TITLE: GCN CIRCULAR NUMBER: 21571 SUBJECT: LIGO/Virgo G298048: Archival VLA observations DATE: 17/08/18 18:16:30 GMT FROM: Kate Alexander at Harvard U P. K. G. Williams (Harvard), K. D. Alexander (Harvard), and E. Berger (Harvard) report on behalf of a larger collaboration: We investigated observations of the candidate optical counterpart to LIGO/Virgo trigger G298048 in the NRAO Very Large Array (VLA) data archive. The field containing the candidate was observed at both 1.51 GHz ("L band") and 4.89 GHz ("C band") on June 10 and 23, 1984, as part of program AW0110. The on-source integration times were 11.5 and 5.5 minutes, respectively. We obtained images generated by the NRAO's VLA/AIPS data calibration pipeline (L. Sjouwerman, in preparation), which automatically processed the data in 2009. We see no persuasive evidence for radio emission at the location of either the host galaxy or the counterpart candidates. We measure image RMS values of ~180 and ~340 microJy near the candidates in the 1.51 and 4.89 GHz images, respectively. Taking a flux density upper limit of three times the RMS and a luminosity distance of 39.5 Mpc, these values correspond to upper limits on the spectral luminosity of 10^27.0 and 10^27.3 erg/s/Hz at 1.51 and 4.89 GHz. Using the relation between synchrotron emission and star formation rate presented by Yun & Carilli (2002 ApJ 568 88), the implied star formation rate of the candidate host galaxy is less than 0.05 solar masses per year. For comparison, Alexander et al. (LVC GCNs 21545, 21548) report a VLA radio detection of 300 microJy at 9.77 GHz, and Bannister et al. (LVC GCN 21559) report ATCA radio detections of 600-400 microJy at 8.5--21.2 GHz. These values are consistent with the archival limits.