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X-ray source IGR J17091-3624 was discovered by INTEGRAL observatory on 2003 April (Kuulkers 2003). A outburst was detected with Swift/Burst Alert Telescope (BAT) in late January 2011 (Krimm 2011). IGR J17091-3624 has a similar timing phenomena to microquasar GRS 1915+105(Belloni 2000; Altamirano 2011). We have analyzed the evolution of temporal and spectral characteristic of IGR J17091-3624 during the 2011 outburst. We find that (1) all the QPOs can be divided into two types, QPO-AB and QPO-C, (2) a small outburst tracks clockwise in the HID, (3) the relationship between hardness and disk color temperature forms a V-shape. Those results will give a strong constraint on the disk radiative process.
We present the statistical properties of molecular clumps in the Galactic center 50 km s−1 molecular cloud based on observations of the CS J = 1 − 0 emission line with the Nobeyama Millimeter Array. The CMF and size spectrum for the whole cloud can be described by power laws of dN/dM ∝ M−2.6 ± 0.1 and dN/dR ∝ R−5.9±0.3, respectively. The CMF observed in the interacting part with the Sgr A East steepens to dN/dM ∝ M−4.0±0.2. On the other hand, the interaction presumably truncates the size spectrum on the larger side of R ∼ 0.4 pc.
We have used high-resolution, HST WFC3/IR, near-infrared imaging to conduct a detailed bulge-disk decomposition of the morphologies of ≃ 200 of the most massive (M* > 1011 M⊙) galaxies at 1 < z < 3 in the CANDELS-UDS field. We find that, while such massive galaxies at low redshift are generally bulge-dominated, at redshifts 1<z<2 they are predominantly mixed bulge+disk systems, and by z > 2 they are mostly disk-dominated. Interestingly, we find that while most of the quiescent galaxies are bulge-dominated, a significant fraction (25–40%) of the most quiescent galaxies, have disk-dominated morphologies. Thus, our results suggest that the physical mechanisms which quench star-formation activity are not simply connected to those responsible for the morphological transformation of massive galaxies.
We perform an unbiased search for outflows from YSOs along the Galactic Plane (GP). Our data has been taken as part of the UWISH2 survey (Froebrich et al. 2011). It uses as tracer the 1-0S(1) emission line of H2, and here we focus on a continuous 33 square degree sized region in Serpens and Aquila. We identify 130 outflows from which 94% are new discoveries. Thus, we increased the number of known MHOs by a factor of 15 in this area (Ioannidis & Froebrich 2012). The flux completeness limit for the flows is 3ċ10−18Wm−2. Typically, the known flows occupy the bright end of the flux distribution. Our survey thus increases the known integrated 1-0S(1) H2 flux from outflows only by a factor of two. We are able to assign possible driving sources to half of the outflows. Brighter MHOs are more likely to have a source candidate assigned to them.
Foreground star counts to GMCs associated with the outflows and the Besancon Galaxy model are used to determine distances. The method is calibrated using objects from the RMS survey. This allows us to estimate distances with a scatter of 25% (Ioannidis & Froebrich 2012). The spatial distribution of the outflows shows that they follow the GMC complexes in the GP. However, there are large areas with high extinction where no flows are detected. About 2/3 of the survey area is more or less devoid of outflows. The flows typically occur in groups of 3–5 members with a size of 5pc. The scale height of flows is ∼25–30pc, similar to young clusters and OB stars. The 1-0S(1) luminosities range from a few 10−4L⊙ to 0.1L⊙, ten times brighter than in nearby SF regions. Our sample is complete for objects brighter than 10−3L⊙ at 5kpc. This corresponds to HH211 behind AK = 1mag. The luminosity distribution of the outflows is a power law with N ∝ LH2−1.9 and the integrated luminosities indicate a Milky Way SF rate (averaged over a typical jet lifetime) of more than 0.4M⊙yr−1. The energy and momentum of the jets is insufficient to sustain the typical local turbulence levels in their parental clouds.
The projected jet length drops exponentially in number for longer jets. The fraction of parsec scale flows is 25%, twice as high as in nearby SF regions. A Monte-Carlo type model of jet speeds of 40–130kms−1 and ages between 4–20 × 103yrs can reproduce the length distribution. These lifetimes are an order of magnitude below estimates for the protostellar phase. For typical jet speeds the time gaps between the ejection of larger amounts of material are about 103yrs. According to the burst mode of SF models the creation of H2 knots is hence linked to low level fluctuations of the mass accretion rate and not FU-Ori type events. Their duty cycle is more in agreement with the total jet lifetime, which suggests these outburst as trigger (or stopping point or both) of a jet ejection phase. However, better constraints of the FU-Ori duty cycle and mechanism as well as more detailed models are required to draw any further conclusions.
We study the evolution of SNRs in starburst regions taking into consideration the role of the high ambient pressure and the influence of gravitational forces from the stellar component within the shell of a SNR. On this basis, we discuss the connection between the radio, infrared, and gamma emissions from starburst regions.
The central engine of AGN is too compact to be observed directly so its structure has to be inferred through the combination of spectral and variability information. Here we study the connection between optical-emitting accretion disc and X-ray emitting corona of the Seyfert NGC3783. Short light curves are consistent with optical fluctuations arising from X-ray reprocessing, but the long-term fluctuations found over the course of several years prove that at least long-term optical variability is not produced by the X-rays: at time-scales longer than 1 year the variability power in the optical is higher than in the X-rays. This indicates variability originating in the thin accretion disc itself, therefore capable of revealing its characteristics.
Based on BATC and SDSS photometric data, we adopt the spectral energy distribution (SED) fitting method to evaluate stellar metallicities in the Galaxy. We find that the mean metallicity shifts from metal-rich to metal-poor with the increase of distance from the Galactic Centre.
Clouds play a significant role for the energy budget in planetary atmospheres. They can scatter incident stellar radiation back to space, effectively cooling the surface of terrestrial planets. On the other hand, they may contribute to the atmospheric greenhouse effect by trapping outgoing thermal radiation. For exoplanets near the outer boundary of the habitable zone, condensation of CO2 can occur due to the low atmospheric temperatures. These CO2 ice clouds may play an important role for the surface temperature and, therefore, for the question of habitability of those planets. However, the optical properties of CO2 ice crystals differ significantly from those of water droplets or water ice particles. Except for a small number of strong absorption bands, they are almost transparent with respect to absorption. Instead, they are highly effective scatterers at long and short wavelengths. Therefore, the climatic effect of a CO2 ice cloud will depend on how much incident stellar radiation is scattered to space in comparison to the amount of thermal radiation scattered back towards the planetary surface. This contribution aims at the potential greenhouse effect of CO2 ice particles. Their scattering and absorption properties are calculated for assumed particle size distributions with different effective radii and particle densities. An accurate radiative transfer model is used to determine the atmospheric radiation field affected by such CO2 particles. These results are compared to less detailed radiative transfer schemes employed in previous studies.
Several pulsars show sudden cessation of pulsed emission, which is known as pulsar nulling. In this paper, the nulling behaviour of 15 pulsars is presented. The nulling fraction of these pulsars, along with the degree of reduction in the pulse energy during the null phase are reported for these pulsars. A unique nulling behaviour is re- ported for PSR J1738-2330, which also showed quasi-periodic bursts. The distributions of lengths of the null and burst phases as well as the typical nulling time scales are estimated for eight strong pulsars. A comparison of the nulling time scales of four pulsars with similar nulling fraction suggests that the fraction of null pulses probably does not quantify the nulling behaviour of a pulsar in full detail. Analysis of these distributions also indicate that while the null and the burst pulses occur in groups, the transition from the null to burst phase and vice verse can be modeled by a Poisson point process.
The purpose of meteor observations in INASAN is the study of meteor showers, as the elements of the migrant substance of the Solar System, and estimation of risk of hazardous collisions of spacecrafts with the particles of streams. Therefore we need to analyze the meteor events with brightness of up to 8 m, which stay in meteoroid streams for a long time and can be a hazardous for the spacecraft. The results of our single station TV observations of autumn meteor showers for the period from 2006 to 2008 are presented. The high-sensitive hybrid camera (the system with coupled of the Image Intensifier) FAVOR with limiting magnitude for meteors about 9m. . .10m in the field of view 20 × 18 was used for observations. In 2006-2008 from October to November more than 3 thousand of meteors were detected, 65% from them have the brightness from 6m to 9m. The identification with autumn meteor showers (Orionids, Taurids, Draconids, Leonids) was carried out. In order to estimate the density of the influx of meteor matter to the Earth for these meteor showers the Index of meteor activity (IMA) was calculated. The IMA distribution for the period 2006 - 2008 is given. The distributions of autumn meteor showers (the meteors with brightness of up to 8 m) by stellar magnitude from 2006 to 2008 are also presented.
We carried out astrometric observations with VERA of H2O masers in ON1 and ON2N. The measured distances to ON1 and ON2N are 2.47 ± 0.11 and 3.83 ± 0.13 kpc, respectively. We found that ON1 and ON2N are located near the tangent point and the Solar circle, respectively. We derive an angular velocity of the Galactic rotation at the Sun's position (i.e. the ratio of the Galactic constants) of 28 ± 2 km s−1 kpc−1 using the measured distances and three-dimensional velocity components of the two sources. This value is consistent with recent estimates obtained using Very Long Baseline Interferometry but different from the IAU-recommended value of 25.9 km s−1 kpc−1.
Massive infrared dark clouds (IRDCs) are believed to be the precursors to star clusters and massive stars (e.g. Bergin & Tafalla 2007). The supersonic, turbulent nature of molecular clouds in the presence of magnetic fields poses a great challenge in understanding the structure and dynamics of magnetized molecular clouds and the star formation therein. Using the high-order radiation-magneto-hydrodynamic adaptive mesh refinement (AMR) code ORION2 (Li et al. 2012), we perform a large-scale driven-turbulence simulation to reveal the 3D filamentary structure and dynamical state of a highly supersonic (thermal Mach number = 10) and strongly magnetized (plasma β=0.02) massive infrared dark molecular cloud. With the high resolution afforded by AMR, we follow the dynamical evolution of the cloud in order to understand the roles of strong magnetic fields, turbulence, and self-gravity in shaping the cloud and in the formation of dense cores.
The Kepler satellite has discovered a number of transiting planets around close binary stars. These circumbinary systems have highly aligned planetary and binary orbits. In this paper, we explore how the mutual inclination between the planetary and binary orbits may reflect the physical conditions of the assembly of protoplanetary discs and the interaction between protostellar binaries and circumbinary discs. Given the turbulent nature of star-forming molecular clouds, it is possible that the infalling gas onto the outer region of a circumbinary disc rotates around a different axis compared to the central protostellar binary. Thus, the newly assembled circumbinary disc can be misaligned with respect to the binary. However, the gravitational torque from the binary produces warp and twist in the disc, and the back-reaction torque tends to align the disc and the binary orbital plane. We present a new, analytic calculation of this alignment torque, and show that the binary-disc inclination angle can be reduced appreciably after the binary accretes a few percent of its mass from the disc. Since mass accretion onto the proto-binary is very likely to occur, our calculation suggests that in the absence of other disturbances, circumbinary discs and planets around close (sub-AU) stellar binaries are highly aligned with the binary orbits, while discs and planets around wide binaries can be misaligned.
We present a brief summary and description of the upcoming 12CO(1-0) Magellanic Mopra Assesment (MAGMA) SMC survey data release. The MAGMA-SMC survey has sampled 100% of the known CO in the SMC (at ∼33″ resolution; 12 pc at D = 60 kpc). Having explored 522 × 103 square parsecs throughout the SMC with 69 5′ × 5′ fields, to a sensitivity of ∼150 mK, we apply the cloudprops (Rosolowsky & Leroy 2006) cloud-search algorithm optimized for low S/N data, to detect more than 30 CO clouds with virial masses between 103–104 M⊙, mean radii ∼5 pc and 0.3–0.9 km s−1 velocity width. Typical brightness temperatures are ∼1 K Tmb. All detected molecular regions are associated with at least one 24 μm compact emission source. Smoothing rarely increases the total detected CO flux, implying the CO emission is typically confined to small spatial scales. As recent dust maps of the SMC imply extended H2 mass, the apparent compact nature of the CO population indicates some departures from the canonical Galactic XCO-factor in the low-metallicity and relatively un-evolved ISM of the SMC.
Hundreds of extrasolar planets have been discovered around various types of stars by various techniques during the past decade. Among them precise radial velocity measurements for stars are fundamental technique to detect and confirm exoplanets. In this paper activities in East-Asian region in this research field are introduced: East-Asian Planet Search Network, which is a network searching for planets around evolved intermediate-mass stars, and Subaru/IRD project, which will search for habitable planets around M-type dwarfs using infrared radial-velocity method.
We outline a project to map the molecular line emission from the Central Molecular Zone across the 3–12 mm wavebands using the Mopra telescope in Australia. The dataset facilitates use of the CMZ as a template against which observations of molecular emission in other galactic nuclei may be interpreted.
Dome Fuji on the Antarctic high plateau may be a good site for terahertz astronomy because of its high altitude of 3,810 m and low average temperature of −54°C. We have demonstrated that the opacity at 220 GHz from Dome Fuji in summer is very good and stable; τ = 0.045 ± 0.007. We have developed a transportable 30 cm telescope to map the Milky Way in the CO (J=4–3) and the [CI] (3P1–3P0) lines at Dome Fuji from 2014. It has a 9′ beam. Physical conditions such as density and temperature of molecular clouds could be derived from a direct comparison of CO (J=4–3) and [CI] (3P1–3P0) with CO (J=1–0) taken by the Columbia–CfA survey. We are also developing a 1.2 m sub-millimeter telescope. It will be equipped with a dual superconducting device (SIS) receiver for 500/800 GHz. The 1.2 m telescope produces a 2.2′ beam at 492 GHz and could map a molecular cloud entirely. It could also observe nearby galaxies in the CO (J=4–3), CO (J=7–6), [CI] (3P1–3P0), [CI] (3P2–3P1) and in continuum emission between 460–810 GHz.
From the observations of radio and HXR bursts, the escape rate of energetic electrons trapped in the flare loops is studied based on the trap-plus-precipitation model for the kinematics of energetic electrons in solar flares. Coulomb collision is regarded as the main pitch angle scattering of trapped electrons in the decay phase of the event on 2004 December 1. The escape rate of trapped electrons decreases firstly and then increases, which indicates the evolution of the plasma density in the flare loops during the decay phase.
Pulsar winds, containing charged particles, waves and a net (phase-averaged) magnetic field, are thought to fuel the high-energy emission from several gamma-ray binaries. They terminate where the ram pressure matches that of the surroundings - which, in binaries, is provided by the wind of the companion. Before termination, pulsed emission can be produced by inverse Compton scattering of photons from the companion by particles in the waves. After termination, both the bulk kinetic energy of the particles and the Poynting flux in the waves are dissipated into an energetic particle population embedded in the surviving phase-averaged magnetic field. Pulsed emission is no longer possible, but a substantial flux of unpulsed high-energy photons can be produced. I will present results showing that the physical conditions at the termination shock can be divided into two regimes: a high density one, where current sheets in the wind are first compressed by an MHD shock and subsequently dissipate by reconnection, and a low density one, where the wind can first convert into an electromagnetic wave in the shock precursor, which then damps and merges into the wind nebula. The shocks surrounding isolated pulsars fall into the low-density category, but those around pulsars in binary systems, may transit from one regime to the other according to binary phase. The implications of the shock-structure dichotomy for these objects will be discussed.
The occurrence of grand minima like the Maunder minimum is an intriguing aspect of the sunspot cycle. We use the flux transport dynamo model to explain the grand minima, showing that they arise when either the poloidal field or the meridional circulation falls to a sufficiently low value due to fluctuations. Assuming these fluctuations to be Gaussian and determining the various parameters from the data of the last 28 cycles, we carry on a dynamo simulation with both these fluctuations. The results are remarkably close to the observational data.