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GRS1915+105: a very strong radio flare after a spike in hard X-rays

ATEL # 2899; S.A. Trushkin , N.A. Nizhelskij (SAO RAS, Russia)
on 2 Oct 2010; 6:27 UT
Password Certification: Sergei Trushkin (

Subjects: Radio, Infra-Red, X-ray, Request for Observations, Binaries, Black Holes, Transients

We are monitoring radio states of GRS 1915+105 at 2-22 GHz with the RATAN-600 radio telescope (see also ATEL #1509). On 01 October 2010 (MJD 55470.66) we detected a very strong radio flare from the the black hole X-ray binary and microquasar GRS 1915+105. The spectrum of the detected optically thin synchrotron flare is well fitted by a power law: S_nu[mJy] = 958nu^-0.615[GHz] in 2-11 GHz range. The day before the radio fluxes were less 30 mJy at 5-11 GHz. This flare could be related with the bright event of 0.145 counts/cm^2/s (~0.7 crabs) in hard X-ray band of Swift/BAT ASM (15-50 keV), occured on MJD 55470.17, when X-ray flux increased by the factor ~1.5. The source is in a active state in the soft XTE ASM band (2-12 keV), reaching to 44 counts/s (~0.6 crabs).
See the RATAN-spectrum of the flare:
Here is the recent light curve in Swift/BAT ASM program (data from the Swift site): ,
and the light curve in RXTE ASM program (data from the HEASARC/GSFC/NASA site):

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