Unusual Long and Luminous Optical Transient in the Subaru Deep Field

TL;DR

This paper reports the discovery and analysis of an unusual, long-lasting optical transient with high luminosity, possibly a peculiar supernova, observed over 800 days in the Subaru Deep Field at intermediate redshift.

Contribution

The study presents the first detailed observation of a long-duration, luminous optical transient with unique properties, suggesting a new class of supernova at intermediate redshift.

Findings

Transient lasted over 800 days in observer frame.

Maximum brightness reached ~23 mag in i' and z' bands.

Total radiated energy was approximately 10^51 erg.

Abstract

We present observations of SDF-05M05, an unusual optical transient discovered in the Subaru Deep Field (SDF). The duration of the transient is > ~800 d in the observer frame, and the maximum brightness during observation reached approximately 23 mag in the i' and z' bands. The faint host galaxy is clearly identified in all 5 optical bands of the deep SDF images. The photometric redshift of the host yields z~0.6 and the corresponding absolute magnitude at maximum is ~-20. This implies that this event shone with an absolute magnitude brighter than -19 mag for approximately 300 d in the rest frame, which is significantly longer than a typical supernova and ultra-luminous supernova. The total radiated energy during our observation was 1x10^51 erg. The light curves and color evolution are marginally consistent with some of luminous IIn supernova. We suggest that the transient may be a unique and peculiar supernova at intermediate redshift.