Journal article
A Delayed Transition to the Hard State for 4U 1630-47 at the End of Its 2010 Outburst
The Astrophysical journal, Vol.791(1), pp.1-9
07/07/2014
DOI: 10.1088/0004-637X/791/1/70
Abstract
Here we report on Swift and Suzaku observations near the end of an outburst
from the black hole transient 4U 1630-47 and Chandra observations when the
source was in quiescence. 4U 1630-47 made a transition from a soft state to the
hard state ~50 d after the main outburst ended. During this unusual delay, the
flux continued to drop, and one Swift measurement found the source with a soft
spectrum at a 2-10 keV luminosity of L = 1.07e35 erg/s for an estimated
distance of 10 kpc. While such transients usually make a transition to the hard
state at L/Ledd = 0.3-3%, where Ledd is the Eddington luminosity, the 4U
1630-47 spectrum remained soft at L/Ledd = 0.008/M10% (as measured in the 2-10
keV band), where M10 is the mass of the black hole in units of 10 solar masses.
An estimate of the luminosity in the broader 0.5-200 keV bandpass gives L/Ledd
= 0.03/M10%, which is still an order of magnitude lower than typical. We also
measured an exponential decay of the X-ray flux in the hard state with an
e-folding time of 3.39+/-0.06 d, which is much less than previous measurements
of 12-15 d during decays by 4U 1630-47 in the soft state. With the ~100 ks
Suzaku observation, we do not see evidence for a reflection component, and the
90% confidence limits on the equivalent width of a narrow iron Kalpha emission
line are <40 eV for a narrow line and <100 eV for a line of any width, which is
consistent with a change of geometry (either a truncated accretion disk or a
change in the location of the hard X-ray source) in the hard state. Finally, we
report a 0.5-8 keV luminosity upper limit of <2e32 erg/s in quiescence, which
is the lowest value measured for 4U 1630-47 to date.
Details
- Title: Subtitle
- A Delayed Transition to the Hard State for 4U 1630-47 at the End of Its 2010 Outburst
- Creators
- John A Tomsick - University of California, BerkeleyKazutaka Yamaoka - Nagoya UniversityStephane Corbel - Université Paris CitéEmrah Kalemci - Sabancı ÜniversitesiSimone Migliari - Universitat de BarcelonaPhilip Kaaret - University of Iowa
- Resource Type
- Journal article
- Publication Details
- The Astrophysical journal, Vol.791(1), pp.1-9
- DOI
- 10.1088/0004-637X/791/1/70
- ISSN
- 0004-637X
- eISSN
- 1538-4357
- Publisher
- Institute of Physics (IOP)
- Language
- English
- Date published
- 07/07/2014
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199807002771
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