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Far-ultraviolet to Near-infrared Spectroscopy of a Nearby Hydrogen-poor Superluminous Supernova Gaia16apd

Lin YanCaltech Optical Observatories & Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125, USA; [email protected]R. M. QuimbyDepartment of Astronomy, San Diego State University, San Diego, CA 92182, USAA. Gal‐YamDepartment of Particle Physics & Astrophysics, Weizmann Institute of Science, Rehovot 7610001, IsraelPeter J. BrownGeorge P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy, Department of Physics and Astronomy, Texas A. & M. University, 4242 TAMU, College Station, TX 77843, USAN. BlagorodnovaCentre for Astrophysics & Supercomputing, Swinburne University, Hawthorn VIC 3122, AustraliaE. O. OfekDepartment of Particle Physics & Astrophysics, Weizmann Institute of Science, Rehovot 7610001, IsraelR. LunnanCentre for Astrophysics & Supercomputing, Swinburne University, Hawthorn VIC 3122, AustraliaJeff CookeDepartment of Astronomy, California Institute of Technology, Pasadena, CA 91125, USAS. B. CenkoAstrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771, USAJ. E. JencsonCentre for Astrophysics & Supercomputing, Swinburne University, Hawthorn VIC 3122, AustraliaM. M. KasliwalCentre for Astrophysics & Supercomputing, Swinburne University, Hawthorn VIC 3122, Australia

2017en

ABI

Annotatsiya

Abstract We report the first maximum-light far-ultraviolet (FUV) to near-infrared (NIR) spectra (1000 Å − 1.62 μ m, rest) of a hydrogen-poor superluminous supernova, Gaia16apd. At z = 0.1018, it is the second closest and the UV brightest SLSN-I, with 17.4 mag in Swift UVW2 band at −11 days pre-maximum. The coordinated observations with HST , Palomar, and Keck were taken at −2 to +25 days. Assuming an exponential (or t 2 ) form, we derived the rise time of 33 days and the peak bolometric luminosity of 3 × 10 44 erg s −1 . At the maximum, the photospheric temperature and velocity are 17,000 K and 14,000 km s −1 , respectively. The inferred radiative and kinetic energy are roughly 1 × 10 51 and 2 × 10 52 erg. Gaia16apd is extremely UV luminous, and emits 50% of its total luminosity at 1000–2500 Å. Compared to the UV spectra (normalized at 3100 Å) of well studied SN1992A (Ia), SN2011fe (Ia), SN1999em (IIP), and SN1993J (IIb), it has orders of magnitude more FUV emission. This excess is interpreted primarily as a result of weaker metal-line blanketing due to a much lower abundance of iron group elements in the outer ejecta. Because these elements originate either from the natal metallicity of the star, or have been newly produced, our observation provides direct evidence that little of these freshly synthesized material, including 56 Ni, were mixed into the outer ejecta, and the progenitor metallicity is likely sub-solar. This disfavors Pair-instability Supernova models with helium core masses , where substantial 56 Ni material is produced. A higher photospheric temperature definitely contributes to the FUV excess from Gaia16apd. Compared with Gaia16apd, we find PS1-11bam is also UV luminous.

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DOI: 10.3847/1538-4357/aa6b02

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