bluuebunny/crossref_metadata_2025 huggingface dataset:
NANTEN Observations of the Pipe Nebula; A Filamentary Massive Dark Cloud with Very Low Star-Formation Activity
Authors: Onishi Toshikazu , Kawamura Akiko , Abe Rihei , Yamaguchi Nobuyuki , Saito Hiro , Moriguchi Yoshiaki , Mizuno Akira , Ogawa Hideo , Fukui Yasuo
Published: March 2014

We present molecular line observations toward the “Pipe Nebula” in the J = 1−0 lines of 12CO, 13CO, and C18O by using “NANTEN” telescope. An area of ∼ 27 deg2 was covered at a 4′ grid spacing with a 2′.7 beam in 12CO. The 12CO velocity-integrated intensity map and channel maps show a filamentary distribution. The total mass of the 12CO- and 13CO-emitting gas is estimated to be ∼ 10000 M⊙ and ∼ 3000 M⊙ , respectively. We have identified 14 C18O cores whose mass is typically ∼ 30 M⊙ . Star formation is active only in the B 59 region. This activity is best demonstrated by a newly detected CO outflow toward the center of B 59. We suggest that the dynamical effects of tau Sco may be responsible for triggering star formation only in the B 59 region. The C18O column density toward B 59 is extremely high compared with the rest of the cloud. This confirms that high C18O column density is a necessary condition of star formation as previously suggested. Although the star-formation efficiency is estimated to be quite low, ≲ 0.1%, except for B 59, the existence of the C18O cores suggests that there is molecular gas that is massive and dense enough to form stars, and that star formation is likely to occur in the near future.
A New Derivation of the Extinct ion-to-CO Column Density Ratio in the Chamaeleon I Dark Cloud
Authors: Hayakawa Takahiro , Mizuno Akira , Onishi Toshikazu , Yonekura Y. , Hara Atsushi , Yamaguchi Reiko , Fukui Yasuo
Published: March 2014

We have analyzed new datasets of 13CO (J = 1−0) and C18O (J = 1−0) emission obtained with NANTEN and visual extinction, AV, derived from DENIS J-band observations in the Chamaeleon I dark cloud. The column densities of both molecular isotopes, N(13CO) and N(C18O, have been derived assuming LTE. Both N(13CO) and N(C18O are linearly correlated with AV in the range AV≲ 10 mag. We established the relationships N(13CO) (cm-2)=(1.2± 0.1)× 1015AV(mag)+(0.7± 0.3)× 1015 and N(C18O) (cm-2)=(3.5± 0.3)× 1014AV(mag)-(5.7± 1.3)× 1014. In a region of clustered T Tauri stars, however, both the AV-N(13CO) and AV-N(C18O) relationships are by a factor of ∼ 2 steeper than the above. This may be mainly due to underestimates of the AV values, and the J-band star count might deserve a more careful examination for possible underestimates of associated young stars. Compared with the relationships for the other clouds, the slope of the AV-N(13CO) relationship is relatively shallower and that of the AV-N(C18O) relationship in a non-cluster forming region is slightly steeper. These facts suggest that cloud-to-cloud variation is significant in the AV-N(CO) relationships.
Oxygen 6156–8 Å Triplet in Chemically Peculiar Stars of t he Upper Main Sequence: Do HgMn Stars Show an Oxygen Anomaly?
Authors: Takeda Yoichi , Takada-Hidai Masahide , Jugaku Jun , Sakaue Akihiko , Sadakane Kozo
Published: March 2014

An extensive spectrum-fitting analysis in the λ ∼ 6150 Å region was performed for forty late-B and A chemically peculiar (HgMn, Ap, Am, weak-lined) and normal stars of the upper main sequence, in order to quantitatively establish the abundance of oxygen from the O I 6156-8 triplet and to study its behavior/anomaly for each peculiarity group, where special attention was paid to HgMn-type stars. Magnetic Ap variables (Si or SrCrEu type) generally show a remarkably large oxygen depletion (by ∼ −1.6 dex to ∼ −0.4 dex relative to the solar abundance), and classical Am stars also show a clear underabundance (by ∼ −0.6 dex on the average). In contrast, the oxygen abundance in HgMn stars, exhibiting only a mild deficiency relative to the Sun typically by ∼ 0.3−0.4 dex, is not markedly different from the tendency of normal stars, also showing a subsolar abundance ([O/H] ⋍ −0.2). In view of the recent observational implication that the present solar oxygen abundance is enriched by ∼ 0.2−0.3 dex relative to the interstellar gas (from which young stars are formed), and thus unsuitable for the comparison standard, we concluded that the extent of the average O-deficiency in HgMn stars is appreciably reduced down to only ∼ 0.1−0.2 dex (i.e., not much different from the initial composition), which contrasts with their well-known drastically large N-depletion. Yet, as can be seen from the delicate and tight O vs. Fe anticorrelation, this marginal deficiency should be real, and thus some physical process simultaneously producing O-depletion/Fe-enrichment must have actually worked in the atmosphere of HgMn stars.
Intermittent Star-Formation Activities of Dwarf Irregular Galaxies
Authors: Hirashita Hiroyuki
Published: March 2014

On the basis of the propagating star-formation model, we investigated the star-formation activities of dwarf irregular galaxies (dIrrs) by considering two processes: the heating from stellar feedback and the cooling of the heated gas. After examining the timescales of the two processes, we propose that continuous global star-formation activity is difficult in dIrrs, since their small sizes make the feedback efficient and their small metallicities prevent the cooling from becoming effective. Thus, the intermittent nature of the star-formation activities of dIrrs, which is due to the small metallicity as well as the small size, is predicted. We emphasize that the size of a galaxy is an important factor concerning star-formation activity. The intermittence of the star-formation activity is also supported by the observed scatter of the UBV colors and Hα equivalent widths of the dIrr sample. However, we note that efficient interstellar mixing may make the cooling time much shorter.
Helium and Carbon Abundances in Late-B and Early-A Supergiants
Authors: Takeda Yoichi , Takada-Hidai Masahide
Published: March 2014

The abundances of carbon and helium were determined for representative late-B and early-A supergiants based on the CI lines (9078, 9089, 9095, 9112) in the near-IR, CII lines (4267, 6151), and the He I 6678 line, in an aim to investigate the nature of the envelope-mixing in these evolved stars based on the anomaly (if any) of these elements combined with that of N and O published before. It turned out that N tends to increase with a decrease in C, showing a tendency of conserving the sum of C+N nuclei, which suggests that the anomaly of C and N may be reasonably interpreted as being due to mixing of the CN-processed material. However, this increase/decrease in N/C, indicative of dredge-up of the H-burning product, is not accompanied by any He-enrichment. Even surprisingly, the observed tendency is just the opposite, i.e., [He/H] appears to decrease progressively in accordance with a lowering of [C/H]. Instead of regarding this apparent characteristics as being real, we tentatively speculate that some activity-related line-weakening mechanism (e.g., irradiance of X-rays) might act on the formation of He I lines, the extent of which is indirectly related to the efficiency of envelope mixing via stellar rotation.
Galactic Rotation Derived from OB Stars Using Hipparcos Proper Motions and Radial Velocities
Authors: Uemura Makoto , Ohashi Hiroyuki , Hayakawa Tomonori , Ishida Eiji , Kato Taichi , Hirata Ryuko
Published: March 2014

We have examined the systematic velocity field of the solar neighborhood, based on Hipparcos (HIgh Precision PARallax COllecting Satellite) proper motions and ground-based radial velocities of about 240 O-B5 stars. The distances of these stars were derived from either Hipparcos parallaxes or the SKYMAP compilation of the spectroscopic parallaxes. Using a first-order approximation, we obtained the galactic rotation at the solar vicinity of Vθ = 255.52±8.33 km s−1 assuming the galactocentric distance of the Sun, R⊙ = 8.5 kpc. The slope of the galactic-rotation curve is given by (∂Vθ/∂R)R⊙ = −1.98±0.98 km s−1 kpc−1, and the rotation about the axis pointing to the galactic center is −R−1∂Vz/∂θ = 1.33±0.90 km s−1 kpc−1. Our sample shows neither expansion nor contraction with respect to the Local Standard of Rest (LSR).
High-Resolution Near-Infrared Imaging of the Powerful Radio Galaxy 3C 324 at z = 1.21 with the Subaru Telescope
Authors: Yamada Toru , Kajisawa Masaru , Tanaka Ichi , Maihara Toshinori , Iwamuro Fumihide , Terada Hiroshi , Goto Miwa , Motohara Kentaro , Tanabe Hirohisa , Taguchi Tomoyuki , Hata Ryuji , Iye Masanori , Imanishi Masatoshi , Chikada Yoshihiro , Yoshida Michitoshi , Simpson Chris , Sakaki Toshiyuki , Kosugi George , Usuda Tomonori , Omata Koji , Imi Katsumi
Published: March 2014

We have obtained high-resolution K′-band images of the powerful z = 1.206 radio galaxy 3C 324 with the Subaru telescope under seeing conditions of 0″.3–0″.4. We clearly resolved the galaxy and directly compared it to the optical images obtained with the Hubble Space Telescope. The host galaxy of 3C 324 is revealed to be a moderately luminous elliptical galaxy with a smooth light profile. The effective radius of the galaxy, as determined by profile fitting, is 1″.3±0″.1 (1.2 kpc), which is significantly smaller than the value of 2″.2 published in Best et al. (1998a, AAA 69.158.239). The peak of the K′-band light coincides with the position of the radio core, which implies that the powerful AGN lies at the nucleus of the host galaxy. The peak also coincides with the gap in the optical knotty structures which may be a dust lane hiding the UV-optical emission of the AGN from our line of sight; it is very likely that we are seeing the obscuring structure almost edge-on. We clearly detected the ‘aligned component’ in the K′-band image by subtracting a model elliptical galaxy from the observed image. The red RF702W – K color of the outer region of the galaxy avoiding the aligned component indicates that the near infrared light of the host galaxy is dominated by an old stellar population.
Pulse-Phase Resolved Spectroscopy of Hercules X-1 with ASCA
Authors: Endo Takao , Nagase Fumiaki , Mihara Tatehiro
Published: March 2014

We analyzed the archival data of the X-ray pulsar Hercules X-1, observed with ASCA in 1994 August and 1996 April during the Main-High State of the 35-d cycle. The continuous spectrum in the energy range of 0.5–10 keV is found to have three components, i.e., power-law, soft blackbody, and highly absorbed power-law. In addition to the ∼ 6.5 keV iron K-shell line, we confirmed the existence of a broad emission feature around 1 keV that might be attributed to the iron L-shell lines. The line feature at ∼ 6.5 keV was resolved into two narrow lines at 6.4 keV and 6.7 keV from the ASCA/SIS spectrum. We performed a pulse-shape analysis in several energy bands and pulse phase-resolved spectroscopy, and found that a sinusoidal soft pulse consists of a blackbody and a broad ∼ 1 keV component, which is shifted by about 230° in phase from the pulse peak in the hard band which consists of a power-law and a highly absorbed power-law component. Assuming that the main beam, which is dominated by the power-law component, originates from the magnetic poles on the neutron star, we discuss the emission sites of other components in the context of an X-ray irradiated accretion disk.
The Minimum Spanning Tree Problem in the Phase Calibration for the Spatial FFT Interferometer
Authors: Takeuchi Hiroshi , Akamine Yukinori , Fujii Fumiyuki , Kuniyoshi Masaya , Suemitsu Taisei , Gotoh Kentaro , Mizuki Saori , Mizuno Keiju , Suzuki Tomoya , Fukuoka Kohji , Tanaka Naoki , Daishido Tsuneaki
Published: March 2014

Achieving a Nyquist-rate direct-imaging observation using a spatial FFT interferometer, instrumental phase errors in transmission lines must be calibrated before the observation. We improved the phase-calibrating system in the Waseda FFT interferometer by increasing the number of simultaneous obtainable fringe baselines from 84 to 128, and using the algorithm of the minimum spanning tree problem in graph theory. As a result, the main-beam intensity of the interferometer became 1.6 times on average.
Luminosity Function of Galaxies in the Nearby Universe: The Low-Luminosity End of the Nuclear Activity Sequence
Authors: Vila-Vilaro Baltasar
Published: March 2014

We present an estimate of the shape of the luminosity functions in the nearby Universe for the 4 types of extragalactic nuclear activity cited in Ho et al. (1997a, AAA 68.158.311), i.e., H II, LINER, Transition, and Seyfert galaxies, based on a magnitude limited complete sample of objects selected from the same work. This sample includes quite weaker nuclear emission objects than considered in previous studies, which has allowed us to assess the low-luminosity ends of the nuclear activity sequence for each type. It is found that three of the classes (LINER, Transition, and Seyferts) have very similar luminosity function shapes, and basically seem to differ only in the relative numbers. H II objects tend to be found in different hosts (lower luminosity galaxies) and seem to have a bimodal luminosity function, with a fairly large proportion of Irr and dwarf galaxies in this class, which are superposed to a more Schechter-like luminosity function. Several observational properties also suggest that Transition objects are actually LINERs contaminated by H II regions, and should be included in that category. Our fits further suggest the presence of a substantial number of low-luminosity host Seyferts in the nearby Universe. The distribution of absolute magnitudes for Seyferts type 1 and 2 is very similar in our sample. The possibility that the LINER class encompasses several different classes of objects is also discussed.
Ab Initio Calculations for Detectable New Isomers of Interstellar Carbon-Chain Radicals Cn(n=2–8)
Authors: Takahashi Junko
Published: March 2014

Detectable new isomers of interstellar carbon-chain (linear) radicals, Cn(n=2–8), were investigated theoretically based on ab initio quantum chemical calculations. The molecular characteristics of various Cn(n=3–8) isomers were examined, and it was found that 3-ring isomers (isomers with a three-member-carbon-ring) of C3H, C5H, and C7H are at a low energy level relative to linear isomers, and that their dipole moments are sufficiently large. The formation mechanisms of C3H and C5H were also examined, and it was found that both linear- and 3-ring-C3H and C5H can be formed via neutral-neutral reactions, C + C2H2 → C3H + H and C + C4H2 → C5H + H, respectively, in interstellar space. These facts strongly suggest that carbon-ring-chain radicals, C5H and C7H, are a new series of interstellar molecules that will be detectable in the laboratory and interstellar space.
Radix-4 Butterfly LSI in Direct-Imaging Waseda Radio Interferometer for a Pulsar Survey
Authors: Tanaka Naoki , Daishido Tsuneaki , Takeuchi Hiroshi , Akamine Yukinori , Kuniyoshi Masaya , Suemitsu Taisei , Fujii Fumiyuki , Gotoh Kentaro , Suzuki Tomoya , Mizuki Saori , Mizuno Keiju , Fukuoka Koji , Suzuki Masahiro
Published: March 2014

In the Nyquist rate direct-imaging interferometer at Waseda University, a radix-4 butterfly LSI has been developed for the spatial-temporal (2+1)D FFT processor to survey pulsars. In (2+1)D FFT, the first 2D FFT is a 2D directional finding spatial FFT processing for an 8times 8 pixel image. The second 1D FFT is a 1D spectral finding temporal FFT processing for a 64ch frequency analysis in each 64 pixels. Since fewer multipliers are required in radix-4 FFT than in radix-2 FFT, we have implemented radix-4 algorithms in the present butterfly LSI. This implementation, using 512 radix-4 butterfly LSIs, could reduce the circuit size of the parallel and pipeline (2+1)D FFT processor. Additional functions, such as shift registers, digital filters and post-process sections, are also included in the LSI for a radio interferometric pulsar survey.
Magnetic Field Evolution Leading to Solar Flares I. Cases with Low Magnetic Shear and Flux Emergence
Authors: Li Hui , Sakurai Takashi , Ichimoto Kiyoshi , UeNo Satoru
Published: March 2014

We picked up five solar flares larger than GOES X-ray class M/Hα importance 1, and studied the magnetic evolution of the corresponding active regions. In particular, we investigated the spatial relationships among Hα flare ribbons, soft X-ray (SXR) flare loops, and magnetic configurations. Our results show that all of these flares are not associated with high magnetic shear, but with emerging flux, indicating that flux emergence is a common phenomenon in this kind of solar flare with low magnetic shear. The maximum values of the transverse magnetic fields on the neutral lines responsible for these flares are 300-800 G. All of these flares but one have multiple (more than two) Hα ribbons, and almost all of these ribbons are located at the footpoints of SXR flare loops. The flare-related shear changes, which can be both positive and negative, may be determined by the balance of the energy carried by the emerging flux and that required to power the flare.
[OII] λ 3727 Emission from the Companion to the Quasar BR 1202–0725 at z = 4.7
Authors: Ohta Kouji , Matsumoto Tsuyoshi , Maihara Toshinori , Iwamuro Fumihide , Terada Hiroshi , Goto Miwa , Motohara Kentaro , Taguchi Tomoyuki , Hata Ryuji , Yoshida Michitoshi , Iye Masanori , Simpson Chris , Takata Tadafumi
Published: March 2014

Results of a narrow-band imaging for the redshifted [OII] λ3727 emission around a quasar at z = 4.7 obtained with the Subaru telescope and CISCO (a Cassegrain near infrared camera) are presented. A significant emission line is detected in the narrow-band H2 [v = 1–0 S(1)] filter at a location ∼ 2″.4 northwest from the quasar, where the presence of a companion has been reported in Lyman α emission and the rest-frame UV continuum. We identify this line as [OII] λ 3727 emission and confirm that the source really is a companion at z = 4.7. The [OII] λ3727 flux from the companion is estimated to be 2.5 × 10−17 erg s−1 cm−2. If the companion is a star-forming object, the inferred star-formation rate is as high as 45–230 M⊙ yr−1, even without assuming an extinction correction. This value is higher than those derived from the Lyman α emission or from the UV continuum. Thus, provided that the difference is caused by dust extinction, the extinction-corrected star-formation rate is calculated to be 45 to 2300 M⊙ yr−1, depending on the assumed extinction curves.
Deep-Imaging Observations of a Candidate of an Absorbed QSO at z = 0.653, AX J131831+3341
Authors: Akiyama Masayuki , Ohta Kouji , Tamura Naoyuki , Doi Mamoru , Kimura Masahiko , Komiyama Yutaka , Miyazaki Satoshi , Nakata Fumiaki , Okamura Sadanori , Sekiguchi Maki , Shimasaku Kazuhiro , Yagi Masafumi , Hamabe Masaru , Yoshida Michitoshi , Takata Tadahumi
Published: March 2014

The results of deep-imaging observations of a candidate of an absorbed QSO at z = 0.653, AX J131831+3341, are presented. AX J131831+3341 was found during the course of optical follow-up observations of the ASCA Large Sky Survey, and has an X-ray luminosity of 1045 erg s−1 (2–10 keV), which corresponds to those of QSOs. Its optical spectrum shows no significant broad Hβ emission line, suggesting that the object is an absorbed QSO. Deep R and V band images reveal the presence of a point-like nucleus and an asymmetric extended component. The nuclear component has a blue color, and the optical magnitude is much fainter than that expected from the observed X-ray flux for typical type-1 AGNs. These photometric properties and the presence of broad MgII 2800 Å emission can be explained simultaneously if the observed nuclear light is dominated by scattered nuclear light, though there is a possibility that the nuclear component is a slightly absorbed nucleus if its intrinsic X-ray to optical flux ratio is the largest among X-ray selected AGNs. The size of the extended component, which is thought to be the host galaxy of the QSO, is larger than those of normal disk galaxies at z = 0–0.75, and the absolute magnitude is similar to those of the brightest host galaxies of QSOs at redshifts smaller than 0.5. The V – R and R – I colors of the component are consistent with a 1 Gyr-old stellar population model without absorption.
ISO Observations of the Planetary Nebula Lindsay 305 in the Small Magellanic Cloud
Authors: Kučinskas Arūnas , Vansevičius Vladas , Sauvage Marc , Tanabé Toshihiko
Published: March 2014

We present ISO (Infrared Space Observatory) observations of the planetary nebula Lindsay 305 (L 305) in the Small Magellanic Cloud. L 305 is very prominent in the ISOCAM frames at 6.75 and 11.5 μm, although it is under the detection limit at 4.5 μm. The obtained spectral energy distribution shows a strong mid-IR excess, which, depending on the amount of energy radiated at wavelengths longer than 11.5 μm, may be as large as ∼ 1500 L⊙. However, since an accurate estimate of the total nebular luminosity is not available to date, the evolutionary status of L 305 can not yet be constrained precisely.} Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.
X-Ray Observation of the Lynds 1157 Dark Cloud Region with ASCA
Authors: Furusho Tae , Yamasaki Noriko Y. , Ohashi Takaya , Saito Yoshitaka , Voges Wolfgang
Published: March 2014

An ASCA observation of a region containing a Class 0 protostar IRAS 20386+6751 in the Lynds 1157 dark cloud, has been carried out. The protostar was not detected, and the 95% upper limit to the luminosity depends on the assumed NH: LX(0.5–10 keV) < 1.1 × 1031 erg s−1 for NH = 1 × 1023 cm−2. A Class I protostar in Lynds 1152, IRAS 20353+6742, in the same field was also undetected with an upper limit about three-times as much as the Lynds 1157 level. Besides these non detections, nine new X-ray sources were detected and a spectral analysis was performed for 4 sources. One object (AX J2038+6801) shows a hard spectrum with a temperature of kT ∼ 8 keV or a power-law photon index of ∼ 2.0 and absorbed with NH ∼ 2 × 1022 cm−2. Another fainter one (AX J2036 + 6800) has a soft spectrum with most of the emission falling below 2 keV. We examine the possible nature of these new X-ray sources based on their spectral properties.
Transient Optical Emission from a Nonstationary Accretion Disk: A Model for Optical Afterglow of Gamma Ray Bursts
Authors: Lu Ye , Cheng Kwong-Sang , Zhao Gang
Published: March 2014

We consider the time-dependent behavior of nonstationary accretion disk which is formed by the capture and disruption of a main-sequence star around a massive black hole. If an instability is developed in the inner edge of the nonstationary disk and produces a strong magnetic field, a large amount of the black hole rotational energy can be extracted via the Blandford-Znajek process, which results in a Gamma-Ray Burst (GRB) with a typical duration ∼ 10–102 s. Other parameters related to a typical GRB including burst energy, rise time of the burst, number of sub-burst etc are also estimated. The vertical structure and thermal stability properties of the disk are investigated in detail. In the early stage of forming transient accretion disk, the material supplied by the tidally disrupted star is clumped in the relatively cool disk. This eventually leads to a thermal instability, which results in an increase of the viscosity of the disk. As the instability propagates across the disk, the stability of a time-dependent disk and variability of the mass-deposition rate provide a possible explanation for transient optical emission. We speculate that this transient optical emission from a nonstationary accretion disk may relate to the behavior of GRB optical afterglow, and the transient optical afterglow can be reproduced if one takes into account the effect of an evolving viscous parameter, α.
Distribution and Kinematics of Molecular Gas in Barred Spiral Galaxies. I. NGC 3504
Authors: Kuno Nario , Nishiyama Kohta , Nakai Naomasa , Sorai Kazuo , Vila-Vilaró Baltasar , Handa Toshihiro
Published: March 2014

We present the results of CO mapping observations of the barred spiral galaxy NGC 3504 with the Nobeyama 45-m telescope. The distribution of the molecular gas shows offset ridges which correspond to the distribution of H II regions along the bar. The velocity perpendicular to the bar decreases abruptly at the ridge. The velocity change implies that the molecular gas changes the direction of its motion to parallel to the bar at the ridge. Since the position angle of the major axis of the bar and the line of nodes are almost the same in NGC 3504, an upper limit to the pattern speed of the bar can be derived directly from the radial velocity. The resultant upper limit is 41 km s−1 kpc−1, which is much smaller than that derived based on an assumption that the corotation radius is located at the end of the bar (77 km s−1 kpc−1). The corotation radius derived from our upper limit is more than two-times larger than the length of the semi-ma jor axis of the bar in NGC 3504.
Discovery of 172-s Pulsations from a Be/X-Ray Binary Candidate AX J0051.6–7311 in the SMC with ASCA
Authors: Yokogawa Jun , Torii Ken'ichi , Imanishi Kensuke , Koyama Katsuji
Published: March 2014

The results from three ASCA observations of AX J0051.6–7311 = RX J0051.9–7311 are reported. Coherent pulsations with a barycentric period of 172.40 ± 0.03 s were discovered in the third observation, with an exceptionally long exposure time of ∼ 177 ks. The X-ray spectrum was found to remain unchanged through these observations, with a photon index of of ∼ 0.9. Energy-resolved pulse profiles in the third observation reveal that the pulsations are mostly due to photons with an energy above ∼ 2 keV. Archival data of ROSAT and Einstein Observatory indicate that AX J0051.6–7311 exhibits a flux variation having a factor ≳ 20.
Multi-Frequency VLBI Observations of OT 081
Authors: Iguchi Satoru , Fujisawa Kenta , Kameno Seiji , Inoue Makoto , Shen Zhi-Qiang , Hirotani Kouichi , Miyoshi Makoto
Published: March 2014

We have observed OT 081 at 4.8, 8.4, 15, and 22 GHz, with the VLBI Space Observatory Programme (VSOP) and the Very-Long-Baseline Array (VLBA) after its radio burst on 1998 May. Multi-frequency VLBI images show a dominant component D and a weak component C1, which is a knot of the jet extending to the north-west direction. The derived physical parameters of component D are the Doppler factor, δeq ∼ 32.0, the Lorentz factor of 16.0< Γ < 16.9, and the viewing angle, φ < °.68. It appears that although δeq of component C1 is smallar than that of componet D by one order of magnitude, Γ of component C1 is about twice the range as that of component D at the 1 σ level. However, φ of component D is different from that of component C1. The rapid variability of the flux density of OT 081 is suggested to be due to the variation of φ .
VSOP Polarization Observing at 1.6 GHz and 5 GHz
Authors: Kemball Athol , Flatters Chris , Gabuzda Denise , Moellenbrock George , Edwards Philip , Fomalont Edward , Hirabayashi Hisashi , Horiuchi Shinji , Inoue Makoto , Kobayashi Hideyuki , Murata Yasuhiro
Published: March 2014

We present and discuss the results of 1.6 GHz and 5 GHz test polarization observations obtained with HALCA, the VLBA, and phased VLA, specifically to evaluate the feasibility of calibrating and imaging HALCA polarization data. Our analysis provided the first demonstration that centimeter-wavelength polarization imaging using HALCA is technically viable for sources with sufficiently high correlated polarized flux densities, despite a number of factors which conspire to complicate the calibration, including relatively low sensitivity, inability to observe calibrators, lack of varying parallactic angle, and absence of redundant measurements on space baselines. The test data described here are limited and cannot rule out instrumental variability, but indicate that the HALCA instrumental polarization leakage is ∼ 2−5% at 1.6 GHz and ∼ 9−11% at 5 GHz. The prospects for effective polarization calibration on future orbiting VLBI missions are encouraging, especially since improvements in sensitivity are expected.
The Time Lag between V and I in S5 0716+714 during the 1995 January 8 Burst
Authors: Qian Bochen , Tao Jun , Fan Junhui
Published: March 2014

The BL Lac object S5 0716+714 has been one part of our optical monitoring program of blazars since 1994. A burst with a duration of 6 hours was detected on 1995 January 8 and 80 sets of measurements were obtained in V and I, by turn, for the whole burst. An upper limit of the time lag of 0.0041 days (about six minutes) between bands V and I has been determined by using the Interpolation Cross-Correlation Function (ICCF) and the Discrete Correlation Function (DCF).
ASCA Observation of Ultra-Luminous X-Ray Sources in the Nearby Spiral Galaxy NGC 2403
Authors: Kotoku Jun'ichi , Mizuno Tsunefumi , Kubota Aya , Makishima Kazuo
Published: March 2014

The spiral galaxy NGC 2403 was observed with ASCA, and three previously known X-ray sources (sources 3, 4, and 5) were detected. Among them, the observed 0.5-10 keV flux of source 3 is 1.4×10−12 erg s−1 cm−2, implying a bolometric luminosity of 3.0×1039 erg s−1. Its spectrum can be explained by emission from an optically thick accretion disk with an inner-disk temperature of 1.1 keV. The spectrum and the high luminosity suggest that source 3 is a mass-accreting black hole binary. The observed properties of source 3 can be interpreted in terms of a black hole of mass ∼ 15 M⊙, accreting at near the Eddington rate.
Resistive Magnetohydrodynamics of Jet Formation and Magnetically Driven Accretion
Authors: Kuwabara Takuhito , Shibata Kazunari , Kudoh Takahiro , Matsumoto Ryoji
Published: March 2014

We carried out 2.5-dimensional resistive magnetohydrodynamic simulations to study the effects of magnetic diffusivity on magnetically driven mass accretion and jet formation. The initial state is a constant angular-momentum torus threaded by large-scale vertical magnetic fields. Since the angular momentum of the torus is extracted due to magnetic braking, the torus medium falls toward the central region. The infalling matter twists the large-scale magnetic fields and drives bipolar jets. We found that (1) when the normalized magnetic diffusivity,$\bar \eta \equiv \eta/(r_0 V_{\textrm {Ko}})$, where VK0 is the Keplerian rotation speed at a reference radius $r=r_0$, is small $(\bar \eta \leq 10^{-3})$, mass accretion and jet formation take place intermittently; (2) when $10^{-3}\leq \bar \eta \leq 10^{-2}$, the system evolves toward a quasi-steady state; and (3) when $\bar \eta \geq 10^{-2}$ the accretion/mass outflow rate decreases with bar $\bar \eta$ and approaches 0. The results of these simulations indicate that in the center of a galaxy which has a super-massive ( ∼ 109M⊙ ) black hole, a massive ( ∼ 108M⊙ ) gas torus and magnetic braking provide a mass accretion rate which is sufficient to explain the activity of AGNs when $\bar \eta \leq 5 \times10^{-2}$
Basic Properties of Thin-Disk Oscillations
Authors: Kato Shoji
Published: March 2014

In this paper oscillations on geometrically thin disks are reviewed, focusing on two issues. One is the characteristics of disk oscillations. The other is possible excitation mechanisms of these oscillations. The main purpose of this paper is to clarify the physics and dynamics involved in these issues. We consider both Newtonian and general-relativistic disks, since a comparison of the oscillations on both disks clarifies the differences among these two oscillations and is helpful for understanding the unique properties of relativistic disks. Furthermore, we sometimes refer to stellar oscillations, since a comparison with stellar oscillations is helpful to have a deeper understanding of the disk oscillations, especially of the excitation mechanisms.
Spiral Structures and Shocks in Accretion Discs in Close Binary Systems: the Role of the Injection Velocity at the Inner Lagrangian Point
Authors: Lanzafame Giuseppe , Maravigna Fabio , Belvedere Gaetano
Published: March 2014

In our previous paper (Lanzafame et al. 2000, PASJ 52, 515) we showed, through 2D SPH simulations, that the stellar mass ratio, $ M_{2}/M_{1}$, of a close binary system (that determines the $ L_{1}$ position and then the initial specific angular momentum at $ L_{1}$) plays a fundamental role in the formation and development of spiral structures and shock fronts in the radial flow of accretion discs. In that work only a quasi-sonic value of the injection velocity at $ L_{1}$ was considered. In the present work we also carried out 2D SPH simulations with the aim to investigate the development of such structures, while keeping constant the mass of the compact primary ($ M_{1} = 1 M_\odot$) and the separation between the two components, and assuming as an initial condition of two different supersonic injection velocities at $ L_{1}$, characterizing two sets of simulations. For each set we considered four values of the secondary to primary mass ratio, $ M_{2}/M_{1}$. We worked out 2D models because the damping effect of the artificial viscosity is too strong in 3D. Furthermore, the 2D environment seems to be the most suitable in order to be evidence of shock fronts in highly compressible gases. Our aim in these two works was to enhance the initial kinematic conditions (from sonic to strongly supersonic) to stress the idea that spiral structures and shock front development are influenced by the initial specific angular momentum at $ L_{1}$. The results show that these structures are more evident with the increasing injection velocity at $ L_{1}$ and the increasing $ L_{1}$ distance from the primary.
Subaru Deep Survey I. Near-Infrared Observations
Authors: Maihara Toshinori , Iwamuro Fumihide , Tanabe Hirohisa , Taguchi Tomoyuki , Hata Ryuji , Oya Shin , Kashikawa Nobunari , Iye Masanori , Miyazaki Satoshi , Karoji Hiroshi , Yoshida Michitoshi , Totani Tomonori , Yoshii Yuzuru , Okamura Sadanori , Shimasaku Kazuhiro , Saito Yoshihiko , Ando Hiroyasu , Goto Miwa , Hayashi Masahiko , Kaifu Norio , Kobayashi Naoto , Kosugi George , Motohara Kentaro , Nishimura Tetsuo , Noumaru Jun’ichi , Ogasawara Ryusuke , Sasaki Toshiyuki , Sekiguchi Kazuhiro , Takata Tadafumi , Terada Hiroshi , Yamashita Takuya , Usuda Tomonori , Tokunaga Alan T.
Published: March 2014

Deep near-infrared images of a blank 2$^{\prime}$$ \times$ 2$ ^{\prime}$ section of sky near the galactic north pole taken by Subaru Telescope are presented. The total integration times of the $ J$ and $ K^{\prime}$ bands were 12.1 hr and 9.7 hr, resulting in 5$ \sigma$ limiting magnitudes of 25.1 and 23.5 mag, respectively. The numbers of sources within these limiting magnitudes found with an automated detection procedure are 385 in the $ J$ band and 350 in $ K^{\prime}$. Based on photometric measurements of these sources, we present number count vs. magnitude relations, color vs. magnitude diagrams, size vs. color relationships, etc. The slope of the galaxy number count plotted against the AB magnitude scale is about 0.23 in the 22 to 26 AB magnitude range of both bands. The spatial number density of galaxies as well as the slopes in the faint-end region given by the Subaru Deep Field (SDF) survey are consistent with those given by HST-NICMOS surveys, as expressed on the AB magnitude diagram. Several sources having very large $ J - K^{\prime}$ color have been found, including a few $ K^{\prime}$ objects without detection at $ J$. In addition, a number of faint galactic stars were also detected, most of which are assigned to M-subdwarfs, together with a few brown dwarf candidates.
ASCA Observations of the BL Lacertae Object OJ 287 in 1997 April and November
Authors: Isobe Naoki , Tashiro Makoto , Sugiho Masahiko , Makishima Kazuo
Published: March 2014

The X-ray properties of the BL Lacertae object OJ 287, observed with ASCA on 1997 April 26 and November 17, are reported. The 0.5–10 keV flux was lower than that obtained in previous X-ray observations, and no evidence of intensity variations was found during each observation. The obtained flux densities at 1 keV, 0.22–0.26 $\mu\mathrm{Jy}$, exceed the extrapolations from lower frequency synchrotron continua, which were measured in nearly the same period as the present ASCA observations. The X-ray spectra acquired with the GIS and SIS were consistently described with a single power-law model modified by the Galactic absorption, and the derived photon indices, 1.5–1.6, are flatter than those observed so far. These results strongly suggest that the X-ray spectra observed in 1997 arise via an inverse Compton process alone. The X-ray spectra obtained in 1994 (Idesawa et al. 1997, AAA 68.159.334), exhibiting a steeper slope than those in 1997, is thought to be contaminated by a “synchrotron soft tail.”
Detecting Galactic MACHOs with VERA through Astrometric Microlensing of Distant Radio Sources
Authors: Honma Mareki
Published: March 2014

We consider the properties of astrometric microlensing of distant radio sources (QSOs and radio galaxies) due to MACHOs, and discuss their implications for VERA (VLBI Exploration of Radio Astrometry). First, we show that in the case of astrometric microlensing of distant sources, the event duration is only a function of the lens mass and tangential velocity, but independent of the lens distance, in contrast to the well-known three-fold degeneracy for photometric microlensing. Moreover, the lens mass, $M$, is scaled by the tangential velocity, $v_\perp$, as $M\propto v_\perp$, rather than $M\propto v_\perp^2$, which is the case for photometric microlensing. Thus, in astrometric microlensing the dependence of the lens mass on the unknown parameter, $v_\perp$, is weaker, indicating that the duration of an astrometric microlensing event is a better quantity to study the mass of lensing objects than that of photometric microlensing. We also calculate the optical depth and event rate, and show that within 20${}^{\mathrm{\circ}}$ of the galactic center a typical event rate for a $10~\mu\mathrm{as}$-level shift is larger than $2.5 \times 10^{-4}$ event per year, assuming that a quarter of the halo is made up of MACHOs. This indicates that if one monitors a few hundred sources for $\sim$20 years, such an astrometric microlensing event is detectable. Since a typical event duration has been found to be fairly long (5 to 15 years), the frequency of the monitoring observation can be relatively low, i.e., once per six months, which is rather reasonable for practical observations. We discuss a practical strategy for observing astrometric microlensing with VERA, and argue that an astrometric microlensing event due to MACHOs can be detected by VERA within a few decades.
Snapshot VLBI Observations of SiO v=1 and v=2 (J=1-0) Maser Sources
Authors: Imai Hiroshi , Miyoshi Makoto , Ukita Nobuharu , Morimoto Masaki , Iwata Takahiro , Takaba Hiroshi , Kameno Seiji , Matsumoto Kin-ya , Fujisawa Kenta , Kawaguchi Noriyuki
Published: March 2014

We have made snapshot VLBI observations of SiO masers of the $J= 1$−0 transition at two vibrational levels $v=1$ and $v=2$ using the Kashima–Nobeyama Interferometer (KNIFE). Out of 37 sources observed, we detected both of the lines from 16 sources with a typical detection limit of 10 Jy. Most of the SiO masers were significantly spatially resolved with a KNIFE baseline (200 km), indicating extended/complicated structures of the SiO masers with a typical angular size of a few milliarcseconds. Similar fringe-phase profiles along a radial velocity spanning larger than $1.0~\mathrm{km}~\mathrm{s}^{-1}$ between the two lines indicate a similar spatial structure along the velocity spacings. This tendency, shown from 13 SiO maser sources except Orion KL, supports spatial coincidence of the two lines found previously for M-type stars VY CMa and W Hya. The spatial coincidence should enable us to measure group-delays of the SiO masers for stellar astrometry.
Dust–Gas Accretion onto a Luminous Object
Authors: Fukue Jun
Published: March 2014

Spherical accretion of dust and gas onto a gravitating object is examined under the influence of central radiation. We found that, as long as the central luminosity is less than the Eddington one for dust, the gas flow is almost Bondi type, while the dust flow is greatly affected by central radiation. For non-luminous sources, in the outer region where the gravity on the dust is balanced by the drag force, the infall velocity of dust is generally larger than the gas velocity. Both gas and dust freefall in the inner region. As the dust-to-gas ratio increases, the gas accretion rate slightly decreases, while the dust accretion rate increases. As a result, the total accretion rate increases. When the central luminosity is considered, the infall velocity of dust becomes smaller and smaller, as the central luminosity increases. Although the gas accretion rate slightly increases with luminosity, the dust accretion rate linearly decreases due to the radiation pressure. As a result, the total accretion rate decreases with luminosity. Approximate expressions for dust and gas accretion rates were obtained.
Near-IR Observations of IRAS Sources with SiO Masers at the Inner Galactic Bulge
Authors: Deguchi Shuji , Fujii Takahiro , Matsumoto Shigeru , Nakashima Jun-ichi , Wood Peter R.
Published: March 2014

Near-infrared photometric observations in the J-, H-, and K-bands have been made for 86 IRAS sources toward the inner Galactic bulge ($\vert l\vert \lt 3{{}^{\mathrm{\circ}}}$ and $\vert b\vert \lt 3{{}^{\mathrm{\circ}}}$). SiO maser emission has previously been detected in all of these sources; they are well-confirmed, mass-losing, late-type stars having accurate radial velocities derived from SiO observations. For 78 sources, single, unambiguous near-infrared counterparts were found within the errors of the IRAS positions; for the other 8 sources, multiple candidates, candidates with a low confidence level, or candidates overlapped with other stars were found. From the J-, H-, K-band and IRAS 12 and 25 ${\mu \mathrm {m}}$ intensities, we estimated the spectral energy distributions of the sources, and obtained the distances, assuming a constant luminosity. The derived distances of the IRAS/SiO sources are consistent with the current bar model of the Galactic bulge, where the near side of the bar is located in the first quadrant of the galactic longitude. We also reanalyzed the radial velocity shift with distance, and confirmed the presence of streaming motions of stars in the bar-like bulge.
SiO Maser Survey of Southern IRAS Sources
Authors: Deguchi Shuji , Nakashima Jun-ichi , Balasubramanyam Ramesh
Published: March 2014

We have surveyed 163 southern IRAS sources in the SiO $J=2$-$1 v=1$ maser line at 86 GHz, obtaining 38 (22 new and 16 previously known) detections. These detections include 6 stars not previously detected in OH 1612 MHz surveys, and 4 sources assigned incorrect OH radial velocities. The distance reachable in this survey turned out to be about 4 kpc. The local velocity dispersion near the Sun were found to be approximately $30~\mathrm{km}~\mathrm{s}^{-1}$ for these IRAS/SiO sources. A relatively high concentration of the SiO detected sources were found at the area $320{{}^{\mathrm{\circ}}} \lt l \lt 340{{}^{\mathrm{\circ}}}$ (toward “Norma tangent”). The estimated distances for these sources suggest that this concentration is spread between 2 and 6 kpc from the Sun, peaking on the Scutum–Crux arm.
A Graph-Theoretical Approach for Quantifying Two-Dimensional Galaxy Distributions and Comparison with Cold Dark Matter Universe
Authors: Ueda Haruhiko , Takeuchi Tsutomu T. , Itoh Makoto
Published: March 2014

With the help of a graph-theoretical approach, we have quantified two-dimensional galaxy distributions in observation and Cold Dark Matter (CDM) simulations. In our analysis, we adopted the Lyon–Meudon Extragalactic Database as a typical two-dimensional observation. To estimate adjacency matrices, we constructed constellation graphs from galaxy distributions, and calculated the distribution functions of the eigenvalues of these matrices. Using the mean absolute deviations, we compared the two-dimensional galaxy distributions in observations with CDM simulations in a statistical way. From our analysis we found that the CDM model with a density parameter of less than one is preferable to reproduce the galaxy distributions in the observations.
X-Ray Microlensing of Bright Quasars
Authors: Takahashi Rohta , Yonehara Atsunori , Mineshige Shin
Published: March 2014

We calculated the expected microlens light curves for several accretion-flow models and compared the results to find what aspects of distinct flow structures can be extracted from the microlens light curves. As for the flow models, we considered the standard disk, optically thin advection-dominated flow, and the disk-corona model by Kawaguchi et al., which can nicely reproduce the observed quasar spectra. The calculated microlens light curves of the disk-corona model exhibit rapid soft X-ray and slow hard X-ray variations. This is because the former is generated by Compton up-scattering of soft (optical–UV) photons from the innermost part of the disk body, while the latter is emitted via bremsstrahlung within the corona at relatively large radii. Furthermore, an inhomogeneous emissivity distribution over the disk produces humps in the microlens light curves because of enhanced microlens amplification of the bright areas. It is hoped that black-hole accretion theory coupled with future multi-wavelength microlens observations will be able to reveal such spatial and temporal behaviors of flows in the vicinity of black holes.
JHK Spectra of the z = 2.39 Radio Galaxy 53W002
Authors: Motohara Kentaro , Yamada Toru , Iwamuro Fumihide , Hata Ryuji , Taguchi Tomoyuki , Harashima Takashi , Maihara Toshinori , Iye Masanori , Simpson Chris , Yoshida Michitoshi
Published: March 2014

We present low-resolution, near-IR JHK spectra of the weak $z=2.39$ radio galaxy 53W002, obtained with the OH-airglow Suppressor spectrograph (OHS) and Cooled Infrared Spectrograph and Camera for OHS (CISCO) on the Subaru Telescope. They cover rest-frame wavelengths of 3400–7200$Å$, and the emission lines of [O II]$\lambda$3727, H$\beta$, [O III]$\lambda\lambda$4959, 5007, H$\alpha$, [N II]$\lambda\lambda$6548, 6583 and [S II]$\lambda\lambda$6716, 6731 were detected. Using the H$\alpha$/H$\beta$ line ratio, we find an extinction of $E(B\hbox{--}V)=0.14$. The emission-line ratios are reproduced by a cloud of electron density $n_{\mathrm{e}}=1\times 10^{3-4}\,\mathrm{cm}^{-3}$ with solar metallicity, ionized by an $\alpha=-0.7$ power-law continuum with ionizing parameter $U=1\times 10^{-3}$. In addition to these emission lines, we make the first spectroscopic confirmation of the Balmer discontinuity in a high-$z$ radio galaxy. Together with rest-frame UV photometry from the literature, we show that at least 1/3 of the present stellar mass was formed in the current starburst. The stellar mass was estimated to be $(1\hbox{--}1.4)\times10^{11}\,{{{M}_{\odot}}}$ by one-component model fitting, which is smaller than that of typical $z\sim 1$ B2/6C radio galaxies. We suggest that 53W002 is currently assembling a large part of its stellar mass through merger events with the surrounding sub-galactic clumps, some of which can be identified with the L$\alpha$ emitters detected in narrow-band imaging. After a few such events over the next few Gyr, 53W002 will evolve into a massive elliptical galaxy.
Radiative Collimation of Electron–Positron Jets
Authors: Fukue Jun , Tojyo Masaharu , Hirai Yasuo
Published: March 2014

We propose a novel mechanism for the collimation of relativistic outflows emanated from accretion disks via the disk radiation field, itself. In general, winds driven by disk radiation fields diverge, due to the effect of rotation and the nature of radiation. If, however, the disk is divided into an optically thin hot inner region and an optically thick luminous outer region, the outflow ejected from the inner disk is accelerated and collimated by radiation fields produced by the outer disk. Since this mechanism effectively works on electron–positron pair plasmas, in accretion disk systems with inner hot advection-dominated regions, electron–positron jets easily form on the disk-rotation axis. For pure electron–positron pair plasmas, the terminal speed of collimated jets is about $0.9c$, which is very close to the jet speed of galactic superluminal sources.