bluuebunny/crossref_metadata_2025 huggingface dataset:
First Simultaneous Dual-Frequency Phase Referencing VLBI Observation with VERA
Authors: Jung Taehyun , Sohn Bong Won , Kobayashi Hideyuki , Sasao Tetsuo , Hirota Tomoya , Kameya Osamu , Choi Yoon Kyung , Chung Hyun Soo
Published: March 2014

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

We present a series of numerical experiments that model the evolution of magnetic flux tubes with a different amount of initial twist. As a result of calculations, tightly twisted tubes reveal a rapid two-step emergence to the atmosphere with a slight slowdown at the surface, while weakly twisted tubes show a slow two-step emergence waiting longer the secondary instability to be triggered. This picture of the two-step emergence is highly consistent with recent observations. These tubes show multiple magnetic domes above the surface, indicating that the secondary emergence is caused by an interchange mode of magnetic buoyancy instability. In the case of the weakest twist, the tube exhibits an elongated photospheric structure, and never rises into the corona. The formation of the photospheric structure is due to an inward magnetic tension force of the azimuthal field component of the rising flux tube (i.e., tube's twist). When the twist is weak, the azimuthal field cannot hold the tube's coherency, and the tube extends laterally at the subadiabatic surface. In addition, we newly found that the total magnetic energy measured above the surface depends on the initial twist. Strong twist tubes follow the initial relation between the twist and the magnetic energy, while weak twist tubes deviate from this relation, because these tubes store their magnetic energy in the photospheric structure.
A Possible Mechanism of Flux Cancellation via U-Loop Emergence on the Sun
Authors: Magara Tetsuya
Published: March 2014

We have used a 3-dimensional MHD simulation to investigate a dynamic process producing flux cancellation on the solar surface. Our calculations are fully self-consistent in that any prescribed dynamic process is not applied on the surface, which is self-consistently generated via the emergence of a twisted flux tube. Most of the flux that emerges below the surface is in the form of $\Omega$-loops (concave-down geometry), so that dense photospheric plasma can drain down along the legs of the loop as it rises into the corona. We have found, however, that some U-loops (concave-up geometry) can also emerge. A U-loop geometry implies that a field line has a dip below the surface and a local peak somewhere above the surface on either side of the dip. Although the emergence of U-loops can produce flux cancellation on the surface, loops with such a geometry are not expected to emerge easily, due to the trapping of dense plasma in the dipped portion of the loops. Our results indicate that if one of the peaks is sufficiently low, on the order of the photospheric gravitational scale height above the surface, plasma can drain out of the dipped portion by a siphon-like mechanism, allowing the U-part of the loops to emerge, and resulting in cancellation of the magnetic flux on the surface. However, if both peaks of a U-loop are high compared to the photospheric scale height, dense plasma simply settles in the dip of the loop, preventing the U-part from emerging, rather producing reconnection, which is another possible mechanism of flux cancellation. We also discuss the implications of our results for observations.
Measurements of Antenna Surface for Millimeter-Wave Space Radio Telescope
Authors: Kamegai Kazuhisa , Tsuboi Masato , Doi Akihiro , Sato Eiichi
Published: March 2014

In the construction of a space radio telescope, it is essential to use materials with a low noise factor and high mechanical robustness for the antenna surface. We present the results of measurements of the reflection performance of two candidates for antenna surface materials for use in a radio telescope installed in a new millimeter-wave astronomical satellite, ASTRO-G. To estimate the amount of degradation caused by fluctuations in the thermal environment in the projected orbit of the satellite, a thermal cycle test was carried out for two candidates, namely, copper foil carbon fiber reinforced plastic (CFRP) and aluminum-coated CFRP. At certain points during the thermal cycle test, the reflection loss of the surfaces was measured precisely by using a radiometer in the 41–45 GHz band. In both candidates, cracks appeared on the surface after the thermal cycle test, where the number density of the cracks increased as the thermal cycle progressed. The reflection loss also increased in proportion to the number density of the cracks. Nevertheless, the loss of the copper foil surface met the requirements of ASTRO-G at the end of the equivalent life, whereas that of the aluminum-coated surface exceeded the maximal value in the requirement even before the end of the cycle.
Interstellar Meteoroids in the Japanese tv Catalogue
Authors: Hajduková Mária
Published: March 2014

The present work is based on an analysis of the 14763 precise determined meteor orbits collected in the Japanese tv catalogue (SonotaCo (2009)), with the aim of determining the real proportion of interstellar meteors in this database. If interstellar meteors are present among the registered meteor orbits, the distribution of the excesses of their heliocentric velocities should correspond to the distribution of the radial velocities of close stars. For the velocity $v_i$$=$ 20 km s$^{-1}$ of an interstellar meteor, with respect to the Sun, we obtain a heliocentric velocity of $v_H$$=$ 46.6 km s$^{-1}$ of an interstellar meteor arriving at Earth. Any error in the determination of $v_H$, especially near the parabolic limit, can create an artificial hyperbolic orbit that does not really exist. The analysis of the data did not produce any convincing arguments in favour of the existence of true hyperbolic meteors in the catalogue. It was shown that the vast majority of the 484 hyperbolic orbits has been caused by an overestimation of their velocity, and approximately 50% of them belong to meteor showers. Furthermore, the hyperbolic excesses of the velocities in all cases are very low, about one order less than the velocity distribution of neighbouring stars suggest. The upper limit of the proportion of possible interstellar meteors to interplanetary ones among all investigated meteor orbits in the database is 1.3 $\times$ 10$^{-3}$.
Mid-Infrared Spectroscopy of 11 Main-Belt Asteroids
Authors: Takahashi Jun , Itoh Yoichi , Takahashi Shigeru
Published: March 2014

We present mid-infrared (8–13$\ \mu$m) spectra of 11 main-belt asteroids: 1 Ceres, 3 Juno, 7 Iris, 11 Parthenope, 20 Massalia, 24 Themis, 41 Daphne, 42 Isis, 44 Nysa, 67 Asia, and 88 Thisbe. This paper makes the first report on the mid-infrared spectrum for 5 asteroids. Our observation was conducted with Michelle on UKIRT. The modified Standard Thermal Model (STM) has provided a slightly better fit to the observed spectra than the model without any modification. For 1 Ceres, we detected an emission feature that surpasses the thermal continuum by 6.2$\ \pm\ $1.1%. For the other 10 asteroids, no feature has been detected above their observational errors. However, their $S/N$ ratios are sufficient to only detect 6% emission excess. As the causes of the observed spectral distinction, we examine possible (1) chemical and (2) physical differences on the surfaces of the asteroids: (1) 1 Ceres has silicates with a lower degree of polymerization than do the other asteroids; (2a) the dominant grain size on 1 Ceres is nearer to 200$\ \mu$m, and probably smaller than that on the other asteroids; (2b) In addition, 1 Ceres has very small ($\lt\ $5$\ \mu$m) grains on its surface, while the other asteroids have grains that are moderately small, but larger than on 1 Ceres. In either case, the observed spectral distinctiveness of 1 Ceres, the largest asteroid, suggests that the properties of an asteroid surface may be correlated with the asteroid size.
Observations of Plasma Blob Ejection from a Quiescent Prominence by Hinode Solar Optical Telescope
Authors: Hillier Andrew , Isobe Hiroaki , Watanabe Hiroko
Published: March 2014

We report findings from 0$''\!\!\!.$2 resolution observations of the 2007 October 03 quiescent prominence observed with the Solar Optical Telescope on the Hinode satellite. The observations show clear ejections from the top of the quiescent prominence of plasma blobs. The ejections, originating from the top of prominence threads, are impulsively accelerated to approximately Alfvén velocities and then undergo ballistic motion. The ejections have a characteristic size between $\sim$ 1000–2000 km. These characteristics are similar to downwardly propagating knots (typical size $\sim$ 700 km) that have been observed in prominence threads, we suggest that the plasma blob ejections could be the upward moving counterpart to the downwardly propagating knots. We discuss the tearing instability as a possible mechanism to explain the ejections.
Astrometry of Galactic Star-Forming Region G48.61+0.02 with VERA
Authors: Nagayama Takumi , Omodaka Toshihiro , Handa Toshihiro , Honma Mareki , Kobayashi Hideyuki , Kawaguchi Noriyuki , Ueno Yuji
Published: March 2014

We performed the astrometry of H$_2$O masers in the Galactic star-forming region G48.61$+$0.02 with the VLBI Exploration of Radio Astrometry (VERA). We derived a trigonometric parallax of 199$\ \pm\ $7$\ \mu$as, which corresponds to a distance of 5.03$\ \pm\ $0.19 kpc. The distance to G48.61$+$0.02 is about half of its far kinematic distance, which was often assumed previously. This distance places G48.61$+$0.02 in the Sagittarius–Carina arm, and near to the active star-forming region and the supernova remnant W 51. We also obtained the three-dimensional motion of G48.61$+$0.02, and found that it has a large peculiar motion of 40$\ \pm\ $5 km s$^{-1}$. This peculiar motion would have originated along with multiple supernovae explosions in W 51, or streaming motion across the Sagittarius–Carina arm.
Can X-Ray Lasers Exist in Astrophysical Objects ?
Authors: Salzmann David , Takabe Hideaki
Published: March 2014

We consider the possibility of population inversion in astrophysical objects irradiated by high-intensity black-body radiation from a nearby source. As a model, we use the 1s2p $^{1}$P$_{1}$ populations in helium-like ions, which are generated by K-shell photoionization of lithium-like ions. Our conclusion is that the presently known highest astrophysical irradiation conditions are insufficient to produce population inversion for this transition. According to our estimate, population inversion is possible only in the visible or longer wavelength regimes. Our estimates may change for non-black-body radiation distributions.
Correlated Frequency-Changes of Trapped Vertical p-Mode Oscillations and kHz QPOs
Authors: kato Shoji
Published: March 2014

We have examined the frequencies of trapped two-armed ($m$$=$ 2) nearly vertical oscillations (vertical p-mode) in vertically isothermal disks with toroidal magnetic fields. The magnetic fields are stratified so that the Alfvén speed, $c_{\rm A}$, is constant in the vertical direction. We have particularly focused our attention on how frequencies of the fundamental mode ($n_{\rm r}$$=$ 0) and first overtone ($n_{\rm r}$$=$ 1) in the radial direction change with the correlation, when the ratio $c_{\rm A}^2/c_{\rm s}^2$ changes, $c_{\rm s}$ being the isothermal acoustic speed. The results show that in the case where the oscillations are the fundamental mode ($n$$=$ 1) in the vertical direction, the correlated frequency changes of the above-mentioned oscillations seem to well describe, with standard values of the mass and spin of the central sources, the frequency correlation of kHz QPOs observed in neutron-star X-ray binaries.
Particle–Particle Particle–Tree: A Direct-Tree Hybrid Scheme for Collisional N-Body Simulations
Authors: Oshino Shoichi , Funato Yoko , Makino Junichiro
Published: March 2014

In this paper, we present a new hybrid algorithm for the time integration of collisional $N$-body systems. In this algorithm, the gravitational force between two particles is divided into short- and long-range terms, using a distance-dependent cutoff function. The long-range interaction is calculated using a tree algorithm, and integrated with a constant-timestep leapfrog integrator. The short-range term is calculated directly and integrated with the high-order Hermite scheme. We can reduce the calculation cost per orbital period from $O$($N^2$) to $O$($N$log$N$), without significantly increasing the long-term integration error. The results of our test simulations show that close encounters are integrated accurately. Long-term errors of the total energy show random-walk behaviour, because they are dominated by the error caused by the tree approximation.
Drastic Spectroscopic Variability of the Be/X-Ray Binary Ariel 0535+262/V725 Tau during and after the 2009 Giant Outburst
Authors: Moritani Yuuki , Nogami Daisaku , Okazaki Atsuo T. , Imada Akira , Kambe Eiji , Honda Satoshi , Hashimoto Osamu , Ichikawa Kohei
Published: March 2014

We report on high-dispersion optical spectroscopic observations of the Be/X-ray binary A 0535$+$262/V725 Tau during a giant outburst in 2009 November/December, and after it. The observed emission line profiles, reflecting the structure of the geometrically thin circumstellar envelope of the Be star (Be disk), show drastic variabilities, and indicate the existence of a warped component. The enhanced blue shoulder seen after periastron passage implies a gas stream from a dense part of the Be disk to the neutron star.
Photographic and Radiometric Observations of the HAYABUSA Re-Entry
Authors: Borovicka Jirí , Abe Shinsuke , ShrbenÝ Lukáš , SpurnÝ Pavel , Bland Philip A.
Published: March 2014

We analyzed photographic observations of the re-entry of the HAYABUSA spacecraft and capsule over Southern Australia on 2010 June 13, 13:52 UT. Radiometric measurements of the brightness of the associated fireball were obtained as well. We derived the trajectories and velocities of the spacecraft, its four fragments, and the capsule. The capsule trajectory was within a few hundred meters of the trajectory predicted by JAXA prior to re-entry. The spacecraft trajectory was about 1 km higher than the capsule trajectory. Two major fragments separated from the spacecraft at a height of about 62 km with a mutual lateral velocity of 250 m s$^{-1}$. The maximum absolute magnitude of the fireball of $-$12.6 was reached at a height of 67 km. The dynamic pressures acting on the spacecraft at the fragmentation points were only 1–50 kPa. No spacecraft fragment was seen to survive below a height of 47 km. The integral luminous efficiency of the event was 1.3%. As expected, the capsule had a very low luminous efficiency and very low ablation coefficient. The ablation coefficients and masses of the major spacecraft fragments are discussed.
Thermal Structure of a Protoplanetary Disk around HD 163296: A Study of Vertical Temperature Distribution by CO Emission Lines
Authors: Akiyama Eiji , Momose Munetake , Hayashi Hiroyuki , Kitamura Yoshimi
Published: March 2014

This paper presents observations of a protoplanetary disk around the Herbig Ae star HD 163296 in $^{12}$CO ($J$$=$ 1–0), $^{12}$CO ($J$$=$ 3–2), $^{13}$CO ($J$$=$ 1–0), and $^{13}$CO ($J$$=$ 3–2) emission lines. Double-peaked emission profiles originating from the rotating circumstellar disk were detected in all of the lines. The disk parameters were estimated from model calculations in which the radial distribution of the temperature or surface density inside the disk had a power-law form. The surface density should be sufficiently high so that the disk is optically thick for all of the CO lines, as discussed in previous studies based on interferometric observations. The temperature and outer radius of the disk were also confirmed to be consistent with the previous results. Taking advantage of the difference in the position of the photosphere among the CO lines, we revealed the temperature distribution in the vertical direction. The temperature of the $^{12}$CO ($J$$=$ 3–2) emitting region is about twice higher than that of any other CO emitting region; the former is 58.5$\ \pm\ $9.5 K, while the latter is 31$\ \pm\ $15 K at 100 AU from the central star, suggesting that there are at least two distinct temperature regions. The best-fit temperature for $^{13}$CO ($J$$=$ 1–0) that should trace the deepest region of the disk is even lower, implying that there is also a different temperature region deep inside of the disk. Such a vertical temperature distribution in a disk was identified both in T Tauri and Herbig Ae stars (e.g., DM Tau, AB Aur, and HD 31648), and this should be a common feature in protoplanetary disks.
Observational Identification of First Cores: Non-LTE Radiative Transfer Simulation
Authors: Tomisaka Kohji , Tomida Kengo
Published: March 2014

A first core is a first hydrostatic object formed in the course of dynamical contraction of a molecular cloud core. Since the inflow pattern changes drastically both before and after first core formation, it is regarded as a milestone in the star-formation process. In order to identify the first core from a mapping observation, the features expected for the first core are studied for CS rotation transitions at radio wavelengths. The non-LTE (local thermodynamical equilibrium) radiation transfer is calculated for the results of radiation magnetohydrodynamical simulations of the contraction of the magnetized molecular cloud core in rotation (Tomida et al. (2010b), ApJ, 714, L58). We used the Monte-Carlo method to solve the non-LTE radiation transfer in a nested grid hierarchy. In the first core phase, an outflow arises from the vicinity of the first core due to a twisted magnetic field amplified by rotation of the contracting gas disk. The disk and outflow system has several characteristic observational features: (i) relatively opaque lines indicate asymmetry in the emission lines in which the blue side is stronger than the red side (an infall signature of the envelope); (ii) in the edge-on view, the disk has a signature of simultaneous rotation and infall, i.e., the integrated intensity of the approaching side is brighter than that of the receding side and the gradient in the intensity-weighted velocity is larger in the approaching side; (iii) the observed outflow indicates rotation around the rotation axis. The size of the outflow gives the approximate age after the first core is formed, since the outflow is not expected for the earlier runaway isothermal collapse phase.
Fragmentation of the HAYABUSA Spacecraft on Re-Entry
Authors: Watanabe Jun-ichi , Ohkawa Takuya , Sato Mikiya , Ohnishi Kouji , Iijima Yutaka
Published: March 2014

We succeeded in monitoring fragmentation of the main body of the HAYABUSA spacecraft upon its re-entry as a part of an expedition by the National Astronomical Observatory of Japan. The time variation of the number of fragments and their size distribution were derived by analyzing obtained images. The fragmentation started at 13$^{\rm h}$52$^{\rm m}$5$.\!\!\!^{\rm s}$2 UT at 83–84 km above sea level, and the number of fragments increased with time. The maximum number was more than a few hundred at around 13$^{\rm h}$52$^{\rm m}$20$^{\rm s}$, and the fragments dispersed over an area of more than 14 km in length, and 1 km in width along the re-entry trajectory. Fragments decreased in number after the maximum, and almost disappeared at 13$^{\rm h}$52$^{\rm m}$31$.\!\!\!^{\rm s}$3 at around a height of 45 km. Under some assumptions, we managed to derive the size distribution of the fragments, which showed a small power-law index within a range of $-$0.8 to $-$1.0. These values are lower than those of fragmentations of comets, or other examples in our solar system. The obtained flat size distribution is discussed based on a comparison of the intrinsic size distribution of the assembled parts of the HAYABUSA spacecraft.
Spectroscopic Observation of the Re-Entry Capsule of HAYABUSA Spacecraft
Authors: Ohnishi Kouji , Watanabe Jun-ichi , Sato Mikiya , Ohkawa Takuya , Ebizuka Noboru
Published: March 2014

We performed low-resolution spectroscopic observations of the capsule of the HAYABUSA spacecraft during re-entry into the Earth's atmosphere on 2010 June 13 UT as an artificial meteor. We obtained the photometric magnitude of the HAYABUSA capsule using zeroth-order spectra. The efficiency of the zeroth-order spectra was too low for us to measure the magnitude of the capsule without any saturation at all times. The altitude at the maximal flux of the capsule was at around 56 km (13$^{\rm h}$52$^{\rm m}$19$\!\!\!^{\rm s}$81 UT), which is almost similar to the case GENESIS, i.e., the maximal flux at around 55 km. We examined the change in the spectrum shape of the capsule as a function of its altitude, and investigated the emission from the shock layer and the blackbody radiation from the surface of the capsule. It is found that the shock-layer emission was dominant, and/or on the same order of the blackbody radiation at the early phase of re-entry; also, the emission from blackbody radiation was dominant during the last phase of re-entry. We measured the surface temperature of the capsule along the trajectory; during the last phase before dark flight, we found that the blackbody temperature of the capsule was 3100$\ \pm\ $300 K at an altitude of around 50 km, and 2400$\ \pm\ $300 K at an altitude of around 40 km.
Multiple Outflows Traced by H2O Masers around the Ultra-Compact H II Region G 34.26+0.15
Authors: Imai Hiroshi , Omi Rui , Kurayama Tomoharu , Nagayama Takumi , Hirota Tomoya , Miyaji Takeshi , Omodaka Toshihiro
Published: March 2014

We present the results of VLBI observations of the H$_2$O masers associated with the massive-star forming region G 34.26$+$0.15 with the Very Long Baseline Array (VLBA), the Japanese VLBI Network (JVN), and the VLBI Exploration of Radio Astrometry (VERA) to reveal the whole three-dimensional kinematical structure of the H$_2$O maser region (2$''$$\times$ 5$''$). From the result of one of the astrometric observations with VERA and the revealed maser distribution, we found that, in G 34.26$+$0.15, the H$_2$O masers are likely to be associated with four young stellar objects (YSOs), each of which is traced by at least one of millimeter-continuum and molecular-line emission peaks, rather than by centimeter-continuum peaks that may trace H II regions, including the brightest millimeter- and centimeter-continuum emission peak. We also measured the relative proper motions of 33 H$_2$O masers in the VLBA observations (1996 December–1997 May) and 104 ones in JVN/VERA (2006 March–2008 June). We found that these maser motions indicate large random motion (40–70 km s$^{-1}$), but in at least one region they exhibit radial expansion motions. This suggests the existence of outflows originating from accompanying YSOs. We discuss not only the intrinsic physical properties of multiple YSOs that harbor H$_2$O masers within 0.1 pc but also the implications of the existence of these YSOs. The formation history of the cometary H II region in G 34.26$+$0.15 is also discussed.
Binary Formation in Planetesimal Disks. I. Equal Mass Planetesimals
Authors: Kominami Junko D. , Makino Junichiro , Daisaka Hiroshi
Published: March 2014

As of April 2010, 48 TNO (trans-Neptunian Object) binaries have been found. This is about 6% of known TNOs. However, in previous theoretical studies of planetary formation in the TNO region, the effect of binary formation has been neglected. TNO binaries can be formed through a variety of mechanisms, such as a three-body process, dynamical friction on two massive bodies, inelastic collisions between two bodies etc. Most of these mechanisms become more effective as the distance from the Sun increases. In this paper, we describe our study on three-body process using direct $N$-body simulations. We found that chaos-assisted-capture (CAC) is the dominant channel of binary formation. We systematically changed the distance from the Sun, the number density of planetesimals, and the radius of the planetesimals and studied the effect of the binaries on the collision rate of planetesimals. In the TNO region, binaries are involved in 1$/$3–1$/$2 of collisions, and the collision rate increases by a factor of a few compared to the theoretical estimate for direct two-body collisions. Thus, it is possible that the binaries significantly enhance the collision rate and reduce the growth timescale. In the terrestrial planet region, binaries are less important, because the ratio between the Hill radius and the physical size of the planetesimals is relatively small. Although the time scale of our simulations is short, they clearly demonstrated that the accretion process in the TNO region is quite different from that in the terrestrial planet region.
Further Observations of the Tilted Planet XO-3: A New Determination of Spin–Orbit Misalignment, and Limits on Differential Rotation
Authors: Hirano Teruyuki , Narita Norio , Sato Bun’ei , Winn Joshua N. , Aoki Wako , Tamura Motohide , Taruya Atsushi , Suto Yasushi
Published: March 2014

We report on observations of the Rossiter–McLaughlin (RM) effect for the XO-3 exoplanetary system. The RM effect for the system was previously measured by two different groups, but their results were statistically inconsistent. To obtain a decisive result, we observed two full transits of XO-3b with the Subaru 8.2-m telescope. By modeling these data with a new and more accurate analytic formula for the RM effect, we found the projected spin–orbit angle to be ${\lambda}$$=$ 37$^\circ\!\!\!.$3$\ \pm\ $3$^\circ\!\!\!.$0, in good agreement with a previous finding by Winn et al. (2009) (2009 ApJ, 700, 302). In addition, an offset of $\sim\ $22 m s$^{-1}$ was observed between the two transit datasets. This offset could be a signal of a third body in the XO-3 system, a possibility that should be checked with future observations. We also attempted to search for a possible signature of the stellar differential rotation in the RM data for the first time, and put weak upper limits on the differential rotation parameters.
X-Ray Study of the Outer Region of Abell 2142 with Suzaku
Authors: Akamatsu Hiroki , Hoshino Akio , Ishisaki Yoshitaka , Ohashi Takaya , Sato Kosuke , Takei Yoh , Ota Naomi
Published: March 2014

We observed outer regions of a bright cluster of galaxies, A 2142, with Suzaku. Temperature and brightness structures were measured out to the virial radius ( $r_{200}$ ) with good sensitivity. We confirmed a temperature drop from 9 keV around the cluster center to about 3.5 keV at $r_{200}$ , with the density profile well approximated by the $\beta$ -model with $\beta$$=$ 0.85. Within 0.4 $r_{200}$ , the entropy profile agrees with $r^{1.1}$ , as predicted by the accretion shock model. The entropy slope becomes flatter in the outer region and negative around $r_{200}$ . These features suggest that the intracluster medium in the outer region is out of thermal equilibrium. Since the relaxation timescale of electron-ion Coulomb collisions is expected to be longer than the elapsed time after shock heating at $r_{200}$ , one plausible reason for the low entropy is a low electron temperature compared to that of ions. Other possible explanations would be gas clumpiness, turbulence and bulk motions of the ICM. We also searched for a warm-hot intergalactic medium around $r_{200}$ , and set an upper limit on the oxygen line intensity. Assuming a line-of-sight depth of 2 Mpc and oxygen abundance of 0.1 solar, the upper limit of an overdensity is calculated to be 280 or 380, depending on the foreground assumption.
Gas Slit Camera (GSC) onboard MAXI on ISS
Authors: Mihara Tatehiro , Nakajima Motoki , Sugizaki Mutsumi , Serino Motoko , Matsuoka Masaru , Kohama Mitsuhiro , Kawasaki Kazuyoshi , Tomida Hiroshi , Ueno Shiro , Kawai Nobuyuki , Kataoka Jun , Morii Mikio , Yoshida Atsumasa , Yamaoka Kazutaka , Nakahira Satoshi , Negoro Hitoshi , Isobe Naoki , Yamauchi Makoto , Sakurai Ikuya
Published: March 2014

The Gas Slit Camera (GSC) is an X-ray instrument on the MAXI (Monitor of All-sky X-ray Image) mission aboard the International Space Station. It is designed to scan the entire sky every 92-minute orbital period in the 2–30 keV band and to achieve the highest sensitivity among the X-ray all-sky monitors ever flown so far. The GSC employs large-area position-sensitive proportional counters with a total detector area of 5350 cm $^2$. The on-board data processor has functions to format telemetry data as well as to control the high voltage of the proportional counters so as to protect them from particle irradiation. This paper describes the instruments, on-board data processing, telemetry data formats, and performance specifications expected from ground calibration tests.
Improvements in Calibration of GSO Scintillators in the Suzaku Hard X-Ray Detector
Authors: Yamada Shin’ya , Makishima Kazuo , Nakazawa Kazuhiro , Kokubun Motohide , Kawaharada Madoka , Kitaguchi Takao , Watanabe Shin , Takahashi Hiromitsu , Noda Hirofumi , Nishioka Hiroyuki , Hiragi Kazuyoshi , Hayashi Katsuhiro , Nakajima Kenta , Tashiro Makoto , Sasano Makoto , Nishino Sho , Torii Shunsuke , Sakurai Soki , Takahashi Tadayuki , Mizuno Tsunefumi , Enoto Teruaki , Yuasa Takayuki , Tanaka Takaaki , Kouzu Tomomi , Nakano Toshio , Fukazawa Yasushi , Terada Yukikatsu , Uchiyama Yasunobu , Iwakiri Wataru
Published: March 2014

Improvements of the in-orbit calibration of GSO scintillators in the Hard X-ray Detector aboard Suzaku are reported. To resolve an apparent change in the energy scale of GSO, which appeared across the launch for unknown reasons, consistent and thorough re-analyses of both pre-launch and in-orbit data have been performed. With laboratory experiments using spare hardware, the pulse-height offset, corresponding to zero energy input, was found to change by $\sim\ $ 0.5% of the full analog voltage scale, depending on the power supply. Furthermore, by carefully calculating all of the light outputs of secondaries from activation lines used in the in-orbit gain determination, their energy deposits in GSO were found to be effectively lower, by several percent, than their nominal energies. Taking both of these effects into account, the in-orbit data agree with the on-ground measurements within $\sim\ $ 5%, without employing the artificial correction introduced in previous work (Kokubun et al. 2007, PASJ, 59, S53). With this knowledge, we updated the data processing, the response, and the auxiliary files of GSO, and reproduced the HXD-PIN and HXD-GSO spectra of the Crab Nebula over 12–300 keV by a broken power-law with a break energy of $\sim\ $ 110 keV.
Nature of the Unidentified TeV Source HESS J1614−518, Revealed by Suzaku and XMM-Newton Observations
Authors: Sakai Michito , Yajima Yukie , Matsumoto Hironori
Published: March 2014

We report on new Suzaku and XMM-Newton results concerning HESS J1614 $-$ 518, which is one of the brightest extended TeV $\gamma$ -ray sources and has two regions with intense $\gamma$ -ray emission. We newly observed the south and center regions of HESS J1614 $-$ 518 with Suzaku, since the north region, including the position of the 1st brightest peak of the TeV $\gamma$ -ray emission, has already been observed. No X-ray counterpart was found at the position of the 2nd brightest peak of the TeV $\gamma$ -ray emission; we estimated the upper limit of the X-ray flux to be 1.6 $\times$ 10 $^{-13}$ erg cm $^{-2}$ s $^{-1}$ in the 2–10 keV band. The soft X-ray source Suzaku J1614 $-$ 5152, which was found at the edge of the field of view in a previous observation, was also detected at the middle of HESS J1614 $-$ 518. Analyzing the XMM-Newton archival data, we revealed that Suzaku J1614 $-$ 5152 consists of multiple point sources. The X-ray spectrum of the brightest point source, XMMU J161406.0 $-$ 515225, can be described by a power-law model with a photon index of $\Gamma$$=$ 5.2 $^{+0.6}_{-0.5}$ , or a blackbody model with temperature $kT$$=$ 0.38 $^{+0.04}_{-0.04}$ keV. In the blackbody model, the hydrogen-equivalent column density is almost the same as that of the hard extended X-ray emission, Suzaku J1614 $-$ 5141, which was found at the 1st peak position. If true, XMMU J161406.0 $-$ 515225 may be physically related to Suzaku J1614 $-$ 5141 and HESS J1614 $-$ 518.
An X-Ray Spectroscopic Study of the Hot Interstellar Medium toward the Galactic Bulge
Authors: Hagihara Toshishige , Yamasaki Noriko Y. , Mitsuda Kazuhisa , Takei Yoh , Sakai Kazuhiro , Yao Yangsen , Wang Q. Daniel , McCammon Dan
Published: March 2014

We present a detailed spectroscopic study of the hot gas toward the galactic bulge along the 4U 1820 $-$ 303 sight line by a combination analysis of emission and absorption spectra. In addition to the absorption lines of O VII K ${\alpha}$ , O VII K ${\beta}$ , O VIII K ${\alpha}$ , and Ne IX K ${\alpha}$ by Chandra LTGS, as shown by previous studies, Suzaku clearly detected the emission lines of O VII, O VIII, Ne IX, and Ne X from the vicinity. We used simplified plasma models with constant temperature and density. An evaluation of the background and foreground emission was carefully performed, including the stellar X-ray contribution based on the recent X-ray observational results and the stellar distribution simulator. If we assume that one plasma component exists in front of 4U 1820 $-$ 303 and the other one at the back, the obtained temperatures are $T$$=$ (1.7 $\ \pm\ $ 0.2) $\times$ 10 $^{6}$ K for the front-side plasma and $T$$=$ (3.9 $^{+0.4}_{-0.3}$ ) $\times$ 10 $^{6}$ K for the back-side. This scheme is consistent with a hot and thick ISM disk, as suggested by extragalactic source observations and an X-ray bulge around the galactic center.
Suzaku Metal Abundance Patterns in the Outflow Region of M 82 and the Importance of Charge Exchange
Authors: Konami Saori , Matsushita Kyoko , Go Tsuru Takeshi , Gandhi Poshak , Tamagawa Toru
Published: March 2014

We performed spectral analysis of Suzaku data of the galactic disk and outflow regions of the starburst galaxy M 82. Thermal modeling of the central disk regions requires at least three temperature components. The Ly $\beta $ line fluxes of O VIII and Ne X exceed those expected from a plasma in collisional ionization equilibrium. The ratios of the Ly $\beta/$ Ly $\alpha$ lines for O VIII and Ne X are higher than those of collisional ionization equilibrium, which may be caused by the process of charge exchange. In the outflow wind region, the spectra are well reproduced with two-temperature thermal models, and we have derived the metal abundances of O, Ne, Mg, and Fe in the outflow. The ratios of O $/$ Fe, Ne $/$ Fe, and Mg $/$ Fe are about 2, 3, and 2, respectively, relative to the solar value determined by Lodders (2003, ApJ, 591, 1220). Since there is no evidence of charge exchange in the outflow region, the metal abundances should be more reliable than those in the central region. This abundance pattern indicates that starburst activity enriches the outflow through SN II metal ejection into intergalactic space.
Suzaku Measurement of Electron and Magnetic Energy Densities in the East Lobe of the Giant Radio Galaxy DA 240
Authors: Isobe Naoki , Seta Hiromi , Tashiro Makoto S.
Published: March 2014

A careful analysis of the Suzaku data of the giant radio galaxy DA 240, of which the size is 1.48 Mpc, revealed diffuse X-ray emission associated with its east lobe. The diffuse X-ray spectrum was described with a simple power-law model with a photon index of $\Gamma$$=$ 1.92 $_{-0.17}^{+0.13}$$_{-0.06}^{+0.04}$ , where the first and second errors represent the statistical and systematic ones. The agreement with the synchrotron radio photon index, $\Gamma_{\rm R}$$=$ 1.95 $\ \pm\ $ 0.01 in 326–608.5 MHz, ensures that any excess X-ray emission is attributed to inverse Compton emission from the synchrotron-radiating electrons, boosting up the cosmic microwave background photons. From the X-ray flux density, 51.5 $\ \pm\ $ 3.9 $_{-5.4}^{+6.2}\ $ nJy at 1 keV, derived with the photon index fixed at $\Gamma_{\rm R}$ , in comparison with the synchrotron radio intensity of 10.30 $\ \pm\ $ 0.12 Jy at 326 MHz, the magnetic and electron energy densities were estimated as $u_{\rm m}$$=$ (3.0 $\ \pm\ $ 0.2 $\ \pm\ $ 0.4) $\times$ 10 $^{-14}\ $ erg cm $^{-3}$ and $u_{\rm e}$$=$ (3.4 $_{-0.2}^{+0.3}$$_{-0.4}^{+0.5}$ ) $\times$ 10 $^{-14}\ $ erg cm $^{-3}$ integrated over the electron Lorentz factor of 10 $^3$ –10 $^5$ , respectively. Thus, the east lobe is found to reside in an equipartition condition between the electrons and magnetic field parametrized as $u_{\rm e}/u_{\rm m}$$=$ 1.1 $_{-0.1}^{+0.2}$$_{-0.2}^{+0.4}$ . The east lobe of DA 240 is indicated to exhibit the lowest value of $u_{\rm e}$ , among all of the X-ray detected lobes of radio galaxies. A comparison of the energetics in the giant radio galaxies with a size of $\sim\ $ 1 Mpc to those in the smaller objects suggests a possibility that radio galaxies lose their jet power as they evolve from $\sim\ $ 100 kpc to $\sim\ $ 1 Mpc.
Suzaku Observations of Iron K-Lines from the Intracluster Medium of the Coma Cluster
Authors: Sato Takuya , Matsushita Kyoko , Ota Naomi , Sato Kosuke , Nakazawa Kazuhiro , Sarazin Craig L.
Published: March 2014

The Coma cluster was observed with the X-ray Imaging Spectrometer (XIS) onboard Suzaku in six pointings, including the central X-ray peak region, 14 $'$ west offset region, 30 $'$ and 34 $'$ north–west offset regions, and 44 $'$ and 60 $'$ south–west offset regions. Owing to its lower background level, Suzaku has better sensitivity to Fe K $\alpha$ lines than other satellites. Using precise Fe line measurements, we studied the temperature structure, possible bulk motions, and iron abundance distributions in the intracluster medium (ICM). The observed spectra were well-represented by a single-temperature model; a two- or three- temperature model did not improve $\chi^2$ substantially. The temperature, derived from K $\alpha$ line ratios of H-like and He-like Fe, agrees with those derived from the single-temperature model. Because the line ratio is a steep function of temperature, the consistency supports the accuracy of temperature measurements conducted with Suzaku. Within the 34 $'$ region, the redshift derived from the central energy of the He-like Fe line is consistent with that from optical observations, within a calibration error of 18 eV or 818 km s $^{-1}$ in the line of sight. This value is smaller than the sound velocity of the ICM, which is 1500 km s $^{-1}$ . The central energy of Fe lines at the 44 $'$ offset region around the NGC 4839 subcluster is also consistent with those within the 34 $'$ region. These results on the temperature and velocity structure suggest that the core of the cluster is in a relaxed state, and non-thermal electrons relevant to the radio halo are accelerated by intracluster turbulence rather than large-scale shocks. The Fe abundance is almost constant at 0.4 solar within the 34 $'$ region, and decreases with radius. This value is slightly lower than those of other clusters, which means that the gas had been mixed well during a past merger associated with the growth of the cluster.
A Spectral Study of the Black Hole Candidate XTE J1752−223 in the High/Soft State with MAXI, Suzaku, and Swift
Authors: Nakahira Satoshi , Koyama Shu , Ueda Yoshihiro , Yamaoka Kazutaka , Sugizaki Mutsumi , Mihara Tatehiro , Matsuoka Masaru , Yoshida Atsumasa , Makishima Kazuo , Ebisawa Ken , Kubota Aya , Yamada Shin'ya , Negoro Hitoshi , Hiroi Kazuo , Ishikawa Masaki , Kawai Nobuyuki , Kimura Masashi , Kitayama Hiroki , Kohama Mitsuhiro , Matsumura Takanori , Morii Mikio , Nakajima Motoki , Serino Motoko , Shidatsu Megumi , Sootome Tetsuya , Sugimori Kousuke , Suwa Fumitoshi , Tomida Hiroshi , Tsuboi Yoko , Tsunemi Hiroshi , Ueno Shiro , Usui Ryuichi , Yamamoto Takayuki , Yamazaki Kyohei , Tashiro Makoto S. , Terada Yukikatsu , Seta Hiromi
Published: March 2014

We report on an X-ray spectral analysis of the black hole candidate XTE J1752$-$223 in the 2009–2010 outburst, utilizing data obtained with the MAXI/Gas Slit Camera (GSC), the Swift/XRT, and Suzaku, which work complementarily. As already reported by Nakahira et al. (2010, PASJ, 62, L27), MAXI monitored the source continuously throughout the entire outburst for about eight months. All of the MAXI/GSC energy spectra in the high/soft state, lasting for 2 months, are well represented by a multi-color disk plus power-law model. The innermost disk temperature changed from $\sim\ $0.7 keV to $\sim\ $0.4 keV and the disk flux decreased by an order of magnitude. Nevertheless, the innermost radius is constant at $\sim\ $41 $D_{3.5}$(cos $i$)$^{-{1}/{2}}\ $km, where $D_{3.5}$ is the source distance in units of 3.5 kpc and $i$ the inclination. The multi-color disk parameters obtained with the MAXI/GSC are consistent with those with the Swift/XRT and Suzaku. The Suzaku data also suggest a possibility that the disk emission is slightly Comptonized, which could account for broad iron-K features reported previously. Assuming that the obtained innermost radius represents the innermost stable circular orbit for a non-rotating black hole, we estimate the mass of the black hole to be 5.51$\ \pm\ $0.28$\ M_{\odot}$$D_{3.5}$(cos $i$)$^{-{1}/{2}}\ $, where the correction for the stress-free inner boundary condition and color hardening factor of 1.7 are taken into account. If the inclination is less than 49$^{\circ}$, as suggested from radio monitoring of transient jets, and the soft-to-hard transition in 2010 April occurred at 1%–4% of Eddignton luminosity, the fitting of the Suzaku spectra with a relativistic accretion-disk model derives constraints on the mass and the distance to be 3.1–55$\ M_{\odot}$ and 2.3–22 kpc, respectively. This confirms that the compact object in XTE J1752$-$223 is a black hole.
Spatial and Temporal Variations of the Diffuse Iron 6.4 keV Line in the Galactic Center Region
Authors: Chernyshov Dmitrii , Dogiel Vladimir , Nobukawa Masayoshi , Tsuru Takeshi Go , Koyama Katsuji , Uchiyama Hideki , Matsumoto Hironori
Published: March 2014

We analyzed the diffuse Fe I K$\alpha$ line generated in the diffuse interstellar molecular hydrogen by primary photons or subrelativistic protons injected by Sagittarius (Sgr) A$^\ast$. We showed that unlike emission from compact molecular clouds, this emission can be permanently observed in the directions of the Galactic center. We conclude that the diffuse emission of the 6.4 keV line observed at present is probably due to Fe I K$\alpha$ vacancy production by primary photons if the X-ray luminosity of Sgr A$^\ast$ was about $L_{\rm X}$$\sim$ 10$^{39}$–10$^{40}\ $erg s$^{-1}$. In principle these data can also be described in the framework of the model when the 6.4 keV line emission is generated by subrelativistic protons generated by accretion onto the central black hole, but in this case extreme parameters of this model are necessary.
Turbulence Effects on Bremsstrahlung Emission in the Turbulent Solar Plasma
Authors: Jung Young-Dae , Kato Daiji
Published: March 2014

Turbulence effects on bremsstrahlung emission due to the electron–ion interaction were investigated in the turbulent solar plasma. The effective interaction potential, taking into account the correction factor to the nonlinear dielectric function due to plasma turbulence, and the impact-parameter method were employed in order to obtain the bremsstrahlung radiation cross section in a turbulent plasma as a function of the impact parameter, diffusion coefficient, radiation photon energy, projectile energy, and plasma parameters. It has been shown that the turbulence effects considerably enhance the bremsstrahlung radiation cross section. In addition, it was found that the turbulence effects of the solar atmosphere on the bremsstrahlung cross section increase with increasing radiation photon energy, but decrease with increasing thermal energy. It can be expected that the Landau damping effect on the bremsstrahlung spectrum from the solar corona is less important than that from the solar chromospheres due to temperature jumps. However, the effect of the plasma turbulence on the bremsstrahlung spectrum from the solar chromosphere would be smaller than that from the solar corona.
Fully Nonadiabatic Analysis of Vibrational Instability of Population III Stars due to the ɛ-Mechanism
Authors: Sonoi Takafumi , Shibahashi Hiromoto
Published: March 2014

A linear nonadiabatic analysis of the vibrational stability of population III main-sequence stars was carried out. It was demonstrated that, in the case of massive stars with $M$$\gtrsim$ 5 $M_\odot$, helium burning (triple alpha reaction) starts during the main-sequence stage and produces $^{12}$C, leading to the activation of a part of the CNO-cycle. It was found that, despite of that, those stars with $M$$\lesssim$ 13 $M_\odot$ become unstable against the dipole g$_1$- and g$_2$-modes due to the $\varepsilon $-mechanism, during the early evolutionary phase at which the pp-chain is still the dominant nuclear energy source. The instability due to the $\varepsilon $-mechanism occurs against g-modes having a large amplitude in the off-centered $^3$He accumulation shell in the deep interior, and the growth time is much shorter than the evolutionary timescale. This instability is therefore likely to induce mixing in the stellar interior, and have a significant influence on the evolution of these stars.