10 research outputs found
Relativistic Iron Lines in Galactic Black Holes: Recent Results and Lines in the ASCA Archive
Recent observations with Chandra and XMM-Newton, aided by broad-band spectral
coverage from RXTE, have revealed skewed relativistic iron emission lines in
stellar-mass Galactic black hole systems. Such systems are excellent
laboratories for testing General Relativity, and relativistic iron lines
provide an important tool for making such tests. In this contribution to the
Proceedings of the 10th Annual Marcel Grossmann Meeting on General Relativity,
we briefly review recent developments and present initial results from fits to
archival ASCA observations of Galactic black holes. It stands to reason that
relativistic effects, if real, should be revealed in many systems (rather than
just one or two); the results of our archival work have borne-out this
expectation. The ASCA spectra reveal skewed, relativistic lines in XTE
J1550-564, GRO J1655-40, GRS 1915+105, and Cygnus X-1.Comment: to appear in the proc. of the 10th Annual Marcel Grossmann Meeting on
General Relativity, 5 pages, 1 figure, uses specific .cls and .sty file
Chandra/HETGS Spectroscopy of the Galactic Black Hole GX 339-4: A Relativistic Iron Line and Evidence for a Seyfert-like Warm Absorber
We observed the Galactic black hole GX 339-4 with the Chandra High Energy
Transmission Grating Spectrometer (HETGS) for 75 ksec during the decline of its
2002-2003 outburst. The sensitivity of this observation provides an
unprecedented glimpse of a Galactic black hole at about a tenth of the
luminosity of the outburst peak. The continuum spectrum is well described by a
model consisting of multicolor disk blackbody (kT = 0.6 keV) and power-law
(Gamma = 2.5) components. X-ray reflection models yield improved fits. A
strong, relativistic Fe K-alpha emission line is revealed, indicating that the
inner disk extends to the innermost stable circular orbit. The breadth of the
line is sufficient to suggest that GX 339-4 may harbor a black hole with
significant angular momentum. Absorption lines from H-like and He-like O, and
He-like Ne and Mg are detected, as well as lines which are likely due to Ne II
and Ne III. The measured line properties make it difficult to associate the
absorption with the coronal phase of the interstellar medium. A scenario
wherein the absorption lines are due to an intrinsic AGN-like warm-absorber
geometry -- perhaps produced by a disk wind in an extended disk-dominated state
-- may be more viable. We compare our results to Chandra observations of the
Galactic black hole candidate XTE J1650-500, and discuss our findings in terms
of prominent models for Galactic black hole accretion flows and connections to
supermassive black holes.Comment: 20 pages, 11 postscript figure files (many in color), uses
emulateapj.sty and apjfonts.sty, slightly expanded, accepted for publication
in Ap
Evidence for Black Hole Spin in GX 339-4: XMM-Newton EPIC-pn and RXTE Spectroscopy of the Very High State
We have analyzed spectra of the Galactic black hole GX 339-4 obtained through
simultaneous 76 ksec XMM-Newton/EPIC-pn and 10 ksec RXTE observations during a
bright phase of its 2002-2003 outburst. An extremely skewed, relativistic Fe
K-alpha emission line and ionized disk reflection spectrum are revealed in
these spectra. Self-consistent models for the Fe K-alpha emission line profile
and disk reflection spectrum rule-out an inner disk radius compatible with a
Schwarzschild black hole at more than the 8 sigma level of confidence. The
best-fit inner disk radius of 2-3 r_g suggests that GX 339-4 harbors a black
hole with a ~ 0.8-0.9 (where r_g = GM/c^2 and a=cJ/GM^2, and assuming that
reflection in the plunging region is relatively small). This confirms
indications for black hole spin based on a Chandra spectrum obtained later in
the outburst. The emission line and reflection spectrum also rule-out a
standard power-law disk emissivity in GX 339-4; a broken power-law form with
enhanced emissivity inside ~6 r_{g} gives improved fits at more than the 8
sigma level of confidence. The extreme red wing of the line and steep
emissivity require a centrally--concentrated source of hard X-rays which can
strongly illuminate the inner disk. Hard X-ray emission from the base of a jet
- enhanced by gravitational light bending effects - could create the
concentrated hard X-ray emission; this process may be related to magnetic
connections between the black hole and the inner disk. We discuss these results
within the context of recent results from analyses of XTE J1650-500 and
MCG-6-30-15, and models for the inner accretion flow environment around black
holes.Comment: 5 pages, 2 color figures, uses emulateapj.sty and apjfonts.sty, ApJ
Letters, accepte
Probes and Tests of Strong-Field Gravity with Observations in the Electromagnetic Spectrum
Chandra/High Energy Transmission Grating Spectrometer spectroscopy of the Galactic black hole GX 339-4: A relativistic iron emission line and evidence for a Seyfert-like warm absorber
We observed the Galactic black hole GX 339 - 4 with the Chandra High Energy Transmission Grating Spectrometer (HETGS) for 75 ks during the decline of its 2002 - 2003 outburst. The sensitivity of this observation provides an unprecedented glimpse of a Galactic black hole at about a tenth of the luminosity of the outburst peak. The continuum spectrum is well described by a model consisting of multicolor disk blackbody (kT similar or equal to 0.6 keV) and power-law (Gamma similar or equal to 2.5) components. X-ray reflection models yield improved fits. A strong, relativistic Fe Kalpha emission line is revealed, indicating that the inner disk extends to the innermost stable circular orbit. The breadth of the line is sufficient to suggest that GX 339 - 4 may harbor a black hole with significant angular momentum. Absorption lines from H- and He-like O and He-like Ne and Mg are detected, as well as lines that are likely due to Ne II and Ne III. The measured line properties make it difficult to associate the absorption with the coronal phase of the interstellar medium. A scenario wherein the absorption lines are due to an intrinsic AGN-like warm-absorber geometry - perhaps produced by a disk wind in an extended disk-dominated state - may be more viable. We compare our results to Chandra observations of the Galactic black hole candidate XTE J1650 - 500 and discuss our findings in terms of prominent models for Galactic black hole accretion flows and connections to supermassive black holes.</p