Review of 3 years of observations with the low-energy gamma-ray telescope SIGMA onboard GRANAT

Mandrou, P.; Roques, J. P.; Bouchet, L.; Niel, M.; Paul, J.; Leray, J. P.; Lebrun, F.; Ballet, J.; Churazov, E.; Gilfanov, M.; Sunyaev, R.; Novikov, B.; Khavenson, N.; Kuleshova, N.; Sheikhet, A. I.; Tserenin, I.

doi:10.1086/191977

Cited by 18 publications

(14 citation statements)

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“…6). Similar flux levels were observed previously by GRANAT/SIGMA (see Mandrou et al 1994;Churazov et al 1994) and INTEGRAL/IBIS (Del ). In spring 2006 (MJD 53775−53846) the source went below the detection limits of JEM-X ( < ∼ 4 mCrab, 3−25 keV) and IBIS/ISGRI ( < ∼ 1 mCrab, 20−60 keV; (see Fig.…”

Section: Black-hole (Candidate) Binariessupporting

confidence: 89%

“…7). Comparable flux variations on weekly time scales have been observed earlier by INTEGRAL/IBIS (Bazzano et al 2004, 20−40 keV;Falanga et al 2006, 20−100 keV), as well as by GRANAT/SIGMA (Claret et al 1994; see also Mandrou et al 1994). Similar variability is also present in the CGRO/BATSE light curves (Harmon et al 2004; see also Barret et al 1996).…”

Section: X-ray Bursterssupporting

confidence: 78%

“…4.3). Similar "switch-offs" at hard X-rays occurred in 1991/1992 (e.g., Mandrou et al 1994;Harmon et al 2004(Harmon et al 2004) and 2004 . They seem to occur every ∼600 days (Smith et al 2002).…”

Section: Black-hole (Candidate) Binariesmentioning

confidence: 73%

“…The count rates in the two energy bands show that the source is harder than the Crab. Previous INTEGRAL observations (Pottschmidt et al 2006), as well as observations with GRANAT/SIGMA Mandrou et al 1994;Kuznetsov et al 1999) and RXTE and CGRO/BATSE (Smith et al 2001(Smith et al , 2002 showed the source had similar variability, disappearing at various times below the detection limits during a whole season, indicating variability by more than a factor of 10. Note that this is similar to that seen in 1E 1740.7−2942, as described above.…”

Section: Black-hole (Candidate) Binariesmentioning

confidence: 81%

“…Note that the correlated variability between the 20−60 keV and 60−150 keV bands, present during the first season, is absent during the first part of the second season. GRANAT/SIGMA observations already showed similar variability at energies > ∼ 40 keV at monthly time scales (Cordier et al 1993;Mandrou et al 1994;David et al 1998) and half-a-year time scales (Goldwurm et al 1995). CGRO/BATSE shows clearly the 20−100 keV variability on time scales longer than a month with fluxes between below the detection limit to up to 200 mCrab (Harmon et al 2004).…”

Section: X-ray Pulsarsmentioning

confidence: 83%

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The INTEGRAL Galactic bulge monitoring program: the first 1.5 years

Kuulkers¹,

Shaw

Paizis

et al. 2007

A&A

101

106

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Aims. The Galactic bulge region is a rich host of variable high-energy point sources. Since 2005, February 17 we are monitoring the source activity in the Galactic bulge region regularly and frequently, i.e., about every three days, with the instruments onboard INTEGRAL. Thanks to the large field of view, the imaging capabilities and the sensitivity at hard X-rays, we are able to present for the first time a detailed homogeneous (hard) X-ray view of a sample of 76 sources in the Galactic bulge region. Methods. We describe the successful monitoring program and show the first results from the start of the monitoring up to 2006, April 21, i.e., for a period of about one and a half year, during three visibility seasons. We focus on the short (hour), medium (month) and long-term (year) variability in the hard X-ray bands, i.e., 20−60 keV and 60−150 keV. When available, we discuss the simultaneous observations in the soft X-ray, 3−10 keV and 10−25 keV, bands. Results. Almost all the sources in the Galactic bulge region we detect in the 20−60 keV and 60−150 keV bands are variable. During the last two and a half weeks of the third visibility season most of the known persistent (hard) X-ray sources in the Galactic Center region were not detected. Of our sample of sources, per visibility season we detect 32/33 sources in the 20−60 keV band and 8/9 sources in the 60−150 keV band above a signal to noise of 7. On average, we find per visibility season one active bright ( > ∼ 100 mCrab, 20−60 keV) black-hole candidate X-ray transient and three active weaker ( < ∼ 25 mCrab, 20−60 keV) neutron star X-ray transients. Most of the time a clear anti-correlation can be seen between the soft and hard X-ray emission in some of the X-ray bursters. Hard X-ray flares or outbursts in X-ray bursters, which have a duration of the order of weeks are accompanied by soft X-ray drops. On the other hand, hard X-ray drops can be accompanied by soft X-ray flares/outbursts. During the course of our program we found a number of new sources, IGR J17354−3255, IGR 17453−2853, IGR J17454−2703, IGR J17456−2901b, IGR J17536−2339, and IGR J17541−2252. We report here on some of the high-energy properties of these sources. Conclusions. The high-energy light curves of all the sources in the field of view, and the high-energy images of the region, are made available through the WWW, as soon as possible after the observations have been performed, at

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Section: Black-hole (Candidate) Binariessupporting

confidence: 89%