A radio flare from Cyg X-3
ATel #727; Tsuboi (NRO NAOJ), N. Kuno (NRO NAOJ), T. Umemoto (NRO NAOJ), T. Sawada (NRO NAOJ), K. Nakanishi (NRO NAOJ), T. Tosaki (NRO NAOJ), Y. Kurono (NRO NAOJ), K. Fujisawa (Yamaguchi-U), Japanese VLBI Network Team, S. Trushkin (SAO RAS), T. Kotani (Tokyo Tech), N. Kawai (Tokyo Tech)
on 9 Feb 2006; 10:40 UT
Distributed as an Instant Email Notice Request For Observations
Credential Certification: Sergei Trushkin (satr@sao.ru)
Subjects: Radio, Millimeter, Request for Observations, Binary, Black Hole
We report that the microquasar Cyg X-3 is undergoing a significant radio
flare and would request for followup observations at all frequencies.
In the current multi-frequency monitoring observations with RATAN-600
radio telescope, the flux density at 4.8 GHz of the source was found to
drop from 103 mJy on Jan 14.4 (UT) to 43 mJy on Jan 15.4 (UT), and to 22
mJy on Jan 17.4 (UT). The source is known to exhibit the radio flares
typically with a few peaks exceeding 5 Jy following such quenched state
(Waltman et al., 1994, AJ, 108, 179). The source has been monitored from
Jan 25 (UT) with the Nobeyama Radio Observatory 45m Telescope (NRO45m
Telescope), the Nobeyama Millimeter Array (NMA), Yamaguchi-University
32-m Radio Telescope (YRT32m), and Japanese VLBI Network telescopes.
On Feb 2.2 (UT), about 18 days after it entered the quenched state,
the rise of a first peak is detected with the NRO45m Telescope and
YRT32m. On Feb 3.2 (UT), the flux densities reached to the first
peak at all the sampling frequencies from 2.25 GHz to 110.10 GHz.
The typical flux is 1 - 1.2 Jy and the peak spectrum is flat over
the observation band, suggesting an optically thick radio source.
The peak spectrum and light curves are plotted
respectively here: http://www.hp.phys.titech.ac.jp/kotani/cygx3/11.html and http://www.hp.phys.titech.ac.jp/kotani/cygx3/7.html The current
RATAN-600 simultaneous spectra (1-30 GHz) are plotted at: http://cats.sao.ru/~satr/XB/CygX-3/CygX-3_Feb2006sp.gif
After the peak, the flux densities decayed exponentially (or
power-law) with a time scale of 4-8 days, except for rapid variation
of more than 100 mJy in 30 min. On Feb 8.90 (UT), the rise of a
second peak was detected with the NRO45m Telescope. During 1 hour the
flux density increased from 900 mJy to 1340 mJy at 23 GHz.
On Feb 9.5 (UT) the RATAN-600 indicated from 400 mJy at 2.3 GHz to 545 mJy
at 30 GHz.
Further observations are in progress.
