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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
Password Certification: Ashish Mahabal (

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 magg-rr-ii-z
CSS080928:232827+15175223:28:27.22+15:17:52.418.70.4 - - 0.6
CSS080930:020344+30423802:03:44.27+30:42:38.217.6-0.1 - 0.10.4 -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.


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 and in RSS here

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