[vsolj-alert 68] Radio jet? in CI Cam

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

Radio jet? in CI Cam

　CI Camと同定されたＸ線新星（トランジェント）ですが、VLAによる電波観測
　の結果、広がりが観測されている兆候を示しているそうです。Ｘ線新星の仲間
　には "jet source" と呼ばれる一群の天体があり、GRS 1915+105 のように光速
　に近いジェットを放出しているものも観測されています。もし CI Cam がこれ
　らの天体の仲間であった場合、既知の "jet source" に比べて近傍の天体であ
　り、星間吸収量も小さいので、これらの "jet source" の正体に迫るまたとな
　い機会を提供してくれる可能性があります。光での観測では、ドップラーシフ
　トした輝線が観測されないか（SS433のように）、高分解能のイメージングで
　ジェットが実際に確認できないかなどが焦点になりそうです。

Date: Sun, 05 Apr 1998 10:55:11 -0600
From: "Robert M. Hjellming (Bob)" <rhjellmi@aoc.nrao.edu>
Subject: [vsnet-alert 0] preliminary indications of radio jets in CI Cam

    I am convinced enough to be willing to tell people we
have preliminary VLA evidence for twin jets from CI Cam. 
This is derived from VLA imaging April 5.08 UT.
A 10 hour VLBA run was occuring at the same time, so
that (and the April 1 VLBA run) will really tell us what
is going on.
 
We want confirming evidence Monday or Tuesday before
we would put it in an IAUC.

The jets shows up best at 1.3 cm where the half-power beam is
0.07", but we see extensions at the same position angle (-45d) 
on both sides in the 2cm images also.

I am letting people know early, even though there is some chance
that I will end up with "egg on my face," because the right 
spectroscopy/imaging might bring out signs of optical emission 
from the jets.  

Assuming a start when the XR rise began on March 31.06, and a location 
0.1" from the center on April 5.08 UT, if the distance is 1 kpc
as suggested by Chkhikvadze (and quoted in Bergner et al. 1995)
this is ~0.1c apparent lateral motion. Both sides have roughly 
the same flux so there is no large doppler boosting, which is 
reasonable if that is the ballpark of the physical velocity.

The radio spectrum continues to evolve from an optically thick
to thin state, and at the time of the observations just mentioned
preliminary fluxes were 220, 500, 532, 370, and 320 mJy
at 1.4, 4.9, 8.4, 14.9, and 22.5 GHz.  So the spectrum peaked at
4.9 GHz, whereas on April 3.83 UT it peaked at 8.6 GHz.

The public domain GBI data up to about April 5.0 shows the source rising 
at 2.25 GHz and staying at about the same flux levels at 8.3 GHz,
We had enough time span in the April 3.83 UT VLA run to confirm
that the GBI measurements on April 3 correctly observed the
hourly flux changes, and there were even signs of the same
fluctuation in the high frequencies that seemed present in
the GBI 8.3 GHz data.

If you look at the GBI public data, ignore the April 1-2
data for J0421+56 and j0420+56; it needs special processing
to shift the visibilities to the correct position and correct
for beam sensitivity effects before we will have data on those 
(critical!) portions of the radio light curves.

Keep up the observing!  The radio variations are vary rapid so
all aspects of this event in CI Cam are probably short in lifetime,
as was spectacularly true for its X-ray emission.

Bob

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