Massive stars exploding in a He-rich circumstellar medium – VII. The metamorphosis of ASASSN-15ed from a narrow line Type Ibn to a normal Type Ib Supernova

• Published in: Monthly notices of the Royal Astronomical Society Vol. 453; no. 4
• Main Authors: Pastorello, A., Prieto, J. L., Elias-Rosa, N., Bersier, D., Hosseinzadeh, G., Morales-Garoffolo, A., Noebauer, U. M., Taubenberger, S., Tomasella, L., Kochanek, C. S., Falco, E., Basu, U., Beacom, J. F., Benetti, S., Brimacombe, J., Cappellaro, E., Danilet, A. B., Dong, Subo, Fernandez, J. M., Goss, N., Granata, V., Harutyunyan, A., Holoien, T. W. -S., Ishida, E. E. O., Kiyota, S., Krannich, G., Nicholls, B., Ochner, P., Pojmański, G., Shappee, B. J., Simonian, G. V., Stanek, K. Z., Starrfield, S., Szczygieł, D., Tartaglia, L., Terreran, G., Thompson, T. A., Turatto, M., Wagner, R. M., Wiethoff, W. S., Wilber, A., Woźniak, P. R.
• Format: Journal Article
• Language: English
• Published: United States Royal Astronomical Society 09.09.2015
• Subjects: ASTRONOMY AND ASTROPHYSICS; supernovae: general; supernovae: individual: ASASSN-15ed; supernovae: individual: SN 1991D; supernovae: individual: SN 2006jc; supernovae: individual: SN 2010al
• ISSN: 0035-8711; 1365-2966

In this paper, we present the results of the spectroscopic and photometric monitoring campaign of ASASSN-15ed. The transient was discovered quite young by the All Sky Automated Survey for SuperNovae (ASAS-SN) survey. Amateur astronomers allowed us to sample the photometric SN evolution around maximum light, which we estimate to have occurred on JD = 2457087.4 ± 0.6 in the r band. Its apparent r-band magnitude at maximum was r = 16.91 ± 0.10, providing an absolute magnitude Mr ≈ -20.04 ± 0.20, which is slightly more luminous than the typical magnitudes estimated for Type Ibn SNe. The post-peak evolution was well monitored, and the decline rate (being in most bands around 0.1 mag d-1 during the first 25 d after maximum) is marginally slower than the average decline rates of SNe Ibn during the same time interval. The object was initially classified as a Type Ibn SN because early-time spectra were characterized by a blue continuum with superimposed narrow P-Cygni lines of He I, suggesting the presence of a slowly moving (1200–1500 km s-1), He-rich circumstellar medium. Later on, broad P-Cygni He I lines became prominent. The inferred velocities, as measured from the minimum of the broad absorption components, were between 6000 and 7000 km s-1. Lastly, as we attribute these broad features to the SN ejecta, this is the first time we have observed the transition of a Type Ibn SN to a Type Ib SN.