SN 2008ax

SN 2008ax was a helium-rich type Ib core-collapse supernova in the interacting galaxy NGC 4490.[3] It was independently discovered on 3 March 2008 by LOSS[5] and 4 March by Koichi Itagaki.[6] The site had been monitored six hours before discovery, thus constraining the time of the explosion breakout.[3] It was the third-brightest supernova of 2008.[7] The brightness in the B-band peaked about 20 days after the explosion.[3] X-ray emissions were detected from the event, which are most likely the result of shock heating from the supernova ejecta and circumstellar material.[8]

SN 2008ax
Position of SN 2008ax in NGC 4490; image courtesy of Hunter Wilson
Event typeSupernova
Type Ib[1]
Date3 March 2008
ConstellationCanes Venatici
Right ascension12h 30m 40.80s[2]
Declination+41° 38′ 16.1″[2]
EpochJ2000.0
Galactic coordinatesb = 137.95°, l = +74.88°[2]
Distance31 Mly (9.6 Mpc)[3]
SourceNGC 4490
Peak apparent magnitude+13.0[4]

Images of the source location made using the Hubble Space Telescope in 2011 and 2013 were used to identify the progenitor. If it was a single star, the images are compatible with a supergiant star with a class of B to mid-A type. However, this is not favored by models which indicate the progenitor had a relatively low mass of 4–5 M☉ and extended hydrogen-rich atmosphere with a radius of 30–40 R☉. An alternative, more plausible model suggests the progenitor was part of an interacting binary system where much of the atmosphere was lost through mass transfer to the companion.[1]

References
  1. Folatelli, Gastón; et al. (October 2015). "The Progenitor of the Type IIb SN 2008ax Revisited". The Astrophysical Journal. 811 (2): 13. arXiv:1509.01588. Bibcode:2015ApJ...811..147F. doi:10.1088/0004-637X/811/2/147. S2CID 53463754. 147.
  2. Drake, A. J.; et al. (May 2009). "First Results from the Catalina Real-Time Transient Survey". The Astrophysical Journal. 696 (1): 870–884. arXiv:0809.1394. Bibcode:2009ApJ...696..870D. doi:10.1088/0004-637X/696/1/870. S2CID 7530040.
  3. Pastorello, A.; et al. (September 2008). "The Type IIb SN 2008ax: spectral and light curve evolution". Monthly Notices of the Royal Astronomical Society. 389 (2): 955–966. arXiv:0805.1914. Bibcode:2008MNRAS.389..955P. doi:10.1111/j.1365-2966.2008.13618.x. S2CID 16483475.
  4. David Bishop. "Supernova 2008ax in NGC 4490". supernovae.net (International Supernovae Network). Archived from the original on 8 April 2010. Retrieved 7 June 2010.
  5. Mostardi, R.; et al. (March 2008). Green, D. W. E. (ed.). "Possible Supernova in NGC 4490". Central Bureau Electronic Telegrams. 1280 (1): 1. Bibcode:2008CBET.1280....1M.
  6. Nakano, S. (March 2008). Green, D. W. E. (ed.). "Supernova 2008ax in NGC 4490". Central Bureau Electronic Telegrams. 1286 (1): 1. Bibcode:2008CBET.1286....1N.
  7. David Bishop. "Bright Supernovae - 2008". supernovae.net (International Supernovae Network). Archived from the original on 27 September 2011. Retrieved 7 June 2010.
  8. Roming, P. W. A.; et al. (October 2009). "Multi-Wavelength Properties of the Type IIb SN 2008ax". The Astrophysical Journal Letters. 704 (2): L118–L123. arXiv:0909.0967. Bibcode:2009ApJ...704L.118R. doi:10.1088/0004-637X/704/2/L118. S2CID 51315301.
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