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Swope Photometric Observations of SN 2017cbv = DLT17u

ATel #10167; D. A. Coulter, C. D. Kilpatrick, R. J. Foley (UCSC), J. Anais, M. M. Phillips (LCO), M. R. Drout, B. F. Madore, A. L. Piro, B. J. Shappee (Carnegie), E. Y. Hsiao (FSU)
on 11 Mar 2017; 23:40 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Ryan Foley (foley@ucsc.edu)

Subjects: Optical, Supernovae, Transient

Referred to by ATel #: 10237

We report on ongoing observations of SN 2017cbv (= DLT17u; Tartaglia et al., ATEL #10158) in NGC 5643 (z = 0.004; D = 16.9 Mpc; mu = 31.14 mag) with the Swope 1-m telescope at Las Campanas Observatory. We obtained a single observation on 2017 March 10 UT, and after classification as a very young SN Ia (Hosseinzadeh et al., ATEL #10164), we obtained 3 observations on 2017 March 11 UT over the course of ~5 hours. We detected a significant rise between all observations, further indicating that the SN was discovered shortly after explosion. Our preliminary V-band light curve is reported below. While the SN position is relatively isolated, because of the lack of template subtraction, we estimate our uncertainties to be ~0.1 mag.

MJD      | V (mag)
57822.33 | 15.8
57823.18 | 15.0
57823.29 | 14.9
57823.39 | 14.8

Assuming the above distance modulus and a Milky Way extinction of Av = 0.463 mag, the SN rose from Mv = -15.8 mag to -16.8 mag in about a day. Comparing the Swope V-band light curve of SN 2017cbv to the early V-band light curve of SN 2011fe (e.g., Pereira et al., 2013, A&A, 554, 27), we find that the rises are best matched when our first observation corresponds to a phase of -16.1 d. However, at this phase, SN 2016cbv would be ~0.8 mag more luminous than SN 2011fe, implying either SN 2016cbv is at a later phase, has a faster rise, is intrinsically more luminous, and/or the assumed distance is incorrect (see e.g., Childress et al., 2015, MNRAS, 454, 3816). We note that the SN Ia 2013aa (Parker et al., CBET #3416) also occurred in NGC 5643, and an independent distance to SN 2017cbv could be obtained from the SN 2013aa light curves.

Further follow-up observations of SN 2017cbv are encouraged.