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SN 2016coi
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 Host galaxy UGC 11868 imaged by Legacy Surveys | |
| Event type | Supernova  |
|---|---|
| SN.Ic | |
| Date | 27 May 2016 |
| Constellation | Pegasus |
| Right ascension | 21h 59m 04.14s[1] |
| Declination | +18° 11′ 10.5″[1] |
| Epoch | J2000 |
| Redshift | 0.0036[1] |
| Host | UGC 11868 |
| Colour (B-V) | 0.075[2] |
| Peak apparent magnitude | 14.76±0.01[3] |
| Total energy output | (7–8)×1051 erg[2] |
| Other designations | iPTF 16coi, AT 2016coi, ASASSN -16fp, SN 2016coi, DLT 16d |
SN 2016coi (also known as ASASSN-16fp), was a broad-lined supernova in the barred spiral galaxy UGC 11868.[2] It was first discovered on May 27, 2016, by the All Sky Automated Survey for SuperNovae (ASAS-SN), whilst the actual explosion happened around 2 to 3 days prior.[2] It had an apparent brightness of 15.7 in the V band when it was discovered. Its peak absolute magnitude was around −17.7.[3] It is about 51.5 million light years away from the Earth, and located in the constellation Pegasus.[1] It is located around 31.7" north and 7.9" west from the center of its galaxy.[4]
The energy produced by the supernova was around (7–8)×1051 ergs, and ejected 4 to 7 solar masses worth of material. It also ejected around 0.15 solar masses worth of nickel-56 from the explosion.[2]
Characteristics
[edit]It was initially classified as a broad-lined Type Ic supernova based on its spectral features.[5] Later studies classified it as an intermediate object between a Type Ib and a Type Ic, due to spectral analysis finding traces of helium within the ejecta.[2][5][6] The ejecta expansion velocity reached around 16,000 km/s and then slowed down to roughly 8,000 km/s just one month after reaching its maximum.[3] There are helium absorption features that also were observed with velocities around 20,000 km/s before maximum light.[2]
The supernova came from a massive progenitor star, most likely a Wolf–Rayet star. Radio and X-ray observations indicated it was surrounded by a very dense circumstellar envelope.[2][7] It experienced a phase of higher mass loss around 30 years before its collapse, and it was losing material at twice the rate when compared to its final decade of life.[7] It had an estimated initial main-sequence mass of around 23 to 28 solar masses.[1] It experienced a significant amount of mass loss before its collapse and it was left with a final core mass of 6 to 10 solar masses. The star did not completely strip out from its outer layers before the explosion.[2]
There were nebular spectral features that began appearing in the spectra around 90 days after the explosion.[1] It showed the optical spectra had a low calcium to oxygen emission line ratio of around 0.2. This can indicate the progenitor had a large core mass during the time of its explosion. There are also forbidden oxygen emission lines that blueshifted to around 400 km/s. The blueshift may indicate some asymmetry in the distribution of the ejecta. The V band brightness decreased by around 1.7 magnitudes per 100 days after the explosion.[2] This decrease is quicker than expected from the radioactive decay of cobalt-56. It can also indicate that gamma rays were leaking outward from the increasing ejecta.[1]
The supernova's helium features disappeared after reaching maximum light, which is uncommon for normal Type Ib supernovae. The helium is likely caused by the nickel-56 mixing with the outer ejecta layers. It has a broad bolometric light curve, with it being Δ15 ≈ 0.41 magnitudes. This indicates a relatively long photon diffusion timescale within the ejecta.[2]
References
[edit]- ^ a b c d e f g Prentice, S. J.; et al. (2018). "SN 2016coi/ASASSN-16fp: An example of residual helium in a typeIc supernova?". Monthly Notices of the Royal Astronomical Society. 478 (3): 4162. arXiv:1709.03593. Bibcode:2018MNRAS.478.4162P. doi:10.1093/mnras/sty1223.
- ^ a b c d e f g h i j k Terreran, G.; Margutti, R.; Bersier, D.; Brimacombe, J.; Caprioli, D.; Challis, P.; Chornock, R.; Coppejans, D. L.; Dong, Subo; Guidorzi, C.; Hurley, K.; Kirshner, R.; Migliori, G.; Milisavljevic, D.; Palmer, D. M.; Prieto, J. L.; Tomasella, L.; Marchant, P.; Pastorello, A.; Shappee, B. J.; Stanek, K. Z.; Stritzinger, M. D.; Benetti, S.; Chen, Ping; Demarchi, L.; Elias-Rosa, N.; Gall, C.; Harmanen, J.; Mattila, S. (2019). "SN 2016coi (ASASSN-16fp): An Energetic H-stripped Core-collapse Supernova from a Massive Stellar Progenitor with Large Mass Loss". The Astrophysical Journal. 883 (2): 147. arXiv:1905.02226. Bibcode:2019ApJ...883..147T. doi:10.3847/1538-4357/ab3e37.
- ^ a b c Kumar, Brajesh; Singh, A.; Srivastav, S.; Sahu, D. K.; Anupama, G. C. (2018). "ASASSN-16fp (SN 2016coi): A transitional supernova between Type Ic and broad-lined Ic". Monthly Notices of the Royal Astronomical Society. 473 (3): 3776. arXiv:1709.08832. Bibcode:2018MNRAS.473.3776K. doi:10.1093/mnras/stx2498.
- ^ "ATel #9086: ASASSN-16fp: Discovery of A Probable Supernova in UGC 11868". The Astronomer's Telegram.
- ^ a b Yamanaka, Masayuki; et al. (2017). "Broad-lined Supernova 2016coi with a Helium Envelope". The Astrophysical Journal. 837 (1): 1. arXiv:1702.02035. Bibcode:2017ApJ...837....1Y. doi:10.3847/1538-4357/aa5f57.
- ^ "ATel #9124: Spectroscopic follow-up observations of AT 2016coi (ASASSN-16fp) : possible detection of helium". The Astronomer's Telegram.
- ^ a b Nayana, A. J.; Chandra, Poonam (2020). "Radio view of a broad-line Type Ic supernova ASASSN-16fp". Monthly Notices of the Royal Astronomical Society. 494 (1): 84. arXiv:2003.02709. Bibcode:2020MNRAS.494...84N. doi:10.1093/mnras/staa700.
