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ATEL # 1841; J. L. Blum, J. M. Miller, E. Cackett (Univ. of Michigan), K. Yamaoka (Aoyama Gakuin Univ.), H. Takahashi (Hiroshima Univ.), J. Raymond (SAO), C. S. Reynolds (Maryland), A. C. Fabian (Cambridge)
on 12 Nov 2008; 17:33 UT
Password Certification: Jon Miller (email@example.com)
Subjects: X-ray, Binaries, Black Holes, Transients
We observed the Galactic black hole candidate H 1743-322 on 2008 October 07 for approximately 32 ksec, while the source was in a low/hard state. Here we report the preliminary results of spectral fits to XIS spectra made over the 1.0-10.0 keV band. Spectra from the three XIS detectors were fit jointly using XSPEC.
We find that the spectra can be fit with a single power-law, with an index of Gamma = 1.60+/-0.01, with a column density of 2.10 +/- 0.01 E+22. The power-law index is typical of black holes in the low/hard state. The spectra do not statistically require a disk component, likely as a result of the high column density.
Previously, Chandra observations of H 1743-322 found evidence of an ionized disk wind in the high/soft state, in the form of Fe XXV and XXVI absorption lines (Miller et al., 2006, ApJ, 646, 394). These lines were absent when Chandra observed H 1743-322 in the very high state. Similar results were obtained from Chandra observations of GRO J1655-40 in the high/soft and very high states (Miller et al., 2006, Nature, 441, 953; Miller et al., 2008, ApJ, 680, 1359; also see Kubota et al. 2007 PASJ 59S 185).
Narrow Fe XXV and Fe XXVI absorption lines are absent in the Suzaku spectra of H 1743-322 in the low/hard state, with 90% confidence limits of 1.7 eV and 3.0 eV (equivalent width), respectively. The limits are commensurate with those obtained in the very high state, despite the much lower flux level in the low/hard state. This suggests that disk winds are state-dependent, at least partially modulated by changes in the disk. It is interesting to note that radio jets appear in states where winds are absent, and vice versa. Given that models for winds and jets invoke magnetic fields, it may be possible that changes in magnetic fields emerging from the disk affect the character of outflows.
We thank the US and Japanese Suzaku teams for observing H 1743-322.