SN 2002cx
Event type | Colour (B-V) 0.04±0.05[4] | |
---|---|---|
Peak apparent magnitude | +17.57±0.15[5] | |
Other designations | SN 2002cx | |
Related media on Commons | ||
] |
SN 2002cx is a peculiar type Ia supernova.[6][7][8] It was discovered in May 2002 by a team of researchers from LBL.[2] It behaved differently from normal type Ia supernovae, and differently from several other previously observed peculiar type Ia supernovae including SN 1991T and SN 1991bg.[4][9]
SN 2002cx is now classified as type Iax supernova, which are subluminal and do not result in complete destruction of the progenitor white dwarf.[10]
Discovery
SN 2002cx was discovered on 2002 May 12.21 UT by W. M. Wood-Vasey,
Features
Light curve
SN 2002cx hit maximum light in the B-band at 2452415.2
SN 2002cx is peculiar in the R-band, as it brightens very fast in a manner wholly different from SN 1999ac.[13] It has no secondary maximum in R-band as expected if it were similar to SN 1991T, but instead has a plateau after max.[13] The R-band also declines more slowly than normal.[13] The I-band behaves similarly to the R-band, with a quick brightening, a plateau and slow decline.[13] While a plateau in the I-band is expected for sub-luminous supernovae, the following slow decline is not.[13]
Spectra
The first spectrum of SN 2002cx was obtained with FLWO on 2002 May 17, 4 days before B-band max.[14] At this point SN 2002cx is similar to SN 1997br as both have a blue continuum, with absorption lines from Fe III λ4404 and Fe III λ5129.[14] Si II λ6355 though is not apparent in SN 2002cx at this point, and it has very weak Ca II H & K lines suggesting that SN 2002cx is similar to SN 1991T which also lacked such lines.[14] This spectrum for SN 2002cx has a low expansion velocity measuring only ~6400 km s−1.[14] This marked one way in which it was different from SN 1997br, as SN 1997br's expansion velocity was ~10,400 km s−1 at the same point relative to its own B-band maximum.[14] At the time of measurement SN 2002cx's expansion velocity was the lowest measured for an early time type Ia,[14] Another spectrum taken on 2002 May 20, 1 day before B-band maximum light, showed little evolution from the one taken on 2002 May 17.[15]
Four later spectra were taken on June 2, June 6, June 12, and June 16 at FLWO.[16] The spectrum of SN 2002cx has evolved by this point to have a redder continuum.[16] It has also lost the Fe III absorption lines and its Fe II lines have gained prominence at λ4555 and λ5129.[16] The Ca II H & K lines continue to remain weak, a further departure from SN 1997br.[16] Unlike another type of sub-luminous type Ia, SN 1991bg, SN 2002cx does not show Ti II lines around 4100–4400 Å.[16]
Spectra were taken at Keck corresponding to 20, 25, and 26 days after maximum light in the B-band.
A final spectrum of SN 2002cx was taken on July 16, 56 days after B-band maximum.[19] SN 2002cx was by then in the nebular phase, with emission lines dominating over absorption lines.[19] The lines were far narrower than previously observed type Ia supernovae and are less pronounced as well.[19] SN 2002cx most clearly differs from other type Ia supernovae in the region between 6500 Å and 8500 Å where it has a primarily flat continuum and weak Ca II infrared triplet absorption.[19] Because this is the region covered by the R and I-bands, it may explain the odd color evolution of SN 2002cx in these bands.[19]
SN 2002cx did not evolve much between 4 days and 1 day before max, nor did it evolve much from 12 days after max to 27 days after max,[16] However, it underwent dramatic evolution during the two weeks after maximum light in the B-band.[16]
Based on the odd behavior of SN 2002cx's spectrum there are some questions as to whether it is a type Ia supernova or not.[20] Although it does not show Si II lines neat 6150 Å as is required of a type Ia, SN 2002cx's evolution is explainable using the paradigm of other type Ia observations and so Li et al. consider their classification as a type Ia as secure.[20]
Color
SN 2002cx does not suffer from much host related reddening, as evidenced by its very blue spectra.
SN 2002cx is similar to SN 1999ac in B−V at max, but also at times as late as 50 days after max which is unexpected as the two supernovae evolve differently at late times.[4] SN 2002cx has a B−V color of −0.04±0.04 at 4 days before max, and 0.04±0.05 at the time of max in the B-band which is bluer than SN 1991bg at the same time.[4] The color of SN 2002cx is consistent with Lira-Phillips law at late times.[21]
The V−R color of SN 2002cx evolves similar to other type Ia supernovae before 5 days after max, although it is somewhat redder.[21] After 5 days after max SN 2002cx gets progressively redder, although still slightly bluer than SN 1991bg.[4] At 25 days after max SN 2002cx continues to redden, while SN 1991bg starts to get bluer.[4]
SN 2002cx's V−I color is red for all times, only slightly bluer than SN 1991bg before 25 days after max, and redder after 25 days after max.[4]
References
- ^ a b c d e f Li et al., 2003 p. 5
- ^ a b c d e Wood-Vasey et al., 2002
- ^ Li et al., 2003 p. 14
- ^ a b c d e f g h i Li et al., 2003 p. 12
- ^ Li et al., 2003 p. 58
- ^ Li et al., 2003 p. 1
- ^ Branch et al., 2004
- ^ Jha et al., 2006
- ^ a b c d e Li et al., 2003 p. 10
- .
- ^ Matheson et al., 2002
- ^ Li et al., 2003 p. 9
- ^ a b c d e Li et al., 2003 p. 11
- ^ a b c d e f Li et al., 2003 p. 15
- ^ Li et al., 2003 p. 16
- ^ a b c d e f g Li et al., 2003 p. 17
- ^ a b c d e f Li et al., 2003 p. 18
- ^ a b Li et al., 2003 p. 19
- ^ a b c d e Li et al., 2003 p. 20
- ^ a b Li et al., 2003 p. 24
- ^ a b Li et al., 2003 p. 13
Bibliography
- Branch, David; Baron, E.; Thomas, R. C.; Kasen, D.; Li, Weidong; S2CID 118965499.
- Jha, Saurabh; Branch, David; Chornock, Ryan; Foley, Ryan J.; Li, Weidong; Swift, Brandon J.; Casebeer, Darrin; S2CID 6126225.
- Li, Weidong; S2CID 119036991.
- Matheson, T.; S. Jha; P. Challis; R. Kirshner (2002-05-17). "Circular No. 7903". Central Bureau for Astronomical Telegrams. Retrieved 2011-07-05.
- Wood-Vasey, W. M.; Aldering, G.; Nugent, P. (2002-05-17). "Circular No. 7902". Central Bureau for Astronomical Telegrams. Retrieved 2011-07-05.
External links
- Light curves and spectra Archived 2017-10-23 at the Wayback Machine on the Open Supernova Catalog