bluuebunny/crossref_metadata_2025 huggingface dataset:
A Variable Partial Covering Model for the Seyfert 1 Galaxy MCG −6–30–15
Authors: Miyakawa Takehiro , Ebisawa Ken , Inoue Hajime
Published: March 2014

We propose a simple spectral model for the Seyfert 1 Galaxy MCG $-$ 6–30–15 that can explain most of the 1–40 keV spectral variation by a change of the partial covering fraction, similar to that proposed by Miller, Turner, and Reeves (2008, A&A, 483, 437). Our spectral model is composed of three continuum components: (1) a direct power-law component, (2) a heavily absorbed power-law component by mildly ionized intervening matter, and (3) a cold-disk reflection component far from the black hole with a moderate solid-angle ($ \Omega/$ 2$ \pi$$ \simeq$ 0.3) accompanying a narrow fluorescent iron line. The first two components are affected by the surrounding thin highly ionized absorber with $ N_{\rm H}$$ \simeq$ 10$ ^{23.4}$ cm$ ^{-2}$ and log $ \xi$$ \simeq$ 3.4. The heavy absorber in the second component is fragmented into many clouds, each of which is composed of radial zones with different ionization states and different column densities, a main body ($ N_{\rm H}$$ \simeq$ 10$ ^{24.2}$ cm$ ^{-2}$ , log $ \xi$$ \simeq$ 1.6), an envelope ($ N_{\rm H}$$ \simeq$ 10$ ^{22.1}$ cm$ ^{-2}$ , log $ \xi$$ \simeq$ 1.9), and presumably a completely opaque core. Not only the intrinsic spectral shape of the X-ray source but also these parameters of the ionized absorbers are unchanged at all. The central X-ray source extends moderately, and its luminosity is not significantly variable. The observed flux and spectral variations are mostly explained by the variation of the geometrical partial covering fraction of the central source ranging from 0 (uncovered) to $ \sim\ $ 0.63 by the intervening ionized clouds in the line of sight. The ionized iron K-edge of the heavily absorbed component explains most of the seemingly broad line-like features, a well-known spectral characteristic of MCG $-$ 6–30–15. The direct component and the absorbed one are negatively correlated, and their variations cancel out each other, so that the fractional spectral variation becomes the minimum at the iron-energy band; thus, another observational characteristic of MCG $-$ 6–30–15 is explained.
Pilot VLBI Survey of SiO v = 3 J = 1 → 0 Maser Emission around Evolved Stars
Authors: Imai Hiroshi , Oyadomari Miyako , Chong Sze Ning , Nakagawa Akiharu , Kurayama Tomoharu , Nakashima Jun-ichi , Matsumoto Naoko , Nagayama Takumi , Oyama Tomoaki , Mizuno Shota , Deguchi Shuji , Cho Se-Hyung
Published: March 2014

In this letter, we report on detections of SiO $ v$  $ =$ 3 $ J$  $ =$ 1$ \rightarrow$ 0 maser emission in very long-baseline interferometric (VLBI) observations towards 4 out of 12 long-period variable stars: WX Psc, R Leo, W Hya, and T Cep. The detections towards WX Psc and T Cep are new ones. We also present successful astrometric observations of SiO $ v$  $ =$ 2 and $ v$  $ =$ 3 $ J$  $ =$ 1$ \rightarrow$ 0 maser emissions associated with two stars: WX Psc and W Hya and their position-reference continuum sources: J010746.0$ +$ 131205 and J135146.8$-$ 291218 with the VLBI Exploration of Radio Astrometry (VERA). The relative coordinates of the position-reference continuum source and SiO $ v$  $ =$ 3 maser spots were measured with respect to those of an SiO $ v$  $ =$ 2 maser spot adopted as a fringe-phase reference. Thus, the faint continuum sources were inversely phase-referenced to the bright maser sources. This implies possible registration of multiple SiO maser line maps onto a common coordinate system with 10 microarcsecond-level accuracy.
Distribution of Si, Fe, and Ni in the Intracluster Medium of the Coma Cluster
Authors: Matsushita Kyoko , Sato Takuya , Sakuma Eri , Sato Kosuke
Published: March 2014

We studied the distributions of Si, Fe, and Ni in the intracluster medium (ICM) of the Coma cluster, one of the largest clusters in the nearby universe, using XMM-Newton data up to 0.5 $ r_{180}$ and Suzaku data of the central region up to 0.16 $ r_{180}$. Using the flux ratios of the Ly$ \alpha$ line of H-like Si and the 7.8 keV line blend to the K$ \alpha$ line of He-like Fe, the abundance ratios of Si to Fe and Ni to Fe of the ICM were derived using APEC model v2.0.1. The Si$ /$ Fe ratio in the ICM of the Coma cluster shows no radial gradient. The emission-weighted averages of the Si$ /$ Fe ratio in the ICM within 0.0–0.2 $ r_{180}$, 0.2–0.5 $ r_{180}$, and 0.0–0.5 $ r_{180}$ are 0.97 $ \pm$ 0.11, 1.05 $ \pm$ 0.36, and 0.99 $ \pm$ 0.13, respectively, in solar units using the solar abundance table by Lodders (2003, ApJ, 591, 1220). These values are close to those of smaller clusters and groups of galaxies. Using the Suzaku data of the central region, the derived Ni$ /$ Fe ratio of the ICM is 0.6–1.5 in solar units, according to the same solar abundance table. The systematic difference in the derived abundance ratios by different plasma codes are about 10%. Therefore, for the ICM in the Coma cluster, the abundance pattern of Si, Fe, and Ni is consistent with the same mixture of the yields of supernova (SN) II and SN Ia in our Galaxy. Within 0.5 $ r_{180}$ , the cumulative iron mass-to-light ratio increases with radius, and its radial profile is similar to those of relaxed smaller clusters with cD galaxies at their center. Using the observed Si$ /$ Fe ratio, the cumulative metal mass-to-light ratios at 0.5 $ r_{180}$ are compared with theoretical expectations.
A Study of the Long-Term Spectral Variations of 3C 66A Observed with the Fermi and Kanata Telescopes
Authors: Itoh Ryosuke , Fukazawa Yasushi , Chiang James , Hanabata Yoshitaka , Hayashida Masaaki , Hayashi Katsuhiro , Mizuno Tsunefumi , Ohno Masanori , Ohsugi Takashi , Perkins Jeremy S. , Rainò Silvia , Reyes Luis C. , Takahashi Hiromitsu , Tanaka Yasuyuki , Tosti Gino , Akitaya Hiroshiv , Arai Akira , Kino Masaru , Ikejiri Yuki , Kawabata Koji S. , Komatsu Tomoyuki , Sakimoto Kiyoshi , Sasada Mahito , Sato Shuji , Uemura Makoto , Ui Takahiro , Yamanaka Masayuki , Yoshida Michitoshi
Published: March 2014

3C 66A is an intermediate-frequency-peaked BL Lac object detected by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. We present a study of the long-term variations of this blazar seen over ∼ 2 yr at GeV energies with Fermi and in the optical (flux and polarization) and near infrared with the Kanata telescope. In 2008, the first year of the study, we find a correlation between the gamma-ray flux and the measurements taken with the Kanata telescope. This is in contrast to the later measurements performed during 2009–2010 which show only a weak correlation along with a gradual increase of the optical flux. We calculate an external seed photon energy density assuming that the gamma-ray emission is due to external Compton scattering. The energy density of the external photons is found to be higher by a factor of two in 2008 compared to 2009–2010. We conclude that the different behaviors observed between the first year and the later years might be explained by postulating two different emission components.
Identifying Subclasses of Long Gamma-Ray Bursts with Cumulative Light-Curve Morphology of Prompt Emissions
Authors: Tsutsui Ryo , Nakamura Takashi , Yonetoku Daisuke , Takahashi Keitaro , Morihara Yoshiyuki
Published: March 2014

We argue for a new classification scheme of long gamma-ray bursts (LGRBs) using the morphology of the cumulative light curve of prompt emission. We parametrize the morphology by an absolute deviation from their constant luminosity (ADCL), and derive the value for 36 LGRBs that have spectropic redshifts, spectral parameters determined by the Band model, 1-s peak fluxes, fluences, and 64-ms resolution light curves whose peak counts are 10-times larger than background fluctuations. Based on a possible bimodal distribution of the value of ADCL, we divide the sample into two groups (ADCL  $ <$ 0.17 and ADCL  $ >$ 0.17), and for each group derive the spectral peak energy $ E_{\rm p}$ –peak luminosity $ L_{\rm p}$ correlation and the Fundamental Plane of LGRBs, which is a correlation between $ E_{\rm p}$ , the luminosity time $ T_{\rm L}$ ($ \equiv$  $ E_{\rm iso}/L_{\rm p}$ where $ E_{\rm iso}$ is isotropic energy), and $ L_{\rm p}$ . We find that the Fundamental Plane at $ E_{\rm p}$  $ =$ 10$ ^{2.71}$ keV and $ T_{\rm L}$  $ =$ 10$ ^{0.86}$ s for large ADCL events are 2.8-times brighter than that for small ADCL events with 5-$ \sigma$ levels. The Fundamental Planes with small and large ADCL are given by $ L_{\rm p}$  $ =$ 10$ ^{52.53\pm 0.01}$ ($ E_{\rm p}/$ 10$ ^{2.71}$ keV)$ ^{1.84\pm 0.03}$ ($ T_{\rm L}/$ 10$ ^{0.86}$ s)$ ^{0.29\pm0.08}$ with $ \chi^2_{\nu}$  $ =$ 10.93$ /$ 14 and $ L_{\rm p}$  $ =$ 10$ ^{52.98\pm0.08}$ ($ E_{\rm p}/$ 10$ ^{2.71}$ keV)$ ^{1.82\pm 0.09}$ ($ T_{\rm L}/$ 10$ ^{0.86}$ s)$ ^{0.85\pm 0.27}$ with $ \chi^2_{\nu}$  $ =$ 7.58$ /$ 8, respectively. This fact implies the existence of subclasses of LGRBs characterized by the value of ADCL. The other significant difference between the relations for the two subclasses consists in the exponent of $ T_{\rm L}$ , which might provide a hint of the physics of the relations, but the significance is now only at 2-$ \sigma$ levels. Also, there is a hint for the existence of an intermediate-ADCL class, which deviates from both fundamental planes. Both relations are so tight that our result provides a new accurate distance measurement scheme up to the high-redshift universe.
Spatially Resolved Near-Infrared Imaging of a Gravitationally Lensed Quasar, APM 08279+5255, with Adaptive Optics on the Subaru Telescope
Authors: Oya Shin , Minowa Yosuke , Terada Hiroshi , Watanabe Makoto , Hattori Masayuki , Hayano Yutaka , Saito Yoshihiko , Ito Meguru , Pyo Tae-Soo , Takami Hideki , Iye Masanori
Published: March 2014

We present a spatially resolved imaging analysis of a three-component gravitationally lensed quasar at $ z$  $ =$ 3.91, APM 08279$ +$ 5255, in the $ L'$- and $ M'$-bands, and a narrow band centered at 3.05 $ \mu$ m using the 188-element adaptive optics system on the Subaru Telescope. The third, faintest quasar image, component C, has been clearly resolved in all of these bands for the first time. All of the three components are point sources in all three bands. No new component, neither a fourth quasar image nor a lens galaxy, was discovered. The observed bands correspond to the long-wavelength end of the optical power-law continuum of the source quasar in its rest frame, and are little contaminated by strong emission lines like H$ \alpha$ . The measured flux ratio of components C to B is shown to be constant in all of the observed bands, and its achromatic nature agrees well with preceding work done at short near-infrared wavelengths one decade ago. On the other hand, the flux ratio of components A to B shows an increase from that of past measurements. This could be ascribed to a microlensing event.
Beaming Effect in Fermi Blazars
Authors: Fan Junhui , Yang Jiang He , Zhang Jing-Yi , Hua Tong Xu , Liu Yi , Qin Yi-Ping , Huang Yong
Published: March 2014

$\gamma$ -ray loud blazars (flat spectrum radio quasars—FSRQs and BL Lacertae objects—BLs) are very bright in the $\gamma$-ray bands, which is perhaps associated with a beaming effect. Therefore, one can expect that the $\gamma$-ray luminosity is correlated with the beaming factor. In this paper, we consider the relation between the radio Doppler factors and the $\gamma$-ray luminosities. Our analysis suggests that the $\gamma$-ray luminosity be strongly correlated with the factor of $\delta_R$ for the whole sample, FSRQs, and BLs. When the effect of a common redshift is excluded, the correlation still exists for the FSRQs sub-sample, suggesting that the $\gamma$-rays are strongly beamed. However, a partial correlation analysis does not show any correlation for the small BL Lac sample.
Simplified Picture of Low-Mass X-Ray Binaries Based on Data from Aquila X-1 and 4U 1608–52
Authors: Matsuoka Masaru , Asai Kazumi
Published: March 2014

We propose a simplified picture of low-mass X-ray binaries containing a neutron star (NS-LMXBs) based on data obtained from Aql X-1 and 4U 1608$-$ 52, which often produce outbursts. In this picture we propose at least three states and three state transitions: i.e., the states: (1) soft state, (2) hard-high state, and (3) hard-low state, and the state transitions: (i) hard-high state to soft state, (ii) soft state to hard-high state, and (iii) hard-high state to hard-low state or vice versa. Gases from the accretion disc of an NS-LMXB penetrate almost the entire magnetic field and accrete onto the neutron star in cases (1) and (2), whereas in case (3) some gases accrete around the magnetic poles in a manner resembling the behavior of an X-ray pulsar, and considerable gas is dispersed or ejected by the propeller effect. Transition (iii) occurs when the Alfvén radius is equal to the co-rotation radius. Therefore, in this case it is possible to estimate the strength of the neutron star's magnetic field by detecting transition (iii). We also discuss the no-accretion X-ray state or the recycled pulsar state, in which the Alfvén radius is larger than the light cylinder radius.
IRSF SIRIUS JHKs Simultaneous Transit Photometry of GJ 1214b
Authors: Narita Norio , Nagayama Takahiro , Suenaga Takuya , Fukui Akihiko , Ikoma Masahiro , Nakajima Yasushi , Nishiyama Shogo , Tamura Motohide
Published: March 2014

We report on the high-precision transit photometry of GJ 1214b in JHK$ _{\rm s}$ bands simultaneously taken with the SIRIUS camera on the Infrared Survey Facility 1.4 m telescope located in Sutherland, South Africa. Our Markov-Chain Monte Carlo analysis shows that observed planet-to-star radius ratios in the JHK$ _{\rm s}$ bands are $ R_{\rm p}/R_{{\rm s},J}$$ =$ 0.11833 $ \pm$ 0.00077, $ R_{\rm p}/R_{{\rm s},H}$$ =$ 0.11522 $ \pm$ 0.00079, and $ R_{\rm p}/R_{{\rm s},K_{\rm s}}$$ =$ 0.11459 $ \pm$ 0.00099, respectively. The radius ratios are very consistent with previous studies by Bean et al. (2011, ApJ, 743, 92) within 1 $ \sigma$ , while our ratio in the K$ _{\rm s}$ band is shallower than previous measurements in the same band by Croll et al. (2011, ApJ, 736, 78) and inconsistent even at the 4 $ \sigma$ level with them. We have no satisfactory explanation for this discrepancy at this point. Our overall results support a flat transmission spectrum in the observed bands, which can be explained by a water-dominated atmosphere or an atmosphere with extensive high-altitude clouds or haze. To explain the discrepancy of the radius ratios, and to determine a definitive atmosphere model for GJ 1214b in the future, more extended transit observations in around the K$ _{\rm s}$ band would be especially important.
Annual Parallax Distance and Secular Motion of the Water Fountain Source IRAS 18286–0959
Authors: Imai Hiroshi , Kurayama Tomoharu , Honma Mareki , Miyaji Takeshi
Published: March 2014

We report on results of astrometric observations of H$ _{2}$ O masers in the ``water fountain'' source IRAS 18286$-$ 0959 (I18286) with the VLBI Exploration of Radio Astrometry (VERA). These observations yielded an annual parallax of IRAS 18286$-$ 0959, $ \pi$  $ =$ 0.277 $ \pm$ 0.041 mas, corresponding to a heliocentric distance of $ D$  $ =$ 3.61$ ^{+0.63}_{-0.47}$ kpc. The maser feature, whose annual parallax was measured, showed an absolute proper motion of ($ \mu_{\alpha}$ , $ \mu_{\delta}$ ) $ =$ ($-$ 3.2 $ \pm$ 0.3, $-$ 7.2 $ \pm$ 0.2) [mas yr$ ^{-1}$ ]. The intrinsic motion of the maser feature in the internal motions of the cluster of features in I18286 does not seem to trace the motion of the bipolar jet of I18286. Taking into account this intrinsic motion, the derived motion of the maser feature is roughly equal to that of the maser source I18286 itself. The proximity of I18286 to the Galactic midplane ($ z$  $ \approx$ 10 pc) suggests that the parental star of the water fountain source in I18286 should be an intermediate-mass AGB/post-AGB star, but the origin of a large deviation of the systemic source motion from that expected from the Galactic rotation curve is still unclear.
Photopolarimetric Monitoring of the Blazar BL Lac in the Optical and Near-Infrared Bands: Decay of the Long-Lived Component
Authors: Sakimoto Kiyoshi , Uemura Makoto , Sasada Mahito , Kawabata Koji S. , Fukazawa Yasushi , Yamanaka Masayuki , Itoh Ryosuke , Ohsugi Takashi , Yoshida Michitoshi , Akitaya Hiroshi , Sato Shuji , Kino Masaru
Published: March 2014

We report on the results of optical–near-infrared photopolarimetric observations of BL Lac conducted from 2008 to 2011. Our observations are consistent with past studies in which the behavior of the polarization of BL Lac could be understood with two components: short flares whose polarization angles randomly change, and a long-lived component. In addition, we detected a gradually decreasing trend in the total flux, the polarized flux, and the polarization degree without a large variation in the polarization angle from 2008 to mid-2009. These results suggest that the long-lived component decayed from 2008 to mid-2009. We propose that the long-lived component is not stationary, but is probably variable with a time-scale of years. We found no change in the activity of the short flares in 2008 and 2009, when the long-lived component was strong and weak, respectively. Furthermore, there were no clear differences in the mean color and the distribution of the polarization angle of the short flares from 2008 to 2009. These facts indicate that the emitting region of the long-term component was physically disconnected to that of the short flares. The color of the long-term component was bluer than that of the short flares, indicating a higher synchrotron peak-frequency. This could be due to a low efficiency of synchrotron and/or Compton cooling in the emitting region of the long-lived component. The long-term component is possibly originated from a relatively downstream region in the jet where the electron density is low, or the external radiation field is weak.
Modeling Line-Driven Disk Wind for Broad Absorption Lines of Quasars
Authors: Nomura Mariko , Ohsuga Ken , Wada Keiichi , Susa Hajime , Misawa Toru
Published: March 2014

The disk wind, which is powered by the radiation force due to spectral lines (line force), has been studied concerning broad absorption line (BAL) quasars. We investigated the structure of the disk wind based on a non-hydrodynamic method, and compared it with wind properties inferred from X-ray observations of BAL quasars. In the present work, we applied the stellar wind theory to the initial condition (the mass outflow rate at the base of the wind). We found funnel-shaped winds with a half opening angle of $ \sim$ 50$ ^{\circ}$ for the case of $ \epsilon$$ =$ 0.3–0.9 and $ M_{\rm BH}$$ =$ 10$ ^{7-8.5}$$ M_\odot$ , where $ \epsilon$ is the Eddington ratio and $ M_{\rm BH}$ is the black-hole mass. Thus, the absorption features are observed for an observer of which the viewing angle is around 50$ ^{\circ}$ . A probability of BAL quasars is $ \sim$ 7%–11%, which is roughly consistent the abundance ratio of BAL quasars, $ \sim$ 10%–15%. Here, the probability is estimated by the solid angle, that the absorbing features would be detected, divided by 4$ \pi$ . In contrast, if the Eddington ratio is smaller than 0.01, or if the black hole is very massive, $ M_{\rm BH}$$ \gtrsim$ 10$ ^{9}$$ M_{\odot}$ , the disk wind is not launched due to the less effective line force. Then, the quasars are identified as non-BAL quasars independently of the observer's viewing angle.
Two Power-Law States of the Ultraluminous X-Ray Source IC 342 X-1
Authors: yoshida Tessei , isobe Naoki , mineshige Shin , kubota Aya , mizuno Tsunefumi , saitou Kei
Published: March 2014

In order to elucidate the emission properties of ultraluminous X-ray sources (ULXs) during their power-law (PL) state, we examined long-term X-ray spectral data of IC 342 X-1 during its PL state by using our own Suzaku data and archival data by XMM-Newton, Chandra, and Swift observations. The PL state of this source seems to be classified into two sub-states in terms of the X-ray luminosities in the 0.5–10 keV band: the low-luminosity PL state with (4–6) $ \times$ 10$ ^{39}$ erg s$ ^{-1}$ and the high-luminosity one with (1.1–1.4) $ \times$ 10$ ^{40}$ erg s$ ^{-1}$ . During Suzaku observations, which were made in 2010 August and 2011 March, X-1 stayed in the low-luminosity PL state. The observed X-ray luminosity (4.9–5.6 $ \times$ 10$ ^{39}$ erg s$ ^{-1}$ ) and the spectral shape (photon index $ =$ 1.67–1.83) slightly changed between the two observations. Using the Suzaku PIN detector, we for the first time confirmed a PL tail extending up to at least 20 keV with no signatures of a high-energy turnover in both of the Suzaku observations. In contrast, a turnover at about 6 keV was observed during the high-luminosity PL state in 2004 and 2005 with XMM-Newton. Importantly, the photon indices are similar between the two PL states, and so are the Compton $ y$-parameters of $ y$$ \sim$ 1, which indicates a similar energy balance (between the corona and the accretion disk) holding in the two PL states despite different electron temperatures. From spectral similarities with recent studies about other ULXs, and the Galactic black-hole binary GRS 1915$ +$ 105, IC 342 X-1 is also likely to be in a state with a supercritical accretion rate, although more sensitive higher energy observations would be necessary to make any conclusion.
Suzaku Follow-Up Observation of the Activated Magnetar 1E 1547.0 5408
Authors: Iwahashi Takanori , Enoto Teruaki , Yamada Shin'ya , Nishioka Hiroyuki , Nakazawa Kazuhiro , Tamagawa Toru , Makishima Kazuo
Published: March 2014

We present broadband X-ray analyses of the magnetar 1E 1547.0$-$ 5408 observed with Suzaku on 2010 August 7, nearly one and a half years after an intense outburst in 2009 January. The 2–10 keV flux decreased to (1.06 $ \pm$ 0.01) $ \times$ 10$ ^{-11}$ erg cm$ ^{-2}$ s$ ^{-1}$ , while the hard X-ray detection was 3.5 $ \sigma$ (18–40 keV) and 2.4 $ \sigma$ (18–35 keV) significance levels, where the former includes only the 2% systematic error of the non X-ray background, and the latter further takes into account possible near-by contaminating sources, respectively. Our confirmation of both soft and hard X-ray components during the late phase of the outburst strengthened the possibility that most magnetars are composed of the two spectral components, both in burst-active and less-active states. Together with a similar decay speed between the soft and hard components, their radiation mechanisms are suggested to be tightly related to each other. The 1–40 keV broadband spectrum was successfully fitted with the same model as used in the fit just after the onset of the outburst in 2009: a surface blackbody radiation with photoelectric absorption and a hard power-law. The blackbody flux decreased to be $ \sim$ 30% of that in 2009 while keeping its temperature at $ kT$$ =$ 0.65 keV, suggesting a shrinking hotspot on the magnetar surface by a factor of 0.3. The hard power-law extended up to at least $ \sim$ 35 keV with a photon index of $ \Gamma$$ =$ 1.1 $ \pm$ 0.4, which was consistent with the 2009 value. The flux ratio, $ \xi$ , of the 1–60 keV power-law to 1–60 keV thermal component was calculated to be $ \xi$$ =$ 1.2 $ \pm$ 0.7 at the late phase of the outburst for the first time. The obtained $ \xi$ value follows the previously known negative correlation with the characteristic age, implying that the correlation holds for most of the magnetar states: no burst, onset and late phase of outbursts.
A Method to Estimate the Masses of Asymptotic Giant Branch Variable Stars
Authors: Takeuti Mine , Nakagawa Akiharu , Kurayama Tomoharu , Honma Mareki
Published: March 2014

AGB variable stars are at the transient phase between low and high mass-loss rates; estimating the masses of these stars is necessary to study the evolutionary processes and mass-loss processes during the AGB stage. We applied the pulsation constant theoretically derived by Xiong and Deng (2007 MNRAS, 378, 1270) to 15 galactic AGB stars in order to estimate their masses. We found that using the pulsation constant is effective to estimate the mass of a star pulsating with two different pulsation modes, such as S Crt and RX Boo, which provides mass estimates comparable to theoretical results of AGB star evolution. We also extended the use of the pulsation constant to single-mode variables, and analyzed the properties of AGB stars related to their masses.
κH-Mechanism of a Solar Eruption Produced Self-Consistently by Flux Emergence
Authors: Magara Tetsuya
Published: March 2014

We report on a new magnetohydrodynamic simulation for the sequence evolution of a magnetic field from emergence to eruption on the Sun. The magnetic field in the shape of a twisted flux tube emerging below the solar surface forms a pre-eruptive structure in the corona, which is composed of expanding envelop flux and a quasi-static inner core called flux rope; this inner core eventually seems to erupt. The evolution proceeds self-consistently; that is, any preexisting coronal magnetic field that causes additional side effects on the evolution of the emerging magnetic field is not assumed. This highlights a possible eruption mechanism inherent in the dynamic nature of the emerging magnetic field. The mechanism is characterized by two key quantities: the curvature ($ \kappa$ ) and the scale height ($ H$ ) of the emerging magnetic field.
Kinetic Scheme for Solving the M1 Model of Radiative Transfer
Authors: Kanno Yuji , Harada Tetsuya , Hanawa Tomoyuki
Published: March 2014

We show a numerical scheme to solve the moment equations of radiative transfer, i.e., the M1 model, which follows the evolution of the energy density, $E$, and the energy flux, $\boldsymbol{F}$. In our scheme we reconstruct the intensity from $E$ and $\boldsymbol{F}$, so that it is consistent with the closure relation, $\chi = \left(3+4f^2\right)/\big({\rm 5}+{\rm 2}\sqrt{4-3 f^2}\big)$. Here, the symbols $\chi, f = \vert\boldsymbol{F}\vert/$ ($cE$), and $c$, denote the Eddington factor, the reduced flux, and the speed of light, respectively. We evaluate the numerical flux across the cell surface from the kinetically reconstructed intensity. It is an explicit function of $E$ and $\boldsymbol{F}$ in the neighboring cells across the surface considered. We include absorption and reemission within a numerical cell in evaluating the numerical flux. The numerical flux approaches the diffusion approximation when the numerical cell, itself, is optically thick. Our numerical flux gives a stable solution even when some regions computed are very optically thick. We show the advantages of the numerical flux with examples. They include a flash of beamed photons and irradiated protoplanetary disks.
Spectral Variation of Hard X-Ray Emission from the Crab Nebula with the Suzaku Hard X-Ray Detector
Authors: Kouzu Tomomi , S. Tashiro Makoto , Terada Yukikatsu , Yamada Shin’ya , Bamba Aya , Enoto Teruaki , Mori Koji , Fukazawa Yasushi , Makishima Kazuo
Published: March 2014

The Crab Nebula is one of the brightest and most stable sources in the X-ray sky. Year-scale flux variation from the object was recently revealed in the hard X-ray band by four satellites. This marked the first detection of year-scale variability from pulsar wind nebulae in the hard X-ray band. The Crab Nebula has been observed at least once a year for calibration purposes with the Suzaku Hard X-ray Detector (HXD) since its launch in 2005. In order to investigate possible spectral changes as well as flux variation, archival data of the HXD were analyzed. The flux variation reported by other instruments was confirmed in the 25–100 keV band by the HXD at a few percent level, but flux above 100 keV did not follow the trend in variation below 100 keV. The hardness ratios produced utilizing the PIN and GSO sensors installed in the HXD exhibit significant scattering, thereby indicating spectral variations in the hard X-ray band. The spectral changes were quantified by spectral fitting with a broken power-law model. The difference between the two photon indexes of the broken power-law model in harder and softer energy bands is in the range of $<$ 2.54. Taking into account a flux variation of 6.3% and a spectral variation time-scale of a few days, multi components of the broken power-law-shaped synchrotron emission with different cooling times are suggested.
Analysis of a Kepler Light Curve of the Novalike Cataclysmic Variable KIC 8751494
Authors: Kato Taichi , Hiroyuki Maehara
Published: March 2014

We analyzed a Kepler light curve of KIC 8751494, a recently recognized novalike cataclysmic variable in the Kepler field. We detected a stable periodicity of 0.114379(1) d, which we identified as being the binary’s orbital period. The stronger photometric period at around 0.12245 d, which had been detected from a ground-based observation, was found to be variable, and we identified this period as the positive-superhump period. This superhump period showed short-term (10–20 d) strong variations in period most unexpectedly when the object entered a slightly faint state. The fractional superhump excess varied by as much large as $\sim$ 30%. The variation of the period very well traced the variation of the brightness of the system. The time-scale of this variation of superhump periods was too slow to be interpreted as a variation caused by a change of the disk radius due to thermal disk instability. We interpreted the cause of the period variation as a varying pressure effect on the period of positive superhumps. This finding suggests that the pressure effect, in at least novalike systems, plays a very important (up to $\sim$ 30% in the precession rate) role in producing the period of positive superhumps. We also described a possible detection of negative superhumps with a varying period of 0.1071–0.1081 d in the Q14 run of the Kepler data, and found that the variation of frequency of negative superhumps followed that of positive superhumps. The relation between the fractional superhump excesses of negative and positive superhumps can be understood if the angular frequency of positive superhumps is decreased by a pressure effect. We also found that the phase of the variation in the velocity of the emission lines reported in the earlier study is compatible with the SW Sex-type classification. Further, we introduced a new two-dimentional period analysis using least absolute shrinkage and selection operator (Lasso), and showed superior advantages of this method.
Internal Motion of 6.7-GHz Methanol Masers in H ii Region S269
Authors: Sawada-Satoh Satoko , Fujisawa Kenta , Sugiyama Koichiro , Wajima Kiyoaki , Honma Mareki
Published: March 2014

We present the first internal motion measurement of the 6.7-GHz methanol maser within S269, a small H ii region in the outer Galaxy, which was carried out in 2006 and 2011 using the Japanese VLBI Network (JVN). Several maser groups and weak isolated spots were detected in an area spanning $\sim$ 200 mas (1000 AU). Three remarkable maser groups are aligned at a position angle of 80$^{\circ}$. Two of three maser groups were also detected by a previous observation in 1998, which allowed us to study a long-term position variation of maser spots from 1998 to 2011. The angular separation between the two groups increased by $\sim$ 10 mas, which corresponds to an expansion velocity of $\sim$ 10 km s$^{-1}$. Some velocity gradient ($\sim 10^{-2}$ km s$^{-1}$ mas$^{-1}$) in the overall distribution was found. The internal motion between the maser groups support the hypothesis that the methanol masers in S269 could trace a bipolar outflow.
Clumpy Outflows from Supercritical Accretion Flow
Authors: Takeuchi Shun , Ohsuga Ken , Mineshige Shin
Published: March 2014

A significant amount of matter in supercritical (or super-Eddington) accretion flow is blown away by radiation force, thus forming outflows; however, the properties of such radiation-driven outflows have been poorly understood. We have performed global two-dimensional radiaion-magnetohydrodynamic simulations of supercritical accretion flow onto a black hole with 10 or 10$^{8} M_{\odot}$ in a large simulation box of 514 $r_{\rm S} \times 514 r_{\rm S}$ (with $r_{\rm S}$ being the Schwarzschild radius). We confirm that uncollimated outflows with velocities of 10 percent of the speed of light emerge from the innermost part of the accretion flow at a wide angle of 10$^{\circ}$ –50$^{\circ}$ from the disk rotation axis. Importantly, the outflows exhibit clumpy structures above heights of $\sim 250 r_{\rm S}$. The typical size of the clumps is $\sim 10 r_{\rm S}$, which corresponds to one optical depth, and their shapes are slightly elongated along the outflow direction. Since clumps start to form in the layer above which the (upward) radiation is superior in force to the (downward) gravity, the Rayleigh–Taylor instability seems to be a primary cause. In addition, a radiation-hydrodynamic instability, which arises when radiation funnels through a radiation-pressure-supported atmosphere, may also help to form clumps of one optical depth. A magnetic photon bubble instability does not seem to be essential, since a similar clumpy outflow structure is obtained in nonmagnetic radiation-hydrodynamic simulations. Since the spatial covering factor of the clumps is estimated to be $\sim$ 0.3, and since they are marginally optically thick, they will explain at least some of the rapid light variations of active galactic nuclei. We further discuss a possibility of producing broad-line region clouds by the clumpy outflow.
A New Cluster of Galaxies Towards the Galactic Bulge, Suzaku J1759–3450
Authors: Mori Hideyuki , Maeda Yoshitomo , Furuzawa Akihiro , Haba Yoshito , Ueda Yoshihiro
Published: March 2014

We observed an extended X-ray source, designated as Suzaku J1759–3450, with Suzaku and Chandra observations towards 1RXS J175911.0–344921, which is an unidentified X-ray source listed in the ROSAT Bright Source Catalogue. A conspicuous emission line at 6 keV was also found in the Suzaku J1759–3450 spectrum. Assuming the emission line to be K emission from He-like Fe ions, we inferred Suzaku J1759–3450 to be an extragalactic object located at z = 0.13. The radial profile of the surface brightness in the 0.5–10 keV band was explained well with an isothermal β-model of $r_\textrm c=1{.^\prime}61$ and $\beta=0.78$. The X-ray spectrum was well reproduced by an opticallythin thermal plasma with the electron temperature of $kT_e = 5.3$ keV, attenuated by the photoelectric absorption of $N_\textrm H = 2.3 \times 10^{21} \textrm c\textrm m^{-2}$. The bolometric X-ray luminosity of $L_\textrm X(r < r_{500}) = 4.3 \times 10^{44} \textrm {erg} \textrm s^{-1}$ is consistent with that expected from the L  X–T relation of clusters of galaxies. In terms of the spatial extent, the X-ray spectrum, and the bolometric luminosity of the X-ray emitting gas, we concluded that Suzaku J1759–3450 is a new cluster of galaxies.
Toward Understanding the Anisotropic Point Spread Function of Suprime-Cam and Its Impact on Cosmic Shear Measurement
Authors: Hamana Takashi , Miyazaki Satoshi , Okura Yuki , Okamura Tomohiro , Futamase Toshifumi
Published: March 2014

We examined the anisotropic point spread function (PSF) of Suprime-Cam data utilizing dense star field data. We decomposed the PSF ellipticities into three components—the optical aberration, atmospheric turbulence, and chip misalignment in an empirical manner—and evaluated the amplitude of each component. We then tested a standard method for correcting the PSF ellipticities used in weak lensing analysis against a mock simulation. We found that, for long-exposure data, the optical aberration has the largest contribution to the PSF ellipticities, which could be modeled well by a simple analytic function based on the lowest-order aberration theory. The statistical properties of PSF ellipticities resulting from atmospheric turbulence were investigated by using numerical simulations. The simulation results are in a reasonable agreement with the observed data. It follows from these findings that the spatial variation of PSF ellipticities consists of two components: one is a smooth and parametrizable component arising from the optical PSF, and the other is a non-smooth and stochastic component resulting from the atmospheric PSF. The former can be well corrected by the standard correction method with a polynomial fitting function. However, for the latter, its correction is affected by the common limitation caused by sparse sampling of PSFs due to a limited number of stars. We also examined the effects of the residual PSF anisotropies on Suprime-Cam cosmic shear data (5.6-degree2 of i′-band data). We found that the shape and amplitude of the B-mode shear variance are broadly consistent with those of the residual PSF ellipticities measured from the dense star field data. This indicates that most of the sources of residual systematic are understood, which is an important step for cosmic shear statistics to be a practical tool of the precision cosmology.
An Innovative Image Reconstruction Method for High-Precision Astrometry
Authors: Sun Rong-Yu , Zhao Chang-Yin , Zhang Yi-Ping
Published: March 2014

An automatic image-reconstruction method is presented, based on the use of a mathematical morphology operator. Variable structural elements along multiple directions are adopted for image convolution, and then all of the corresponding convolved images are stacked to obtain a final result. To investigate its efficiency, both simulated images and raw CCD images, produced by a trial observation using a 45-cm telescope, are tested. With this method, the influence of degradation in astrometric CCD images is reduced, and the position accuracy of background stars is distinctly improved. This method will contribute significantly to optical data reduction and high-order precision astrometry.
Metals in the Intracluster Medium of MS 1512.4+3647 Observed with Suzaku: Implications for the Metal Enrichment History
Authors: Shimoda Yuya , Kawaharada Madoka , Sato Kosuke , Ohashi Takaya , Ishisaki Yoshitaka , Mitsuishi Ikuyuki , Akamatsu Hiroki , Tashiro Makoto S.
Published: March 2014

The cluster of galaxies MS 1512.4+3647 (z = 0.372) was observed with Suzaku for 270 ks. Besides the Fe abundance, the abundances of Mg, Si, S, and Ni were separately determined for the first time in a medium redshift cluster (z > 0.3). The derived abundance pattern of MS 1512.4+3647 is consistent with those of nearby clusters, suggesting that the system has similar contributions from supernovae (SNe) Ia and SNe II to nearby clusters. The number ratio of SNe II to SNe Ia is ∼3. The estimated total numbers of both SNe II and SNe Ia against the gas mass indicate similar correlations with those for the nearby clusters. The abundance results of MS 1512.4+3647 is consistent with the standard scenario that the SN II rate history roughly follows the star-formation history, which has a peak at 1 < z < 2, and then declines by about one order of magnitude toward z ∼ 0. The similar number of SNe Ia to the nearby clusters suggests that the SN Ia rate declines steeply from z = 0.37 to z = 0, and/or SN Ia explosions occurred predominantly at larger redshifts.
Saturation of StellarWinds from Young Suns
Authors: Suzuki Takeru K. , Imada Shinsuke , Kataoka Ryuho , Kato Yoshiaki , Matsumoto Takuma , Miyahara Hiroko , Tsuneta Saku
Published: March 2014

We investigated mass losses via stellar winds from Sun-like main-sequence stars with a wide range of activity levels. We performed forward-type magnetohydrodynamical numerical experiments for Alfvén wave-driven stellar winds with a wide range of input Poynting flux from the photosphere. Increasing the magnetic field strength and the turbulent velocity at the stellar photosphere from the current solar level, the mass-loss rate rapidly at first increases, owing to suppression of the reflection of the Alfvén waves. The surface materials are lifted up by the magnetic pressure associated with the Alfvén waves, and the cool dense chromosphere is intermittently extended to 10%–20% of the stellar radius. The dense atmospheres enhance the radiative losses, and eventually most of the input Poynting energy from the stellar surface escapes by radiation. As a result, there is no more sufficient energy remaining for the kinetic energy of the wind; the stellar wind saturates in very active stars, as observed in Wood et al. (2002, ApJ, 574, 412; 2005, ApJ, 628, L143). The saturation level is positively correlated with Br,0f0, where Br,0 and f0 are the magnetic field strength and the filling factor of open flux tubes at the photosphere. If Br,0f0 is relatively large ≳5G, the mass-loss rate could be as high as 1000 times. If such a strong mass loss lasts for ∼1 billion years, the stellar mass itself would be affected, which could be a solution to the faint young Sun paradox. We derived a Reimerstype scaling relation that estimates the mass-loss rate from an energetics consideration of our simulations. Finally, we derived the evolution of the mass-loss rates, Ṁ∝t-1.23, of our simulations, combining with an observed time evolution of X-ray flux from Sun-like stars, which are shallower than Ṁ∝t-2.33±0.55 in Wood et al. (2005).
Observations and Orbital Analysis of the High-Amplitude Delta Scuti Star SZ Lyncis: The Unusual Orbital Precession
Authors: Lin-Jia Li , Sheng-Bang Qian
Published: March 2014

We determined forty-two new times of light maximum from our photometry observations and WASP project, and collected all times of light maximum observed between 1961 and 2013 in order to calculate the orbital elements of the SZ Lyncis system and the secular change of the pulsation period with the classical $O-C$ method. We confirmed the decrease of the longitude of the periastron passage with a rate of $(-1.^{\circ}15 \pm 0. ^{\circ}25 )\textrm {yr}^{-1}$, and discussed the causative mechanism. The results show that the precession of the star's orbit might be due to a close binary system, which means that the companion of SZ Lyncis is actually a binary system. We used the Hipparcos Intermediate Astrometric Data to obtain the complete orbital elements of the SZ Lyncis system, and found that the inclination, i , and parallax, $\pi_{t}$, are $39.^{\circ}5 \pm 17.^{\circ}7$ and $2.^{\circ}61\pm 0.^{\circ}98$ mas (corresponds to $380 \pm 140$), respectively. We reanalyzed the mean radial velocities of SZ Lyncis given by Bardin and Imbert (1984), and noticed a weak variation existing in the residuals from a single-Keplerian fit. We suggest that more detailed high-precision spectroscopic observations are definitely needed in the future to check this short periodic change.
WZ Sge-Type Dwarf Novae with Multiple Rebrightenings: MASTER OT J211258.65+242145.4 and MASTER OT J203749.39+552210.3
Authors: Nakata Chikako , Ohshima Tomohito , Kato Taichi , Nogami Daisaku , Masi Gianluca , de Miguel Enrique , Ulowetz Joseph , Littlefield Colin , Goff William N. , Krajci Thomas , Maehara Hiroyuki , Stein William , Sabo Richard , Noguchi Ryo , Ono Rikako , Kawabata Miho , Furukawa Hisami , Matsumoto Katsura , Ishibashi Takehiro , Dubovsky Pavol A. , Kudzej Igor , Dvorak Shawn , HAMBSCH Franz-Josef , Pickard Roger D. , Morelle Etienne , Muyllaert Eddy , Padovan Stefano , Henden Arne
Published: March 2014

We report on photometric observations of two WZ Sge-type dwarf novae, MASTER OT J211258.65+242145.4 and MASTER OT J203749.39+552210.3, which underwent outbursts in 2012. Early superhumps were recorded in both systems. During the superoutburst plateau, ordinary superhumps with a period of 0.060291(4) d (MASTER J211258) and with 0.061368(11) d (MASTER J203749) on average were observed. MASTERJ211258 and MASTERJ203749 exhibited eight post-superoutburst rebrightenings and more than four, respectively. In the final part of the superoutburst, an increase in superhump period was seen in both systems. We made a survey of WZSge-type dwarf novae with multiple rebrightenings, and confirmed that the superhump periods of WZSge-type dwarf novae with multiple rebrightenings were longer than those of WZSge-type dwarf novae without a rebrightening. Although WZSge-type dwarf novae with multiple rebrightenings have been thought to be likely candidates for period bouncers based on their low mass ratio (q), inferred from the period of fully grown (stage B) superhumps, our new method of using the period of growing superhumps (stage A superhumps), however, implies higher q's than those expected from stage B superhumps. These q values appear to be consistent with the duration of the stage A superoutbursts, which likely reflects the growth time of the 3W1 resonance. We present a working hypothesis that the small fractional superhump excesses for stage B superhumps in these systems may be explained by a gas pressure effect that works more efficiently in these systems than in ordinary SU UMa-type dwarf novae. This result forms a new picture that WZSge-type dwarf novae with multiple rebrightenings and SU UMa-type ones without a rebrightening (they are not period bouncers) are located in the same place on the evolutionary track.
Rotation Curve and Mass Distribution in the Galactic Center —From Black Hole to Entire Galaxy—
Authors: Sofue Yoshiaki
Published: March 2014

Analyzing high-resolution longitude–velocity (LV) diagrams of the Galactic Center observed with the Nobeyama 45-m telescope in the CO and CS line emissions, we obtained a central rotation curve of the Milky Way. We combined it with data for the outer disk, and constructed a logarithmic rotation curve of the entire Galaxy. The new rotation curve covers a wide range of radius from r ∽ 1 pc to several hundred kpc without a gap of data points. It links, for the first time, the kinematical characteristics of the Galaxy from the central black hole to the bulge, disk and dark halo. Using this grand rotation curve, we calculated the radial distribution of the surface mass density in the entire Galaxy, where the radius and derived mass densities vary over a dynamical range with several orders of magnitudes. We show that the galactic bulge is deconvolved into two components: the inner (core) and main bulges. Both of the two bulge components are represented by exponential density profiles, but the de Vaucouleurs law was found to fail to represent the mass profile of the galactic bulge.
Low-Resolution Spectrum of the Diffuse Galactic Light and 3.3μm PAH Emission with the AKARI InfraRed Camera
Authors: Tsumura Kohji , Matsumoto Toshio , Matsuura Shuji , Sakon Itsuki , Tanaka Masahiro , Wada Takehiko
Published: March 2014

We first obtained the spectrum of the diffuse Galactic light (DGL) at general interstellar space in the $1.8-5.3 \mu \textrm m $ wavelength region with the low-resolution prism spectroscopy mode of the AKARI Infra-Red Camera (IRC) NIR channel. The $3.3 \mu \textrm m $ PAH band is detected in the DGL spectrum at Galactic latitude $\mid b \mid \lt 15^{\circ}$, and its correlations with the Galactic dust and gas are confirmed. The correlation between the $3.3 \mu \textrm m $ PAH band and the thermal emission from the Galactic dust is expressed not by a simple linear correlation, but by a relation with extinction. Using this correlation, the spectral shape of DGL at an optically thin region ($5^{\circ} \lt \mid b \mid \lt 15^{\circ}$) was derived as a template spectrum. Assuming that the spectral shape of this template spectrum is uniform at any position, the DGL spectrum can be estimated by scaling this template spectrum using the correlation between the $3.3 \mu \textrm m $ PAH band and the thermal emission from the Galactic dust.