The Unusually Luminous Extragalactic Nova SN 2010U

TL;DR

SN 2010U is an exceptionally luminous and fast Fe II type nova with unique spectral and photometric features, challenging existing theories about nova progenitors and spectral types.

Contribution

This paper reports the discovery and detailed analysis of SN 2010U, a highly luminous, fast Fe II nova, providing new insights into nova luminosity, speed, and progenitor characteristics.

Findings

SN 2010U is among the most luminous novae observed.

It exhibits a very fast decline with t_2 = 3.5 days.

Spectral analysis suggests a massive white dwarf progenitor.

Abstract

We present observations of the unusual optical transient SN 2010U, including spectra taken 1.03 days to 15.3 days after maximum light that identify it as a fast and luminous Fe II type nova. Our multi-band light curve traces the fast decline (t_2 = 3.5 days) from maximum light (M_V = -10.2 mag), placing SN 2010U in the top 0.5% of the most luminous novae ever observed. We find typical ejecta velocities of approximately 1100 km/s and that SN 2010U shares many spectral and photometric characteristics with two other fast and luminous Fe II type novae, including Nova LMC 1991 and M31N-2007-11d. For the extreme luminosity of this nova, the maximum magnitude vs. rate of decline relationship indicates a massive white dwarf progenitor with a low pre-outburst accretion rate. However, this prediction is in conflict with emerging theories of nova populations, which predict that luminous novae from massive white dwarfs should preferentially exhibit an alternate spectral type (He/N) near maximum light.