RXTE observations of the black hole candidate H1743-322 in its rising phase of the outburst
ATel #1780; K. Yamaoka (Aoyama Gakuin University), J. H. Swank (NASA/GSFC), T. Belloni (INAF), and H. Takahashi (Hiroshima University)
on 13 Oct 2008; 01:38 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Kazutaka Yamaoka (yamaoka@phys.aoyama.ac.jp)
Subjects: X-ray, Gamma Ray, Binary, Black Hole, Transient
A series of RXTE Public ToO observations of the black hole
candidate H1743-322 (ATel #1739, #1745, #1779) were performed
on Oct. 3, 7, 8, 9 and 11.
The broadband PCA and HEXTE spectra in the 3-200 keV range are
well explained by a power-law with a photon index of 1.34-1.44,
with a high energy cutoff at 83-94 keV, modified with Galactic
absorption and smeared edge at 7.11 keV due to cold iron (instead of
reflection component).
The PCA absorbed flux in 3-20 keV is gradually increasing
from 2.28e-9 erg/cm^2/s (86 mCrab) to 2.50e-9 erg/cm^2/s (94 mCrab),
while the HEXTE measured flux in 20-100 keV is decreasing
from 3.24e-9 erg/cm^2/s to 2.93e-9 erg/cm2/s, suggesting
that the source spectrum is gradually softening.
A low-frequency QPO is detected in the PCA power spectrum,
with frequency increasing from 0.3 to 0.6 Hz (from Oct 3 to 11) and a
clear peak at its first overtone.
The spectral softening and the QPO indicate progression into the hard
intermediate state, as suggested by Corbel et al. (ATel #1766).
The flux is still very low, by comparison to previous outbursts (See http://lheawww.gsfc.nasa.gov/users/craigm/galscan/html/H1743-322.html )
and the QPO frequencies could rise a lot higher in this state.
Further multi-wavelength observations are strongly encouraged.
