Keck spectroscopy of transient in NGC 2770

ATel #7515; G. Duggan (Caltech), Eric Bellm (Caltech), G. Leloudas (Weizmann, DARK/NBI), M. M. Kasliwal (Carnegie-Princeton) and S. R. Kulkarni (Caltech) report on behalf of a larger collaboration
on 16 May 2015; 14:16 UT
Credential Certification: Mansi Manoj Kasliwal (mansi@astro.caltech.edu)

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Alerted by C.C.Thoene and A. de Ugarte Postigo, at UT 2015 May 16.25, we obtained a spectrum of the optical transient noted in ATEL#7514 (also ATEL#7409) with the Keck I telescope. The LRIS instrument (Oke et al. 1995) was set up to cover 3075 to 10305 angstroms (400/3400 grism, 400/8500 grating with a central wavelength of 7830 angstroms). We see a hot, blue continuum with prominent Balmer, Helium II and Helium I emission with peak redshifts consistent with the velocity of NGC2770. The H-alpha line is asymmetric and not Gaussian with an approximate full width half maximum of ~1200 km/s. This transient was first reported by S. Howerton (SNHunt275; see ATEL#7042). Note that this transient was flagged in the intermediate Palomar Transient Factory database during a previous eruption in 2013 and designated as iPTF13efv.