iPTF discovery of iPTF15ayt, a young Type II Supernova showing flash-spectroscopy signatures, and an HST target

ATel #7567; A. Gal-Yam, I. Sagiv, O. Yaron, A. Horesh, E. Ofek (Weizmann), F. Taddia, R. Amanullah, T. Petrushevska, R. Ferretti (OKC), S. R. Kulkarni, M. Kasliwal, Y. Cao, D. Perley (Caltech), S. B. Cenko (NASA/GSFC) S. Ben-Ami (Harvard/CfA) on behalf of the iPTF collaboration.
on 26 May 2015; 20:33 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Avishay Gal-Yam (avishay.gal-yam@weizmann.ac.il)

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The intermediate Palomar Transient Factory (ATel#4807) reports the discovery of iPTF15ayt, a young type II SN in a nearby galaxy (redshift z=0.045715, mean distance modulus DM=36.52, metric distance d~202 Mpc; NED). The transient was discovered on 2015 May 26.32 UT at RA(J2000) = 14:56:27.85, DEC(J2000) = +18:22:24.7, at a magnitude of 19.6 in the PTF g-band (calibrated with respect to SDSS), which corresponds to an absolute magnitude of -16.9 (according to the above DM). A non-detection (3-sigma, to a limiting PTF g-band magnitude of 21.4) was obtained at the location ~24 hr earlier on 2015 May 25.35 UT. A spectrum was promptly obtained on 2015 May 26.45 (~2.5 hours from event confirmation) with the GMOS spectrograph mounted on Gemini-N, showing flash-spectroscopy signatures (Gal-Yam et al., 2014, Nature, 509, 471) - narrow to intermediate width Balmer series emission lines and broader prominent He II 4686 and C IV 5806, all on top of a hot blue continuum. We have triggered the Hubble Space Telescope in order to obtain a series of prompt UV spectra of this event, as well as numerous other follow-up programs. We encourage additional monitoring at all wavelengths of this young supernova.