bluuebunny/crossref_metadata_2025_split huggingface dataset:
Japanese VLBI Network Mapping of SiO v = 3 J = 1–0 Maser Emission in W Hydrae
Authors: Imai Hiroshi , Nakashima Jun-ichi , Deguchi Shuji , Yamauchi Aya , Nakagawa Akiharu , Nagayama Takumi 
Published: March 2014

Abstract
We report first on two-epoch mapping observations of SiO $v =$ 3 $J =$ 1–0 maser emission in the semiregular variable W Hydrae using the Japanese VLBI Network. The flux density of the $v =$ 3 $J =$ 1–0 emission detected on 2009 February 28 was two orders of magnitude smaller than those of the $v =$ 1 and $v =$ 2 emissions, while a month and half later the $v =$ 3 flux density suddenly increased by a factor of $\sim $25. In contrast, the $v =$ 1 and $v =$ 2 flux densities decreased during this period, as expected from the optical light curve. At the first epoch, the $v =$ 3 maser features were located inside of a ring composed of the $v =$ 1 and $v =$ 2 features by 6 mas ($\gtrsim $0.5 AU) toward the central star. These offsets are meaningfully larger than the error of the fitted ring radius and the difference in the ring sizes of $v =$ 1 and $v =$ 2 masers ($\lesssim $0.2 AU). The present result at the first epoch suggests that $v =$ 3 $J =$ 1–0 SiO masers are predominantly excited in a pumping mechanism (e.g., collisional pumping) different from that recently proposed on the basis of the line overlap with infrared H$_{2}$O lines. Interestingly, the second-epoch observation revealed that the $v =$ 3 features were located on almost the same ring as the $v =$ 2 ring, which is consistent with what line-overlap theory suggests.
Spectral-Lag Relations in GRB Pulses Detected with HETE-2
Authors: Arimoto Makoto , Kawai Nobuyuki , Asano Katsuaki , Hurley Kevin , Suzuki Motoko , Nakagawa Yujin E. , Shimokawabe Takashi , Pazmino Nicolas Vasquez , Sato Rie , Matsuoka Masaru , Yoshida Atsumasa , Tamagawa Toru , Shirasaki Yuji , Sugita Satoshi , Takahashi Ichiro , Atteia Jean-Luc , Pelangeon Alexandre , Vanderspek Roland , Graziani Carlo , Prigozhin Gregory , Villasenor Joel , Jernigan J. Garrett , Crew Geoffrey B. , Sakamoto Takanori , Ricker George R. , Woosley Stanford E. , Butler Nat , Levine Alan , Doty John P. , Donaghy Timothy Q. , Lamb Donald Q. , Fenimore Edward , Galassi Mark , Boer Michel , Dezalay Jean-Pascal , Olive Jean-François , Braga João , Manchanda Ravi , Pizzichini Graziella 
Published: March 2014

Abstract
Using a pulse-fit method, we investigated the spectral lags between the traditional gamma-ray band (50–400 keV) and the X-ray band (6–25 keV) for 8 GRBs with known redshifts (GRB 010921, GRB 020124, GRB 020127, GRB 021211, GRB 030528, GRB 040924, GRB 041006, and GRB 050408), detected with the WXM and FREGATE instruments aboard the HETE-2 satellite. We found several relations for individual GRB pulses between the spectral lag and other observables, such as the luminosity, pulse duration, and peak energy, $E_{\rm peak}$. The obtained results are consistent with those for BATSE, indicating that the BATSE correlations are still valid at lower energies (6–25 keV). Furthermore, we found that the photon energy dependence for the spectral lags can be reconciled with the simple curvature effect model. We discuss the implications of these results from various points of view.
Molecular Clouds as Cosmic-Ray Barometers
Authors: Casanova Sabrina , Aharonian Felix A. , Fukui Yasuo , Gabici Stefano , Jones David I. , Kawamura Akiko , Onishi Toshikazu , Rowell Gavin , Sano Hidetoshi , Torii Kazufumi , Yamamoto Hiroaki 
Published: March 2014

Abstract
The advent of high sensitivity, high resolution $\gamma$-ray detectors, together with a knowledge of the distribution of the atomic hydrogen and especially of the molecular hydrogen in the Galaxy on a subdegree scale, creates a unique opportunity to explore the flux of cosmic rays in the Galaxy. We here present the new data on the distribution of the molecular hydrogen from a large region of the inner Galaxy obtained by the NANTEN Collaboration. We then introduce a methodology which aims to provide a test bed for current and future $\gamma$-ray observatories to explore the cosmic-ray flux at various positions in our Galaxy. In particular, for a distribution of molecular clouds, as provided by the NANTEN survey, and local cosmic-ray density as measured at the Earth, we estimate the expected GeV to TeV $\gamma$-ray signal, which can then be compared with observations, and use to test the cosmic-ray flux.
The Abundance Pattern of O, Ne, Mg, and Fe in the Interstellar Medium of S0 Galaxy NGC 4382 Observed with Suzaku
Authors: Nagino Ryo , Matsushita Kyoko 
Published: March 2014

Abstract
We derived the O, Ne, Mg, and Fe abundances in the interstellar medium (ISM) of a relatively isolated S0 galaxy, NGC 4382, observed with the Suzaku XIS instruments, and compared the O/Ne/Mg/Fe abundance pattern with that of the ISM in elliptical galaxies. The derived temperature and Fe abundance in the ISM are $\sim$ 0.3 keV and 0.6–2.9 solar, respectively. The abundance ratios are derived with considerable accuracy than the abundances, themselves; that is, the O$/$Fe, Ne$/$Fe, and Mg$/$Fe ratios are 0.3, 0.7, and 0.6 in solar units, respectively. The O$/$Fe ratio is smaller than those of the ISM in elliptical galaxies (NGC 720, NGC 1399, NGC 1404, and NGC 4636) observed with Suzaku. Since O, Ne, and Mg are predominantly synthesized by supernovae (SNe) of type II, the observed abundance pattern indicates that the contribution of SN Ia products is higher in the S0 galaxy than in the elliptical galaxy. Since the hot ISM in early-type galaxies is an accumulation of stellar mass and SN Ia products, the low O$/$Fe ratio in the ISM of NGC 4382 reflects a higher rate of present SNe Ia, or stars containing more SN Ia products than those in elliptical galaxies.
Suzaku Observation of the Southeastern Rim of the Cygnus Loop
Authors: Kosugi Hiroko , Tsunemi Hiroshi , Katsuda Satoru , Uchida Hiroyuki , Kimura Masashi 
Published: March 2014

Abstract
X-ray measured metal abundances of the rim of the Cygnus Loop are known to have two patterns. One, seen at narrow regions along the outermost edge, is 0.5-times the solar value, and the other, seen in the remainder of the rim, is 0.2-times the solar value. While the former is “normal”, as the ISM around the Cygnus Loop, the latter is unexpectedly depleted, and its origin has been puzzling. We have been tackling this issue by observing the rims with X-ray observatories. So far, the normal abundance was observed only at regions where no cloud-shock interactions are suggested. On the contrary, based on our recent Suzaku observations, we find the normal abundance at the southeastern rim where cloud-shock interactions are evident. The spatial variation of the abundance there is similar to that in other normal abundance rims: the normal abundance is present along the outermost edge (4$^\prime$ width regions), while the inner region shows strongly depleted abundances. This structure has been confirmed both by the plasma model fit and by the model-free fit. We noticed that the rim regions showing normal abundance correspond to those with a relatively weak radio intensity. Since the Cygnus Loop is believed to be the result of a cavity explosion, we discuss that the abundance distribution is due to the abundance difference between the cavity wall and its outside. The origin of the depleted abundance still remains an open question.
Optical and Near-Infrared Photometry of Nova V2362 Cyg: Rebrightening Event and Dust Formation
Authors: Arai Akira , Uemura Makoto , Kawabata Koji S. , Maehara Hiroyuki , Nakajima Kazuhiro , Kiyota Seiichiro , Kato Taichi , Ohsugi Takashi , Yamashita Takuya , Isogai Mizuki , Nagae Osamu , Chiyonobu Shingo , Fukazawa Yasushi , Mizuno Tsunefumi , Katagiri Hideaki , Takahashi Hiromitsu , Okita Kiichi , Yoshida Michitoshi , Yanagisawa Kenshi , Sato Shuji , Kino Masaru , Kitagawa Masahiro , Sadakane Kozo 
Published: March 2014

Abstract
We present optical and near-infrared (NIR) photometry of a classical nova, V2362 Cyg ($=$ Nova Cygni 2006). V2362 Cyg experienced a peculiar rebrightening during the period between 100 and 240 d after the maximum of the nova. Our multicolor observation indicates the emergence of a pseudophotosphere with an effective temperature of $\sim\ $9000 K at the rebrightening maximum. After the rebrightening maximum, the object showed a slow fading homogeneously in all of the used bands for one week. This implies that the fading soon after the rebrightening maximum ($\lesssim\ $1 week) was caused by a slowly shrinking pseudophotosphere. Then, the NIR flux drastically increased, while the optical flux steeply declined. The optical and NIR fluxes were consistent with blackbody radiation with a temperature of $\sim\ $1500 K during this NIR rising phase. These facts are likely to be explained by dust formation in the nova ejecta. Assuming an optically thin case, we estimated the dust mass to be 10$^{-10}$–10$^{-8}\ M_{\odot}$, which is less than those in typical dust-forming novae. These results support the senario that a second, long-lasting outflow which caused the rebrightening interacted with a fraction of the initial outflow and formed dust grains.
Time Variability of the Geocoronal Solar-Wind Charge Exchange in the Direction of the Celestial Equator
Authors: Ezoe Yuichiro , Ebisawa Ken , Yamasaki Noriko Y. , Mitsuda Kazuhisa , Yoshitake Hiroshi , Terada Naoki , Miyoshi Yoshizumi , Fujimoto Ryuichi 
Published: March 2014

Abstract
We report on the detection of a time variable OVII line emission in a deep 100 ks Suzaku X-ray Imaging Spectrometer spectrum of the galactic ridge X-ray emission. The observed line intensity is too strong (11$\ \pm\ $2 line unit or photon cm$^{-2}\ $s$^{-1}\ $sr$^{-1}\ $) to be emitted inside the heavily obscured galactic disk. It showed a factor of two time variation that showed a significant ($\sim\ $4$\ \sigma$) correlation with the solar-wind O$^{7+}$ ion flux. The high line intensity and good time correlation with the solar wind strongly suggests that it originated from geocoronal solar-wind charge-exchange emission. We discuss the X-ray line intensity while considering a line-of-sight direction and also theoretical distribution models of the neutral hydrogen and solar wind around Earth. Our results indicate that X-ray observations of geocoronal solar-wind charge-exchange emission can be used to constrain these models.
Generation of Alfvén Waves by Magnetic Reconnection
Authors: Kigure Hiromitsu , Takahashi Kunio , Shibata Kazunari , Yokoyama Takaaki , Nozawa Satoshi 
Published: March 2014

Abstract
In this paper, the results of 2.5-dimensional magnetohydrodynamical simulations are reported for the magnetic reconnection of non-perfectly antiparallel magnetic fields. The magnetic field has a component perpendicular to the computational plane, that is, a guide field. The angle $\theta$ between the magnetic field lines in two half regions was a key parameter in our simulations, whereas the initial distribution of the plasma was assumed to be simple; the density and pressure were uniform, except for the current sheet region. Alfvén waves were generated at the reconnection point and propagated along the reconnected field line. The energy fluxes of the Alfvén waves and the magneto-acoustic waves (slow mode and fast mode) generated by magnetic reconnection were measured. Each flux shows a similar time evolution independent of $\theta$. The percentages of the energies (time integral of energy fluxes) carried by the Alfvén waves and magneto-acoustic waves to the released magnetic energy were calculated. The Alfvén waves carry 38.9%, 36.0%, and 29.5% of the released magnetic energy at the maximum ($\theta =$ 80$^\circ$) in the cases of $\beta =$ 0.1, 1, and 20, respectively, where $\beta$ is the plasma $\beta$ (the ratio of gas pressure to magnetic pressure). The magneto-acoustic waves carry 16.2% ($\theta =$ 70$^\circ$), 25.9% ($\theta =$ 60$^\circ$), and 75.0% ($\theta =$ 180$^\circ$) of the energy at the maximum. Implications of these results for solar coronal heating and acceleration of high-speed solar wind are discussed.
Redshifts of Distant Blazars Limited by Fermi and VHE γ-Ray Observations
Authors: Yang Jianping , Wang Jiancheng 
Published: March 2014

Abstract
Our goal is to limit the redshifts of three blazars, PG 1553$+$113, 3C 66A, and PKS 1424$+$240, through an investigation of their Fermi and VHE (very high energy) $\gamma$-ray observations. We assume that the intrinsic spectra of PG 1553$+$113, 3C 66A, and PKS 1424$+$240 have no cutoff across the Fermi and VHE $\gamma$-ray energy ranges. The intrinsic spectra of VHE $\gamma$-rays are obtained through extrapolation of the Fermi spectra. Comparing the measured and intrinsic VHE spectra due to extragalactic background light (EBL) absorption, we give the redshift upper limits of three blazars, while assuming a specific EBL model. The redshift upper limits of PG 1553$+$113, 3C 66A, and PKS 1424$+$240 are 0.78, 0.58, and 1.19, respectively. Near to the TeV energy the optical depth of VHE $\gamma$ photons might be overestimated by the Franceschini EBL model (Franceschini et al. 2008, A&A, 487, 837), or the second emission component might be present in the VHE spectra and lead the intrinsic photon index to be harder than the Fermi ones.
Suzaku Observation of the Anomalous X-Ray Pulsar 1E 1841−045
Authors: Morii Mikio , Kitamoto Shunji , Shibazaki Noriaki , Kawai Nobuyuki , Arimoto Makoto , Ueno Masaru , Kohmura Takayoshi , Terada Yukikatsu , Yamauchi Shigeo , Takahashi Hiromitsu 
Published: March 2014

Abstract
We report on the results of a Suzaku observation of the anomalous X-ray pulsar (AXP) 1E 1841$-$045 at the center of the supernova remnant Kes 73. We confirmed that the energy-dependent spectral models obtained by previous separate observations were also satisfied over a wide energy range from 0.4 to $\sim$70 keV, simultaneously. Here, the models below $\sim$10 keV were a combination of blackbody (BB) and power-law (PL) functions, or of two BBs with different temperatures at 0.6–7.0 keV (Morii et al. 2003, PASJ, 55, L45), and that above $\sim$20 keV was a PL function (Kuiper et al. 2004, ApJ, 613, 1173). The combination BB $+$ PL $+$ PL was found to best represent the phase-averaged spectrum. Phase-resolved spectroscopy indicated the existence of two emission regions, one with a thermal and the other with a non-thermal nature. The combination BB $+$ BB $+$ PL was also found to represent the phase-averaged spectrum well. However, we found that this model is physically unacceptable due to an excessively large area of the emission region of the blackbody. Nonetheless, we found that the temperatures and radii of the two blackbody components showed moderate correlations in the phase-resolved spectra. The fact that the same correlations have been observed between the phase-averaged spectra of various magnetars (Nakagawa et al. 2009, PASJ, 61, 109) suggests that a self-similar function can approximate the intrinsic energy spectra of magnetars below $\sim$10 keV.
On the Rebrightenings of Classical Novae during the Early Phase
Authors: Tanaka Jumpei , Nogami Daisaku , Fujii Mitsugu , Ayani Kazuya , Kato Taichi 
Published: March 2014

Abstract
We report on the spectral evolution of 6 classical novae (V1186 Sco, V2540 Oph, V4745 Sgr, V5113 Sgr, V458 Vul, and V378 Ser), based on low-resolution spectra obtained at the Fujii-Bisei Observatory and the Bisei Astronomical Observatory, Japan. In the light curves, these 6 novae show several rebrightenings during the early phase lasting $\sim\ $10 d after the first maximum in fast novae, and $\sim\ $100 d in slow novae. The early spectra of all of these novae had emission lines with a P-Cygni profile at the maximum brightness. The absorption component of the P-Cygni profiles then disappeared after the maximum, and reappeared when the novae brightened to the next maximum. We suggest that the re-appearance of the absorption component at the rebrightening can be attributable to a re-expansion of the photosphere after it once shifts sufficiently inside. From the light curves, we found that the time intervals of the rebrightenings of these 6 novae show a similar systematic trend, which is applicable to all types of novae; fast and slow, and Fe II type and hybrid type. Moreover, we note the difference between the spectra at the rebrightenings during the early phase and at the rebrightening in V2362 Cyg, and at the oscillation during the transition phase in V1494 Aql, which means a difference in the physical mechanism of the rebrightening during the early phase and the later oscillations.
First Detection of Ar-K Line Emission from the Cygnus Loop
Authors: Uchida Hiroyuki , Tsunemi Hiroshi , Tominaga Nozomu , Katsuda Satoru , Kimura Masashi , Kosugi Hiroko , Takahashi Hiroaki , Takakura Satoru 
Published: March 2014

Abstract
We observed the Cygnus Loop with XMM-Newton (9 pointings) and Suzaku (32 pointings) between 2002 and 2008. The total effective exposure time is 670.2 ks. By using all of the available data, we intended to improve a signal-to-noise ratio of the spectrum. Accordingly, the accumulated spectra obtained by the XIS and the EPIC show some line features around 3 keV that are attributed to the S He$\beta$ and Ar He$\alpha$ lines, respectively. Since the Cygnus Loop is an evolved ($\sim\ $ 10000 yr) supernova remnant whose temperature is relatively low ($\lt\ $ 1 keV) compared with other young remnants, its spectrum is generally faint above 3.0 keV, no emission lines, such as the Ar-K line, have ever been detected. The detection of the Ar-K line is the first time, and we found that its abundance is significantly higher than that of the solar value: 9.0$^{+4.0}_{\-3.8}$ and 8.4$^{+2.5}_{\-2.7}$ (in units of solar), estimated from the XIS and the EPIC spectra, respectively. We conclude that the Ar-K line originated from the ejecta of the Cygnus Loop. Follow-up X-ray observations to tightly constrain the abundances of Ar-rich ejecta will be useful to accurately estimate the progenitor's mass.
Suzaku X-Ray Follow-Up Observation of Weak-Lensing-Detected Halos in the Field around ZwCl 0823.2+0425
Authors: Watanabe Eri , Takizawa Motokazu , Nakazawa Kazuhiro , Okabe Nobuhiro , Kawaharada Madoka , Babul Arif , Finoguenov Alexis , Smith Graham P. , Taylor James E. 
Published: March 2014

Abstract
We present the results of a Suzaku X-ray follow-up observation of weak-lensing-detected halos in the field around galaxy cluster ZwCl 0823.2$+$0425. We clearly detected X-ray emission associated with most of these halos, and determined their detailed physical parameters, such as the X-ray luminosity, temperature, and metal abundance, for the first time. We found that the X-ray luminosity–temperature relation for these halos agrees with the former typical results. With the mass determined from the weak gravitational lensing data, the mass–temperature relation for them was also investigated, and was found to be consistent with the prediction from a simple self-similar model and the results of previous studies with both lensing and X-ray data. We would like to emphasize that the self-similar scaling relation of the mass and the temperature is shown here for the first time using a weak-lensing selected sample, whereas previous studies of the mass scaling relation used X-ray-selected samples of clusters. Therefore, our study demonstrates the importance of X-ray follow-up observations of shear-selected clusters, and shows that a joint X-ray and lensing analysis will be crucial for clusters discovered by the forthcoming weak-lensing surveys, such as the one planned with Subaru/Hyper-Suprime-Cam.
First Simultaneous Dual-Frequency Phase Referencing VLBI Observation with VERA
Authors: Jung Taehyun , Sohn Bong Won , Kobayashi Hideyuki , Sasao Tetsuo , Hirota Tomoya , Kameya Osamu , Choi Yoon Kyung , Chung Hyun Soo 
Published: March 2014

Abstract
We present the results of the first simultaneous dual-frequency phase referencing VLBI observation with VLBI Exploration of Radio Astrometry (VERA). The experiment was designed to simultaneously observe two adjacent VLBI sources at two different frequencies to test the feasibility of multifrequency phase referencing for the Korean VLBI Network (KVN). The KVN has introduced a multifrequency receiver system that performs simultaneous observations at four frequencies, such as 22, 43, 86, and 129 GHz, in order to calibrate the atmospheric phase fluctuations at 43, 86, or 129 GHz from the phase at 22 GHz. A pair of two bright continuum sources, a BL Lac object NRAO 512 (22 GHz) and a quasar 3C 345 (43 GHz), with a separation angle of 0.$^{\!\!\!\circ}$5 were observed simultaneously. The connected fringe phases of 22 and 43 GHz show very tight correlation that is proportional to the frequency, exhibiting a clearly non-dispersive characteristic of the neutral troposphere to the radio systems. The residual phase, which is the difference of the fringe phase between 43 GHz and a scaled-up phase of 22 GHz by multiplying the frequency ratio of 1.926 ($\nu_{43}/\nu_{22}$), remained constant for more than 2 hr, and showed a weak sinusoidal variation at the first and second half of the observations, respectively. The Allan standard deviation of the residual phase is mostly dominated by white phase noise, implying that the dual-frequency phase referencing can compensate for the atmospheric phase fluctuation effectively. The coherence function of the residual phase indicates that an arbitrarily long-time integration of the fringe visibility is attainable. There is an excellent agreement between the self-calibrated and the phase referenced images of 3C 345. These results are promising for realizing multifrequency phase referencing with the KVN and opening new perspectives in the multifrequency study of VLBI.
Dependence of the Magnetic Energy of Solar Active Regions on the Twist Intensity of the Initial Flux Tubes
Authors: Toriumi Shin , Miyagoshi Takehiro , Yokoyama Takaaki , Isobe Hiroaki , Shibata Kazunari 
Published: March 2014

Abstract
We present a series of numerical experiments that model the evolution of magnetic flux tubes with a different amount of initial twist. As a result of calculations, tightly twisted tubes reveal a rapid two-step emergence to the atmosphere with a slight slowdown at the surface, while weakly twisted tubes show a slow two-step emergence waiting longer the secondary instability to be triggered. This picture of the two-step emergence is highly consistent with recent observations. These tubes show multiple magnetic domes above the surface, indicating that the secondary emergence is caused by an interchange mode of magnetic buoyancy instability. In the case of the weakest twist, the tube exhibits an elongated photospheric structure, and never rises into the corona. The formation of the photospheric structure is due to an inward magnetic tension force of the azimuthal field component of the rising flux tube (i.e., tube's twist). When the twist is weak, the azimuthal field cannot hold the tube's coherency, and the tube extends laterally at the subadiabatic surface. In addition, we newly found that the total magnetic energy measured above the surface depends on the initial twist. Strong twist tubes follow the initial relation between the twist and the magnetic energy, while weak twist tubes deviate from this relation, because these tubes store their magnetic energy in the photospheric structure.