs. We demonstrate that AHQs comprise at least 11% and most likely approximately one quarter of the SDSS Type I quasar population at 0.2 $&lt;$ z $&lt;$ 0.8. For AHQs, the [O iii]$\lambda$ 4959, 5007 profile is often better fit by de-linking it from the H$\beta$ core, while a more standard linked fit produces a tight correlation between narrow- and broad-line velocities. We find that [O iii] in AHQs sometimes has a standard narrow-line profile and other times matches the H$\beta$ core, but is rarely in between the two, implying that the broadened core emission arises from a distinct physical region. Another feature of AHQs is a diminished [O ii] line, which might indicate a connection between AHQs and the interstellar mediums of their host galaxies, through reduced photoionization or star formation. We find that it is difficult to produce AHQs using the current quasar standard model.
Suzaku X-Ray Observations of the Accreting NGC 4839 Group of Galaxies and a Radio Relic in the Coma Cluster
Authors: Akamatsu Hiroki , Inoue Susumu , Sato Takuya , Matsusita Kyoko , Ishisaki Yoshitaka , Sarazin Craig L. 
Published: March 2014

Abstract
Based on Suzaku X-ray observations, we studied the hot gas around the NGC 4839 group of galaxies and a radio relic in the outskirts of the Coma cluster. We found a gradual decline in the gas temperature from 5 keV around NGC 4839 to 3.6 keV at the radio relic, across which there is a further, steeper drop down to 1.5 keV. This drop as well as the observed surface brightness profile are consistent with a shock with Mach number ${\cal M} =$ 2.2 $\pm$ 0.5 and velocity $v_{\rm s} =$ (1410 $\pm$ 110) km s$^{-1}$. A lower limit of $B \gt $ 0.33 $\mu$G was derived based on the magnetic field strength around the relic from the upper limits to inverse Compton X-ray emission. Although this suggests that the non-thermal electrons responsible for the relic are generated by diffusive shock acceleration (DSA), the relation between the measured Mach number and the electron spectrum inferred from radio observations are inconsistent with that expected from the simplest, test-particle theory of DSA. Nevertheless, DSA is still viable if it is initiated by the injection of a pre-existing population of non-thermal electrons. Combined with previous measurements, the temperature profile of Coma in the southwest direction is shallower outside NGC 4839, and also slightly shallower in the outermost region. The metal abundance around NGC 4839 is confirmed to be higher than that in its vicinity, implying a significant peak in the abundance profile that decreases to 0.2 solar toward the outskirts. We interpret these facts as being due to ram pressure stripping of metal-enriched gas from NGC 4839 as it falls into Coma. The relic shock may result from the combined interaction of pre-existing intracluster gas, gas associated with NGC 4839, and cooler gas flowing in from the large-scale structure filament in the southwest.
Submillimeter ALMA Observations of the Dense Gas in the Low-Luminosity Type-1 Active Nucleus of NGC1097
Authors: Izumi Takuma , Kohno Kotaro , Martín Sergio , Espada Daniel , Harada Nanase , Matsushita Satoki , Hsieh Pei-Ying , Turner Jean L. , Meier David S. , Schinnerer Eva , Imanishi Masatoshi , Tamura Yoichi , Curran Max T. , Doi Akihiro , Fathi Kambiz , Krips Melanie , Lundgren Andreas A. , Nakai Naomasa , Nakajima Taku , Regan Michael W. , Sheth Kartik , Takano Shuro , Taniguchi Akio , Terashima Yuichi , Tosaki Tomoka , Wiklind Tommy 
Published: March 2014

Abstract
We present the first 100 pc scale view of the dense molecular gas in the central ∼1.3 kpc of the type-1 Seyfert NGC 1097, traced by HCN (J = 4–3) and HCO+ (J = 4–3) lines afforded with ALMA band 7. This galaxy shows significant HCN enhancement with respect to HCO+ and CO in the low-J transitions, which seems to be a common characteristic in AGN environments. Using the ALMA data, we consider the characteristics of the dense gas around this AGN, and search for the mechanism of HCN enhancement. We find a high HCN (J = 4–3) to HCO+ (J = 4–3) line ratio in the nucleus. The upper limit of the brightness temperature ratio of HCN (v 2 = 11f , J = 4–3) to HCN (J = 4–3) is 0.08, which indicates that IR pumping does not significantly affect the pure rotational population in this nucleus. We also find a higher HCN (J = 4–3) to CS (J = 7–6) line ratio in NGC 1097 than in starburst galaxies, which is more than 12.7 on the brightness temperature scale. Combined with similar observations from other galaxies, we tentatively suggest that this ratio appears to be higher in AGN-host galaxies than in pure starburst ones, similar to the widely used HCN to HCO+ ratio. LTE and non-LTE modeling of the observed HCN and HCO+ lines using J = 4–3 and 1–0 data from ALMA, and J = 3–2 data from SMA, reveals a high HCN to HCO+ abundance ratio (5 ≤ [HCN]/[HCO+] ≤ 20: non-LTE analysis) in the nucleus, and that the high-J lines (J = 4–3 and 3–2) are emitted from dense (104.5 cm-3 ≤ n H2 ≤ 106 cm-3), hot (70K ≤ T kin ≤ 550 K) regions. Finally we propose that “high-temperature chemistry” is more plausible to explain the observed enhanced HCN emission in NGC 1097 than pure gas-phase PDR/XDR chemistry.
A Relation of the PAH3.3μm Feature with Star-forming Activity for Galaxies with aWide Range of Infrared Luminosity
Authors: Yamada Rika , Oyabu Shinki , Kaneda Hidehiro , Yamagishi Mitsuyoshi , Ishihara Daisuke , Kim Ji Hoon , Im Myungshin 
Published: March 2014

Abstract
For star-forming galaxies, we investigated a global relation between the polycyclic aromatic hydrocarbon (PAH) emission luminosity at 3.3μm, LPAH3.3, and the infrared (8–1000μm) luminosity, LIR, to understand how the PAH3.3μm feature relates to star-formation activity. With AKARI, we performed near-infrared (2.5–5μm) spectroscopy of 184 galaxies having LIR ∼ 108–1013L⊙. We classified the samples into infrared galaxies (IRGs: LIR &lt; 1011L⊙), luminous infrared galaxies (LIRGs: LIR ∼ 1011–1012L⊙) and ultra-luminous infrared galaxies (ULIRGs: LIR &gt; 1012L⊙). We excluded sources likely to be contaminated by AGN activity, based on the restframe equivalent width of the PAH emission feature (&lt;40 nm) and the power-law index, representing the slope of continuum emission (Γ &gt; 1; Fv ∝ λΓ). Of these samples, 13 IRGs, 67 LIRGs, and 20 ULIRGs show the PAH emission feature at λrest = 3.3μm in their spectra. We find that the LPAH3.3/LIR ratio considerably decreases toward the luminous end. Utilizing the mass and temperature of dust grains as well as the Brα emission for the galaxies, we discuss the cause of the relative decrease in the PAH emission with LIR.
Density-Independent Smoothed Particle Hydrodynamics for a Non-Ideal Equation of State
Authors: Hosono Natsuki , Saitoh Takayuki R. , Makino Junichiro 
Published: March 2014

Abstract
The smoothed particle hydrodynamics (SPH) method is a useful numerical tool to study a variety of astrophysical and planetlogical problems. However, it turned out that the standard SPH algorithm has problems in dealing with hydrodynamical instabilities. This problem is due to the assumption that the local density distribution is differentiable. In order to solve this problem, a new SPH formulation, which does not require the differentiability of the density, was proposed. This new SPH method improved the treatment of hydrodynamical instabilities. This method, however, is applicable only to the equation of state (EOS) of an ideal gas. In this paper, we describe how to extend the new SPH method to non-ideal EOS. We present the results of various standard numerical tests for non-ideal EOS. Our new method works well for non-ideal EOS. We conclude that our new SPH can handle hydrodynamical instabilities for an arbitrary EOS, and that it is an attractive alternative to the standard SPH.
Study of Superoutbursts and Superhumps in SU UMa Stars by the Kepler Light Curves of V344Lyrae and V1504 Cygni
Authors: Osaki Yoji , Kato Taichi 
Published: March 2014

AbstractWe have studied the short-cadence Kepler public light curves of two SU UMa stars, V344 Lyr and V1504 Cyg, extending over a period of more than two years by using power spectral analysis. We determined the orbital period of V344 Lyr to be Porb = 0.087903(1)d. We also reanalyzed the frequency variation of the negative superhump in a complete supercycle of V1504 Cyg with additional data of the O – C diagram, confirming that its characteristic variation is in accordance with the thermal-tidal instability model. We present a new two-dimensional period analysis based on a new method of a least absolute shrinkage and selection operator (Lasso). The new method gives very sharp peaks in the power spectra, and it is very useful for studying the frequency variation in cataclysmic variable stars. We have analyzed simultaneous frequency variations of the positive and negative superhumps. If they are appropriately converted, it is found that they vary in unison, indicating that they represent a disk-radius variation. We have also studied the frequency (or period) variations of positive superhumps during superoutbursts. These variations can be understood in a qualitative way by combining the disk-radius variation and the variation of pressure effects during a superoutburst. A sudden excitation of oscillation with a frequency range near to the negative superhump (which we call “impulsive negative superhump”) was observed in the descending branch of several outbursts of V344 Lyr. These events seem to have occurred just prior to the next superoutburst, and to act as a “lead” of the impending superoutburst.
Analysis of Three SU UMa-Type Dwarf Novae in the Kepler Field
Authors: Kato Taichi , Osaki Yoji 
Published: March 2014

Abstract
We studied Kepler light curves of three SU UMa-type dwarf novae: a background dwarf nova of KIC 4378554, V585 Lyr, and V516 Lyr. Both the background dwarf nova and V516 Lyr showed a combination of a precursor and a main superoutburst, during which superhumps always developed in the fading branch of the precursor. This finding supports that the thermal-tidal instability theory explains the origin of superoutburst. A superoutburst of V585 Lyr recorded by Kepler did not show a precursor outburst, and the superhumps developed only after the maximum light: namely, the first-ever example in the Kepler data. Such a superoutburst is understood based on the thermaltidal instability model to be a “case B” superoutburst, discussed by Osaki and Meyer (2003, A&A, 401, 325). From the observation of V585 Lyr, Kepler first clearly revealed the positive period derivative commonly seen in the “stage B” superhumps of dwarf novae with a short orbital period. In all three objects, there was no strong signature of a transition to the dominating stream impact-type component of superhumps. This finding suggests that there is no strong indication of an enhanced mass-transfer following the superoutburst. In V585 Lyr, there were “mini-rebrightenings” with an amplitude of 0.2–0.4 mag and its period of 0.4–0.6d during the period between the superoutburst and the rebrightening. We have determined that the orbital period of V516 Lyr is 0.083999(8)d. In V516 Lyr, some of outbursts were double outbursts with varying degrees. The preceding outburst in the double was of the inside-out nature, while the following one was of the outside-in nature. One of the superoutbursts in V516 Lyr was preceded by a double precursor. The preceding precursor failed to trigger a superoutburst, and the following precursor triggered a superoutburst by developing positive superhumps. We have also developed new methods of reconstructing the light curve of superhumps, and of measuring the times of maxima from poorly sampled Kepler LC data.
An Observational Study of the Temperature and Surface Density Structures of a Typical Full Disk around MWC480
Authors: Akiyama Eiji , Momose Munetake , Kitamura Yoshimi , Tsukagoshi Takashi , Shimada Shota , Koyamatsu Shin , Hayashi Masahiko 
Published: March 2014

Abstract
This paper presents observations of a protoplanetary disk around a Herbig Ae star,MWC480, in $^{12}\textrm {CO} (J=1-0),^{12}\textrm {CO} (J=3-2),^{13}\textrm {CO} (J=1-0), \textrm {and} \textrm {C}^{18} \textrm{O} (J=1-0) $ emission lines. Double-peaked emission profiles originating from the rotating circumstellar disk were detected in all of the lines. The vertical temperature and radial surface density structures of the outer region of the disk were derived by applying the similarity solution in the standard accretion disk model. Taking advantage of differences in the height of the photosphere among the CO lines, the temperature in the uppermost $^{12}\textrm {CO} (J=3-2)$ emitting layer was shown to be about 3-times higher than that of any other CO emitting region, suggesting that there are at least two distinct temperature regions. Our modeling succeeds in describing all of the observational results obtained in the four CO lines, particularly different emission extents at different frequencies, by a single set of the parameters for a disk model. Since the similarity solution model could be the most suitable for the radial surface density structure, it is likely that the disk around MWC480 evolves by transferring angular momentum outward via viscous diffusion. Although further quantitative studies are required for identifying what disk model is the best for describing physical disk structures, our results suggest the potential advantage of the similarity solution model, indicating that disks around Herbig Ae/Be stars likely have diffused gas in the outer regions, and that the disk surface density exponentially decreases with increasing radial distance.
Measurements of Coronal and Chromospheric Magnetic Fields Using Polarization Observations by the Nobeyama Radioheliograph
Authors: Iwai Kazumasa , Shibasaki Kiyoto 
Published: March 2014

Abstract
Coronal and chromospheric magnetic fields are derived from polarization and spectral observations of the thermal free-free emission using the Nobeyama Radioheliograph (NoRH). In magnetized plasma, the ordinary and extraordinary modes of free-free emission have different optical depths. This creates a circularly polarized component in an atmosphere with a temperature gradient. We observed an active region on 2012 April 13 to derive its coronal and chromospheric magnetic fields. The observed degree of circular polarization was between 0.5% and 1.7%. The radio circular polarization images were compared with ultraviolet images observed by the Atmospheric Imaging Assembly and the photospheric magnetic field observed by the Helioseismic and Magnetic Imager, both on board the Solar Dynamic Observatory. At the edge of the active region, the radio circular polarization was emitted mainly from coronal loops, and the coronal magnetic field was derived to be about 70 G. At the center of the active region, the chromospheric and coronal components cannot be separated. The derived magnetic field is about 20% to 50% of the corresponding photospheric magnetic field, which is an emission-measure-weighted average of the coronal and chromospheric magnetic fields.