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

¹ Astrophysics Research Centre, School of Mathematics and Physics, Queen's University Belfast, BT7 1NN, UK e-mail: dhunter$07$@qub.ac.uk
² Astrophysics Group, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ, UK
³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85741 Garching bei München, Germany
⁴ INAF – Osservatorio Astronomico, vicolo dell'Osservatorio 5, 35122 Padova, Italy
⁵ CENTRA - Centro Multidisciplinar de Astrofísica, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal
⁶ Pulkovo Central Astronomical Observatory, Pulkovskoe shosse 65, 196140, St. Petersberg, Russia
⁷ Astronomical Institute of St Petersburg State University, Universitetskij Prospect 28, Petrodvorets, 198504 St Petersburg, Russia
⁸ INAF Osservatorio Astronomico di Collurania, via M. Maggini, 64100 Teramo, Italy
⁹ Spitzer Science Center, California Institute of Technology, 1200 E.California Blvd., Pasadena, CA 91125, USA
¹⁰ Institut for Fysik og Astronomi, rhus Universitet, Ny Munkegade, Bygn. 1520, 8000 rhus C, Denmark
¹¹ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
¹² Universitäts-Sternwarte München, Scheinenstr. 1, 81679 München, Germany
¹³ Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstr, 85748 Garching bei München, Germany
¹⁴ Scuola Normale Superiore, Piazza Cavalieri, 7, 56126 Pisa, Italy
¹⁵ Joint Astronomy Centre, 660 N. A'ohoku Place, Hilo, HI 96720, USA
¹⁶ Sternberg Astronomical Institute, University Ave. 13, 119992 Moscow, Russia

Received: 15 July 2009
Accepted: 17 September 2009

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 d. We find a peak B-band magnitude of , 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 of ⁵⁶Ni 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.