The very young type Ia supernova 2012cg: Discovery and early-time follow-up observations

Jeffrey M. Silverman, Mohan Ganeshalingam, S. Bradley Cenko, Alexei V. Filippenko, Weidong Li, Aaron J. Barth, Daniel J. Carson, Michael Childress, Kelsey I. Clubb, Antonino Cucchiara, Melissa L. Graham, G. H. Marion, My L. Nguyen, Liuyi Pei, Brad E. Tucker, Jozsef Vinko, J. Craig Wheeler, Gabor Worseck

Research output: Contribution to journalArticle

Abstract

On 2012 May 17.2 UT, only 1.5 ± 0.2 days after explosion, we discovered SN 2012cg, a Type Ia supernova (SN Ia) in NGC4424 (d ≈ 15Mpc). As a result of the newly modified strategy employed by the Lick Observatory Supernova Search, a sequence of filtered images was obtained starting 161s after discovery. Utilizing recent models describing the interaction of supernova (SN) ejecta with a companion star, we rule out a ∼ 1 M companion for half of all viewing angles and a red-giant companion for nearly all orientations. SN 2012cg reached a B-band maximum of 12.09 ± 0.02 mag on 2012 June 2.0 and took ∼17.3days from explosion to reach this, typical for SNe Ia. Our pre-maximum-brightness photometry shows a narrower-than-average B-band light curve for SN 2012cg, though slightly overluminous at maximum brightness and with normal color evolution (including some of the earliest SN Ia filtered photometry ever obtained). Spectral fits to SN 2012cg reveal ions typically found in SNe Ia at early times, with expansion velocities ≳14,000kms-1 at 2.5days past explosion. Absorption from C II is detected early, as well as high-velocity components of both Si II λ6355 and Ca II. Our last spectrum (13.5days past explosion) resembles that of the somewhat peculiar SN Ia 1999aa. This suggests that SN 2012cg will have a slower-than-average declining light curve, which may be surprising given the faster-than-average rising light curve.

Original languageEnglish
Article numberL7
JournalAstrophysical Journal Letters
Volume756
Issue number1
DOIs
Publication statusPublished - 2012

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supernovae
explosion
explosions
light curve
ejecta
observatory
photometry
brightness
young
ion
companion stars
observatories
color
expansion

Keywords

  • supernovae: general
  • supernovae: individual: SN 2012cg

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Silverman, J. M., Ganeshalingam, M., Cenko, S. B., Filippenko, A. V., Li, W., Barth, A. J., ... Worseck, G. (2012). The very young type Ia supernova 2012cg: Discovery and early-time follow-up observations. Astrophysical Journal Letters, 756(1), [L7]. https://doi.org/10.1088/2041-8205/756/1/L7

The very young type Ia supernova 2012cg : Discovery and early-time follow-up observations. / Silverman, Jeffrey M.; Ganeshalingam, Mohan; Cenko, S. Bradley; Filippenko, Alexei V.; Li, Weidong; Barth, Aaron J.; Carson, Daniel J.; Childress, Michael; Clubb, Kelsey I.; Cucchiara, Antonino; Graham, Melissa L.; Marion, G. H.; Nguyen, My L.; Pei, Liuyi; Tucker, Brad E.; Vinko, Jozsef; Wheeler, J. Craig; Worseck, Gabor.

In: Astrophysical Journal Letters, Vol. 756, No. 1, L7, 2012.

Research output: Contribution to journalArticle

Silverman, JM, Ganeshalingam, M, Cenko, SB, Filippenko, AV, Li, W, Barth, AJ, Carson, DJ, Childress, M, Clubb, KI, Cucchiara, A, Graham, ML, Marion, GH, Nguyen, ML, Pei, L, Tucker, BE, Vinko, J, Wheeler, JC & Worseck, G 2012, 'The very young type Ia supernova 2012cg: Discovery and early-time follow-up observations', Astrophysical Journal Letters, vol. 756, no. 1, L7. https://doi.org/10.1088/2041-8205/756/1/L7
Silverman, Jeffrey M. ; Ganeshalingam, Mohan ; Cenko, S. Bradley ; Filippenko, Alexei V. ; Li, Weidong ; Barth, Aaron J. ; Carson, Daniel J. ; Childress, Michael ; Clubb, Kelsey I. ; Cucchiara, Antonino ; Graham, Melissa L. ; Marion, G. H. ; Nguyen, My L. ; Pei, Liuyi ; Tucker, Brad E. ; Vinko, Jozsef ; Wheeler, J. Craig ; Worseck, Gabor. / The very young type Ia supernova 2012cg : Discovery and early-time follow-up observations. In: Astrophysical Journal Letters. 2012 ; Vol. 756, No. 1.
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abstract = "On 2012 May 17.2 UT, only 1.5 ± 0.2 days after explosion, we discovered SN 2012cg, a Type Ia supernova (SN Ia) in NGC4424 (d ≈ 15Mpc). As a result of the newly modified strategy employed by the Lick Observatory Supernova Search, a sequence of filtered images was obtained starting 161s after discovery. Utilizing recent models describing the interaction of supernova (SN) ejecta with a companion star, we rule out a ∼ 1 M ⊙ companion for half of all viewing angles and a red-giant companion for nearly all orientations. SN 2012cg reached a B-band maximum of 12.09 ± 0.02 mag on 2012 June 2.0 and took ∼17.3days from explosion to reach this, typical for SNe Ia. Our pre-maximum-brightness photometry shows a narrower-than-average B-band light curve for SN 2012cg, though slightly overluminous at maximum brightness and with normal color evolution (including some of the earliest SN Ia filtered photometry ever obtained). Spectral fits to SN 2012cg reveal ions typically found in SNe Ia at early times, with expansion velocities ≳14,000kms-1 at 2.5days past explosion. Absorption from C II is detected early, as well as high-velocity components of both Si II λ6355 and Ca II. Our last spectrum (13.5days past explosion) resembles that of the somewhat peculiar SN Ia 1999aa. This suggests that SN 2012cg will have a slower-than-average declining light curve, which may be surprising given the faster-than-average rising light curve.",
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