Recent results on transient behaviour, state transitions and X-ray spectroscopy in Galactic BHCs L.Natalucci and collaborators IASF-Roma/INAF
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Recent X-ray Nova outbursts H1743-322 = IGR J17464-3213
• known transient, past detections by Ariel-V,HEAO-1,Exosat,TTM • outburst in 2003 seen by INTEGRAL and RXTE • Radio, infrared and optical counterparts • Relativistic radio jets (v/c ~ 0.8) • No direct mass measurement, but likely BH candidacy due to HF QPO identification
The 2003 outburst, ASM data (2-12 keV)
(Kalemci et al., astro-ph/0512387)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
H1743-322 spectral variability Typical X-ray nova evolution
1. 2. 3. 4. Hard state during rise Intermediate (steep power-law) state Go to soft state (disk prominent) Return to hard state at the end, through intermediate state
Rev#58 Rev#56
Rev#55
INTEGRAL pattern of hardness behaviour
(Joinet et al., ApJ 2005; see also Capitanio et al., ApJ 2005)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
New bright X-ray transient: XTE J1817-330
• discovered by RXTE/ASM on 2006 Jan 26th, with immediate follow-up by RXTE/PCA: revealed a bright, soft source (> 1 Crab in 2-10 keV)
• INTEGRAL detection of hard X-rays up to ~ 200 keV, during GB monitoring and subsequent TOO observation • The source seems to be predominantly in the soft state • Column density constrained by CHANDRA to a very low value: < 1021 cm-2
Reported in several ATELs (#714 to 749)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Rapid flux variability in SAX J1819.3-2525 Coincident with variable star V4641 Sgr
• harbours a ~10M BH; estimated distance 7.4-12.3 kpc • variations as high as a factor 4 within s, and 500 within minutes, are observed on Sept 1999 • strong band limited noise (30-55% rms)
• observed again in 2003, with similar behaviour (Maitra & Baylin, 2006)
The 1999 outburst of V4641 Sgr
(Wijnands & Van der Klis, ApJ Lett, 2000 )
• source appears in hard state during violent activity
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
V4641 Sgr is a peculiar source within an optically thick cloud?
• in 2003, rapid variability is observed in radio, optical and Xrays. The X-ray spectrum of the flares reveal no visible blackbody component • the 2-10 keV range is dominated by prominent, wide Fe line emission and by a PL component. The resolution of RXTE/PCA does not allow to determine the energy/shape of the line(s) • modelling of the spectrum during the flare seems to require a huge variation of the column density (up to ~ 8 1023 cm-2).
• an optically thick cloud can be enshrouding the source (is it formed by the presence of outflows from the region close to the central BH?)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Another peculiar object: XTE J0421+560 = CI Cam
• Source with short outbursts (~hours to days) and flaring activity
Soft flares (light curves and spectra detected by ASCA)
(Ueda et al.1999)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
X-ray flares from XTE J1650-500
• discovered in 2001 by RXTE ASM
• orbital period 5.1 h) • outburst followed by Chandra/XMM in the X-rays
• detection of 6 bright flares occurring near the end of the outburst (duration ~100s, one order of magnitude increase in flux)
• if the flares are related to a real increase in accretion rate, they must originate very close to the central BH (within ˜20-100 Rs) Flares from XTE J1650-500 (Tomsick et al., ApJ 2003)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Variability and state transitions: Cyg X-1
Hard state
Soft state
Different spectral states of Cyg X-1 (Zdziarski al 2002)
Long term ASM and radio light curves, and new jet detection (Fender et al., astro-ph/0602307) L.Natalucci,Transients/GRB Meeting,
Roma, 22 March 2006
Cyg X-1 could power a “dark jet”
Gallo et al., Nature 2005
• Presence of a ring-like structure around the source (extent 5 pc).
Shock of the ambient ISM by a continuous jet?
• An important fraction of the accretion energy is used to power the jet (3 to 50% of the bolometric luminosity). Possible alternative to dissipation in accretion flows or advection through event horizon)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Chandra observation of Fe emission lines from Cyg X-1
Cyg X-1
• Detection of both a narrow Fe line and a broad feature near ˜ 6 keV (the latter is a combination of an edge and emission line) • could originate by reflection on both inner accretion disk (broad) and disk (narrow)
CHANDRA/HETGS spectrum of Cyg X-1 during intermediate state in January 2001
(Miller et al., ApJ 2004)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Relativistic iron emission lines from GX 339-4
GX 339-4
Detection of Fe K line from Chandra/HETGS obs of GX339-4. The line has an intrinsically broad and skewed profile (relativistic effects at the inner edge of accretion disk).
Detection of low Z absorption lines (O,Ne,Mg). The authors suggest they may be due to an outflowing absorber, other than ISM Low Z lines also detected in XTE J1650-500, but not the same
(Miller et al., ApJ 2004)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Iron absorption lines from H1743-322
Detection of variable He-like Fe XXV and H-like Fe XXVI absorption lines from H1743-322.
• The variation is detected down to ˜ min timescale • absence of Fe emission lines • does absorption occur in the inner accretion disk structure, or in a (possibly clumpy) outflow
H1743-322
(Miller et al., ApJ 2004)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Weak, narrow emission lines from 1E 1740.7-2942?
Reported (marginal) detection of emission lines, but very poor statistic on individual line measurements • Lines should be emitted in highly ionized medium (accretion disk?) • needs confirmation!
(Cui et al., ApJ 2004)
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006
Conclusions
• the development of the studies for BH and accretion phenomena have led to challenging the relativistic regime present near the central BH, especially by detailed X-ray spectroscopy. But improvement in spectral resolution, and sensitivity are needed
• the claimed evidence of absorbing structures in some of the sources need more investigation (similarity with AGN?)
• the large variability of the phenomena at any time scale involves a large energy bandwidth, good transient event coverage (fast response?) and of course, sensitivity
L.Natalucci,Transients/GRB Meeting, Roma, 22 March 2006