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TOPIC: 1E 1740.7-2942

Blobrana

L

Posts: 131433

Date: May 10 08:22 2010

RE: 1E 1740.7-2942	Permalink

Title: Suzaku Observations of the Galactic Centre Microquasar 1E 1740.7-2942 Authors: Mark Reynolds, Jon Miller We present two Suzaku observations of the Galactic centre microquasar 1E 1740.7-2942 separated by approximately 700 days. The source was observed on both occasions after a transition to the spectrally hard state. Significant emission from 1E 1740.7-2942 is detected out to an energy of 300 keV, with no spectral break or turnover evident in the data. We tentatively measure a lower limit to the cut-off energy of ~ 380 keV. The spectra are found to be consistent with a Comptonised corona on both occasions, where the high energy emission is consistent with a hard power-law (\Gamma ~ 1.8) with a significant contribution from an accretion disc with a temperature of ~ 0.4 keV at soft X-ray energies. The measured value for the inner radius of the accretion disc is found to be inconsistent with the picture whereby the disc is truncated at large radii in the low-hard state and instead favours a radius close to the ISCO (R_in ~ 10 - 20 R_g). Read more (104kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: May 7 21:43 2010

	Permalink
Position (2000): RA 17 43 54.83, Dec -29 44 42.6 __________________

Blobrana

L

Posts: 131433

Date: May 4 01:32 2010

Great Annihilator	Permalink

Title: Suzaku Observations of the Great Annihilator and the Surrounding Diffuse Emissions Authors: Shinya Nakashima, Masayoshi Nobukawa, Takeshi Go Tsuru, Katsuji Koyama, Hideki Uchiyama We report the Suzaku observation of 1E 1740.7-2942, a black hole candidate called the "Great Annihilator" (GA). The high-quality spectrum of Suzaku provides the severest constraints on the parameters of the GA. Two clumpy structures are found around the GA in the line images of FeI Kalpha at 6.4 keV and SXV Kalpha at 2.45 keV. One clump named M359.23-0.04 exhibits the 6.4-keV line with an equivalent width of ~ 1.2 keV, and is associated with a molecular cloud in the radio CS(J=1-0) map. Thus the 6.4-keV line from M359.23-0.04 is likely due to X-ray fluorescence irradiated by an external X-ray source. The irradiating X-rays would be either the past flare of Sagittarius A* or the bright nearby source, the GA. The other clump named G359.12-0.05 is associated with the radio supernova remnant candidate G359.07-0.02. We therefore propose that G359.12-0.05 is an X-ray counterpart of G359.07-0.02. G359.12-0.05 has a thin thermal plasma spectrum with a temperature of kT ~ 0.9 keV. The plasma parameters of G359.12-0.05 are consistent with those of a single supernova remnant in the Galactic center region. Read more (1921kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Nov 23 22:28 2008

1E 1740.7-2942	Permalink

Title: Unveiling the high energy tail of 1E 1740.7-2942 with INTEGRAL Authors: L. Bouchet (1), M. Del Santo (2), E. Jourdain (1), J. P. Roques (1), A. Bazzano (2), G. De Cesare (2,3,1); ((1) CESR--Universite de Toulouse/CNRS, (2) INAF/Istituto di Astrofisica Spaziale e Fisica cosmica - Roma, (3) Dipartimento di Astronomia, Universita' degli Studi di Bologna) The microquasar 1E 1740.7-2942 is observed with Integral since Spring 2003. Here, we report on the source high energy behaviour by using the first three years of data collected with SPI and IBIS telescopes, taking advantage of the instruments complementarity. Light curves analysis showed two main states for 1E 1740.7-2942: the canonical low/hard state of black-hole candidates and a "dim" state, characterised by a ~ 20 times fainter emission, detected only below 50 keV and when summing more than 1Ms of data. For the first time the continuum of the low/hard state has been measured up to ~ 600 keV with a spectrum that is well represented by a thermal Comptonisation plus an additional component necessary to fit the data above 200 keV. This high energy component could be related to non-thermal processes as already observed in other black-hole candidates. Alternatively, we show that a model composed by two thermal Comptonisation provides an equally representative description of the data: the temperature of the first population of electrons results as (kTe)_1 ~ 30 keV while the second, (kTe)_2, is fixed at 100 keV. Finally, searching for 511 keV line showed no feature, either narrow or broad, transient or persistent. Read more (294kb, PDF) __________________

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