The Astronomer's Telegram
Telegram Index | Search
To The Parent Site

[ Previous | Next ]

Blazar 1ES 1959+650 shows high and hard X-ray state

ATEL # 1315; E. Bottacini (MPE), V. Beckmann, W. Ishibashi (ISDC), M. Ajello, J. Greiner (MPE)
on 30 Nov 2007; 13:13 UT
Distributed as an Instant Email Notice (Request for Observations)
Password Certification: Volker Beckmann (

Subjects: X-ray, Gamma Ray, AGN

The TeV blazar 1ES 1959+650 has been observed by INTEGRAL within the north-ecliptic pole key program. The source was detected by IBIS/ISGRI within revolution 625 (199 ksec: 2007-11-25T19:47 until 2007-11-28T08:43) with 5.3 sigma in the 20-40 keV energy band with a flux of about 4 mCrab. The source was not covered by JEM-X and OMC. The spectrum is well represented by a single power law with photon index 1.9+-0.4 which gives a model flux of 5.6e-11 erg/cm**2/sec in the 20-100 keV band (Lx = 5.5e44 erg/sec). Based on the model, we expect the source to have a 2-10 keV flux of about 4e-11 erg/cm**2/sec, half the value the blazar exhibited during the strong outburst in 2001. The spectral slope implies that the peak of the synchrotron emission lies within or near to the band covered by IBIS/ISGRI. Based on models of the spectral energy distribution (Tagliaferri et al. 2003), we expect a flux of >1e-12 photons/cm**2/sec above 1 TeV, which would make 1ES 1959+650 again detectable for e.g. MAGIC.

Time resolved analysis of the IBIS/ISGRI data shows that the flux varied throughout the INTEGRAL observation: 2.9+-1.0 mCrab (2007-11-24T16:52 - 2007-11-26T08:43), 4.2+-1.0 mCrab (2007-11-26T08:45 - 2007-11-27T17:23), and 2.1+-1.1 mCrab (2007-11-27T17:25 - 2007-11-29T11:43).

INTEGRAL will continue to observe the field until 2007-12-04T08:35.

[ Telegram Index ]

R. E. Rutledge , Editor
ATEL Mirror v1.0 Updates