Extensive optical and near-infrared observations of the nearby, narrow-lined type Ic SN 2007gr: days 5 to 415

Creators: Hunter, D. J.; Valenti, S.; Kotak, R.; Meikle, W. P. S.; Taubenberger, S.; Pastorello, A.; Benetti, S.; Stanishev, V.; Smartt, S. J.; Trundle, C.; Arkharov, A. A.; Bufano, F.; Cappellaro, E.; Di Carlo, E.; Dolci, M.; Elias-Rosa, N.; Frandsen, S.; Fynbo, J. U.; Hopp, U.; Larionov, V. M.; Laursen, P.; Mazzali, P.; Navasardyan, H.; Ries, C.; Riffeser, A.; Rizzi, L.; Tsvetkov, D. Y.; Turatto, M.; Wilke, S.

Abstract

We present photometric and spectroscopic observations at optical and near-infrared wavelengths of the nearby type Ic supernova 2007gr. These represent the most extensive data-set to date of any supernova of this sub-type, with frequent coverage from shortly after discovery to more than one year post-explosion. We deduce a rise time to B-band maximum of 11.5 ± 2.7 d. We find a peak B-band magnitude of M_B = −16.8, and light curves which are remarkably similar to the so-called "hypernova" SN 2002ap. In contrast, the spectra of SNe 2007gr and 2002ap show marked differences, not least in their respective expansion velocities. We attribute these differences primarily to the density profiles of their progenitor stars at the time of explosion i.e. a more compact star for SN 2007gr compared to SN 2002ap. From the quasi-bolometric light curve of SN 2007gr, we estimate that 0.076 ± 0.010 M_⊙ of ^(56)Ni was produced in the explosion. Our near-infrared (IR) spectra clearly show the onset and disappearance of the first overtone of carbon monoxide (CO) between ~70 to 175 d relative to B-band maximum. The detection of the CO molecule implies that ionised He was not microscopically mixed within the carbon/oxygen layers. From the optical spectra, near-IR light curves, and colour evolution, we find no evidence for dust condensation in the ejecta out to about +400 d. Given the combination of unprecedented temporal coverage, and high signal-to-noise data, we suggest that SN 2007gr could be used as a template object for supernovae of this sub-class.

Additional Information

© ESO 2009. Received 15 July 2009. Accepted 17 September 2009. Published online 24 September 2009. We would like to thank all the staff from the Asiago Ekar Telescope, Campo Imperatore Telescope, Calar Alto Observatory, Gemini North Telescope, Nordic Optical Telescope (operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden), Osservatorio di Teramo, Sternberg Astronomical Institute Telescope, Telescopio Nazionale Galileo, UKIRT, and the Wendelstein Telescope. The Gemini data reported here were obtained via programmes GN-2007B-DD-3 and GN-2008B-Q-58. We are grateful to the staff at the NOT: Amanda Djupvik, Thierry Morel, Jarkko Niemela, Tapio Pursimo, Auni Somero, John Telting and Helena Uthas, for observing SN 2007gr. We would also like to thank the staff at Gemini North: Thomas Dall, Tom Geballe, Silas Laycock, Atsuko Nitta, Kathy Roth, Ricardo Schiavon, Chad Trujillo and Kevin Volk, and also to the observers at the TNG: Avet Harutyunyan, Lorenzi Vania, and the Wendelstein observatory: Remus Bergemann, Florian Lang and Johannes Koppenhoefer. J. Fynbo acknowledges the Dark Cosmology Centre which is supported by the DNRF; R.K. and S.J.S acknowledge financial support from STFC. V. Stanishev acknowledges financial support from the Fundação para a Ciência e a Tecnologia. This paper has made use of data obtained from the Isaac Newton Group Archive which is maintained as part of the CASU Astronomical Data Centre at the Institute of Astronomy, Cambridge. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication has made use of data products from the TwoMicron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

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