bluuebunny/crossref_metadata_2025 huggingface dataset:
A 168-s X-Ray Pulsar in the Small Magellanic Cloud Observed with ASCA
Authors: Yokogawa Jun , Torii Ken’ichi , Kohmura Takayoshi , Koyama Katsuji
Published: March 2014

We report on the detection of $167.8 \pm 0.2\,\mathrm{s}$ pulsations from AX J0052.9$-$7157 in the Small Magellanic Cloud with ASCA. The pulsations show an energy-independent sinusoidal profile. The X-ray spectrum has been described by an absorbed hard power-law (photon index $\sim 0.7$) with a luminosity of $\sim 8.8 \times 10^{35}\,\mathrm{erg}\,\mathrm{s}^{-1}$ at a distance of $60\,\mathrm{kpc}$. The position is determined to be $\mathrm{(R.A.,~Dec.)}_{\mathrm{J2000}} = (00{}^{\mathrm{h}}52{}^{\rm m}59\rlap{.}{}^{\rm s}2, -71{71{}^{\mathrm{\circ}}57{}^{\mathrm{\prime}}58{}^{\mathrm{\prime\prime}}})$, with an error radius of $\sim {30{}^{\mathrm{\prime\prime}}}$. We have found that a variable Be/X-ray binary RX J0052.9$-$7158 is located within the $30{}^{\mathrm{\prime\prime}}$ error circle, and is also located at the edge of the $10{}^{\mathrm{\prime}}$ error circle of the 169-s pulsar XTE J0054$-$720. We therefore conclude that these are the same source, a Be/X-ray binary pulsar.
Contribution of Supernova Gamma-Rays to the Gamma-Ray Background Emission
Authors: Iwabuchi Kousei , Kumagai Shiomi
Published: March 2014

Diffuse $ \gamma $-ray background emission has been observed by a number of satellites and balloons. The spectrum spreads over a wide range of photon energies, and the emission is almost isotropic. Although the origin of diffuse $ \gamma $-ray background emission is still unclear, some candidates are suggested, such as Seyfert galaxies, blazars, and type-Ia supernovae. The type-Ia supernovae synthesize a large amount of ${{56\atop}\mathrm{Ni}}$, which emit $ \gamma $-ray photons while decaying into ${{56\atop}\mathrm{Co}}$ and then to ${{56\atop}\mathrm{Fe}}$, and thus emit strong $ \gamma $-rays of energy around 1 MeV. We estimate the intensity of the diffuse $ \gamma $-ray background emission from supernovae, and compare the result with the recent observation of COMPTEL. The resultant spectrum is too small to explain the observation, because it is only 10% of the observed flux, implying contributions from other sources.
Eclipsing and Precessional Light Curves of SS 433 with Superdisks
Authors: Hirai Yasuo , Fukue Jun
Published: March 2014

We theoretically calculated light curves of SS 433 during eclipse and precession, under a picture in which SS 433 consists of a geometrically thick superdisk around a compact star and a companion star filling its Roche lobe. The main parameters are the binary mass ratio, the relative thickness of the superdisk, and the surface temperature of the companion. Combinations of eclipsing and precessional light curves impose constraints on the parameter ranges. The favorite values of the parameters are a mass ratio of about 1 to 1.5 (a compact star is a black hole), a relative disk-thickness of about $ {25{}^{\mathrm {\circ }}}$, and a companion surface-temperature of 14000–20000 K.
A Diffuse X-Ray Source, AX J1843.80352: Association with the Radio Complex G28.6-0.1 and Identification of a New Supernova Remnant
Authors: Bamba Aya , Ueno Masaru , Koyama Katsuji , Yamauchi Shigeo
Published: March 2014

ASCA discovered an extended source in the constellation Scutum. The X-ray morphology is an elliptical shape elongated from north to south with a mean diameter of about $ {10{}^{\mathrm {\prime }}}$. The image center is located at $ \mathrm{RA}_{2000}$ = $ {18{}^{\mathrm {h}}43{}^{\mathrm {m}}53{}^{\mathrm {s}}}$, $ \mathrm{DEC}_{2000}$ = $ - {03{}^{\mathrm {\circ }}52{}^{\mathrm {\prime }}55{}^{\mathrm {\prime \prime }}}$ (hereafter, AX J1843.8–0352). The north and south rims of AX J1843.8–0352 are associated with non-thermal radio sources C and F of the G28.6–0.1 complex (Helfand et al. 1989, AAA $ 49.125.029$). The X-ray spectrum was fitted with a model of either a thin thermal plasma in non-equilibrium ionization of a temperature 5.4keV or a power-law of photon index 2.1. The absorption column is $ (2.4$-$ 4.0)\times 10^{22}\mathrm{cm}^{-2}$, which probably places this source in the Scutum arm. With a reasonable distance assumption of about 7kpc, we estimate the mean diameter and X-ray luminosity to be $ \sim 20 \,\mathrm{pc}$ and $ \sim 3 \times 10^{34}\,\mathrm{erg} \,\mathrm{s}^{-1}$, respectively. Although a Sedov solution for a thin thermal plasma model gives parameters of a young shell-like SNR, no strong emission lines are found with the metal abundances being $ \sim$ solar. Thus, a more likely scenario for both the radio and X-ray spectra and the morphologies is that AX J1843.8–0352 is a shell-like SNR which predominantly emits synchrotron X-rays.
A New Look at CO Outflows in the Dark Cloud Complex near IC 5146
Authors: Dobashi Kazuhito , Yonekura Yoshinori , Hayashi Yoshikazu
Published: March 2014

This paper presents the results of a search for CO outflows in a dark cloud complex near IC 5146 carried out using the 45-m telescope at Nobeyama Radio Observatory ($\mathrm{HPBW} = 17^{\prime\prime}$) equipped with the S115Q multi-beam receiver system. A CO outflow was discovered by the present survey toward IRAS 21428$+$4732, whose physical parameters, such as molecular mass, mechanical momentum, and kinetic energy, were derived. In addition to IRAS 21428$+$4732, there are 5 other IRAS point sources accompanied by CO outflows in this cloud complex, which were found by earlier observations with lower angular resolutions ($\mathrm{HPBW} \simeq 1^\prime$). We also made 12 CO ($J = 1-0$), 13CO ($J = 1-0$), and C18O ($J = 1-0$ observations toward the 5 sources with the 45-m telescope in order to obtain new data with higher angular resolutions. CO maps as well as physical parameters of these outflows obtained by the 45-m telescope are also presented.
2 Millimeter Dust around NGC 7538 — IRS 1, 2, and 3: I. Unfilled Structure of Dust Cloud
Authors: Akabane Kenji , Matsuo Hiroshi , Kuno Nario , Sugitani Koji
Published: March 2014

A 2-mm continuum mapping observation around NGC 7538 — IRS 1, 2, and 3 was made by the Nobeyama Bolometer Array (NOBA) with a spatial resolution of 12$^{\prime\prime}$. An extended source of $\sim {32{}^{\mathrm {\prime \prime }}} \times {44{}^{\mathrm {\prime \prime }}}$ ($\Delta\alpha \times \Delta\delta$), having a hardly resolved central core structure, was observed. The core gives a flux density of $3.1 \,\mathrm{Jy} \pm 1 \,\mathrm{Jy}$, and is clearly identified with the free-free emission from the compact H II regions. A smooth and extended source gives an integrated flux density of $5 \,\mathrm{Jy} \pm 1.5 \,\mathrm{Jy}$, and an intensity spectrum of $\nu^{3}$–$\nu^{3.5}$ in the millimeter wave region. The fitting of a gray body function to the observational data shows that an absorption index, $\beta$, of 1.8–2.0, a dust filling factor, $\eta$, of 0.3–0.5, and a dust temperature, $T_\mathrm{d}$, of 34 K–45 K are reasonable parameters for this 2-mm extended dust. Astronomical silicate grains were examined for a dust model. The total dust mass and luminosity were obtained as $M_\mathrm{d} \simeq 0.85 \times 10^{2} \,{{{M}_{\odot}}}$ and $L_\mathrm{d} \simeq 2.2 \times 10^{5} \,{{{L}_{\odot}}}$, respectively. The extent of 2-mm dust emission partly coincides with those of the 100-$/mu$ m map, of the 57-$/mu$ m map, and of the total intensity of the wing parts of the CO ($J = 1-0$) line emission of the region. The absorbing silicate dust layer must be distinct from the extended 2-mm dust, and must arise on smaller scales than the extended 2-mm dust.
When Did the Hubble Sequence Appear?: Morphology, Color, and Number-Density Evolution of the Galaxies in the Hubble Deep Field North
Authors: Kajisawa Masaru , Yamada Toru
Published: March 2014

Using the HST WFPC2/NICMOS archival data of the Hubble Deep Field North, we constructed a nearly complete sample of the $M_{V} \lt-20$ ($\sim L^\ast +1$) galaxies to $z=2$, and investigate when the Hubble sequence appeared, namely, the evolution of the morphology, colors, and the comoving number density of the sample. Even if taking into account the uncertainty of the photometric redshift technique, the number density of relatively bright bulge-dominated galaxies in the HDF-N decreases significantly at $z \gt 1$, and their rest-frame $U-V$ color distribution is wide-spread over $0.5 \lt z \lt 2$. On the other hand, while the number density of both disk-dominated and irregular galaxies does not show a significant change at $0.5 \lt z \lt 2$, their distribution of the rest-frame $U-V$ color alters at $z \sim 1.5$; there is no relatively red (rest $U-V \gtrsim 0.3$) galaxies at $z \gt 1.5$, while a significant fraction of these red disk-dominated or irregular galaxies exist at $z \lt 1.5$. These results suggest that the significant evolution of the Hubble sequence, which is seen in the present Universe, occurs at $1 \lt z \lt2$.
The 1996–1997 Fading of V651 Monocerotis, the Binary Central Star of the Planetary Nebula NGC 2346
Authors: Kato Taichi , Nogami Daisaku , Baba Hajime
Published: March 2014

V651 Mon is the binary central star of the bipolar planetary nebula NGC 2346. The star showed the second-ever deep fading in 1996–1997, which was presumably caused by obscuration by a dust cloud in the planetary nebula, as was proposed to explain the 1981–1985 event. The entire duration of the 1996–1997 event was $\sim 400 \,\mathrm{d}$, remarkably shorter than the 1981–1985 event, suggesting that the obscuring body was smaller or had a larger tangential velocity. The most remarkable feature in this event was the presence of a sharply defined transient clearing (brightening). From the time-scale of the variation, we propose an upper limit of the projected scale of several times $\sim 10^{11} \,\mathrm{cm}$ of the structure responsible for the brightening. This observation provides the first evidence for a sharply defined, small lucent structure within the obscuring body around the central star of NGC 2346.
A 350 GHz SIS Receiver on the Nobeyama 10 m Submillimeter Telescope
Authors: Sekimoto Yutaro , Sakai Takeshi , Saito Gaku , Tatematsu Ken’ichi , Tanaka Kunihiko , Kohno Kotaro , Noguchi Takashi , Iwashita Hiroyuki , Takahashi Toshikazu , Satou Naohisa , Yokogawa Sozo , Sakamoto Seiichi , Ukita Nobuharu , Kawabe Ryohei , Ito Tetsuya , Maezawa Hiroyuki , Yamamoto Satoshi
Published: March 2014

We have developed a low-noise submillimeter-wave SIS receiver (320–360 GHz) for a 10 m submillimeter telescope, which was installed at Nobeyama in 2000 February. This receiver and a millimeter-wave SIS receiver are mounted on the ceiling of the Cassegrain receiver cabin of the 10 m telescope. Two curved mirrors couple a shaped Cassegrain beam from the subreflector to mixer horns. The minimum noise temperature measured in front of the receiver was 52 K in double sideband (DSB) at a local oscillator (LO) frequency of 354 GHz, which corresponds to three-times quantum limits ($3h\nu/k_{\mathrm{B}}$). This noise temperature contributions are resolved into the optics, mixer, and IF parts. The temperature ripple of a two-stage Gifford–McMahon cryocooler has been reduced to be 2 mK peak-to-peak at the mixer block with a helium pot temperature stabilizer. Mechanical vibration (30 ${\mu \mathrm {m}}$ peak-to-peak) of the cold head degrades the receiver stability.
Hipparcos Proper-Motion System with Respect to SPM 2.0
Authors: Zhu Zi
Published: March 2014

On the basis of Hipparcos data, whose system is believed to be quasi-inertial to within $\pm 0.25 \,\mathrm{mas} \,\mathrm{yr}^{-1}$ and to represent an internally consistent reference frame, we carried out an analysis of the SPM 2.0 proper-motion system. Comparing the Hipparcos proper motions with those of the SPM 2.0 Catalog, which provides absolute proper motions of objects measured directly relative to external galaxies, we found that the two components of the spin vector, $\omega_x$ and $\omega_z$, are apparently less than the value of $0.25 \,\mathrm{mas} \,\mathrm{yr}^{-1}$ for the uncertainty of the Hipparcos inertiality, while the component $\omega_y$ is almost twice that value. Inspecting the magnitude - and color-dependent pattern of the proper-motion difference, we found that the SPM 2.0 Catalog seems to suffer a slight color systematics with respect to the Hipparcos proper-motion system, though the result is inconclusive due to the small number of the Hipparcos and SPM 2.0 common stars.
A Survey for High-Latitude Molecular Clouds toward Infrared-Excess Clouds with NANTEN
Authors: Onishi Toshikazu , Yoshikawa Nao , Yamamoto Hiroaki , Kawamura Akiko , Mizuno Akira , Fukui Yasuo
Published: March 2014

A survey for high Galactic latitude molecular clouds was carried out toward the far-infrared-excess clouds of Reach et al. (1998, AAA 070.131.207) using the NANTEN telescope. All 68 infrared-excess clouds that are observable from NANTEN were mapped in the $J = 1 \hbox{--} 0$ line of 12CO. CO emission was detected from 32 infrared excess clouds, corresponding to a CO detection rate of 47%. Most of these CO clouds were identified and mapped as high-latitude clouds for the first time. The CO detection rate for the cold ($T_\mathrm{dust} \lt 17 \,\mathrm{K}$) infrared excess clouds is 72%, which is more than a factor of two higher than that of warmer ones, 33%. This indicates that the cold clouds are well shielded from external UV radiation, resulting in a high CO abundance and a low temperature of the clouds. The infrared-excess clouds with no CO emission are most likely to be molecular hydrogen clouds because the temperature is similar to, or lower than, that of the surrounding H i gas. The molecular gas without CO emission seems to occupy more than 90% of the area of the infrared-excess clouds.
A Large-Scale Study of H13CO+ and C18 (J=1–0) in Orion B
Authors: Aoyama Hiroko , Mizuno Norikazu , Yamamoto Hiroaki , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo
Published: March 2014

We have made a new survey for dense cloud cores in the Orion B region using the NANTEN telescope. Two molecular transitions, the $J = 1 - 0$ line of $\mathrm{H}{{13\atop} \mathrm{CO}}^{+}$ and the $J = 1 - 0$ line of $\mathrm{C}{{18\atop} \mathrm{O}}$, were used to study the distribution of dense molecular gas with densities of $10^{4} - 10^{5} \,\mathrm{cm}^{-3}$. We detected 19 $\mathrm{C}{{18\atop} \mathrm{O}}$ clumps, and the mass and the size of the $\mathrm{C}{{18\atop} \mathrm{O}}$ clumps ranged from 13${M}_{\odot}$ to 990${M}_{\odot}$ and from 0.26 pc to 0.69 pc, respectively. Among the physical parameters of these $\mathrm{C}{{18\atop} \mathrm{O}}$ clumps, the molecular column density, $N(\mathrm{H}_2)$, has been found to be the best indicator of star formation; the molecular column density averaged within a $\mathrm{C}{{18\atop} \mathrm{O}}$ clump shows a good correlation with the IRAS luminosity as $L_\mathrm{IRAS} / {{{L}_{\odot}}} \propto N(\mathrm{H}_{2}) \; (\mathrm{cm}^{-2})^{4.8 \pm 0.6}$ (C.C.$= 0.96$). We also detected 11 $\mathrm{H}{{13\atop} \mathrm{CO}}^{+}$ clumps, whose mass ranges from a few ${M}_{\odot}$ to 480${M}_{\odot}$. Five of the $\mathrm{H}{{13\atop} \mathrm{CO}}^{+}$ clumps are of smaller mass, and show no indication of massive star formation; they were newly found in this survey. Five of the eleven $\mathrm{H}{{13\atop} \mathrm{CO}}^{+}$ clumps are particularly massive with an average mass of $\sim 200 \,{{{M}_{\odot}}}$. It is found that these massive $\mathrm{H}{{13\atop} \mathrm{CO}}^{+}$ clumps exhibit active formation of massive stars, as indicated by associated protostellar IRAS point sources, whose luminosities are $10^{2} - 10^{4} \,{{{L}_{\odot}}}$.
A Large Scale 12CO (J=1−0) Survey toward the Chamaeleon Region with NANTEN
Authors: Mizuno Akira , Yamaguchi Reiko , Tachihara Kengo , Toyoda Shuichiro , Aoyama Hiroko , Yamamoto Hiroaki , Onishi Toshikazu , Fukui Yasuo
Published: March 2014

We carried out a large-scale survey for molecular clouds in 12CO ($J = 1-0$) emission toward the Chamaeleon region with the NANTEN 4-meter radio telescope at Las Campanas Observatory in Chile. The survey covered $\sim 491 \,\mathrm{deg}^2$ toward $284 {{}^{\circ }} \lesssim l \lesssim 320 {{}^{\circ }}$ and $-34 {{}^{\circ }} \lesssim b \lesssim-6 {{}^{\circ }}$ at an $8^{\prime}$ grid spacing. The total molecular mass in the observed area is estimated to be $\sim 8300 \,{{{M}_{\odot}}}$. More than 60% of the total mass is concentrated in and around the previously known Cha I, II, and III dark clouds. Two cloud complexes having molecular hydrogen masses of $\sim 430 \,{{{M}_{\odot}}}$ and $\sim 1300 \,{{{M}_{\odot}}}$, respectively, have been found at $\sim 10 {{}^{\circ }}$ galactic-east of the Chamaeleon major clouds. We have identified a prominent filament extending from Cha I to the galactic-east direction, which is remarkably long ($\gtrsim 40 \,\mathrm{pc}$) compared with filamentary features found in other dark-cloud complexes. A correlation study between the CO distribution and isolated X-ray emitting T Tauri stars (TTSs) indicates that $\gtrsim 65\%$ of the TTSs are located within 1 pc of the 12CO cloud boundaries. This suggests that low-density parental molecular gas still remains around the isolated TTSs, although the dense parts with density greater than $10^3 \,\mathrm{cm}^{-3}$ have almost dissipated. This provides further support for the local formation of “isolated” T Tauri stars in small clouds.
CO Column Density and Extinction in the Chamaeleon II–III Dark-Cloud Complex
Authors: Hayakawa Takahiro , Cambrésy Laurent , Onishi Toshikazu , Mizuno Akira , Fukui Yasuo
Published: March 2014

We carried out 13CO ($J = 1 - 0$) and $\mathrm{C}{{18\atop} \mathrm{O}}$ ($J = 1 - 0$) observations of the Chamaeleon II-III dark-cloud complex with the NANTEN radio telescope. The column densities of both molecular isotopes were derived assuming LTE. The $A_{V}$ values were obtained by scaling the $A_{J}$ values that were derived using an adaptive-grid star-count method applied to the DENIS $J$-band data. We established the $A_{V}-$CO isotope column-density relations in Cha II and III, and compared them with those in Cha I. The slopes of the $A_{V}$-13CO relations for Cha II and III are steeper than that for Cha I. Those of the $A_{V} - \mathrm{C}{{18\atop} \mathrm{O}}$ relations are similar among the three clouds. The total column density ratio, $N({{13\atop} \mathrm{CO}})/N(\mathrm{C}{{18\atop} \mathrm{O}})$, in Cha I tends to be small compared with those in Cha II or Cha III; the ratios range from $\sim 5$ to $\sim 25$ at low extinction in Cha II and III, but at most $\sim 10$ in Cha I. We suggest that the increase of $N({{13\atop} \mathrm{C}}{{\atop} \mathrm{O}})$ due to the ${{13\atop} \mathrm{C}}{{\atop} \mathrm{O}}$ formation process causes cloud-to-cloud variations in the $A_{V} - N({{13\atop} \mathrm{C}}{{\atop} \mathrm{O}})$ correlation.
ASCA Observation of the Nearest Gravitational Lensing Cluster Candidate — A 3408
Authors: Katayama Haruyoshi , Hayashida Kiyoshi , Hashimotodani Kiyoshi
Published: March 2014

We observed the nearest gravitational lensing cluster candidate, A 3408 ($z = 0.042$), with ASCA. The projected mass profile of A 3408 was determined from the ICM temperature and the $\beta$-model parameters obtained with ASCA, assuming that the hot gas is spherically symmetric and in hydrostatic equilibrium. The projected mass within an arc radius, $r_\mathrm{arc}$, of 110 kpc is $M(r_\mathrm{arc}) = 1.2^{+0.8}_{-0.4} \times10^{13} \,{{{M}_{\odot}}}$. This is 18–45% of the mass previously derived from a lensing analysis by Campusano et al. (1998, AAA 069.160.189) without any X-ray information.

The primary cause of this discrepancy is in their assumption that the center of the cluster potential coincides with the position of the brightest cluster galaxy (BCG), while we reveal the BCG position to be $60^{\prime\prime}$ outside of the X-ray center. We further calculated a model for the source galaxy position and the gravitational potential that can reproduce both the X-ray data and the arc image. In this model, the magnification factor of the lens for the source galaxy was evaluated to be $\Delta m = 0.07 \pm 0.03 \,\mathrm{mag}$; i.e., the source galaxy is slightly magnified by the lens cluster A 3408.
An Abundance Study in the Hg-Mn Star 46 Aquilae (HD 186122) with the SUBARU/HDS
Authors: Sadakane Kozo , Takada-Hidai Masahide , Takeda Yoichi , Ando Hiroyasu , Aoki Wako , Honda Satoshi , Izumiura Hideyuki , Kajino Toshitaka , Kambe Eiji , Kawanomoto Satoshi , Noguchi Kunio , Okita Kiichi , Sato Bun’ei , Watanabe Etsuji
Published: March 2014

A detailed abundance analysis has been carried out for the Hg-Mn star 46 Aql using high-resolution spectra in the visual region (5100–6400 ${Å}$) obtained with the High Dispersion Spectrograph of the Subaru Telescope. Our attention has been mainly focused on those elements which have not been analyzed previously. He, C, N, and O are underabundant, while Na shows the solar abundance. We have confirmed previously reported underabundances of Mg, Al, and Si, and have found an overabundances of P ($+1.5\,\mathrm{dex}$) and Ti ($+1.0 \,\mathrm{dex}$) and a significant underabundance of S ($-1.8 \,\mathrm{dex}$). Fe is overabundant by $+0.8 \pm 0.1 \,\mathrm{dex}$ and a microturbulent velocity of $0.3 \,\mathrm{km} \,\mathrm{s}^{-1}$ was found from an analysis of the Fe ii lines. Among a few hundred unidentified absorption lines, we identified lines of As ii and Xe ii and a very large ($+4.0 \,\mathrm{dex}$) overabundance of Xe is obtained. We have confirmed emission lines of Mn ii and Ti ii near 6100 ${Å}$, while those of Cr ii cannot have been seen.
First Results of a CO Survey of the Small Magellanic Cloud with NANTEN
Authors: Mizuno Norikazu , Rubio Mónica , Mizuno Akira , Yamaguchi Reiko , Onishi Toshikazu , Fukui Yasuo
Published: March 2014

We present the first results from a new 12CO ($J = 1 \hbox{--} 0$) survey of the Small Magellanic Cloud (SMC) with the NANTEN millimeter-wave telescope. The survey covered the northeast and southwest regions of the main Bar, and the H ii regions N 84, N 88 in the Wing at a linear resolution of $\sim 50 \,\mathrm{pc}$. Twenty-one giant molecular clouds (GMCs), whose masses are $\sim 10^{4} \hbox{--} 10^{6} \,{{{M}_{\odot}}}$, were identified. Significant CO emission, $T_\mathrm{R}^{\ast} \sim 0.36 \,\mathrm{K}$, was first detected toward the N 84 region in the Wing, which is comparable to those of the prominent CO clouds associated with infrared sources LIRS 36, LIRS 49 in the Bar. The GMCs exhibit a good spatial correlation with the H ii regions and young clusters, indicating that cluster formation is on-going in these GMCs. On the other hand, they show little correlation with older clusters or with supernova remnants, suggesting rapid dissipation of CO.
α Element Abundances in Mildly Metal-Poor Stars
Authors: Qiu Hong-Mei , Zhao Gang , Takada-Hidai Masahide , Chen Yu-Qin , Takeda Yoichi , Noguchi Kunio , Sadakane Kozo , Aoki Wako
Published: March 2014

We present [O/Fe] and other $\alpha$-elements/Fe ratios in a sample of 24 mildly metal-poor stars. The sample stars are thought to be brighter than 9.0 magnitude and have available $\mathit{uvby}$ photometric data. Also, based on the typical LTE abundance analysis, we find that [Si/Fe] and [Ca/Fe] are correlated with each other. Combining the kinematic data and the metallicity, we can classify the sample stars into three groups. An abundance analysis shows some evidence that these groups are chemically discrete from each other. Further, the general trend of a decreasing overabundance of the $\alpha$ elements with increasing metallicity has been confirmed.
Excitation of Non-Axisymmetric g-Mode Oscillations by Corotation Resonance in Thin Relativistic Disks
Authors: Kato Shoji
Published: March 2014

Various modes of oscillations are trapped in the inner region of geometrically thin relativistic disks. Among these oscillations, non-axisymmetric g-mode oscillations have been less studied compared with other modes of oscillations. The modes are, however, interesting since a corotation resonance appears in the trapped region. We mathematically examine whether the modes can be excited by the effects of the corotation resonance. This examination is made under an assumption that the inner and outer Lindblad radii are sufficiently separated in the opposite directions from the corotation radius. The results of analyses suggest that the waves are excited by the corotation resonance. The presence of the excitation suggests that the non-axisymmetric trapped g-mode oscillations are one of possible candidates for the quasi-periodic oscillations of a few hundred to kHz observed in some X-ray sources.
Centrally Peaked X-Ray Supernova Remnants in the Small Magellanic Cloud Studied with ASCA and ROSAT
Authors: Yokogawa Jun , Imanishi Kensuke , Koyama Katsuji , Nishiuchi Mamiko , Mizuno Norikazu
Published: March 2014

This paper presents ASCA/SIS and ROSAT/HRI results of three supernova remnants (SNRs) in the Small Magellanic Cloud: 0103$-$726, 0045$-$734, and 0057$-$7226. The ROSAT/HRI images of these SNRs indicate that the most of the X-ray emissions are concentrated in the center region. Only from 0103$-$726 are faint X-rays along the radio shell also detected. The ASCA/SIS spectra of 0103$-$726 and 0045$-$734 exhibit strong emission lines from highly ionized metals. The spectra were well-fitted with non-equilibrium ionization (NEI) plasma models. The metal abundances are found to be larger than the mean chemical compositions in the interstellar medium (ISM) of the SMC. Thus, X-rays from these two SNRs are attributable to the ejecta gas, although the ages estimated from the ionization timescale are significantly large, $\gtrsim 10^4 \,\mathrm{yr}$. The chemical compositions are roughly consistent with the type-II supernova origin of a progenitor mass $\lesssim 20 \,{{{M}_{\odot}}}$. The SIS spectrum of 0057$-$7226 was also fitted with an NEI model of an estimated age $\gtrsim 6 \times 10^3 \,\mathrm{yr}$. Although no constraint on the metal abundances was obtained, the rather weak emission lines are consistent with the low metal abundances in the ISM of the SMC. A possible scenario for the evolution of the morphologies and spectra of SNRs is proposed.
The 1999 Optical Outburst of the Fast X-Ray Nova, V4641 Sagittarii
Authors: Uemura Makoto , Kato Taichi , Watanabe Tsutomu , Stubbings Rod , Monard Berto , Nobuyuki Kawai
Published: March 2014

We report on the detection of an optical outburst which preceded the X-ray main flare of the fast X-ray nova V4641 Sagittarii. The object became active since early August 1999, and then experienced an optical outburst reaching 8.8 mag on 1999 September 15. The observed maximum was between two X-ray flares, that is, 12.1 hr after the X-ray sub-flare and 7.4 hr before the main one. The brightness returned to the quiescent level within 5 d, which indicates that the optical outburst rapidly faded as those at other wavelengths, while typical X-ray novae exponentially decay with an $e$-folding time of 30–40 d. We confirmed ellipsoidal modulations in our observations at quiescence. Using them with the previously reported observations, we calculated the period of modulations to be $2.817284\pm 0.000018 \,\mathrm{d}$. From the $\mathrm{H}\alpha$ absorption line in quiescent spectra, we obtained the semi-amplitude of the radial velocity for the secondary star to be $176 \pm 20 \,\mathrm{km} \,\mathrm{s}^{-1}$. Assuming the mass ratio reported in Orosz et al. (2001, ApJ, 555, 489) we estimated the lower limit of the compact object mass to be $5.84 \,{{{M}_{\odot}}}$. To interpret the short outburst and the large luminosity during the outburst, we propose a scenario of a transient supercritical accretion onto a black hole.
Scaling Relation to Understand Non-Detection of Cold Gas at the Cluster Center
Authors: Sasaki Shin , Yamasaki Noriko Y.
Published: March 2014

Recent XMM-Newton observations of clusters of galaxies have indicated the soft X-ray spectra to be inconsistent with the simple isobaric cooling flow model. There is almost no feature of the cold gas expected from the model. This shows that we have not yet understood the physics of the hot gas in clusters of galaxies well. A quantitative evaluation of the behavior of gas cooling is important not only for understanding the clusters, themselves, but also for studying cosmology and galaxy formation. To clarify the problem of this reported discrepancy, we have studied scaling relations for clusters of galaxies based on the self-similarity assumption. We also propose an observational strategy to solve this problem.
The Multiwavelength Doppler Factors for a Sample of Gamma-Ray Loud Blazars
Authors: Zhang Li , Fan Jui-Hui , Cheng Kwong-Sang
Published: March 2014

The high luminosity and rapid variability detected in $ \gamma$-ray loud blazars imply that the beaming effect plays an important role in these sources. The Doppler factor, depending on two unobservable parameters (Lorentz factor and viewing angle), is very important for understanding the basic properties of blazars. Although the viewing angle is unobservable, increasing direct and indirect evidence has shown up to indicate that the jet is bent, and therefore the viewing angle also varies. In this sense, the Doppler factor, which is dependent on the viewing angle and the Lorentz factor, should also vary. In the present paper, using available data of blazars at different (radio, optical, X-ray, and $ \gamma$-ray) wavebands and assuming that multi-waveband radiation is produced by the radiation of accelerated particles in a jet, we discuss the properties of the Doppler factors of blazars at different wavebands. Our results indicate that the Doppler factor of a blazar is a function of frequency. The Doppler factor decreases with frequency from radio to X-ray bands, but increases with frequency from X-ray to $ \gamma$-ray bands. The $ \gamma$-ray Doppler factors found in the present paper are correlated with those by Ghisellini et al. (1998, AAA070.159.155), suggesting that our estimation is reasonable. Furthermore, BL Lacertae objects are found to show lower Doppler factors and higher synchrotron peak frequencies compared with FSRQs; the promising TeV sources are BL Lacertae objects.
The Variability Mechanism of Seyfert Galaxy NGC 4151
Authors: Fan Jun-Hui , Su Cheng-Yue , Lin Rui-Guang
Published: March 2014

Based on compilation by Fan and Su (1998, AAA 70.158.417), the variability property is discussed for the Seyfert galaxy NGC 4151 using the structure function, $ V(\tau)^{\frac{1}{2}} \sim \tau^{k}$. The derived $ k$ is $ 0.35 \pm 0.03$, suggesting that the disk-instability favors the star-burst model as an explanation for the mechanism of the variability in this source.
Supercritical Accretion Disks with Superwinds
Authors: Kitabatake Etsuko , Fukue Jun , Matsumoto Katsura
Published: March 2014

We construct a model for supercritical accretion disks with winds, where the mass-accretion rate highly exceeds the Eddington rate and a significant fraction of the accreting gas is expelled as a superwind, under a self-similar treatment. The mass-accretion rate $ \dot{M}$ decreases with radius $ r$ as $ \dot{M} \propto r^{s+1/2}$, where $ s$ ($ \geq-1/2$) is some arbitrary constant. The surface density $ \Sigma$ and the disk central temperature $ T_\mathrm{c}$ vary as $ \Sigma \propto r^s$ and $ T_\mathrm{c} \propto r^{s/4-1/2}$, respectively. In spite of such a modification, we found that the scaleheight $ H$ and the surface temperature $ T$ of such a superdisk with a superwind is very similar to those of a superdisk without winds; $ H \propto r$ and $ T \propto r^{-1/2}$. Furthermore, the optical depth of the wind becomes remarkably smaller than that in the spherical case, because mass loss takes place at various radii on the disk, and the gas distribution in the wind is not concentrated, but diluted in space. Hence, the observational appearances of both superdisks are quite similar, except for the existence of a strong wind, unless the wind mass-loss rate highly exceeds the critical rate. We then apply a superdisk with a superwind to supersoft X-ray sources. In our picture, although the accretion rate in these objects is of the order of $10^{-5} \,{{{M}_{\odot}}} \,\mathrm{yr}^{-1}$ at the outer edge of the disk and a sufficiently thick superdisk may be established, most of the gas is expelled by the superwind, and the accretion rate at the center becomes of the order of $10^{-7} \hbox{--} 10^{-6} \,{{{M}_{\odot}}} \mathrm{yr}^{-1}$.
Kilo-Second Quasi-Periodic Oscillations in the Cataclysmic Variable DW Cancri
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Novak Rudolf , Pietz Jochen
Published: March 2014

Our photometric monitoring revealed that DW Cnc, which was originally classified as a dwarf nova ($ V=15 \hbox{--} 17.5$), remained at a bright state of $ R_\mathrm{c}=14.68\pm 0.07$ for 61 days. In conjunction with optical spectra lacking a strong He II emission line, we propose that the object is not a dwarf nova, but a non-magnetic nova-like variable. Throughout our monitoring, the object showed strong quasi-periodic oscillations (QPOs) with amplitudes reaching about 0.3 mag. Our period analysis yielded a power spectrum with two peaks of QPOs, whose center periods are $ 37.5\pm 0.1$ and $ 73.4\pm 0.4 \,\mathrm{min}$ and, furthermore, with a significant power in frequencies lower than the QPOs. DW Cnc is a unique cataclysmic variable in which kilo-second QPOs were continuously detected for 61 days. We propose two possible interpretations of DW Cnc: (i) A permanent superhumper below the period minimum of hydrogen-rich cataclysmic variables. (ii) A nova-like variable having an orbital period over 3 hours. In this case, the QPOs may be caused by trapped disk oscillations.
Wide-Field TV Observation of the Leonid Meteor Storm in 2001: Main Peak over Japan
Authors: Watanabe Jun-ichi , Sekiguchi Tomohiko , Shikura Masato , Naito Seiichiro , Abe Shinsuke
Published: March 2014

We carried out a wide-field TV observation of the strong activity of the Leonid meteor shower from $ {17{}^{\mathrm {h}}17{}^{\mathrm {m}}}$ UT through $ {20{}^{\mathrm {h}}20{}^{\mathrm {m}}}$ UT on 2001 November 18. We detected 869 Leonid meteors, along with 32 non-Leonids. A broad peak of the activity was recognized at around $ {18{}^{\mathrm {h}}25{}^{\mathrm {m}}}$ UT, when the peak influx rate of meteoroids was $ 1.4 \times 10^{-5} \,\mathrm{km}^{-2} \,\mathrm{s}^{-1}$ ($ \mathrm{mag} \le +3$). The activity of this main peak was comparable to that of a storm observed in 1999 over Europe. The activity of this peak was rich in bright meteors, including fireball class. The magnitude distribution index was $ 1.5 \pm 0.3$ ($-3 \le \mathrm{mag} \le +1$). The relationship between the observed peak and several theoretical predictions is discussed. We also discuss an “outburst”, which consisted of at least 15 faint meteors which appeared within four seconds at $ {17{}^{\mathrm {h}}56{}^{\mathrm {m}}22{}^{\mathrm {s}}}$.
Study of the X-Ray Background Spectrum and Its Large-Scale Fluctuation with ASCA
Authors: Kushino Akihiro , Ishisaki Yoshitaka , Morita Umeyo , Yamasaki Noriko Y. , Ishida Manabu , Ohashi Takaya , Ueda Yoshihiro
Published: March 2014

We studied the energy spectrum and the large-scale fluctuation of the X-ray background with the ASCA GIS instrument based on the ASCA Medium Sensitivity Survey and Large Sky Survey observations. A total of 91 fields with Galactic latitude $|b| \gt 10^\circ$ were selected with a sky coverage of 50 deg$^2$ and 4.2 Ms of exposure. For each field, non-X-ray events were carefully subtracted and sources brighter than $\sim 2\times 10^{-13} \,\mathrm{erg} \,\mathrm{cm}^{-2} \,\mathrm{s}^{-1}$ (2–10 keV) were eliminated. Spectral fits with a single power-law model for the individual 0.7–10 keV spectra showed a significant excess below $\sim 2 \,\mathrm{keV}$, which could be expressed by an additional thermal model with $kT\simeq 0.4 \,\mathrm{keV}$ or a steep power-law model with a photon index of $\Gamma^\mathrm{soft}\simeq 6$. The 0.5–2 keV intensities of the soft thermal component varied significantly from field to field by $1\,\sigma= 52^{+4}_{-5}\%$, and showed a maximum toward the Galactic Center. This component is considered to be entirely Galactic. As for the hard power-law component, an average photon index of 91 fields was obtained to be $\Gamma^\mathrm{hard} = 1.412\pm 0.007\pm 0.025$ and the average 2–10 keV intensity was calculated as $F_\mathrm{X}^\mathrm{hard} = (6.38\pm 0.04\pm 0.64)\times 10^{-8} \,\mathrm{erg} \,\mathrm{cm}^{-2} \,\mathrm{s}^{-1} \,\mathrm{sr}^{-1}$ ($1\,\sigma$ statistical and systematic errors). The Galactic component is marginally detected in the hard band. The 2–10 keV intensities show a $1\,\sigma$ deviation of $6.49^{+0.56}_{-0.61}\%$, while deviation due to the reproducibility of the particle background is 3.2%. The observed deviation can be explained by the Poisson noise of the source count in the f.o.v. ($\sim 0.5 \,\mathrm{deg}^2$), even assuming a single $\log{N} \hbox{--} \log{S}$ relation on the whole sky. Based on the observed fluctuation and the absolute intensity, an acceptable region of the $\log{N} \hbox{--} \log{S}$ relation was derived, showing a consistent feature with the recent Chandra and XMM-Newton results. The fluctuation of the spectral index was also examined; it implied a large amount of hard sources and a substantial variation in the intrinsic source spectra ($\Gamma_\mathrm{S}\simeq 1.1\pm 1.0$).
Detection of Iron Emission in the z = 5.74 QSO SDSSp J104433.04$-$012502.2
Authors: Aoki Kentaro , Murayama Takashi , Denda Kiyomi
Published: March 2014

We obtained near-infrared spectroscopy of the $z = 5.74$ QSO, SDSSp J104433.04$-$012502.2, with the Infrared Camera and Spectrograph of the Subaru Telescope. The redshift of 5.74 corresponds to a cosmological age of 1.0 Gyr for the current $\Lambda$-dominated cosmology. We found a similar strength of the Fe ii (3000–3500 Å) emission lines in SDSSp J104433.04$-$012502.2 as in low-redshift QSOs. This is the highest redshift detection of iron. We subtracted a power-law continuum from the spectrum and fitted model Fe ii emission and the Balmer continuum. The rest equivalent width of Fe ii (3000–3500 Å) is $\sim 30 \,$ Å, which is similar to those of low-redshift QSOs measured in the same manner. The chemical-enrichment models that assume the lifetime of the progenitor of SNe Ia is longer than 1 Gyr predict that weaker Fe ii emission in high-redshift ($z \gt 3$) QSOs than low-redshift ones. However, none of the observed high redshift QSOs show a systematic decrease of Fe ii emission compared with low-redshift QSOs. This may be due to a shorter lifetime of SNe Ia in QSO nuclei than in the solar neighborhood. Another reason for the strong Fe ii emission at $z = 5.74$ may be a longer cosmological age due to a smaller $\Omega _\mathrm{M}$.
Fluence–Hardness Correlation in Gamma-Ray Bursts
Authors: Liang En-Wei , Xie Guang-Zhong
Published: March 2014

We have studied the total fluence, $F_{\mathrm{total}}$, as a function of the hardness ratio, $\mathit{HR}_{32}$, on gamma-ray bursts (GRBs) observed by BATSE, and suggested two subsets of bursts divided by division of $\log\, (F_{\mathrm{total}}) = 4.5 \times \log\, (\mathit{HR}_{32})-8.5$, then investigated correlations between $\mathit{HR}_{32}$ and $F_{\mathrm{total}}$ as well as the distributions of the duration, $T_{90}$, and $\mathit{HR}_{32}$ in the two subsets. The results show that $F_{\mathrm{total}}$ is not correlated with $\mathit{HR}_{32}$ in the entire set of GRBs, while it is in the two subsets, and the division statistically coincides with the division of $T_{90} \sim 2 \,\mathrm{s}$. A brief discussion along with the results seems to support the point that the anti-correlation between $\mathit{HR}_{32}$ and $T_{90}$ is intrinsic.
Chemical Composition of Carbon-Rich, Very Metal-Poor Subgiant LP 625-44 Observed with the Subaru/HDS
Authors: Aoki Wako , Ando Hiroyasu , Honda Satoshi , Iye Masanori , Izumiura Hideyuki , Kajino Toshitaka , Kambe Eiji , Kawanomoto Satoshi , Noguchi Kunio , Okita Kiichi , Sadakane Kozo , Sato Bun’ei , Shelton Ian , Takada-Hidai Masahide , Takeda Yoichi , Watanabe Etsuji , Yoshida Michitoshi
Published: March 2014

We have obtained high-resolution ($R\sim 90000$) spectra of the carbon-and s-process-element-rich, very metal-poor ($\mathrm{[Fe/H]} =-2.7$) subgiant LP 625-44, as well as those of HD 140283 (a metal-poor subgiant with normal abundance ratio) for a comparison, with the High Dispersion Spectrograph (HDS) for the Subaru Telescope for detailed abundance study. The excess of oxygen in LP 625-44 seems to be remarkable (perhaps by nearly a factor 10) compared with that of HD 140283 derived from the O i triplet around 7770 Å, though the oxygen abundance derived from these lines is uncertain. The Na enhancement in LP 625-44 is by about a factor 50, suggesting hydrogen burning in the ${{22\atop} \mathrm{Ne}}$-rich layer in an asymptotic giant branch star which produced the abundance pattern of this object. In our new spectrum of LP 625-44, the Pb i$\lambda$3683 Å line has been detected, confirming the Pb abundance [$\log \epsilon \mathrm{(Pb)} \sim 1.9$] derived from the Pb i$\lambda$4057 Å line by previous work. The abundance ratio of s-process elements at the second peak (e.g., La, Ce, and Nd) to that at the third peak (Pb) in LP 625-44 is significantly higher (by a factor 5) than that in other three s-process element-rich objects recently studied by van Eck et al. Recent theoretical studies have modeled s-process nucleosynthesis in the radiative layer of asymptotic giant branch stars in the inter-pulse phase. The above results mean that these processes produced a large scatter in the abundance ratios, or different processes (e.g., s-process nucleosynthesis during thermal pulses) contributed to heavy elements in the early Galaxy.
Mars: Dissipating Behavior of the Cloud Belt
Authors: Nakakushi Takashi , Akabane Tokuhide , Iwasaki Kyosuke , Larson Stephen M.
Published: March 2014

This is a brief report on the Martian climate, based on our observations in 2001 as well as those in 1997 and 1999. The focus is the dissipating behavior of the low-latitude cloud belt appearing around the aphelion, the behavior of which has never been explicitly examined. We derive the optical thickness of water ice clouds (WICs) as $ \tau_{\mathrm{WIC}} \approx 0.1$ ($ \lambda \simeq 4400\,{Å}$) at the solar longitude $ L_{\mathrm{s}} = 174^\circ$ in 2001. The latitudinal coverage of the cloud belt is approximately $ L_{\mathrm{s}}$-independent just until its end. The cloud belt divides into a “semi-encircling” cloud band and discrete WICs before its dissipation (over $ L_{\mathrm{s}} \sim 100^\circ \hbox{--} 110^\circ$) in many cases. We suggest that this cloud division should embody localization of the cross-equatorial Hadley circulation.
Dwarf Nova-Like Outburst of Short-Period Intermediate Polar HT Camelopardalis
Authors: Ishioka Ryoko , Kato Taichi , Uemura Makoto , Billings Gary W. , Morikawa Koichi , Torii Ken’ichi , Tanabe Kenji , Oksanen Arto , Hyvönen Harri , Itoh Hitoshi
Published: March 2014

We report on the first time-series observations of a short outburst of the proposed intermediate polar HT Cam ($=$ RX J0757.0$+$6306). On 2001 December 29, we detected that the object was undergoing a bright outburst at a magnitude of $m_\mathrm{vis}=12.2$. Following this detection, we started international joint observations through VSNET. The light curve showed a gradual decline for the first 0.5 d. Following this short plateau phase, the rate of decline dramatically increased to more than $4 \,\mathrm{mag} \,\mathrm{d}^{-1}$. Within 1.5 d from the outburst detection, the object almost declined to the quiescent level. During the rapidly declining phase, long-term modulations with a period of 86min and strong pulses with a period of 8.6 min were observed. We concluded that 86 min and 8.6 min are the orbital period and the spin period of HT Cam, respectively. By detecting the spin period, we confirmed the IP classification of HT Cam. However, its outburst behavior rather resembles that of dwarf novae. The discrepancy between the declining rates of the total flux and the pulse flux strongly suggests that disk instabilities took place during the outburst.
Superhump Evolution in the Ultrashort Period Dwarf Nova 1RXS J232953.9+062814
Authors: Uemura Makoto , Kato Taichi , Ishioka Ryoko , Yamaoka Hitoshi , Schmeer Patrick , Krajci Tom , Starkey Donn R. , Torii Ken’ichi , Kawai Nobuyuki , Urata Yuji , Kohama Mitsuhiro , Yoshida Atsumasa , Ayani Kazuya , Kawabata Tetsuya , Tanabe Kenji , Matsumoto Katsura , Kiyota Seiichiro , Pietz Jochen , Vanmunster Tonny , Oksanen Arto , Giambersio Antonio
Published: March 2014

We report on the evolution of superhumps and late superhumps in an ultrashort period dwarf nova, 1RXS J232953.9$+$062814, during the superoutburst in 2001 November. Ordinary superhumps were observed throughout a plateau phase, a rapid fading phase, and a rebrightening phase. During the plateau phase, the superhump period increased with time at a large rate of $P_\mathrm{dot} = 1.19 \pm 0.24 \times 10^{-4}$. In conjunction with the rebrightening phenomenon, these characteristics indicate that an accretion disk expanded further outward from the $3:1$ resonance radius, which caused a large amount of left over matter at the outer disk, even after the superoutburst. In the post-outburst phase, we detected late superhumps superimposed on dominant double-peak modulations. Late superhumps were observed at least for 10 d without a significant period change. We detected the first normal outburst of this object on 2001 December 26. The interval between the superoutburst and this normal one is 53 d. This short recurrence time supports a high mass-transfer rate in this system. Concerning the evolutionary status of 1RXS J232953.9$+$062814, we propose that it is a progenitor of AM CVn stars on the evolutionary course of the cataclysmic variable channel in which systems have a secondary star with a hydrogen-exhausted core.
Energy Spectra and Normalized Power Spectral Densities of X-Ray Nova GS 2000+25
Authors: Terada Kentaro , Kitamoto Shunji , Negoro Hitoshi , Iga Sayuri
Published: March 2014

The X-ray energy spectra and Normalized Power Spectral Densities (NPSDs) of an X-ray nova, GS 2000$+$25, were investigated. The X-ray energy spectra of the source consist of two components: a hard component, which can be represented by a power-law, and an ultra-soft component, represented by radiation from an optically-thick accretion disk (the disk component). In a model in which the power-law component is the Compton-scattered radiation, it is found that the temperature of the incident blackbody radiation to the Compton cloud decreases from 0.8 keV to 0.2 keV according to the decay of the intensity, which coincides with that of the inner accretion disk. When the source changed from the high-state to the low-state, both the photon index of the power-law component (or Compton $y$-parameter) and the NPSD of the hard component dramatically changed as did GS 1124$-$683. That is, the photon index changed from 2.2–2.6 to 1.7–1.8 and the absolute values of the NPSDs at 0.3 Hz of the hard component in the low-state became about 10-times larger than those of the hard component in the high-state. These X-ray properties were similar to those of other black-hole candidates, such as Cyg X-1, GX 339-4, and LMC X-3.