Recent searches by unbiased, wide-field surveys have uncovered a group of extremely luminous optical transients. The initial discoveries of SN 2005ap by the Texas Supernova Search and SCP-06F6 in a deep Hubble pencil beam survey were followed by the Palomar Transient Factory confirmation of host redshifts for other similar transients. The transients share the common properties of high optical luminosities (peak magnitudes ∼ −21 to −23), blue colors, and a lack of H or He spectral features. The physical mechanism that produces the luminosity is uncertain, with suggestions ranging from jet-driven explosion to pulsational pair-instability. Here we report the most detailed photometric and spectral coverage of an ultra-bright transient (SN 2010gx) detected in the Pan-STARRS 1 sky survey. In common with other transients in this family, early-time spectra show a blue continuum, and prominent broad absorption lines of O II. However, about 25d after discovery, the spectra developed type Ic supernova features, showing the characteristic broad Fe II and Si II absorption lines. Detailed, post-maximum follow-up may show that all SN 2005ap and SCP-06F6 type transients are linked to supernovae Ic. This poses problems in understanding the physics of the explosions: there is no indication from late-time photometry that the luminosity is powered by 56 Ni, the broad lightcurves suggest very large ejected masses, and the slow spectral evolution is quite different from typical Ic timescales. The nature of the progenitor stars and the origin of the luminosity are intriguing and open questions. Subject headings: supernovae: general -supernovae: individual(SN 2010gx, SCP-06F6, SN 2005ap)
New mid-infrared (10 and 20 km) spectrophotometry of the ultraluminous infrared galaxy IRAS 08572]3915 is presented. The 10 km spectrum reveals a deep silicate absorption feature, while the 20 km spectrum shows no clear evidence for an 18 km silicate absorption feature. An interstellar extinction curve is Ðtted to IRAS 08572]3915 and two other deep silicate infrared galaxies, NGC 4418 and Arp 220. It is found that pure extinction cannot explain the spectral energy distributions of these sources. On the other hand, both the strength of the silicate absorption and the overall spectral energy distributions of the three galaxies agree well with scaled-up models of galactic protostars. From this agreement, we conclude that the infrared emission comes from an optically thick dust shell surrounding a compact power source. The size of the power source is constrained to be smaller than a few parsecs. We argue that a signiÐcant portion of the total luminosities of these galaxies arises from an active galactic nucleus deeply embedded in dust.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.