bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular and Atomic Gas toward HESS J1745−303 in the Galactic Center: Further Support for the Hadronic Scenario
Authors: Hayakawa Takahiro , Torii Kazufumi , Enokiya Rei , Amano Takanobu , Fukui Yasuo
Published: March 2014

We compared TeV $\gamma$-rays with new $^{12}$CO $J$$=$ 2–1 data toward HESS J1745$-$303 in the Galactic center, and confirmed that the molecular cloud MG358.9$-$0.5 toward ($l$, $b$) $=$ (358$^\circ\!\!\!.$9, $-$0$^\circ\!\!\!.$5) at $V_\mathrm{LSR}$$=$$-$100–0 km s$^{-1}$ shows a reasonable positional agreement with the primary peak (northern part) of the $\gamma$-ray source. For the southern part of HESS J1745$-$303, we have seen no CO counterpart, whereas H I gas in the SGPS H I dataset shows a possible counterpart to the $\gamma$-ray source. This H I gas may be optically thick, as supported by the H I line shape similar to the optically thick $^{12}$CO. We estimate the total mass of interstellar protons including both the molecular and atomic gas to be 2 $\times$ 10$^{6}M\odot$ and the cosmic-ray proton energy to be 6 $\times$ 10$^{48}\ $erg in the hadronic scenario. We discuss possible origins of the cosmic-ray protons including the nearby SNR G359.1$-$0.5. The SNR may be able to explain the northern $\gamma$-ray source, but the southern source seems to be too far to be energized by the SNR. As an alternative, we argue that the second-order Fermi acceleration in the inter-clump space surrounded by randomly moving high-velocity clumps may offer a possible mechanism to accelerate protons across the entire HESS source. The large turbulent motion with a velocity dispersion of $\sim\ $15 km s$^{-1}$ has an energy density two orders of magnitude higher than in the solar vicinity, and is viable as the energy source.
Distance and Reddening of the Isolated Dwarf Irregular Galaxy NGC 1156
Authors: Kim Sang Chul , Park Hong Soo , Kyeong Jaemann , Lee Joon Hyeop , Ree Chang Hee , Kim Minjin
Published: March 2014

We present a photometric estimation of the distance and reddening values to the dwarf irregular galaxy NGC 1156, that is one of the best targets for the study of isolated dwarf galaxies in the nearby universe. We used imaging data sets of the Hubble Space Telescope (HST) Advanced Camera for Surveys, High Resolution Channel of the central region of NGC 1156 (26$''$  $\times$ 29$''$) available in the HST archive for this study. From the ($U$  $-$  $B$, $B$  $-$  $V$) color–color diagram, we first estimated the total (foreground $+$ internal) reddening toward NGC 1156 of $E$($B$  $-$  $V$) $=$ 0.35$\ \pm\ $0.05 mag, whereas only the foreground reddening was previously known to be $E$($B$  $-$  $V$) $=$ 0.16 mag (1984, ApJS, 54, 33) or 0.24 mag (1998, ApJ, 500, 525). Based on the brightest-star method, selecting the three brightest blue supergiant (BSG) stars with a mean $B$ magnitude of $\langle B$(3$B$)$\rangle$  $=$ 21.94 and the three brightest red supergiant (RSG) stars with a mean $V$ magnitude of $\langle V$(3$R$)$\rangle$  $=$ 22.76, we derived the distance modulus to NGC 1156 to be ($m$  $-$  $M$)$_{0,{\rm BSG}}$  $=$ 29.16 mag and $(m-M)_{0,{\rm RSG}}$  $=$ 29.55 mag. By using weights of 1 for BSGs and 1.5 for RSGs, we finally obtained a weighted mean distance modulus to NGC 1156, $(m-M)_0$  $=$ 29.39$\ \pm\ $0.20 mag (distance $=$ 7.6$\ \pm\ $0.7 Mpc), which is in agreement with previous estimates. Combining the photometry data of this study with those of Karachentsev, Musella, and Grimardi (1996, A&A, 310, 722) gives a smaller distance to NGC 1156, which is discussed together with the limits of the data.
Digital Spectro-Correlator System for the Atacama Compact Array of the Atacama Large Millimeter/Submillimeter Array
Authors: Kamazaki Takeshi , Okumura Sachiko K. , Chikada Yoshihiro , Okuda Takeshi , Kurono Yasutaka , Iguchi Satoru , Mitsuishi Shunji , Murakami Yuji , Nishimuta Naomitsu , Mita Haruo , Sano Ryo
Published: March 2014

We have developed an FX-architecture digital spectro-correlator for the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array. The correlator is able to simultaneously process four pairs of dual polarization signals with a bandwidth of 2 GHz, which are received by up to sixteen antennas. It can calculate auto- and cross-correlation spectra, including cross-polarization in all combinations of all the antennas, and output correlation spectra with flexible spectral configuration, such as multiple frequency ranges and multiple frequency resolutions. Its spectral dynamic range is estimated to be higher than 10$^{4}$ relative to $T_{\rm sys}$ from processing results of thermal noise for eight hours with a typical correlator configuration. The sensitivity loss is also confirmed to be 0.9% with the same configuration. In this paper, we report on the detailed design of the correlator and the verification results of the developed hardware.
A Study on the Correlations between Diffuse Interstellar Bands
Authors: Xiang Fuyuan , Liu Zhou , Yang Xuejuan
Published: March 2014

Correlations between diffuse interstellar band equivalent widths (EWs) were sought, using a database of 45 prominent diffuse interstellar bands (DIBs) and seven $ C_{2}$ bands in 278 sightlines collected from the literature. We found that 11 pairs of DIBs ($ \lambda\ $ 5544/5797 Å, $ \lambda\ $ 5544/6196 Å, $ \lambda\ $ 5544/6614 Å, $ \lambda\ $ 5809/6196 Å, $ \lambda\ $ 5809/6203 Å, $ \lambda\ $ 5809/6270 Å, $ \lambda\ $ 5809/6614 Å, $ \lambda\ $ 6196/6614 Å, $ \lambda\ $ 6196/6699 Å, $ \lambda\ $ 6203/6284 Å, and $ \lambda\ $ 6270/6699 Å) show a strong correlation with high coefficient ($ R$$ \geq$ 0.95), 416 pairs show a good correlation (0.7 $ \leq$$ R$$ \lt$ 0.95) and 358 pairs show a poor correlation ($ R$$ \lt$ 0.7). According to the values of the correlation coefficients and the spectroscopic features, we divided some of the 45 prominent DIBs into two isolated families.
Subaru Constraint on Circular Polarization in I-Band Emission from the Magnetar 4U 0142+61
Authors: Wang Zhongxiang , Tanaka Yasuyuki T. , Zhong Jing
Published: March 2014

We present the first imaging circular polarimetry of the anomalous X-ray pulsar (AXP) 4U 0142$+$61 at optical wavelengths. The AXP is the only magnetar that has been well studied at optical and infrared wavelengths, and is known to have a complicated broad-band spectrum over the wavelength range. The optical polarimetric observation was carried out with the 8.2-m Subaru telescope at the $I$-band. From the observation, the degree of circular polarization, $V$, was measured to be $V$  $=$ 1.1$ \pm $2.0%, or $\vert V\vert$  $\leq$ 4.3% (90% confidence). The relatively large uncertainty was due to the faintness of the source ($I$  $=$ 23.4–24.0). Considering the currently suggested models for optical emission from magnetars, our result is not sufficiently conclusive to discriminate the models. We suggest that because linear polarization is expected to be strong in the models, linear polarimetry of this magnetar should be conducted.
The Active Contact Binary FU Draconis: Four Color Light Curves and Period Changes
Authors: Liang Liu , Sheng-Bang Qian , Jia-Jia He , Wen-Ping Liao , Li-Ying Zhu , Ergang Zhao
Published: March 2014

Secured four color light curves of FU Dra were analyzed with the 2003 version of the Wilson and Devinney (WD) code. It was shown that FU Dra is still a W-type contact binary system, but might have a high fill-out factor ($f$$=$ 26.7% $\pm$ 1.0%). A dark spot was introduced on the massive cool component. A period investigation based on all available data shows that the period of the system may include a long-term increase ($dP/dt$$=$ 8.8 $\pm$ 2.9 $\times$ 10$^{-8}$ d yr$^{-1}$) and an oscillation (semi-amplitude of 0.0024 d, $P_3$$=$ 7.8 yr). The long-term period decrease may be caused by mass transfer, though the periodic oscillation may be rooted in cyclic magnetic activity.
Peculiar Black-Hole Unipolar Induction
Authors: Okamoto Isao
Published: March 2014

It is argued that a posteriori without conflicting with the dubbed no-hair theorem, a Kerr black hole acquires its own proper magnetosphere in the steady eigen-state. The angular frequency of field lines, $ {\Omega_{\rm F}}$ , given as the eigenvalue in terms of the hole’s angular frequency, $ {\Omega_{\rm H}}$ , couples with the frame-dragging angular frequency, $ \omega$ , to create an inner general-relativistic domain of $ {\Omega_{\rm H}} \gt \omega$  $ \gt {\Omega_{\rm F}}$ , in which the gradient of the electric potential is, when viewed by the fiducial observers (FIDOs), reversed in direction from that in the outer quasi-classical domain of $ {\Omega_{\rm F}} \gt \omega$  $ \gt$ 0. The field lines are pinned down in the plasma source at the interface between the two domains (upper null surface S$ _{\rm N}$ ), from which pair-particles well up, charge-separated into the ingoing and outgoing winds. The EMFs due to unipolar induction operate to drive the surface currents, following Ohm’s law, on the resistive membranes terminating the force-free domains (say, S$ _{\rm ffH}$ and S$ _{{\rm ff}\infty}$ ), to exert the surface torques onto the respective membranes, thereby extracting angular momentum from the hole and transferring to the domain of astrophysical loads.
A Suzaku Study of Ejecta Structure and Origin of Hard X-Ray Emission in the Supernova Remnant G 156.2+5.7
Authors: Uchida Hiroyuki , Tsunemi Hiroshi , Katsuda Satoru , Mori Koji , Petre Robert , Yamaguchi Hiroya
Published: March 2014

We report on an X-ray study of the evolved Galactic supernova remnant (SNR) G 156.2$+$5.7 based on six pointing observations with Suzaku. The remnant’s large extent (100$'$ in diameter) allows us to investigate its radial structure in the northwestern and eastern directions from the apparent center. The X-ray spectra were well fit with a two-component non-equilibrium ionization model representing the swept-up interstellar medium (ISM) and the metal-rich ejecta. We found prominent central concentrations of Si, S, and Fe from the ejecta component; the lighter elements of O, Ne, and Mg were distributed more uniformly. The temperature of the ISM component suggests a slow shock ($\sim $610–960 km s$^{-1}$); hence, the remnant’s age is estimated to be $\sim $7000–15000 yr, assuming its distance to be $\sim $1.1 kpc. G 156.2$+$5.7 has also been thought to emit hard, non-thermal X-rays, despite being considerably older than any other such remnant. In response to a recent discovery of a background cluster of galaxies (2XMM J045637.2$+$522411), we carefully excluded its contribution, and reexamined the origin of the hard X-ray emission. We found that the residual hard X-ray emission is consistent with the expected level of the cosmic X-ray background. Thus, no robust evidence for non-thermal emission was obtained from G 156.2$+$5.7. These results are consistent with the picture of an evolved SNR.
Characterization of Dwarf Novae Using SDSS Colors
Authors: Kato Taichi , Maehara Hiroyuki , Uemura Makoto
Published: March 2014

We have developed a method for estimating the orbital periods of dwarf novae from the Sloan Digital Sky Survey (SDSS) colors in quiescence using an artificial neural network. For typical objects below the period gap with sufficient photometric accuracy, we were able to estimate the orbital periods with accuracy to a 1 $\sigma$ error of 22%. The error of the estimation is worse for systems with longer orbital periods. We have also developed a neural-network-based method for categorical classification. This method has proven to be efficient in classifying objects into three categories (WZ Sge type, SU UMa type, and SS Cyg/Z Cam type), and works for very faint objects to a limit of g$=$ 21 mag. Using this method, we have investigated the distribution of the orbital periods of dwarf novae from a modern transient survey (Catalina Real-Time Survey). Using a Bayesian analysis developed by Uemura et al. (2010, PASJ, 62, 613), we have found that the present sample tends to give a flatter distribution to the shortest period and a shorter estimate of the period minimum, which may have resulted from uncertainties in the neural-network analysis and photometric errors. We also provide estimated orbital periods, estimated classifications, and supplemental information on known dwarf novae with the quiescent SDSS photometry.
Grand Rotation Curve and Dark-Matter Halo in the Milky Way Galaxy
Authors: Sofue Yoshiaki
Published: March 2014

A grand rotation curve of the Milky Way Galaxy was constructed, which covers a wide range of radius from the Galactic Center to $ \sim$ 1 Mpc, and was deconvolved into bulge, disk, and halo components by least-squares fittings. We determined the masses and scale radii of the bulge and disk to be $ {M_{\rm b}}$$ =$ (1.652 $ \pm$ 0.083) $ \times$ 10$ ^{10}{\ M_\odot}$ , $ {a_{\rm b}}$$ =$ 0.522 $ \pm$ 0.037 kpc, $ {M_{\rm d}}$$ =$ (3.41 $ \pm$ 0.41) $ \times$ 10$ ^{10}{\ M_\odot}$ , and $ {a_{\rm d}}$$ =$ 3.19 $ \pm$ 0.35 kpc. The dark halo was fitted by the Navaro–Frenk–White (NFW) density profile, $ \rho$$ =$$ \rho_0/$ [($ R/h$ )(1 $ +$$ R/h$ )$ ^2$ ], and the fit yielded $ h$$ =$ 12.5 $ \pm$ 0.9 kpc and $ \rho_0$$ =$ (1.06 $ \pm$ 0.14) $ \times$ 10$ ^{-2}\ M_{\odot}$ pc$ ^{-3}$ . The local dark-matter density near the Sun at $ R_0$$ =$ 8 kpc was estimated to be $ \rho_0^\odot$$ =$ (6.12 $ \pm$ 0.80) $ \times$ 10$ ^{-3}\ M_{\odot}$ pc$ ^{-3}$$ =$ 0.235 $ \pm$ 0.030 GeV cm$ ^{-3}$ . The total mass inside the gravitational boundary of the Galaxy at $ R$$ \sim$ 385 kpc, a half distance to M 31, was estimated to be $ {M_{\rm b+d+h}}$$ =$ (7.03 $ \pm$ 1.01) $ \times$ 10$ ^{11}\ M_{\odot}$ . This leads to a stellar baryon fraction of $ {M_{\rm b+d}}/{M_{\rm b+d+h}}$$ =$ 0.072 $ \pm$ 0.018. Considering the expected baryon fraction in the Local Group, we suggest that baryons in the form of hot gas are filling the dark halo with a temperature of $ \sim$ 10$ ^{6}$ K and an emission measure of $ \sim$ 10$ ^{-5}$ pc cm$ ^{2}$ . Such hot halo gas may share a small fraction of the observed X-ray background emission.
Image Slicer for the Subaru Telescope High Dispersion Spectrograph
Authors: Tajitsu Akito , Aoki Wako , Yamamuro Tomoyasu
Published: March 2014

We report on the design, manufacturing, and performance of the image slicer for the High Dispersion Spectrograph on Subaru Telescope. This instrument is a Bowen–Walraven type image slicer, providing five images of 0$.\!\!\!”$3 $\times$ 1$.\!\!\!”$5 with a resolving power of $R$$=$$\lambda/\delta \lambda$$=$ 110000. The resulting resolving power and line profiles have been investigated in detail, including estimates of the defocusing effect on the resolving power. The throughput in a wavelength range of from 400 to 700 nm is higher than 80%, thereby improving the efficiency of the spectrograph under a seeing condition of 0$.\!\!\!”$7 by a factor of 1.8.
New Photometric Investigation of the G-Type Contact Binary GSC 0763-0572
Authors: Jing-Jing Wang , Sheng-Bang Qian , Er-Gang Zhao , Li-Ying Zhu , Wen-Ping Liao , Kai Li , Jia Zhang , Liang Liu , Lin-Jia Li
Published: March 2014

We present new CCD photometric light curves of the W UMa-type binary system GSC 0763-0572 in the $ V$ , $ R$ , and $ I$ bands. Here, the light curves in the $ R$ and $ I$ bands are the first to be obtained. The primary component of this system belongs to a G-type solar-like star; our new observation indicates that the activities of GSC 0763-0572 may be stable. Based on all available times of the light minimum, we found that the orbital period is variable. The $ O$$-$$ C$ curve suggested that the period of GSC 0763-0572 is undergoing a continuous increase at a rate of $ dP/dt$$ =$$ +$ 5.81(33) $ \times$ 10$ ^{-7}$ d yr$ ^{-1}$ . Photometric solutions were derived by using the Wilson–Devinney code. We confirmed that this system is A-subtype overcontact binary with a degree of contact factor of $ f$$ =$ 31.0% ($ \pm$ 1.5%), a mass ratio of $ q$$ =$ 0.2330, and a temperature difference of $ \Delta{T}$$ =$ 31 K. The long-term increase of the orbital period can be explained by mass transfer from the less-massive component to the more-massive one. It's inferred that GSC 0763-0572 may presently be in an expanding state of thermal relaxation oscillation, and may finally evolve into a rapid-rotating single star.
Detection of Methyl Formate in the Second Torsionally Excited State (υt = 2) in Orion KL
Authors: Takano Shuro , Sakai Yusuke , Kakimoto Suguru , Sasaki Mutsumi , Kobayashi Kaori
Published: March 2014

We report on the detection of rotational transitions of methyl formate (HCOOCH$ _{3}$ ) in the second torsionally excited state ($ v_{\rm t}$$ =$ 2) of the methyl internal rotation in Orion Kleinmann–Low (KL). Recent progress in the microwave spectroscopy of methyl formate in laboratories and sensitive radioastronomical observations have made it possible to assign $ \sim$ 20 emission lines to methyl formate in the $ v_{\rm t}$$ =$ 2 state. The beam-averaged column density obtained with the Nobeyama 45 m radiotelescope is (3.0 $ \pm$ 1.5) $ \times$ 10$ ^{14}$ cm$ ^{-2}$ in this state. In addition to this state, we also observed lines in the ground and the first torsionally excited states ($ v_{\rm t}$$ =$ 0 and 1) in Orion KL. The obtained rotational temperatures for the $ v_{\rm t}$$ =$ 0 and 1 states are 43 $ \pm$ 9 and 53 $ \pm$ 8 K, respectively. The column densities for the $ v_{\rm t}$$ =$ 0 and 1 states are (3.8 $ \pm$ 1.2) $ \times$ 10$ ^{15}$ and (9.8 $ \pm$ 2.3) $ \times$ 10$ ^{14}$ cm$ ^{-2}$ , respectively, which are 13 and 3 times the column density in the $ v_{\rm t}$$ =$ 2 state. Data of these three states can be explained by a single vibrational temperature of 124 $ \pm$ 5 K, which is significantly higher than the rotational temperatures. As excitation mechanisms, there are two possibilities: collision with H$ _2$ and pumping by far-infrared radiation from star-formation activities. Considering the temperature difference and Einstein's $ A$ coefficients of the torsional states, we cannot rule out either of these possibilities. This detection further indicates that many more unidentified lines in Orion KL will be due to low-lying excited states of methyl formate and other organic molecules.
Erratum: 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

In the paper [PASJ 63, S1019 (2012)], there was an error in the estimation of gas mass. The correct gas mass at the virial radius is 2.40$\ \pm\ $0.20 $\times$ 10$^{14}\ M_{\bigodot}$. Thus, the gas mass fraction also changes from 14.4$^{+7.1}_{-4.1}$% to 21.8$^{+10.7}_{-6.3}$%. Although this value is still consistent with the weak-lensing result of $\sim\ $18% (Okabe & Umetsu 2008, PASJ, 60, 345), our result allows possibilities for the low electron temperature compared with that of ions, gas clumpiness in the cluster outskirts as reported in the Perseus cluster (Simionescu et al. 2011, Science, 331, 1576) and non-thermal pressure such as turbulence and bulk motions in ICM (Kawaharada et al. 2010, ApJ, 714, 423). The conclusions in the paper are not affected by this change.
Initial Results from Nobeyama Molecular Gas Observations of Distant Bright Galaxies
Authors: Iono Daisuke , Hatsukade Bunyo , Kohno Kotaro , Kawabe Ryohei , Ikarashi Soh , Ichikawa Kohei , Kodama Tadayuki , Motohara Kentaro , Nakajima Taku , Nakanishi Koichiro , Ohta Kouji , Ota Kazuaki , Saito Toshiki , Suzuki Kenta , Tadaki Ken-ichi , Tamura Yoichi , Ueda Junko , Umehata Hideki , Yabe Kiyoto , Yoshida Tessei , Yuma Suraphong , Kuno Nario , Takano Shuro , Iwashita Hiroyuki , Handa Kazuyuki , Higuchi Aya , Hirota Akihiko , Ishikawa Shinichi , Kimura Kimihiro , Maekawa Jun , Mikoshiba Hiroshi , Miyazawa Chieko , Miyazawa Kazuhiko , Muraoka Kazuyuki , Ogawa Hideo , Onodera Sachiko , Saito Yasufumi , Sakai Takeshi , Takahashi Shigeru , Yun Min S.
Published: March 2014

We present initial results from the CO survey toward high-redshift galaxies using the Nobeyama 45 m telescope. Using a new wide bandwidth spectrometer equipped with a two-beam SIS receiver, we have obtained three new detections of high-redshift (z$=$ 1.6–3.4) submillimeter galaxies (SXDF 1100.001/HXMM02, SDP9, and SDP17), one tentative detection (SDSS J160705$+$533558), and one non-detection (COSMOS-AzTEC1). The galaxies observed during the commissioning phase are sources with known spectroscopic redshifts from previous optical or wide-band submillimeter spectroscopy. The derived molecular gas mass and line widths from Gaussian fits are $\sim$ 10$^{11}\ M_{\odot}$ and 430–530 km s$^{-1}$, respectively, which are consistent with previous CO observations of distant submillimeter galaxies and quasars. The spectrometer, which realizes a maximum of 32 GHz instantaneous bandwidth, will provide new science capabilities at the Nobeyama 45 m telescope, allowing us to determine redshifts of bright submillimeter selected galaxies without any prior redshift information.
Imaging Simulations of the Sunyaev–Zel'dovich Effect for ALMA
Authors: Yamada Kenkichi , Kitayama Tetsu , Takakuwa Shigehisa , Iono Daisuke , Tsutsumi Takahiro , Kohno Kotaro , Takizawa Motokazu , Yoshikawa Kohji , Akahori Takuya , Komatsu Eiichiro , Suto Yasushi , Matsuo Hiroshi , Kawabe Ryohei
Published: March 2014

We present imaging simulations of the Sunyaev–Zel'dovich effect of galaxy clusters for the Atacama Large Millimeter/submillimeter Array (ALMA), including the Atacama Compact Array (ACA). In its most compact configuration at 90 GHz, ALMA will resolve the intracluster medium with an effective angular resolution of 5$ ''$ . It will provide a unique probe of shock fronts and relativistic electrons produced during cluster mergers at high redshifts, that are hard to spatially resolve by current and near-future X-ray detectors. The quality of image reconstruction is poor with the 12 m array alone, but improved significantly by adding ACA; the expected sensitivity of the 12 m array based on the thermal noise is not valid for the Sunyaev–Zel'dovich effect mapping unless accompanied by an ACA observation of at least equal duration. The observations above 100 GHz will become excessively time-consuming owing to the narrower beam size and the higher system temperature. On the other hand, significant improvement of the observing efficiency is expected once Band 1 is implemented in the future.
Radiative Transfer in Accretion Disks Under Irradiation of the Central Star
Authors: Fukue Jun
Published: March 2014

Radiative transfer in a geometrically thin accretion disk, which is irradiated by a central star, is examined under a non-gray frequency-dependent treatment. The emergent intensity as well as other radiative quantities were analytically obtained under the Eddington approximation. In the case where the irradiation heating dominates the viscous one, the emergent spectra generally have two components. One is a multi-color blackbody part, which is reprocessed light of the irradiation flux, with a lower peak-frequency than that of the central star. The other is a single blackbody part, which is scattered light, with the same peak-frequency as that of the central star. When the vertical optical depth of the disk is small, the emergent intensity decreases in the poleward direction, but increases in the edgeward direction (limb-brightning), due to a scattering effect of the irradiated light. The overall spectra were calculated for a passive disk around a white dwarf and a neutron star. They exhibit multi-color blackbody spectra modified by the scattering light in the high-frequency region.
Outer Rotation Curve of the Galaxy with VERA I: Trigonometric Parallax of IRAS 05168+3634
Authors: Sakai Nobuyuki , Honma Mareki , Nakanishi Hiroyuki , Sakanoue Hirofumi , Kurayama Tomoharu , Shibata Katsunori M. , Shizugami Makoto
Published: March 2014

We report on a measurement of the trigonometric parallax of IRAS 05168$ +$ 3634 with VERA. The parallax is 0.532 $ \pm$ 0.053 mas, corresponding to a distance of 1.88$ ^{+0.21}_{-0.17}$ kpc. This result is significantly smaller than the previous distance estimate of 6 kpc, based on the kinematic distance. This drastic change in the source distance revises not only the physical parameters of IRAS 05168$ +$ 3634, but also its location of the source, placing it in the Perseus arm, rather than the Outer arm. We also measured the proper motions of the source. A combination of the distance and the proper motions with the systemic velocity yields a rotation velocity ($ \Theta$ ) of 227$ ^{+\ 9}_{-11}$ km s$ ^{-1}$ at the source, assuming $ \Theta_{\rm {0}}$$ =$ 240 km s$ ^{-1}$ . Our result combined with previous VLBI results for six sources in the Perseus arm indicates that the sources rotate systematically slower than the Galactic rotation velocity at the LSR. In fact, we show observed disk peculiar motions averaged over the seven sources in the Perseus arm as ($ U_{\rm {mean}}$ , $ V_{\rm {mean}}$ ) $ =$ (11 $ \pm$ 3, $-$ 17 $ \pm$ 3) km s$ ^{-1}$ , indicating that these seven sources are systematically moving toward the Galactic center, and lag behind the Galactic rotation.
Suzaku Observations of Unidentified X-Ray Sources toward the Galactic Bulge
Authors: Mori Hideyuki , Maeda Yoshitomo , Ueda Yoshihiro , Dotani Tadayasu , Ishida Manabu
Published: March 2014

We present Suzaku observations of two unidentified sources towards the Galactic bulge, 1RXS J165256.3$-$264503 and 1RXS J174459.5$-$172640, both of which were discovered with the ROSAT All-Sky Survey. We obtained wide-band spectra of these sources above 2 keV for the first time. The X-ray spectrum of 1RXS J165256.3$-$264503 consists of two absorbed thin thermal plasma components with temperatures of 0.7 and 2.4 keV. An RS CVn star, HD 152178, was found within a 90% error circle of the source position. Due to this position coincidence, and an X-ray spectrum analogous to those of other RS CVn binaries, we concluded that 1RXS J165256.3$-$264503 is an RS CVn-type active binary. The X-ray spectrum of 1RXS J174459.5$-$172640 was dominated by continuum emission extending up to $\sim$ 20 keV, which can be explained by an absorbed cutoff power-law or a combination of absorbed multicolor disk-blackbody and Comptonized emission. We inferred that the source is a new Galactic-bulge low-mass X-ray binary (LMXB) with a luminosity of 2 $\times$ 10$^{35}$ erg s$^{-1}$, based on its X-ray spectrum and lightcurve. Hence, 1RXS J174459.5$-$172640 may be an intriguing example of an LMXB in an intermediate state in which X-ray emission mechanisms can be readily explored.
Suzaku Observations of Abell 1555 and Abell 1558: Searching for Non-Thermal Emission from Large-Scale Structure Formation
Authors: Makiya Ryu , Totani Tomonori , Nakazawa Kazuhiro
Published: March 2014

We report on X-ray observations of two galaxy clusters, Abell 1555 and Abell 1558, with Suzaku, which are included in a large-scale filamentary structure and a supercluster, to search for non-thermal emission driven by shocks produced during structure formation. These two clusters were detected by Suzaku/XIS for the first time in the X-ray band of 0.5–7 keV. No significant flux has been detected by HXD in the energy band of 13–40 keV, and upper limits are reported. From an analysis of the XIS data, we found that the spectrum of A 1555 could be fit by a thermal plus power-law model, significantly better than a single-temperature pure thermal spectrum. If this power-law component is due to inverse-Compton scattering, the fraction of the total baryon energy imparted to non-thermal electrons is consistent with the typical value inferred from observations of other clusters. However, other scenarios (e.g., underlying AGNs, multi-temperature thermal models) cannot be excluded, and further investigation of this system is desired. Basic physical properties of A 1555 (e.g., total mass) are also reported.
Environmental Dependence of Stellar Mass, Star Formation Rate, Specific Star Formation Rate, and AGN Activity for an Apparent Magnitude Limited Main Galaxy Sample of the SDSS DR7
Authors: Deng Xin-Fa , Wu Ping , Qian Xiao-Xia , Luo Cheng-Hong
Published: March 2014

In this study, we used an apparent magnitude limited Main galaxy sample of the Sloan Digital Sky Survey Data Release 7 (SDSS DR7), and investigated the environmental dependence of stellar mass, the star formation rate (SFR), the specific star formation rate (SSFR, the star formation rate per unit stellar mass) and active galactic nucleus (AGN) activity. To decrease the Malmquist bias, we divided the whole apparent magnitude limited Main galaxy sample into many subsamples with a redshift binning size of $ \Delta{z}$$ =$ 0.01, and analysed the environmental dependence of these properties of subsamples in each redshift bin. It turns out that a strong environmental dependence of the stellar mass, SFR and SSFR could be observed in nearly all redshift bins of the apparent magnitude limited Main galaxy sample, and that in most redshift bins (except for a low redshift region of $ z$$ =$ 0.02 to 0.06), the fraction of AGNs in the sample at low density apparently was larger than that in the sample at high density.
Suzaku Observations of the Hydra A Cluster out to the Virial Radius
Authors: Sato Takuya , Sasaki Toru , Matsushita Kyoko , Sakuma Eri , Sato Kosuke , Fujita Yutaka , Okabe Nobuhiro , Fukazawa Yasushi , Ichikawa Kazuya , Kawaharada Madoka , Nakazawa Kazuhiro , Ohashi Takaya , Ota Naomi , Takizawa Motokazu , Tamura Takayuki
Published: March 2014

We report on Suzaku observations of the northern half of the Hydra A cluster out to $ \sim$ 1.4 Mpc, reaching the virial radius. There are the first Suzaku observations of a medium-size ($ kT$$ \sim$ 3 keV) cluster out to the virial radius. Two observations were conducted, north-west and north-east offsets, which continue in a filament direction and a void direction of the large-scale structure of the Universe, respectively. The X-ray emission and distribution of galaxies elongate in the filament direction. The temperature profiles in the two directions are mostly consistent with each other within the error bars, and drop to 1.5 keV at 1.5 $ r_{500}$ . As observed by Suzaku in hot clusters, the entropy profile becomes flatter beyond $ r_{500}$ , in disagreement with the $ r^{1.1}$ relationship, which is expected from accretion shock heating models. When scaled with the average intracluster medium (ICM) temperature, the entropy profiles of clusters observed with Suzaku are universal, and do not depend on the system mass. The hydrostatic mass values in the void and filament directions are in good agreement, and the Navarro, Frenk, and White universal mass profile represents the hydrostatic mass distribution up to $ \sim$ 2$ r_{500}$ . Beyond $ r_{500}$ , the ratio of the gas mass to the hydrostatic mass exceeds the result of the Wilkinson microwave anisotropy probe, and at $ r_{100}$ , these ratios in the filament and void directions reach 0.4 and 0.3, respectively. We discuss possible deviations from the hydrostatic equilibrium at cluster outskirts. We derived radial profiles of the gas-mass-to-light ratio and the iron-mass-to-light ratio out to the virial radius. Within $ r_{500}$ , the iron-mass-to-light ratio of the Hydra A cluster was compared with those in other clusters observed with Suzaku.
Period Analysis using the Least Absolute Shrinkage and Selection Operator (Lasso)
Authors: Kato Taichi , Uemura Makoto
Published: March 2014

We introduced least absolute shrinkage and selection operator (Lasso) in obtaining periodic signals in unevenly spaced time-series data. A very simple formulation with the combination of a large set of sine and cosine functions has been shown to yield a very robust estimate; also, the peaks in the resultant power spectra were very sharp. We studied the response of Lasso to low signal-to-noise data, asymmetric signals and very closely separated multiple signals. When the length of the observation was sufficiently long, all of them were not serious obstacles to Lasso. We analyzed the 100-year visual observations of $ \delta $ Cep, and obtained a very accurate period of 5.366326(16) d. The error in the period estimation was several times smaller than in the phase dispersion minimization. We also modeled the historical data of R Sct, and obtained a reasonable fit to the data. The model, however, lost its predictive ability after the end of the interval used for modeling, which is probably a result of the chaotic nature of the pulsations of this star. We also provided a sample R code for making this analysis.
High-Resolution Near-Infrared Polarimetry of a Circumstellar Disk around UX Tau A
Authors: Tanii Ryoko , Itoh Yoichi , Kudo Tomoyuki , Hioki Tomonori , Oasa Yumiko , Gupta Ranjan , Sen Asoke K. , Wisniewski John P. , Muto Takayuki , Grady Carol A. , Hashimoto Jun , Fukagawa Misato , Mayama Satoshi , Hornbeck Jeremy , Sitko Michael L. , Russell Ray W. , Werren Chelsea , CurÉ Michel , Currie Thayne , Ohashi Nagayoshi , Okamoto Yoshiko , Momose Munetake , Honda Mitsuhiko , Inutsuka Shu-ichi , Takeuchi Taku , Dong Ruobing , Abe Lyu , Brandner Wolfgang , Brandt Timothy D. , Carson Joseph , Egner Sebastian E. , Feldt Markus , Fukue Tsubasa , Goto Miwa , Guyon Olivier , Hayano Yutaka , Hayashi Masahiko , Hayashi Saeko S. , Henning Thomas , Hodapp Klaus W. , Ishii Miki , Iye Masanori , Janson Markus , Kandori Ryo , Knapp Gillian R. , Kusakabe Nobuhiko , Kuzuhara Masayuki , Matsuo Taro , Mcelwain Michael W. , Miyama Shoken , Morino Jun-ichi , Moro-MartÍn Amaya , Nishimura Tetsuro , Pyo Tae-Soo , Serabyn Eugene , Suto Hiroshi , Suzuki Ryuji , Takami Michihiro , Takato Naruhisa , Terada Hiroshi , Thalmann Christian , Tomono Daigo , Turner Edwin L. , Watanabe Makoto , Yamada Toru , Takami Hideki , Usuda Tomonori , Tamura Motohide
Published: March 2014

We present $ H$-band polarimetric imagery of UX Tau A taken with HiCIAO/AO188 on the Subaru Telescope. UX Tau A has been classified as a pre-transitional disk object, with a gap structure separating its inner and outer disks. Our imagery taken with the 0$ \rlap{\hskip1pt .}''$ 15 (21 AU) radius coronagraphic mask has revealed a strongly polarized circumstellar disk surrounding UX Tau A, which extends to 120 AU, at a spatial resolution of 0$ \rlap{\hskip1pt .}''$ 1 (14 AU). It is inclined by 46$ ^{\circ}$$ \pm$ 2$ ^{\circ}$ , since the west side is nearest. Although SED modeling and sub-millimeter imagery have suggested the presence of a gap in the disk, with the inner edge of the outer disk estimated to be located at 25–30 AU, we detect no evidence of a gap at the limit of our inner working angle (23 AU) at the near-infrared wavelength. We attribute the observed strong polarization (up to 66%) to light scattering by dust grains in the disk. However, neither polarization models of the circumstellar disk based on Rayleigh-scattering nor Mie-scattering approximations were consistent with the observed azimuthal profile of the polarization degrees of the disk. Instead, a geometric optics model of the disk with nonspherical grains with radii of 30 $ \mu$ m is consistent with the observed profile. We suggest that the dust grains have experienced frequent collisional coagulations, and have grown in the circumstellar disk of UX Tau A.
V369 Gem: A New Ellipsoidal Variable System with High-level Chromospheric Activity
Authors: Dal Hasan Ali , Sipahi Esin , ÖZdarcan Orkun
Published: March 2014

In this study, we present BVR photometry of V369 Gem in 2006–2008. We combined our $ V$ data with the data taken from the literature. We analysed all of the data together, and calculated new light elements. General features of the light curves were discussed. The light curves were modelled with the Fourier method, and the Fourier coefficients were calculated. The cos (2$ \theta$ ) term was found to be dominant. The pre-whitened $ V$ light curves demonstrated that stellar spot activity also exists. There are generally two minima in the pre-whitened light curves. Thus, there must be two spotted areas, which are separated by about 180$ ^{\circ}$ from each other. As conclusions, we have remarked for the first time that V369 Gem is an ellipsoidal variable with high-level chromospheric activity.
Slow-Scan Observations with the Infrared Camera (IRC) aboard AKARI
Authors: Takita Satoshi , Ikeda Norio , Kitamura Yoshimi , Ishihara Daisuke , Kataza Hirokazu , Kawamura Akiko , Oyabu Shinki , Ueno Munetaka , Yamamura Issei
Published: March 2014

We present the characterization and calibration of the slow-scan observation mode of the Infrared Camera (IRC) aboard AKARI. The IRC Slow-scan observations were operated at the S9W (9 $ \mu$ m) and L18W (18 $ \mu$ m) bands. We developed a toolkit for data reduction of the IRC Slow-scan observations. We introduced a ``self-pointing reconstruction'' method to improve the positional accuracy to as good as 1$ ''$ . The sizes of the point spread functions were derived to be $ \sim$ 6$ ''$ at the S9W band and $ \sim$ 7$ ''$ at the L18W bands in full width at half maximum. Flux calibrations were achieved with observations of 3 and 4 infrared standard stars at the S9W and L18W bands, respectively. The flux uncertainties are estimated to be better than 20% from comparisons with the AKARI IRC PSC and the WISE preliminary catalog.
Spatial Variation of PAH Ionization in the Orion Nebula
Authors: Haraguchi Kentaro , Nagayama Takahiro , Kurita Mikio , Kino Masaru , Sato Shuji
Published: March 2014

We have carried out near-infrared imaging observations of the Orion Nebula with Wide Field Cryogenic Telescope-II. The observations covered a 1$^{\circ}$$\times$ 1$^{\circ}$ area with a resolution of 12$''$ through two narrow-band filters at 3.3 $\mu $ m, tuned to the C–H band and 3.7 $\mu $ m off-the-band emissions of PAHs. We detected diffuse emissions extending larger than 10$'$ from the Trapezium cluster in both filters. We extracted the fluxes of the 3.3 $\mu $ m band emission (${F}_{\rm band}$ ) and of the 3.7 $\mu $ m continuum emission (${F}_{\rm cont}$ ) from the 3.3 $\mu $ m and 3.7 $\mu $ m filter data, respectively. The ${F}_{\rm band}$ and ${F}_{\rm cont}$ maps have similar extension over a 10$'$$\times$ 10$'$ area centered on the Trapezium cluster. Although an overall morphological resemblance can be seen between the ${F}_{\rm band}$ and ${F}_{\rm cont}$ maps, the ratio ${F}_{\rm band}/{F}_{\rm cont}$ varies from region to region in the area. The variation of ${F}_{\rm band}/{F}_{\rm cont}$ is attributed to differences of the PAH ionization degree. Adopting emissivities of neutral and ionized PAHs, we calculated the PAH ionization degrees, and constructed a PAH ionization map in the Orion Nebula. The ionization degree varies significantly from region to region in the Orion Nebula, being $\sim$ 50% at the photo-dissociation regions of the Orion Bar, and less ionized at both sides. This partial ionization revealed based on near-infrared observations is consistent with the ionization states estimated from recent mid-infrared observations.
Detection of Low-Level Activities in Solar-Analog Stars from Emission Strengths of the Ca II 3934 Line
Authors: Takeda Yoichi , Tajitsu Akito , Honda Satoshi , Kawanomoto Satoshi , Ando Hiroyasu , Sakurai Takashi
Published: March 2014

Activity studies of solar-type stars, especially with reference to the status of our current Sun among them, have exposed the importance of (1) homogeneously selecting the sample stars and (2) reliably evaluating their activities down to a considerably low level. Motivated by these requirements, we conducted an extensive study on the activities of 118 solar-analog stars (of sufficiently similar properties to each other) by measuring the emission strength at the core of Ca II 3933.663 line (K line) on the high-dispersion spectrogram obtained by Subaru/HDS, where special attention was paid to correctly detecting the chromospheric emission by removing the wing-fitted photospheric profile calculated from the classical solar model atmosphere. This enabled us to detect low-level activities down to log $R'$$\sim$$-$ 5.4 ($R'$ is the ratio of the chromospheric core emission flux to the total bolometric flux), by which we could detect subtle activity differences that were indiscernible in previous studies. Regarding the Sun, we found log $R'_{\odot}$$=$$-$ 5.33 near to the low end of the distribution, which means that it belongs to the distinctly low-activity group among solar analogs. This excludes the once-suggested possibility for the high frequency of Maunder-minimum stars showing appreciably lower activities than the minimum-Sun.
NRO M 33 All-Disk Survey of Giant Molecular Clouds (NRO MAGiC). II Dense Gas Formation
Authors: Onodera Sachiko , Kuno Nario , Tosaki Tomoka , Muraoka Kazuyuki , Miura Rie E. , Kohno Kotaro , Nakanishi Kouichiro , Sawada Tsuyoshi , Komugi Shinya , Kaneko Hiroyuki , Hirota Akihiko , Kawabe Ryohei
Published: March 2014

We report the results of our observations of the $ ^{12}$ CO (J$ =$ 1–0) and $ ^{12}$ CO (J$ =$ 3–2) line emission of 74 major giant molecular clouds (GMCs) within the galactocentric distance of 5.1 kpc in the Local Group galaxy M 33. The observations have been conducted as part of the Nobeyama Radio Observatory M 33 All-disk survey of Giant Molecular Clouds project (NRO MAGiC). The spatial resolutions are 80 pc for $ ^{12}$ CO (J$ =$ 1–0) and 100 pc for $ ^{12}$ CO (J$ =$ 3–2). We detect $ ^{12}$ CO (J$ =$ 3–2) emission of 65 GMCs successfully. Furthermore, we find that the correlation between the surface density of the star formation rate, which is derived from a linear combination of H$ \alpha$ and 24 $ \mu$ m emissions, and the $ ^{12}$ CO (J$ =$ 3–2) integrated intensity still holds at this scale. This result shows that the star-forming activity is closely associated with warm and dense gases that are traced with the $ ^{12}$ CO (J$ =$ 3–2) line, even in the scale of GMCs. We also find that the GMCs with a high star-forming activity tend to show a high integrated intensity ratio ($ R_{3-2/1-0}$ ). Moreover, we also observe a mass-dependent trend of $ R_{3-2/1-0}$ for the GMCs with a low star-forming activity. From these results, we speculate that the $ R_{3-2/1-0}$ values of the GMCs with a low star-forming activity mainly depend on the dense gas fraction and not on the temperature, and therefore, the dense gas fraction increases with the mass of GMCs, at least in the GMCs with a low star-forming activity.
Asymmetric Dust Jets and Extended Structure of 22P/Kopff Observed During 2009 Appearance
Authors: Hanayama Hidekazu , Ishiguro Masateru , Watanabe Jun-Ichi , Sarugaku Yuki , Fukushima Hideo , Miyaji Takeshi , Yanagisawa Kenshi , Kuroda Daisuke , Yoshida Michitoshi , Ohta Kouji , Kawai Nobuyuki
Published: March 2014

22P/Kopff images were taken with Multicolor Imaging Telescopes for Survey and Monstrous Explosions (MITSuME) 3ch simultaneous CCD cameras on the Ishigakijima astronomical observatory 105-cm telescope and a 2kCCD camera on the Kiso 105-cm Schmidt telescope from 2009 August to December after the passage of its perihelion on 2009 May 25. We confirmed that the near-nuclear fan-shaped jet structure extended toward the south. Whereas we detected a dust trail structure on the project orbit of the parent nucleus, we could not confirm the obvious neck-line structure. We deduced a pole orientation of ($ \alpha_{\rm pl}$ , $ \delta_{\rm pl}$ ) $ =$ (302$ \pm$ 30, 62$ \pm$ 10) or ($ \alpha_{\rm pl}$ , $ \delta_{\rm pl}$ ) $ =$ (122$ \pm$ 30, $-$ 62 $ \pm$ 10) in the case of prograde or retrograde rotation, based on the fan-shaped jet. In addition, we conducted a model simulation of the dust orbital evolution, and found that the observed dust morphology of the fan-shaped jet and dust trail can well explain the dust emission near the south polar region. Finally, we conclude that the surface of 22P/Kopff is becoming largely dormant, but the polar region is still active, as we saw in the Deep Space 1 image of 19P/Borrelly.
Substellar Companions to Seven Evolved Intermediate-Mass Stars
Authors: Sato Bun'ei , Omiya Masashi , Harakawa Hiroki , Izumiura Hideyuki , Kambe Eiji , Takeda Yoichi , Yoshida Michitoshi , Itoh Yoichi , Ando Hiroyasu , Kokubo Eiichiro , Ida Shigeru
Published: March 2014

We report on the detections of substellar companions orbiting around seven evolved intermediate-mass stars from precise Doppler measurements at Okayama Astrophysical Observatory. $o$ UMa (G4 II-III) is a giant with a mass of 3.1 $M_{\odot}$ , and hosts a planet with a minimum mass of $m_2$ sin $i$$=$ 4.1 $M_{\rm J}$ in an orbit with a period $P$$=$ 1630 d and an eccentricity $e$$=$ 0.13. This is the first planet candidate ($\lt $ 13 $M_{\rm J}$ ) ever discovered around a star more massive than 3 $M_{\odot}$ . $o$ CrB (K0 III) is a 2.1 $M_{\odot}$ giant, and has a planet of $m_2$ sin $i$$=$ 1.5 $M_{\rm J}$ in a 187.8 d orbit with $e$$=$ 0.19. This is one of the least-massive planets ever discovered around an $\sim$ 2 $M_{\odot}$ star. HD 5608 (K0 IV) is an 1.6 $M_{\odot}$ subgiant hosting a planet of $m_2$ sin $i$$=$ 1.4 $M_{\rm J}$ in a 793 d orbit with $e$$=$ 0.19. The star also exhibits a linear velocity trend, suggesting the existence of an outer, more massive companion. 75 Cet (G3 III:) is a 2.5 $M_{\odot}$ giant hosting a planet of $m_2$ sin $i$$=$ 3.0 $M_{\rm J}$ in a 692 d orbit with $e$$=$ 0.12. The star also shows a possible additional periodicity of about 200 d and 1880 d with a velocity amplitude of $\sim$ 7–10 m s$^{-1}$ , although these are not significant at this stage. $\nu $ Oph (K0 III) is a 3.0 $M_{\odot}$ giant, and has two brown-dwarf companions of $m_2$ sin $i$$=$ 24 $M_{\rm J}$ and 27 $M_{\rm J}$ , in orbits with $P$$=$ 530.3 d and 3190 d, and $e$$=$ 0.126 and 0.17, respectively, which were independently announced by Quirrenbach, Reffert, and Bergmann (2011, AIP Conf. Proc. 1331, 102). The ratio of the periods is close to 1:6, suggesting that the companions are in mean motion resonance. We also independently confirmed planets around $\kappa $ CrB (K0 III-IV) and HD 210702 (K1 IV), which were announced by Johnson et al. (2008, ApJ, 675, 784) and Johnson et al. (2007a, ApJ, 665, 785), respectively. All of the orbital parameters we obtained are consistent with the previous results.
A Resonantly Excited Disk-Oscillation Model of High-Frequency QPOs of Microquasars
Authors: Kato Shoji
Published: March 2014

A possible model of twin high-frequency QPOs (HF QPOs) of microquasars is examined. The disk is assumed to have global magnetic fields and to be deformed with a two-armed pattern. In this deformed disk, a set of a two-armed ($ m$$ =$ 2) vertical $ p$-mode oscillation and an axisymmetric ($ m$$ =$ 0) $ g$-mode oscillation is considered. They resonantly interact through the disk deformation when their frequencies are the same. This resonant interaction amplifies the set of the above oscillations in the case where these two oscillations have wave energies of opposite signs. These oscillations are assumed to be excited most efficiently in the case where the radial group velocities of these two waves vanish at the same place. The above set of oscillations is not unique, depending on the node number, $ n$ , of oscillations in the vertical direction. We consider that the basic two sets of oscillations correspond to the twin QPOs. The frequencies of these oscillations depend on the disk parameters, such as the strength of the magnetic fields. For observational mass ranges of GRS 1915$ +$ 105, GRO J1655$-$ 40, XTE J1550$-$ 564, and HEAO H 1743$-$ 322, the spins of these sources are estimated. High spins of these sources can be described if the disks have weak poloidal magnetic fields as well as toroidal magnetic fields of moderate strength. In this model the 3 : 2 frequency ratio of high-frequency QPOs is not related to their excitation, but occurs by chance.