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天文館

臺北天文館學報(出版品)

臺北天文館學報第9期 (English)

JTAM VOL. 9 (2011)


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FieldAuthorTitleReceived DateAccepted Date
Refereed PaperStars
ISM
Astrophysics
IR
Jia-Wei Wang, Shih-Ping LaiSearching for the physical conditions that determine the disk evolution(pdf檔案)2010.10.292010.12.28
Refereed PaperBinary
X-ray
Yi-Hao Su,
Yi Chou
Constraint on the Spin of the Black Hole in GX 339-4 from X-ray Continuum(pdf檔案)2011.10.242011.12.12
Refereed Paper X-rayChun-Cheng Lin,
Lin-Wen Chen
The mass function and origins of intermediate-mass black holes in the local universe(pdf檔案)2011.10.152011.12.16


Refereed Paper 01

Title:Searching for the physical conditions that determine the disk evolution

Author:Jia-Wei Wang, Shih-Ping Lai

Keywords:pre--main-sequence, planetary systems: formation, planetary systems: protoplanetary disks

Abstract:
   Understanding how primordial circumstellar disks of young stellar objects dissi-pate gas and small dust grains and evolve into debris disks is crucial for advancing our knowledge in planet formation. Recent observations suggest that multiple pathways may exist for the disk evolution. In order to clearly identify the physical conditions in-fluencing the evolutionary paths, here we perform a statistical analysis on two morphological parameters of the spectral energy distributions (SEDs), λturnoff and αexcess. λturnoff is the wavelength where the disk flux is equal to the stellar flux, which indicates the size of the inner disk, and αexcess is the spectral slope at wavelengths longer than λturnoff, which traces the total mass of the disk. Since one of the main issues in disk dissipating theories is whether the disks are cleared from the inside out, these two parameters are ideal for examining the theories. We compare λturnoff and αexcess of the theoretical SEDs from Robitaille et al. (2006) to those of the observational results from the Spitzer’s c2d Legacy project, and derive the upper limit and lower limit of the transition disk population in the c2d regions. The results show that homologously depleted disks and canonical transition disks do exists in Chameleon II, Lupus, Ophiuchus, Perseus, and Serpens clouds. In the five clouds, the population ratios of homologously depleted disks and canonical transition disks are different by a factor of ~2, which suggest that the physical condition or evolutionary stage may be different in these regions. Further work on comparing the physical conditions of these regions could advance our knowledge of disk evolution theory.

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Refereed Paper 02

Title:Constraint on the Spin of the Black Hole in GX 339-4 from X-ray Continuum

Author:Yi-Hao Su, Yi Chou

Keywords:X-rays: binaries, black hole physics, accretion disks

Abstract:
   We present our analysis result for constraining the spin of the stellar-mass black hole (BH) in the X-ray binary GX 339-4 by fitting its X-ray continuum spectra. Reis et al. (2008) determined its spin to be a*=0.935±0.01 by modeling the profile of Fe Kα line. However, Kolehmainen & Done (2010) concluded that its spin is no more than 0.9 from X-ray continuum fitting method. To resolve these contradictive results and estimate its spin, we first adopted two fully relativistic, thin accretion disk models combined with a simple comptonization model to fit X-ray continuum spectra of GX 339-4 observed by the Proportional Counter Array (PCA) on Rossi X-Ray Timing Ex-plorer(RXTE) during its 2002-2010 outbursts. We set up constraints suggested by McClintock et al. (2006) and Steiner et al. (2009a & 2010) to select the data suitable for thin accretion disk model to further analyze. Using the same constraints described by McClintock et al. (2006) and Steiner et al. (2009a & 2010) to select the data, we employed a newly developed fully relativistic accretion disk model (McClintock et al. 2006) to further constrain the black hole spin. Our result indicates that the BH spin is no less than a*=0.94, which is likely favorable to the results from Reis et al. (2008) and Miller et al. (2009).

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Refereed Paper 03

Title:The mass function and origins of intermediate-mass black holes in the local universe

Author:Chun-Cheng Lin, Lin-Wen Chen

Keywords:ULXs, IMBH, Mass function

Abstract:
   We have merged ULXs (ultra-luminous X-ray sources, Lx>1039 ergs/s) data ob-tained from XMM-Newton (Winter et al. 2006) and Chandra (Berghea et al. 2008) and identified 66 intermediate-mass black holes (IMBH, M > 20M) from the compilation. We find that the ULXs X-ray luminosity correlates relatively well with their intrinsic column density, suggesting a possible physical relationship between X-ray luminosity and local environment, and a clue to the hidden IMBH population located in a gas-poor environment. With our IMBH sample, we have constructed the luminosity function and mass function of the IMBH in the local universe, although the faint part is likely incomplete. Based on the X-ray data combined with follow-up observations in other wavelengths and the properties of the host galaxies, we have examined four scenarios for IMBH formation, and discuss the possible fate of IMBH as the supermassive black hole in the galactic center.

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