bluuebunny/crossref_metadata_2025 huggingface dataset:
Atlas and Catalog of Dark Clouds Based on the 2 Micron All Sky Survey. II. Correction of the Background Using the Besançon Galaxy Model
Authors: Dobashi Kazuhito , Marshall Douglas J. , Shimoikura Tomomi , Bernard Jean-Philippe
Published: March 2014

In this paper, we give a correction to the large scale color excess maps of $ E$ ($ J$$-$$ H$ ) and $ E$ ($ H$$-$$ K_{\rm S}$ ) derived by Dobashi (2011, PASJ, 63, S1) based on the 2 Micron All Sky Survey Point Source Catalog (2MASS PSC). These maps were produced using a new technique named $ X$ percentile method, and they cover all of the sky at the $ 1'$ grid. The maps, however, suffer from an apparent error on a large scale arising from an ambiguity in determining the background star colors. The error is relatively large in the inner region of the Galaxy at $ \vert l\vert$$ \lesssim$ 90$ ^\circ$ , and the maps may overestimate the true extinction by a few magnitudes in $ A_V$ in this region. To improve the background determination, we performed a Monte Carlo simulation to generate a star catalog equivalent to the 2MASS PSC based on the Besançon Galaxy Model described by Robin et al. (2003, A&A, 409, 523). The simulated catalog contains $ \sim$ 7.7 $ \times$ 10$ ^{8}$ stars whose apparent magnitudes in the $ J$ , $ H$ , and $ K_{\rm S}$ bands are calculated assuming no interstellar dust throughout the Galaxy. We applied the $ X$ percentile method to the simulated star catalog, and regarded the resulting star color maps as the background. As a result, the overestimation in the original color excess maps has been significantly improved. Extinction maps of $ A_J$ , $ A_H$ , and $ A_{K_{\rm S}}$ made by Dobashi (2011) were also improved utilizing the resulting color excess maps. In this paper, we further investigated possible errors arising from the $ X$ percentile method itself by setting an artificial diffuse dust disk in the simulated star catalog, and found that the diffuse dust on a large scale can be underestimated by $ \sim$ 20% for the galactic latitude range $ \vert b\vert$$ >$ 5$ ^\circ$ at most, which should be noted when the color excess maps are compared with other dataset including the far-infrared dust emission detected by Planck and Herschel satellites.
X-Ray Echo from the Sagittarius C Complex and 500-year Activity History of Sagittarius A*
Authors: Ryu Syukyo Gando , Nobukawa Masayoshi , Nakashima Shinya , Tsuru Takeshi Go , Koyama Katsuji , Uchiyama Hideki
Published: March 2014

This paper presents Suzaku results obtained for the Sagittarius (Sgr) C region using the concept of X-ray reflection nebulae (XRNe) as the echo of past flares from a super-massive black hole, Sgr A*. The Sgr C complex is composed of several molecular clouds proximately located in projected distance. The X-ray spectra of Sgr C were analyzed based on the view that XRNe are located inside the Galactic center plasma X-ray emission with an oval distribution around Sgr A*. We found that XRNe are largely separated in the line-of-sight position, and are associated with molecular clouds in different velocity ranges detected by radio observations. We also applied the same analysis to Sgr B XRNe, and completed a long-term light curve for Sgr A* occurring in the past. As a new finding, we determined that Sgr A* has already experienced periods of high luminosity, $ \sim$ 500 years ago, which is longer than the previously reported value. Our results are consistent with a scenario that Sgr A* was continuously active with sporadic flux variabilities of $ L_{\rm X}$  $ =$ (1–3) $ \times$ 10$ ^{39}$ erg s$ ^{-1}$ in the past 50 to 500 years. The average past luminosity was approximately 4–6 orders of magnitude higher than that presently observed. In addition, two short-term flares of 5–10 years have been found. Thus, the past X-ray flare should not be a single short-term flare, but can be interpreted as multiple flares superposed on a long-term high state.
Detection of Far-Infrared Emission from Galaxies and Quasars in the Galactic Extinction Map by Stacking Analysis
Authors: Kashiwagi Toshiya , Yahata Kazuhiro , Suto Yasushi
Published: March 2014

We performed stacking image analyses of galaxies over a Galactic extinction map constructed by Schlegel, Finkbeiner, and Davis (1998, AJ, 500, 525). We selected $ \sim$ 10$ ^{7}$ galaxies in total from the Sloan Digital Sky Survey (SDSS) DR7 photometric catalog. We detected clear signatures of the enhancement of the extinction in the $ r$-band, $ \Delta A_r$ , around galaxies, indicating that the extinction map is contaminated by their FIR (far-infrared) emission. The average amplitude of the contamination per galaxy was well-fitted to $ \Delta A_r$ ($ m_r$ ) $ =$ 0.64 $ \times$ 10$ ^{0.17(18-m_r)}$ [mmag]. While this value is very small, it is directly associated with galaxies, and may have a systematic effect on galaxy statistics. Indeed, this correlated contamination leads to a relatively large anomaly of galaxy surface number densities against the SFD extinction, $ A_{\rm SFD}$ , discovered by Yahata et al. (2007, PASJ, 59, 205). We modeled the radial profiles of stacked galaxy images, and found that the FIR signal around each galaxy does not originate from the central galaxy alone, but is dominated by the contributions of nearby galaxies via galaxy angular clustering. The separation of the single galaxy and the clustering terms enables us to infer the statistical relation of the FIR and $ r$-band fluxes of galaxies, and also to probe the flux-weighted cross-correlation of galaxies, down to magnitudes that are difficult to probe directly for individual objects. We repeated the same stacking analysis for SDSS DR6 photometric quasars, and discovered similar signatures, but with weaker amplitudes. The implications of the present results for galaxy and quasar statistics, and for corrections to the Galactic extinction map, are briefly discussed.
An X-Ray Study of the Galactic-Scale Starburst-Driven Outflow in NGC 253
Authors: Mitsuishi Ikuyuki , Yamasaki Noriko Y. , Takei Yoh
Published: March 2014

The X-ray properties of hot interstellar gas in a bright, nearby edge-on starburst galaxy, NGC 253, were investigated so as to gain a further understanding of starburst-driven outflow activity by utilizing XMM-Newton and Suzaku. Spectroscopic analyses for three regions of the galaxy characterized by multiwavelength observations, i.e., the superwind region, the disk region, and the halo region, were conducted. Various emission lines from O, Ne, Mg, Si, and Fe were observed in the spectra of each region. The hot gas was represented by two thin thermal plasmas with temperatures of $ kT$  $ \sim$ 0.2 and $ \sim$ 0.6 keV. The abundance ratios, i.e., O$ /$ Fe, Ne$ /$ Fe, Mg$ /$ Fe, and Si$ /$ Fe, are consistent between the three regions, which suggests a common origin of the hot gas. The abundance patterns are consistent with those of type II supernova ejecta, indicating that the starburst activity in the central region provides metals toward the halo through a galactic-scale starburst-driven outflow. The energetics can also support this indication on the condition that 0.01–50 $ \eta^{1/2}$ % of the total emission in the nuclear region has flowed to the halo region. To constrain the dynamics of hot interstellar gas, surface brightness, and hardness ratio profiles, which trace the density and temperature, were extracted. Assuming a simple polytropic equation of state for gas, $ T\rho^{1-\gamma}$  $ =$ const, we constrained the physical condition; $ \gamma$ is consistent with 5$ /$ 3 at a hot disk of $ <$ 3 kpc from the center along with the minor axis, and $ T$ is constant ($ \gamma$  $ =$ 1) in the halo, the distance of which is between 3 and 10 kpc from the center. It is suggested that the hot gas expands adiabatically from the central region towards the halo region while it moves as free expansion from the inner part of the halo towards the outer part of the halo as the outflow. We constrained the outflow velocity to be $ >$ 100 km s$ ^{-1}$ based on the observed temperature gradient in the halo. In comparison with the escape velocity of $ \sim$ 220 km s$ ^{-1}$ for NGC 253, it is indicated that the hot interstellar gas can escape from the gravitational potential of NGC 253 by combining the outflow velocity and the thermal velocity.
High-Precision Measurements of the Brightness Variation of Nereid
Authors: Terai Tsuyoshi , Itoh Yoichi
Published: March 2014

Nereid, the outer satellite of Neptune, has a highly eccentric prograde orbit with a semimajor axis of larger than 200 in units of Neptune's radius, and is classified as an irregular satellite. Although the capture origin of irregular satellites has been widely accepted, several previous studies suggest that Nereid was formed in the circumplanetary disk of Neptune and ejected outward to the present location by Triton. A series of our photometric observations confirm that Nereid's rotation period, 11.5 hr, is stable and nonchaotic, as indicated by Grav, Holman, and Kavelaars (2003, ApJ, 591, L71). The optical colors of Nereid are indistinguishable from those of trans-Neptunian objects and Centaurs, especially from these objects with neutral colors. We also found the consistency of Nereid's rotation period based on the size–rotation distribution of small outer bodies. It is likely that Nereid originated as an immigrant body captured from the heliocentric orbit that was 4–5 AU away from Neptune's orbit.
Can Superflares Occur on Our Sun?
Authors: Shibata Kazunari , Isobe Hiroaki , Hillier Andrew , Choudhuri Arnab Rai , Maehara Hiroyuki , Ishii Takako T. , Shibayama Takuya , Notsu Shota , Notsu Yuta , Nagao Takashi , Honda Satoshi , Nogami Daisaku
Published: March 2014

Recent observations of Sun-like stars, similar to our Sun in their surface temperature (5600–6000 K) and slow rotation (rotational period $ >$ 10 d), using the Kepler satellite by Maehara et al. (2012, Nature, 485, 478) have revealed the existence of superflares (with energy of 10$ ^{33}$ –10$ ^{35}$ erg). From statistical analyses of these superflares, it was found that superflares with energy of 10$ ^{34}$ erg occur once in 800 yr, and superflares with 10$ ^{35}$ erg occur once in 5000 yr. In this paper, we examine whether superflares with energy of 10$ ^{33}$ –10$ ^{35}$ erg could occur on the present Sun through the use of simple order-of-magnitude estimates based on current ideas related to the mechanisms of the solar dynamo. If magnetic flux is generated by differential rotation at the base of the convection zone, as assumed in typical dynamo models, it is possible that the present Sun would generate a large sunspot with a total magnetic flux of $ \sim$ 2 $ \times$ 10$ ^{23}$ Mx ($ =$ G cm$ ^{2}$ ) within one solar cycle period, and lead to superflares with an energy of 10$ ^{34}$ erg. To store a total magnetic flux of $ \sim$ 10$ ^{24}$ Mx, necessary for generating 10$ ^{35}$ erg superflares, it would take $ \sim$ 40 yr. Hot Jupiters have often been argued to be a necessary ingredient for the generation of superflares, but we found that they do not play any essential role in the generation of magnetic flux in the star itself, if we consider only the magnetic interaction between the star and the hot Jupiter. This seems to be consistent with Maehara et al.'s finding of 148 superflare-generating solar-type stars that do not have a hot Jupiter-like companion. Altogether, our simple calculations, combined with Maehara et al.'s analysis of superflares on Sun-like stars, show that there is a possibility that superflares of 10$ ^{34}$ erg would occur once in 800 yr on our present Sun.
Detection of Change in Supercycles in ER Ursae Majoris
Authors: Zemko Polina , Kato Taichi , Shugarov Sergei Yu.
Published: March 2014

We examined data from observations of ER UMa during a period of $ \sim$ 20 years available in the AAVSO, VSNET, AFOEV, NSVS, and VSOLJ databases together with published light curves. The obtained $ O$$-$$ C$ diagram revealed a systematic change of the supercycle (time interval between two successive superoutbursts) ranging from 43.6 to 59.2 d. The time-scale of this cycle variation is from 300 to $ \sim$ 1900 d. The number of normal outbursts within the supercycles also varied between 4 and 6, although no strong correlation between this number and the supercycle length was found. We suggest that the appearance of negative superhumps is responsible for the observed variations in the number of normal outbursts. Our results generally confirm the expectations based on the thermal-tidal instability theory.
Tidal Instability and Superhump in Dwarf Novae Described by a Wave-Wave Resonant Process
Authors: Kato Shoji
Published: March 2014

On a disk deformed to a non-axisymmetric form, a set of oscillations can be excited by their resonant interaction through the disk deformation (Kato et al. 2011). This resonant instability process has been proposed to suggest a possible cause of the high-frequency quasi-periodic oscillations (HFQPOs) observed in black-hole low-mass X-ray binaries. In the present paper, we examine whether the above-mentioned wave-wave resonant process can describe the tidal instability and superhump in dwarf novae. The results show that the process seems to well describe the observations. If this process is really the cause of the tidal instability and superhump, a two-armed oscillation with high frequency roughly on the magnitude of three-times the orbital frequency is present on disks, although its expected amplitude may be small.
Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020 4320: Recently Restarted Jet Activity?
Authors: Doi Akihiro , Murata Yasuhiro , Mochizuki Nanako , Takeuchi Hiroshi , Asada Keiichi , Hayashi Takayuki J. , Nagai Hiroshi , Shibata Katsunori M. , Oyama Tomoaki , Jike Takaaki , Fujisawa Kenta , Sugiyama Koichiro , Ogawa Hideo , Kimura Kimihiro , Honma Mareki , Kobayashi Hideyuki , Koyama Shoka
Published: March 2014

This paper reports on very-long-baseline interferometry observations of the radio-loud broad absorption line (BAL) quasar J1020$ +$ 4320 at 1.7, 2.3, 6.7, and 8.4 GHz using the Japanese VLBI network (JVN) and European VLBI network (EVN). The radio morphology is compact with a size of $ \sim$ 10 pc. The convex radio spectrum has been stable over the last decade; an observed peak frequency of 3.2 GHz is equivalent to 9.5 GHz in the rest frame, suggesting an age on the order of $ \sim$ 100 years as a radio source, according to an observed correlation between the linear size and the peak frequency of compact steep spectrum (CSS) and giga-hertz peaked spectrum (GPS) radio sources. A low-frequency radio excess suggests a relic of past jet activity. J1020$ +$ 4320 may be one of the quasars with recurrent and short-lived jet activity during a BAL-outflowing phase.
Numerical Simulations of Solar Chromospheric Jets Associated with Emerging Flux
Authors: Takasao Shinsuke , Isobe Hiroaki , Shibata Kazunari
Published: March 2014

We studied the acceleration mechanisms of chromospheric jets associated with emerging flux using a two-dimensional magnetohydrodynamic (MHD) simulation. We found that slow-mode shock waves generated by magnetic reconnection in the chromosphere and the photosphere play key roles in the acceleration mechanisms of chromospheric jets. An important parameter is the height of magnetic reconnection. When magnetic reconnection takes place near the photosphere, the reconnection outflow collides with the region where the plasma beta is much larger than unity. Then, the plasma moves along a magnetic field. This motion generates a slow-mode wave. The slow-mode wave develops to a strong slow shock as it propagates upward. When the slow shock crosses the transition region, this region is lifted up. As a result, we obtain a chromospheric jet as the lifted transition region. When magnetic reconnection takes place in the upper chromosphere, the chromospheric plasma is accelerated due to the combination of the Lorentz force and the whip-like motion of the magnetic field. We found that the chromospheric plasma is further accelerated through the interaction between the transition region (steep density gradient) and a slow shock emanating from the reconnection point. In the process, the magnetic energy released by magnetic reconnection is efficiently converted into the kinetic energy of jets. This is an MHD effect that has not been discussed before.
Carbon Abundances of Metal-Poor Stars Determined from the C I 1.068–1.069 μm Lines
Authors: Takeda Yoichi , Takada-Hidai Masahide
Published: March 2014

A non-LTE analysis of C I lines at 1.068–1.069 $ \mu$ m was carried out for selected 46 halo/disk stars covering a wide metallicity range ($-$ 3.7 $ ≲$ [Fe$ /$ H] $ ≲$  $ +$ 0.3), based on spectral data collected with IRCS $ +$ AO188 of the Subaru Telescope. This was done in order to examine whether and how these strong neutral carbon lines of multiplet 1 can be exploited for establishing stellar carbon abundances, especially for very metal-poor stars where CH molecular lines have been commonly used. These C I lines were confirmed to be clearly visible for all stars down to [Fe$ /$ H] $ \sim$  $-$ 3.7, from which the C abundances could be successfully determined. The resulting [C$ /$ Fe] vs. [Fe$ /$ H] diagram revealed almost the same trend established from previous studies. When the results for individual stars are compared with published data collected from various literature, while a reasonable agreement is seen as a whole, a tendency is observed that our abundances are appreciably higher than those from CH lines, especially for very metal-poor giants of low gravity. Since the abundances of these C I lines are subject to rather large non-LTE corrections (typically by several tenths dex), whose importance progressively grows as the metallicity is lowered, attention should be paid to how the collisional rates (especially due to neutral hydrogen) are treated in non-LTE calculations.
Non-Thermal Radio and Gamma-Ray Emissions from a Supernova Remnant by Blast Wave Breaking Out of the Circumstellar Matter
Authors: Shimizu Takafumi , Masai Kuniaki , Koyama Katsuji
Published: March 2014

We calculated synchrotron radio emission and $ \gamma $-ray emission due to bremsstrahlung, inverse-Compton scattering, and $ \pi ^0$-decay from the remnant of supernova that exploded in the circumstellar matter (CSM) formed by the progenitor's stellar wind. This sort of situation is a possible origin of mixed-morphology supernova remnants (SNRs), like W 49B, which exhibit recombination-radiation spectra in X-ray emission. We assumed that the CSM of 1.5 $ M_{\odot}$ exists at 0.07–3 pc away from the supernova in the interstellar medium (ISM) of density 0.016 cm$ ^{-3}$ . When the blast wave breaks out of the CSM into the ISM, its velocity rapidly increases, and hence particle acceleration is enhanced. The maximum energy of protons reaches $ \sim$ 1300 TeV just after the break-out with $ \sim$ 0.5% of the explosion energy. We considered the non-thermal emission from the blast-shocked ISM shell after the break-out. Synchrotron radio flux at 1 GHz is tens of Jy, comparable to that observed from mixed-morphology SNRs. Because of low density, the $ \gamma $-ray luminosity is dominated by inverse-Compton scattering, which is higher than the $ \pi ^0$-decay luminosity by an order of magnitude. The total $ \gamma $-ray luminosity, including bremsstrahlung, is on the order of 10$ ^{33}$ erg s$ ^{-1}$ lower than the typical value of 10$ ^{35}$ –10$ ^{36}$ erg s$ ^{-1}$ observed from mixed-morphology SNRs. However, if, e.g., $ \sim$ 10% of accelerated protons interact with some matter of density of $ \sim$ 100 cm$ ^{-3}$ , the $ \pi ^0$-decay $ \gamma $-ray luminosity would be enhanced to be comparable with the observed value.
Resonant Excitation of Disk Oscillations in Deformed Disks. VI. Stability Criterion Revisited
Authors: Kato Shoji
Published: March 2014

We re-examine the excitation of a set of disk oscillations in a deformed disk by a resonant process. We assume that the disk is deformed from an axisymmetric steady state by an oscillatory deformation with frequency $\omega_{\rm D}$ and azimuthal wavenumber $m_{\rm D}$. Then, we consider two normal mode oscillations with a set of frequencies and the azimuthal wavenumber being ($\omega_1, m_1$) and ($\omega_2, m_2$) and satisfying the resonant conditions ($\omega_1 + \omega_2 + \omega_{\rm D} =$ 0 and $m_1 + m_2 + m_{\rm D} =$ 0). These oscillations are resonantly excited if $E_1E_2 \gt $ 0, where $E_1$ and $E_2$ are the wave energies of the above two oscillations, when the deformation is maintained by external forces, or has a large amplitude compared with the oscillations. This instability condition is rather general as long as the unperturbed density and pressure vanish on the surface of the system. The possibility of applications to superhumps and negative superhumps in the superoutburst state of dwarf novae are briefly discussed.
Spectroscopic Variations of the Be-Shell Star EW Lacertae in the V/R Variation Periods
Authors: Mon Masahiro , Suzuki Masakazu , Moritani Yuki , Kogure Tomokazu
Published: March 2014

EW Lac showed remarkable $V/R$ variations in 1976–1986, and a similar $V/R$ variation started again in around 2007, after some quasi-periodic $V/R$ variations. For the first $V/R$ variation event, we analyzed the spectroscopic behaviors of emission lines and shell absorption lines of the Balmer series. The $V/R$ variations of the H$\alpha$ through H$\delta$ lines are characterized by the different manner of variations of the individual emission line in time lag and in duration of the $V/R$ phases. Weak correlation is also notable between the $V/R$ variations and other variations of the line-profile parameters, such as the peak velocities, emission-line intensities, and peak separations. We analyzed shell absorption lines for higher members of the Balmer series concerning their central depths and radial velocities. The optical depth of the H$\alpha$ line is in the range of 2000 to 6000, and its long-term variation discloses different behaviors as compared to the $V/R$ variations. Combining the analyses of emission and shell absorption lines, and regarding the $V/R$ variation as wave propagation phenomena, we find for the 1976–1986 event that the $V/R$ variation is of retrograde structure, and that a spiral structure is likely formed inside the disk in the latter half of this event. The weak correlations among physical parameters are suggestive of the disk being truncated at some radius. It is noticed that remarkable stellar brightening occurred in the latter half of the event, accompanying a marked decrease of the emission-line intensities. As for a $V/R$ variation that appeared in around 2007, which looks like a recurrence of a previous event, we found a less developed state of the disk without an appreciable time lag.
A 1.85-m mm-submm Telescope for Large-Scale Molecular Gas Surveys in 12CO, 13CO, and C18O (J = 2–1)
Authors: Onishi Toshikazu , Nishimura Atsushi , Ota Yuya , Hashizume Akio , Kojima Yoshiharu , Minami Akihito , Tokuda Kazuki , Touga Shiori , Abe Yasuhiro , Kaiden Masahiro , Kimura Kimihiro , Muraoka Kazuyuki , Maezawa Hiroyuki , Ogawa Hideo , Dobashi Kazuhito , Shimoikura Tomomi , Yonekura Yoshinori , Asayama Shin’ichiro , Handa Toshihiro , Nakajima Taku , Noguchi Takashi , Kuno Nario
Published: March 2014

We have developed a new mm-submm telescope with a diameter of 1.85-m installed at the Nobeyama Radio Observatory. The scientific goal is to precisely reveal the physical properties of molecular clouds in the Milky Way Galaxy by obtaining a large-scale distribution of molecular gas, which can also be compared with large-scale observations at various wavelengths. The target frequency is $\sim$230 GHz; simultaneous observations at the molecular rotational lines of $J =$2–1 of three carbon monoxide isotopes ($^{12}$CO, $^{13}$CO, C$^{18}$O) are achieved with a beam size (HPBW) of 2${.}{}^\prime$7. In order to accomplish the simultaneous observations, we have developed waveguide-type sideband-separating SIS mixers to obtain spectra separately in the upper and lower side bands. A Fourier digital spectrometer with a 1 GHz bandwidth having 16384 channels is installed, and the bandwidth of the spectrometer is divided into three parts, corresponding to each of the three spectra; the IF system has been designed so as to inject these three lines into the spectrometer. A flexible observation system was created mainly in Python on Linux PCs, enabling effective OTF (On-The-Fly) scans for large-area mapping. The telescope is enclosed in a radome with a membrane covered to prevent any harmful effects of sunlight, strong wind, and precipitation in order to minimize errors in the telescope pointing, and to stabilize the receiver and the IF devices. From 2011 November, we started science operation, resulting in a large-scale survey of the Orion A/B clouds, Cygnus OB7, Galactic Plane, Taurus, and so on. We also updated the receiver system for dual-polarization observations.
Precessing Warped Be Disk Triggering the Giant Outbursts in 2009 and 2011 in A 0535 + 262/V725 Tau
Authors: Moritani Yuki , Nogami Daisaku , Okazaki Atsuo T. , Imada Akira , Kambe Eiji , Honda Satoshi , Hashimoto Osamu , Mizoguchi Sahori , Kanda Yuichi , Sadakane Kozo , Ichikawa Kohei
Published: March 2014

We carried out optical high-dispersion spectroscopic monitoring of the Be disk in a Be/X-ray binary, A 0535$+$ 262/V725 Tau, from 2009 to 2012, covering two giant outbursts and several normal ones. This monitoring was performed in order to investigate any variabilities of the Be disk due to interactions with the neutron star in the recent X-ray active phase from 2008 to 2011. Such variabilities give a clue to any uncleared detailed mechanism for very bright X-ray outbursts, which are unique to some Be/X-ray binaries with a relatively wide and eccentric orbit. In a previous letter (Moritani et al. 2011, PASJ, 63, L25), a brief overview of the line-profile variabilities around the 2009 giant outburst was given, and the possibility of a warped Be disk was discussed. In this paper, a full analysis of the H$\alpha$ line profiles as well as other line profiles is carried out. A bright blue component, or blue “shoulder,” showing up after periastron indicates the presence of a dense gas stream toward the neutron star, which is associated with observed outbursts. We re-analyze the H$\alpha$ line profiles before 2009 (down to 2005) in order to investigate the variability of the disk structure in the innermost region, which seems to have detached from the Be star surface by 2008. A redshifted enhanced component is remarkable in all emission lines observed around the 2009 giant outburst, occasionally forming a triple peak. These features indicate that the Be disk was warped in the X-ray active phase. We estimated the position of the warped region from fitting the radial velocity of the redshifted enhanced component of H$\alpha$, and found that it was very close to the periastron when two giant outbursts in 2009 and 2011 and a bright normal outburst in 2010 March occurred. These facts strongly suggest that the precessing warped Be disk triggered these giant outbursts.
Direct Imaging Search for Extrasolar Planets in the Pleiades
Authors: Yamamoto Kodai , Matsuo Taro , Shibai Hiroshi , Itoh Yoichi , Konishi Mihoko , Sudo Jun , Tanii Ryoko , Fukagawa Misato , Sumi Takahiro , Kudo Tomoyuki , Hashimoto Jun , Kusakabe Nobuhiko , Abe Lyu , Brandner Wolfgang , Timothy D. Brandt , Carson Joseph , Currie Thayne , Sebastian E. Egner , Feldt Markus , Goto Miwa , Grady Carol , Guyon Olivier , Hayano Yutaka , Hayashi Masahiko , Hayashi Saeko , Henning Thomas , Hodapp Klaus , Ishii Miki , Iye Masanori , Janson Markus , Kandori Ryo , Gillian R. Knapp , Kuzuhara Masayuki , Kwon Jungmi , McElwain Mike , Miyama Shoken , Jun-Morino Ichi , Amaya Moro-Martin , Nishikawa June , Nishimura Tetsuo , Tae-Pyo Soo , Serabyn Eugene , Suto Hiroshi , Suzuki Ryuji , Takami Michihiro , Takato Naruhisa , Terada Hiroshi , Thalmann Christian , Tomono Daigo , Edwin L. Turner , Wisniewski John , Watanabe Makoto , Yamada Toru , Takami Hideki , Usuda Tomonori , Tamura Motohide
Published: March 2014

We carried out an imaging survey for extrasolar planets around stars in the Pleiades (125 Myr, 135 pc) in the $H$ and $K_{\rm S}$ bands using HiCIAO combined with adaptive optics, AO188, on the Subaru telescope. We found 13 companion candidates fainter than 14.5 mag in the $H$ band around 9 stars. Five of these 13 were confirmed to be background stars by measurement of their proper motion. One was not found in the second epoch observation, and thus was not a background or companion object. One had multi-epoch images, but the precision of its proper motion was not sufficient to conclude whether it was a background object. Four other candidates are waiting for second-epoch observations to determine their proper motion. Finally, the remaining two were confirmed to be 60 $M_{\rm {J}}$ brown dwarf companions orbiting around HD 23514 (G0) and HII 1348 (K5), respectively, as had been reported in previous studies. In our observations, the average detection limit for a point source was 20.3 mag in the $H$ band beyond 1$.{\prime\prime}$ 5 from the central star. On the basis of this detection limit, we calculated the detection efficiency to be 90% for a planet with 6 to 12 Jovian masses and a semi-major axis of 50–1000 AU. For this reason we extrapolated the distribution of the planet mass and the semi-major axis derived from radial velocity observations, and adopted the planet evolution model Baraffe et al. (2003, A&A, 402, 701). Since there was no detection of a planet, we estimated the frequency of such planets to be less than 17.9% (2 $\sigma$) around one star of the Pleiades cluster.
Observational Appearance and Spectrum of Black-Hole Winds: Effect of Electron Scattering
Authors: Ogura Kazuyuki , Fukue Jun
Published: March 2014

We examine the observational appearance and expected spectrum of an optically thick, spherically symmetric black-hole wind, taking into account the effect of electron scattering. In spherical outflows, the apparent photosphere, where the optical depth observed from infinity is unity, is not spherical, but becomes a nonspherical shape, because the flow density gradually changes. In addition, for relativistic outflows, we should carefully consider the apparent photosphere, because it is further modified due to a relativistic effect. As a result, if the flow temperature changes with radius, the temperature distribution on the photosphere is not uniform (the limb-darkening becomes prominent), and we may observe a multitemperature spectrum. On the other hand, in such a high-temperature outflow, electron scattering plays an important role; photons created at the thermalization surface deep into the flow are scattered off in the flow, and finally escape from the apparent photosphere (last scattering surface), which can be observed. Taking this scattering effect into considerations, we examined the black-hole wind. Unexpectedly, we found that the shape of the thermalization surface is nearly spherical, and the spectrum is almost blackbody, although the apparent photosphere is highly aspherical.
Erratum: Hard X-Ray Spectrum from the West Lobe of Radio Galaxy Fornax A Observed with Suzaku
Authors: Tashiro Makoto S. , Isobe Naoki , Seta Hiromi , Matsuta Keiko , Yaji Yuichi
Published: March 2014

In the paper [PASJ 61, S327–S335 (2009)], there were two kinds of typos in the units of flux density and the column density. The correct unit of flux density at 1 keV employed in this paper is $\mu$ Jy not nJy, which appears in line 9 of abstract, line 29 of subsection 3.3, and row (d) of table 2. The correct column density in table 2 row (a) is 2.06 $\times 10^{20}$ cm$^{-2}$ not 2.06 $\times 10^{22}$ cm$^{-2}$. Both the discussion and coclusions are based on the correct units and are not affected by these changes.
Recurrent Outbursts and Jet Ejections Expected in Swift J1644+57: Limit-Cycle Activities in a Supermassive Black Hole
Authors: Kawashima Tomohisa , Ohsuga Ken , Usui Ryuichi , kawai Nobuyuki , Negoro Hitoshi , Matsumoto Ryoji
Published: March 2014

A tidal disruption event by a supermassive black hole in Swift J1644$+$57 can trigger limit-cycle oscillations between a supercritically accreting X-ray bright state and a subcritically accreting X-ray dim state. The time evolution of debris gas around a black hole with mass $M = 10^{6} M_\odot$ is studied by performing axisymmetric, two-dimensional radiation hydrodynamic simulations. We assume the $\alpha$-prescription of viscosity, in which the viscous stress is proportional to the total pressure. The mass supply rate from the outer boundary was assumed to be ${\dot M}_{\rm supply} = 100 L_{\rm Edd}/c^2$, where $L_{\rm Edd}$ is the Eddington luminosity, and $c$ is the light speed. Since the mass accretion rate decreases inward by outflows driven by radiation pressure, the state transition from a supercritically accreting slim disk state to a subcritically accreting Shakura–Sunyaev disk starts from the inner disk, and propagates outward on a timescale of one day. The sudden drop of the X-ray flux observed in Swift J1644$+$57 in 2012 August can be explained by this transition. As long as ${\dot M}_{\rm supply}$ exceeds the threshold for the existence of a radiation pressure dominant disk, the accumulation of accreting gas in the subcritically accreting region triggers the transition from a gas pressure dominant Shakura–Sunyaev disk to a slim disk. This transition takes place at $t {\sim} 50 /$ (${\alpha}/$ 0.1) d after the X-ray darkening. We expect that if $\alpha \gt $ 0.01, X-ray emission with luminosity $\gtrsim 10^{44}$ erg s$^{-1}$ and jet ejection will revive in Swift J1644$+$57 in 2013–2014.
High-Dispersion Spectroscopy of the Superflare Star KIC 6934317
Authors: Notsu Shota , Honda Satoshi , Notsu Yuta , Nagao Takashi , Shibayama Takuya , Maehara Hiroyuki , Nogami Daisaku , Shibata Kazunari
Published: March 2014

We conducted high-resolution spectroscopic observation with Subaru/HDS for a G-type star (KIC 6934317). We selected this star from the data of the Kepler spacecraft. It produces many superflares, and the total energy of the largest recorded superflare on this star was ∼103-times larger (∼2.2 × 1035 erg) than that of the most energetic flare on the Sun (∼1032 erg). The core depth and the emission flux of the Ca II infrared triplet lines and the Hα line show high chromospheric activity in this star, in spite of its low lithium abundance and small amplitude of the rotational modulation. Using empirical relations between the emission flux of chromospheric lines and the X-ray flux, this star is considered to show much higher coronal activity than that of the Sun. It probably has large starspots that can store a large amount of magnetic energy, sufficient to give rise to superflares. We also estimated the stellar parameters, such as the effective temperature, surface gravity, metallicity, projected rotational velocity (v sin i ), and radial velocity. KIC 6934317 is then confirmed to be an early G-type main-sequence star. The value of v sin i is estimated to be ∼1.91 km s-1. In contrast, the rotational velocity is calculated to be ∼20 km s-1 by using the period of the brightness variation as the rotation period. This difference can be explained by its small inclination angle (nearly pole-on). The small inclination angle is also supported by the contrast between the large superflare amplitude and the small stellar brightness variation amplitude. The lithium abundance and isochrones implies that the age of this star is more than about a few Gyr, though a problem why this star with such an age has such strong activity remains unsolved.
Effect of the Remnant Mass in Estimating the Stellar Mass of Galaxies
Authors: Shimizu Ikkoh , Inoue Akio K.
Published: March 2014

The definition of the galactic stellar mass estimated from the spectral energy distribution is ambiguous in the literature; whether the stellar mass includes the mass of the stellar remnants, i.e., white dwarfs, neutron stars, and black holes, is not well described. The remnant mass fraction in the total (living + remnant) stellar mass of a simple stellar population monotonically increases with the age of the population, and the initial mass function and metallicity affect the increasing rate. Since galaxies are composed of a number of stellar populations, the remnant mass fraction may depend on the total stellar mass of galaxies in a complex way. As a result, the shape of the stellar mass function of galaxies may change, depending on the definition of the stellar mass. In order to explore this issue, we ran a cosmological hydrodynamical simulation, and subsequently found that the remnant mass fraction indeed correlates with the total stellar mass of galaxies. However, this correlation is weak, and the remnant fraction can be regarded as a constant that depends only on the redshift. Therefore, the shape of the stellar mass function is almost unchanged, but it simply shifts horizontally if the remnant mass is included or not. The shift is larger at lower redshift, and it reaches 0.2-dex at z = 0 for a Chabrier IMF. Since this causes a systematic difference, we should take care of the definition of the ‘stellar’ mass, when comparing one's result with others.
Viscous Decretion Discs around Rapidly Rotating Stars
Authors: Lee Umin
Published: March 2014

We discuss steady viscous Keplerian decretion discs around rapidly rotating stars. We assume that low-frequency modes, which may be excited by the opacity bump mechanism, convective motion in the core, or tidal force if the star is in a binary system, can transport a sufficient amount of angular momentum to the region close to the stellar surface. Under this assumption, we construct a star-disc system, in which there forms a viscous decretion disc around a rapidly rotating star because of the angular-momentum supply. We find a series of solutions of steady viscous decretion discs around a rapidly rotating star that extend to $R_{\textrm{disc}} \gtrsim 10 R_{\ast}$, with $R_{\ast}$ being the equatorial radius of the star, depending on the amount of angular momentum supply.
Extremely Microwave-Rich Solar Flare Observed with Nobeyama Radioheliograph
Authors: Satoshi Masuda , Masumi Shimojo , Kawate Tomoko , Ishikawa Shin-nosuke , Ohno Masanori
Published: March 2014

A compact flare was observed with Nobeyama Radioheliograph (NoRH) slightly behind the west limb on 2011 March 10. The microwave peak flux values at 17 and 34 GHz were about 210 and 133 sfu, respectively. From the correlation between the 17 GHz peak flux and the GOES 1-8 Å soft X-ray peak flux, M1.5-class is expected for this microwave flux. However, only the B1-level enhancement was detected in the GOES 1-8 Å soft X-ray light curve on the C1-level background during the flare period. In addition to microwaves, Suzaku detected hard X-ray emissions, even in the energy range above 100 keV. It is clear that high-energy electrons were effectively produced in this flare, while the thermal emission was very weak. Why did this flare have this unique feature? The following two cases are considered. One is the case that a magnetic trap for electrons works effectively, and that each electron continues to emit microwaves in its relatively long lifetime. The other is that the magnetic field around the looptop region is intense, and relatively a large number of lower-energy electrons emit microwaves. Considering the observational facts, such as the short duration and the small flare loop, the latter case is more plausible.
Microwave Negative Bursts as Indications of Reconnection Between Eruptive Filaments and a Large-Scale Coronal Magnetic Environment
Authors: Grechnev Victor V. , Kuz'Menko Irina V. , Uralov Arkadiy M. , Chertok Ilya M. , Kochanov Alexey A.
Published: March 2014

Low-temperature plasma ejected in solar eruptions can screen active regions as well as quiet solar areas. Absorption phenomena can be observed in microwaves as “negative bursts” and in various spectral domains. We analyze two very different recent events with such phenomena, and present an updated systematic view of solar events associated with negative bursts. Related filament eruptions can be normal, without essential changes of shape and magnetic configuration, and “anomalous.” The latter are characterized by disintegration of an eruptive filament and dispersal of its remnants as a cloud over a large part of the solar disk. Such phenomena can be observed as giant depressions in the He II 304 Å line. One of possible scenarios for an anomalous eruption is proposed in terms of reconnection of the filament's internal magnetic fields with an external large-scale coronal surrounding.
Long-Term Oscillations of Sunspots from Simultaneous Observations with the Nobeyama Radioheliograph and Solar Dynamics Observatory
Authors: Abramov-Maximov Vladimir E. , Efremov Vyacheslav I. , Parfinenko Leonid D. , Solov'Ev Alexander A. , Shibasaki Kiyoto
Published: March 2014

We present an investigation of oscillatory processes with periods in the range of several tens of minutes for some single sunspots of a new solar cycle, observed in 2010-2011 at the same time intervals in the optical and radio ranges. We used magnetograms from SDO/HMI with a cadence of 45 s, and radio images at a frequency of 17 GHz obtained with the Nobeyama Radioheliograph (NoRH). Radio images in intensity (Stokes parameter I ) and circular polarization (Stokes parameter V ) were synthesized with a cadence of ten seconds and ten-second averaging. Time profiles obtained with NoRH and SDO/HMI show a correlation between the radio emission of sunspots and a magnetic field. Wavelet spectra and cross-wavelet transforms give similar oscillation periods: 30-40 min, 60-70 min, 100-110 min, and 150-200 min. The same periods found by fundamentally different methods from ground-based and space observations confirm the solar nature of these oscillations. One of the possible interpretations of our results is that detected oscillations reflect eigen oscillations of a sunspot as a whole predicted by the shallow sunspot model.
Long-Term Global Solar Activity Observed by the Nobeyama Radioheliograph
Authors: Shibasaki Kiyoto
Published: March 2014

The Nobeyama Radioheliograph has been observing the Sun at a frequency of 17 GHz regularly since 1992, providing synthesized full-disk images. This long period of continuous and consistent operation, providing wellcalibrated data of a uniform standard, makes possible long-term studies of solar activity, from full-disk down to the angular resolution of the instrument. By using about 7200 daily, full-disk images, it has been possible to generate a radio version of the butterfly diagram, which differs significantly from the sunspot butterfly diagram. The polar regions are bright at 17 GHz, with their brightness well-correlated with the polar magnetic field strengths. Both are anti-correlated with activity at low latitudes, such as active regions and solar flares. The 17 GHz butterfly diagram shows both high and low-latitude activity. The brightness of both these facets of solar activity shows a significant decline over the 20+ years observations that have been made. In the northern hemisphere, the radio brightnesses at low and high latitudes are strongly anti-correlated. However, this anti-correlation is weak in the southern hemisphere. We find a weakening of the synchronization of activity between the northern and southern hemispheres, and also between high and low latitude activity in the southern hemisphere. Possible causes of polar brightening and the meaning with respect to the general scenario of solar activity are discussed.
Clinical and Radiographic Outcomes From Repeat Whole-brain Radiation Therapy for Brain Metastases in the Age of Stereotactic Radiosurgery
Authors: Guo Susan , Balagamwala Ehsan H. , Reddy Chandana , Elson Paul , Suh John H. , Chao Samuel T.
Published: March 2014

Objectives:

Repeating whole-brain radiation therapy (WBRT) in patients with progressive/recurrent brain metastases is controversial. We retrospectively reviewed our experience of repeat WBRT in an era where stereotactic radiosurgery was also available.

Methods:

In our IRB-approved database, 49 patients received repeat WBRT from 1996 to 2011. Median initial dose of WBRT was 30 Gy in 10 fractions (range, 27 to 37.5 Gy); median reirradiation dose was 20 Gy in 10 fractions (range, 14 to 30 Gy). Median Karnofsky performance status (KPS) at reirradiation was 70 (range, 40 to 90). Median number of discrete lesions at reirradiation was 6 (range, 1 to 30). Median interval between initial diagnosis of brain metastases and relapse requiring repeat WBRT was 11.5 months (range, 1.5 to 49.2 mo). Overall survival and relapse-free survival were summarized using the Kaplan-Meier method. The log-rank test was used to compare outcomes between groups.

Results:

Ninety percent of patients completed repeat WBRT. Median survival after repeat WBRT was 3 months (95% CI, 1.9-4.0). Thirteen patients had improved neurological symptoms (27%), 12 were stable (24%), and 14 had worsening symptoms (29%). On radiographic follow-up of 22 patients, 10 (46%) were improved, 4 (18%) were stable, and 8 (36%) progressed. Improved neurological symptoms after repeat WBRT and higher KPS at first follow-up were associated with improved survival (P=0.05 and 0.02).

Conclusions:

Repeat WBRT was well tolerated. Modest survival times are seen. Prognostic factors for survival include improved neurological symptoms after repeat WBRT and higher KPS at first follow-up. Repeat WBRT may be useful to improve neurological symptoms in patients with limited treatment options, especially those who are not appropriate stereotactic radiosurgery candidates.
Update to the Management of Pediatric Acute Pancreatitis
Authors: Abu‐El‐Haija Maisam , Lin Tom K. , Palermo Joseph
Published: March 2014

Acute pancreatitis is an emerging problem in pediatrics, with an incidence that is rising in the last 2 decades. Data regarding the optimal management and physician practice patterns are lacking. We present a literature review and updates on the management of pediatric pancreatitis. Prospective multicenter studies defining optimal management of pediatric pancreatitis are needed to guide care and improve outcomes for this patient population.