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There are 13 papers published in subject: > since this site started. |
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1. Are crystalline silicates and amorphous silicates spatially separated in protoplanetary disks ? | |||
LI Moping,LI Aigen | |||
Astronomy 09 May 2017 | |||
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Abstract:Crystalline silicates have been found in comets, in protoplanetary disks around young pre-main sequence stars, in debris disks around main-sequence stars, and in dust shells around evolved stars. Their infrared (IR) emission spectra indicate that they are predominantly magnesium (Mg)-rich and iron (Fe)-poor or even Fe-free. The Stardust cometary samples of crystalline silicate minerals are also predominantly Fe-poor. The Fe content of crystalline silicates not only affects the peak wavelength, width and strength of their vibrational features in the IR, but also affects their ultraviolet (UV) and visual absorptivities. Taking the young Herbig Ae star HD 142527 as a test case, we quantitatively demonstrate that, as a consequence of the latter effect, the crystallinity degree of silicate dust might have been substantially underestimated in various astrophysical regions, and the non-detection of the crystalline silicate emission features does not necessarily imply the absence of crystalline silicate dust; instead, crystalline silicates could be present but are just not heated sufficiently to emit at their characteristic IR vibrational bands. | |||
TO cite this article:LI Moping,LI Aigen. Are crystalline silicates and amorphous silicates spatially separated in protoplanetary disks ?[OL].[ 9 May 2017] http://en.paper.edu.cn/en_releasepaper/content/4732592 |
2. The universal “heartbeat” oscillications in black hole systems accross the mass-scale | |||
Wu Qingwen,Bozena Czerny,Mikolaj Grzedzielski,Agnieszka Janiuk,Wei-Min Gu,Ai-jun Dong,Xiao-Feng Cao,Bei You,Zhen Yan,Mou-Yuan Sun | |||
Astronomy 09 October 2016 | |||
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Abstract:The hyperluminous X-ray source (HLX-1, the peak X-ray luminosity $sim 10^{42} m erg s^{-1}$) near the spiral galaxy ESO 243-49 is possibly the best candidate for intermediate mass black hole (IMBH), which underwent recurrent outbursts with a period of $sim 400$ days. The physical reason for this quasi-periodic variability is still unclear. We explore the possibility of radiation-pressure instability in accretion disk by modeling the light curve of HLX-1, and find that it can roughly reproduce the duration, period and amplitude of the recurrent outbursts HLX-1 with an IMBH of $sim 10^5$ Msun. Our result provides a possible mechanism to explain the recurrent outbursts in HLX-1. We further find a universal correlation between the outburst duration and the bolometric luminosity for the BH sources with a very broad mass range (e.g., X-ray binaries, XRBs, HLX-1 and active galactic nuclei, AGNs), which is roughly consistent with the prediction of radiation-pressure instability of the accretion disk. These results imply that ``heartbeat" oscillations triggered by radiation-pressure instability may appears in different-scale BH systems. | |||
TO cite this article:Wu Qingwen,Bozena Czerny,Mikolaj Grzedzielski, et al. The universal “heartbeat” oscillications in black hole systems accross the mass-scale[OL].[ 9 October 2016] http://en.paper.edu.cn/en_releasepaper/content/4706442 |
3. The Redshifted Hydrogen Balmer and Metastable $m He ~I$ Absorption System in Iron Mini-LoBAL Quasar SDSS J112526.12+002901.3: the Parsec Scale Accretion Inflow? | |||
Xi-Heng Shi,Peng Jiang,Hui-Yuan Wang,Shao-Hua Zhang,Tuo Ji,Wen-Juan Liu,Hong-Yan Zhou | |||
Astronomy 24 May 2016 | |||
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Abstract:The accretion of interstellar medium onto the central super massive black holes is widely accepted as the source of the gigantic energy released by the active galactic nuclei. But few observational evidence has been confirmed directly demonstrating the existence of the inflows. The absorption system in the spectra of quasar SDSS J112526.12+002901.3 presents an interesting example, in which the rarely detected features hydrogen Balmer and metastable hei absorption lines are found redshifted to the quasar's rest frame along with the low-ionization metal absorption lines mgii, eii, extit{et al.}. The repeated SDSS spectroscopic observations suggest a transverse velocity smaller than the radial velocity. The motion of the absorbing medium is dominated by infall. The hei lines present a direct indicator to the strength of ionizing flux, while the Balmer lines imply a dense environment. With the help of photoionization simulations, we find the absorbing medium is exposed to the radiation with $Upprox 10^{-1.8}$, and the density is $n(mathrm{H})pprox 10^9 mathrm{cm}^{-3}$. Thus the absorbing medium is located $sim 4 mathrm{pc}$ away from the central engine. According to the similarity in the distance and physical conditions between the absorbing medium and the clumpy torus, the absorption system is strongly proposed as a candidate for the accretion inflow which originates from the inner surface of the torus. | |||
TO cite this article:Xi-Heng Shi,Peng Jiang,Hui-Yuan Wang, et al. The Redshifted Hydrogen Balmer and Metastable $m He ~I$ Absorption System in Iron Mini-LoBAL Quasar SDSS J112526.12+002901.3: the Parsec Scale Accretion Inflow?[OL].[24 May 2016] http://en.paper.edu.cn/en_releasepaper/content/4692939 |
4. ESO 323-G077 in an X-ray low state observed with Suzaku: evidence for variable circum-nuclear absorber | |||
SHU Xinwen,WANG Junxian,YANG Huan | |||
Astronomy 17 May 2016 | |||
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Abstract:We report on a Suzaku observation of the Seyfert 1 galaxy ESO323-G077 obtained in 2011, in which the source is at an historical extremely low X-ray state. A comparison with XMM observation obtained in 2006, Chandra observations in 2010, and other previous X-ray observations, indicates the source has diminished in 2 - 10 keV flux by a factor of up to ~20, the lowest X-ray flux in this object ever been seen. During the Suzaku observation, the source appears heavily absorbed, with an extremely hard X-ray spectrum at energies above 1.5 keV ( ~0.7), and a strong narrow Fe K line (EW~600 eV), typical for a Compton-thick AGN. We find dramatic changes of spectra in the energy band ~1.5-10 keV between the Suzaku, XMM and Chandra observations, which could be best interpreted by variations in the column density of the absorber along the line of sight on time scale of years ( ). If confirmed, this object would be one of the few AGNs displaying extremely transitions between Compton-thin and Compton-thick states. Both the ionized absorbers and a relativistically broadened Fe K line observed with the XMM appear to be absent in the Suzaku spectra. ESO 323-G077 is a rare AGN with almost all key X-ray spectral features detected in one single object, making it a best laboratory to further investigate the geometry and structure of the circumnuclear obscuring material and test for the unification model. | |||
TO cite this article:SHU Xinwen,WANG Junxian,YANG Huan. ESO 323-G077 in an X-ray low state observed with Suzaku: evidence for variable circum-nuclear absorber[OL].[17 May 2016] http://en.paper.edu.cn/en_releasepaper/content/4687957 |
5. THE TIMESCALE DEPENDENT COLOR VARIABILITY OF QUASARS VIEWED WITH GALEX | |||
Zhu Feifan,Wang Junxian,Cai Zhenyi,Sun Yuhan | |||
Astronomy 13 May 2016 | |||
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Abstract:In recent work done by Sun et al., the color variation of quasars, namely the bluer-when-brighter trend, was found to be timescale-dependent using SDSS g/r band light curves in the Stripe 82. Such timescale dependency, e.g. bluer variation at shorter timescales, supports the thermal fluctuation origin of the UV/optical variation in quasars, and can be well modeled with an inhomogeneous accretion disk model. In this paper, we extend the study to much shorter wavelengths in the rest frame (down to extreme UV), using GALEX's photometric data of quasars collected in two ultraviolet bands (NUV and FUV). We develop Monte Carlo simulations to correct possible biases due the considerably larger photometric uncertainties in GALEX light curves (particularly in FUV, comparing with SDSS g/r band), which otherwise could produce artificial results. We securely confirm the previously discovered timescale dependence of the color variability with independent datasets and at shorter wavelengths. | |||
TO cite this article:Zhu Feifan,Wang Junxian,Cai Zhenyi, et al. THE TIMESCALE DEPENDENT COLOR VARIABILITY OF QUASARS VIEWED WITH GALEX[OL].[13 May 2016] http://en.paper.edu.cn/en_releasepaper/content/4688638 |
6. Physical properties of massive compact galaxies at high redshift | |||
Lin Xiaozhi,Fan Lulu | |||
Astronomy 09 May 2016 | |||
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Abstract:Recently, the massive galaxies at high redshift have been found to be more compact than their analogs at lower redshift. It is very important to help us understanding how they form and evolve by studying their physical properties. We combine high-resolution Hubble Space Telescope/WFC3 images with multi-wavelength photometry to track the evolution of structure and activity of massive (M > 10^{10} M_{odot} ) galaxies at redshifts (z=1-3) in the GOODS-S field of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and the COSMOS/UltraVISTA field. We devide our compact samples into compact star-forming galaxies (cSFGs) and compact quiescent galaxies (cQGs) and find that cQGs at (1< z< 2) are very close to cSFGs at (2< z< 3) in morphology and color. Our result approve the model that quenched cSFGs fading into cQGs at (zsim2), and that cSFGs are likely progenitors of compact, quiescent, massive galaxies at (z=2-3). | |||
TO cite this article:Lin Xiaozhi,Fan Lulu. Physical properties of massive compact galaxies at high redshift[OL].[ 9 May 2016] http://en.paper.edu.cn/en_releasepaper/content/4686421 |
7. The cross confirmation in determining astronomical distances to high-redshift type Ia supernovae | |||
Zhiping Li, Ran Li | |||
Astronomy 11 September 2014 | |||
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Abstract:In this paper, using the theory and formula of cosmological redshift as the validation technique in determining distances to high-redshift supernovae, we present the results of 43 high-redshift (0.172 $leq z leq$ 1.755) type Ia supernovae. The results show that the distances determined by the cosmological redshift formula and the Standard Candle Method have a good match within the measurement uncertainties. This cosmological redshift formula can not only describe the universe beyond the boundary of Hubble's Law, but also evolve back to Hubble's Law in low-redshift scale. All these results have nothing to do with the assumption of dark energy and the average density of the universe. | |||
TO cite this article:Zhiping Li, Ran Li. The cross confirmation in determining astronomical distances to high-redshift type Ia supernovae[OL].[11 September 2014] http://en.paper.edu.cn/en_releasepaper/content/4607137 |
8. The cosmological redshift originated from running inertia | |||
Zhiping Li, Ran Li | |||
Astronomy 02 May 2014 | |||
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Abstract:This paper suggests a model of cosmological redshift, in which the amount of redshift is proportional to distances between the galaxies. Rather than the effects of Doppler redshift, this principle of redshift arises from both of the running inertia deviated from the local equivalence principle at cosmological distances and the De Broglie's basic equation related the wavelength to the momentum. According to this principle, the Hubble's law could be explained without Doppler redshift. | |||
TO cite this article:Zhiping Li, Ran Li. The cosmological redshift originated from running inertia[OL].[ 2 May 2014] http://en.paper.edu.cn/en_releasepaper/content/4595519 |
9. Puzzle of Angular Momentum Transfer in Black Hole Accretion Disc | |||
GAN Zhaoming,YE Yongchun,WANG Dingxiong | |||
Astronomy 16 January 2012 | |||
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Abstract:Angular momentum transfer is of fundamental importance in the theory of accretion disc. Accreting matter lose its angular momentum to move inward a smaller radius, and eventually falls onto the central object. In the classical theory of accretion disc, interior viscous process is invoked to transfer angular momentum from smaller radii to larger ones. It is noted that the angular momentum accumulated in the outer disc will block the disc accretion, since the interior viscous torque increases with the disc radius. We propose that this puzzle can be resolved by invoking the Blandford-Payne (BP) process, in which part of accreting matter is launched centrifugally along magnetic field lines anchored in the disc, and angular momentum can be extracted continuously from the disc with the outflow. A criterion related to overall equilibrium of angular momentum in accretion disc is derived. | |||
TO cite this article:GAN Zhaoming,YE Yongchun,WANG Dingxiong. Puzzle of Angular Momentum Transfer in Black Hole Accretion Disc[OL].[16 January 2012] http://en.paper.edu.cn/en_releasepaper/content/4462496 |
10. Stochastic Electron Acceleration in SNR RX J1713.7-3946 | |||
Fan Zhonghui,Liu Siming | |||
Astronomy 31 December 2011 | |||
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Abstract:Stochastic acceleration of charged particles due to their interactions with plasma waves may be responsible for producing superthermal particles in a variety of astrophysical systems. This process can be described as a diffusion process in the energy space with the Fokker-Planck equation. In this paper, a time-dependent numerical code is used to solve the reduced Fokker-Planck equation involving only time and energy variables with general forms of the diffusion coefficients. We also propose a self-similar model for particle acceleration in Sedov explosions and use the TeV SNR RX J1713.7-3946 as an example to demonstrate the model characteristics. Markov Chain Monte Carlo method is utilized to constrain model parameters with observations. | |||
TO cite this article:Fan Zhonghui,Liu Siming. Stochastic Electron Acceleration in SNR RX J1713.7-3946[OL].[31 December 2011] http://en.paper.edu.cn/en_releasepaper/content/4458565 |
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