Stringent radio constraint on the exceptional super-luminous supernova SN2017egm
ATel #10537; Cristina Romero-Canizales (MAS/UDP, Chile), Robert Beswick (JBCA, UK), Subo Dong (KIAA-PKU, China), Jose L. Prieto (UDP/MAS, Chile)
on 27 Jun 2017; 17:40 UT
Credential Certification: Cristina Romero-Canizales (cristina.romero.fdi@mail.udp.cl)
Subjects: Radio, Supernovae
We report radio observations of supernova SN2017egm (TNS Discovery Report, 591) at 10GHz with the Very Large Array (VLA; project 17A-464) on UT 22.9 June 2017, and at 1.5GHz with the electronic Multi-Element Remotely-Linked Interferometer Network (e-MERLIN) on UT 21 to 22 June 2017. SN2017egm is the nearest hydrogen-poor super-luminous supernova (SNSL-I; ATel #10498). These observations were made at a time near the optical peak and represent the most stringent radio constraint on the early evolution of such objects.
In the 2.5"x2.2" at PA=42deg VLA beam (C-configuration) we measure a peak intensity >2.5*r.m.s. at the reported SN position. At an r.m.s of ~ 7.5 uJy/b and taking into account the background emission from the host at the SN position, we obtain a 3*sigma upper limit of 33 uJy/b, which corresponds to a 10GHz luminosity upper limit of 7E+26 erg/s/Hz (at D_L=134Mpc). This is almost a factor of 30 better than previous upper limits for SLSN-I (SN2015bn, taken at 238d after its optical peak; Nicholl et al. 2016).
e-MERLIN observations were made with a bandwidth of 512MHz (effective ~400MHz after flagging) at a central frequency of 1.5GHz, and resulted in a circular fitted beam of 250mas. MKII telescope was not available in the observations due to other observing commitments. A number of mJy and sub-mJy radio sources within the field of view were detected. At a resolution of 250mas, we do not detect background emission from the host at the SN position, and we measure an r.m.s. of 32 uJy/b, which corresponds to a 1.5GHz luminosity upper limit of 2E+27 erg/s/Hz.
Further observations aiming at confirming the detection at different frequencies have been planned.
We thank the VLA and e-MERLIN Directors for approval of the observations reported here and the observatory staff who provided support.
