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EVLA Observations of CSS100217:102913+404220

ATEL # 2629; Dale A. Frail (NRAO), Andrew Drake (Caltech), George Djorgovski (Caltech), Ashish Mahabal (Caltech)
on 22 May 2010; 21:36 UT
Password Certification: Dale A. Frail (

Subjects: Radio, AGN, Black Holes, Nova, Supernova, Transients

We used the Expanded Very Large Array (EVLA) to observe the field of view toward a luminous optical transient CSS100217:102913+404220, discovered by the Catalina Real-time Transient Survey (CRTS) (ATel #2544). The EVLA observations were made on April 29.22 UT and May 14.07 UT. For each epoch we observed the source simultaneously at frequencies of 4495 MHz and 7915 MHz for a total of 35 minutes.

We detect point-like radio emission that is spatially coincident with the optical transient (1 sigma=+/-0.2 arcsec). On April 29.22 UT the flux densities were 447+/-26 uJy (4495 MHz) and 399+/-24 uJy (7915 MHz). On May 14.07 UT the flux densities were 312+/-24 uJy (4495 MHz) and 349+/-24 uJy (7915 MHz).

We estimate the peak 5 GHz spectral luminosity to be 2e29 erg/s/Hz. This value is brighter than a typical Type Ib, Ic or IIn radio supernova at maximum light (Chevalier, Fransson & Nymark, ApJ, 641 1029, 2006). The spectral luminosity, flat spectral index and the degree of variability are reasonable for a radio quiet AGN.

The simplest hypothesis, which is consistent with these data, is that the radio emission is dominated by the nucleus and may be unrelated to the optical and UV transient (ATel #2554). However, we cannot yet exclude at least a partial association with this unusual transient.

Further observations are planned.

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