* Astronomy

Title: SN 2015bp: adding to the growing population of transitional type Ia supernovae
Author: Shubham Srivastav, G. C. Anupama, D. K. Sahu, C. D. Ravikumar

Photometric and spectroscopic observations of type Ia supernova 2015bp are presented, spanning ~-6 to ~+141 days since B-band maximum. Also presented are unpublished HCT spectra of type Ia iPTF13ebh between ~11 to +34 days since B-band maximum. SN 2015bp shows rapidly declining light curves with delta_m15(B)=1.72±0.04. The I-band light curve shows a clear secondary maximum and peaks before the B-band maximum, placing SN 2015bp in the transitional category of SNe Ia. The spectral evolution of SN 2015bp resembles other transitional SNe Ia rather than 1991bg-like events. The C ii lambda6580 feature is detected in both SN 2015bp and iPTF13ebh, though it is present till the epoch of B-band maximum in the case of SN 2015bp. The velocity gradients of Si ii lambda6355 place SN 2015bp and iPTF13ebh in the FAINT subclass, whereas pseudo-equivalent widths of Si ii features place them in the Cool (CL) subclass of SNe Ia. The bolometric light curve of SN 2015bp indicates that ~0.2 solar masses of 56Ni was synthesized in the explosion, with a total ejected mass of ~0.9 solar masses, suggesting a sub-Chandrasekhar mass white dwarf progenitor.

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