Two optically variable radio sources from CRTS
ATel #1802; A. Mahabal, A. J. Drake, S. G. Djorgovski (Caltech), G. Pooley (Cavendish Lab, Cambridge), M. Catelan (PUC), M. J. Graham, R. Williams (CACR/Caltech), E. C. Beshore, S. M. Larson (LPL), E. Christensen (Gemini Obs)
on 22 Oct 2008; 19:12 UT
Credential Certification: Ashish Mahabal (aam@astro.caltech.edu)
Subjects: Radio, Optical, Variables
We have discovered two optically variable radio sources in the data from the
Catalina Real-time Transient Survey (CRTS). The discovery J2000 coordinates
are as follows. The colors are from 3 follow-up epochs at the Palomar 60-inch
telescope.
| ID | RA | Dec
| mag | g-r | r-i | i-z |
|---|
| CSS080928:232827+151752 | 23:28:27.22 | +15:17:52.4 | 18.7 | 0.4
- 1.0 | 0.2 | 0.1 - 0.6 |
| CSS080930:020344+304238 | 02:03:44.27 | +30:42:38.2 | 17.6 | -0.1
- 0.1 | 0.4 | -0.8 - -1.1 |
Radio observations using the AMI/LA (the upgraded Ryle Telescope) show no
radio variability based on observations taken a week apart.
Archival NVSS fluxes (at 1.4 GHz) along with the AMI/LA
fluxes (at 15 GHz) are summarized in the table below.
Spectroscopic observations were carried out with Palomar 200" on Oct 1st using
the Double Beam Spectrograph.
| ID | NVSS | AMI/LA |
|---|
| CSS080930:020344+304238 | 174 | 150+/-10% |
| CSS080928:232827+151752 | 16 | 113+/-10% |
CSS080928:232827+151752:
Jackson et al. 2007, MNRAS 376, 371, quote it
(J2000 23:28:27.225 +15:17:52.12) as having S(8.4GHz) = 38 mJy.
The three flux densities suggest that the spectrum is rising and likely
to be variable.
The P200 spectrum is noisy, without obvious, prominent features, and likely to be a blazar.
The NVSS compact source (69.4 mJy at 1.4 GHz;
J2000 23:28:37.84 +15:18:42.8) about 2'.6 to the E is not seen at 15 GHz in the AMI/LA
to a limit of approximately 10mJy. There is no evidence for a connection
between the two sources.
CSS080930:020344+304238:
The radio spectral index is ~-0.07 and the source is likely to be a flat-spectrum blazar.
Initial analysis of the spectrum indicates it to be at a
redshift of 0.76 based on a single broad emission line, very likely to be
MgII.
Further observations are encouraged.
CRTS optical transients are detected and published as VOEvents in real-time at
http://voeventnet.org/feeds/Catalina.shtml
and in RSS here http://voeventnet.caltech.edu/feeds/Catfeed.xml
