PESSTO monitoring of SN 2012hn: Further heterogeneity among faint type I supernovae

We present optical and infrared monitoring data of SN 2012hn collected by the Public European Southern Observatory Spectroscopic Survey for Transient Objects. We show that SN 2012hn has a faint peak magnitude (MR ? ?15.65) and shows no hydrogen and no clear evidence for helium in its spectral evolution. Instead, we detect prominent Ca?ii lines at all epochs, which relates this transient to previously described ‘Ca-rich’ or ‘gap’ transients. However, the photospheric spectra (from ?3 to +32?d with respect to peak) of SN 2012hn show a series of absorption lines which are unique and a red continuum that is likely intrinsic rather than due to extinction. Lines of Ti?ii and Cr?ii are visible. This may be a temperature effect, which could also explain the red photospheric colour. A nebular spectrum at +150?d shows prominent Ca?ii, O?i, C?i and possibly Mg?i lines which appear similar in strength to those displayed by core-collapse supernovae (SNe). To add to the puzzle, SN 2012hn is located at a projected distance of 6 kpc from an E/S0 host and is not close to any obvious star-forming region. Overall SN 2012hn resembles a group of faint H-poor SNe that have been discovered recently and for which a convincing and consistent physical explanation is still missing. They all appear to explode preferentially in remote locations offset from a massive host galaxy with deep limits on any dwarf host galaxies, favouring old progenitor systems. SN 2012hn adds heterogeneity to this sample of objects. We discuss potential explosion channels including He-shell detonations and double detonations of white dwarfs as well as peculiar core-collapse SNe.

[1]  J. Lyman,et al.  Environment-derived constraints on the progenitors of low-luminosity Type I supernovae , 2013, 1306.2474.

[2]  R. Scalzo,et al.  Locations of peculiar supernovae as a diagnostic of their origins , 2013, 1304.2400.

[3]  S. E. Persson,et al.  TYPE Iax SUPERNOVAE: A NEW CLASS OF STELLAR EXPLOSION , 2012, 1212.2209.

[4]  E. Gall,et al.  Interpreting the near-infrared spectra of the 'golden standard' Type Ia supernova 2005cf , 2012, 1208.5949.

[5]  K. Maguire,et al.  The progenitor mass of the Type IIP supernova SN 2004et from late-time spectral modeling , 2012, 1208.2183.

[6]  J. Prochaska,et al.  An empirical relation between sodium absorption and dust extinction , 2012, 1206.6107.

[7]  A. Gal-yam,et al.  WISeREP—An Interactive Supernova Data Repository , 2012, 1204.1891.

[8]  R. Kotak,et al.  A SPECTROSCOPICALLY NORMAL TYPE Ic SUPERNOVA FROM A VERY MASSIVE PROGENITOR , 2012, 1203.1933.

[9]  D. Frail,et al.  CALCIUM-RICH GAP TRANSIENTS IN THE REMOTE OUTSKIRTS OF GALAXIES , 2011, 1111.6109.

[10]  W. Hillebrandt,et al.  2D simulations of the double-detonation model for thermonuclear transients from low-mass carbon-oxygen white dwarfs , 2011, 1111.2117.

[11]  A. Filippenko,et al.  The rise-time distribution of nearby Type Ia supernovae , 2011, 1107.2404.

[12]  Physics,et al.  SN 2009jf: a slow-evolving stripped-envelope core-collapse supernova , 2011, 1106.3030.

[13]  P. Mazzali,et al.  nero– a post-maximum supernova radiation transport code , 2011, 1105.3049.

[14]  M. Stritzinger,et al.  The nebular spectrum of the Type Ia supernova 2003hv: evidence for a non-standard event , 2011, 1105.1298.

[15]  M. Sullivan,et al.  THE SUBLUMINOUS AND PECULIAR TYPE Ia SUPERNOVA PTF 09dav , 2011, 1103.1797.

[16]  J. Fynbo,et al.  The properties of SN Ib/c locations , 2011, 1102.2249.

[17]  G. C. Anupama,et al.  Optical studies of SN 2009jf: a Type Ib supernova with an extremely slow decline and aspherical signature , 2011, 1101.2068.

[18]  J. Truran,et al.  HELIUM SHELL DETONATIONS ON LOW-MASS WHITE DWARFS AS A POSSIBLE EXPLANATION FOR SN 2005E , 2010, 1009.3829.

[19]  Richard Walters,et al.  RAPIDLY DECAYING SUPERNOVA 2010X: A CANDIDATE “.Ia” EXPLOSION , 2010, 1009.0960.

[20]  P. Mazzali,et al.  FALLBACK SUPERNOVAE: A POSSIBLE ORIGIN OF PECULIAR SUPERNOVAE WITH EXTREMELY LOW EXPLOSION ENERGIES , 2010, 1006.5336.

[21]  R. Kotak,et al.  The Type Ic SN 2007gr: a census of the ejecta from late-time optical–infrared spectra , 2010, 1006.4259.

[22]  D. Kasen,et al.  THERMONUCLEAR.Ia SUPERNOVAE FROM HELIUM SHELL DETONATIONS: EXPLOSION MODELS AND OBSERVABLES , 2010, 1002.2258.

[23]  W. Hillebrandt,et al.  Double-detonation sub-Chandrasekhar supernovae: can minimum helium shell masses detonate the core? , 2010, 1002.2173.

[24]  R. Nichol,et al.  THE RISE AND FALL OF TYPE Ia SUPERNOVA LIGHT CURVES IN THE SDSS-II SUPERNOVA SURVEY , 2010, 1001.3428.

[25]  J. Bloom,et al.  An Unusually Fast-Evolving Supernova , 2009, Science.

[26]  M. L. Pumo,et al.  EC-SNe FROM SUPER-ASYMPTOTIC GIANT BRANCH PROGENITORS: THEORETICAL MODELS VERSUS OBSERVATIONS , 2009, 0910.0640.

[27]  Ulrich Hopp,et al.  Extensive optical and near-infrared observations of the nearby, narrow-lined type Ic SN 2007gr : days 5 to 415 , 2009, 0909.3780.

[28]  Chris L. Fryer,et al.  SPECTRA AND LIGHT CURVES OF FAILED SUPERNOVAE , 2009, 0908.0701.

[29]  J. Anderson,et al.  Comparisons of the radial distributions of core‐collapse supernovae with those of young and old stellar populations★ , 2009, 0907.0034.

[30]  Oxford,et al.  Exploring the Optical Transient Sky with the Palomar Transient Factory , 2009, 0906.5355.

[31]  E. Pian,et al.  A massive star origin for an unusual helium-rich supernova in an elliptical galaxy , 2009, Nature.

[32]  E. O. Ofek,et al.  A faint type of supernova from a white dwarf with a helium-rich companion , 2009, Nature.

[33]  A. Pastorello,et al.  Nebular emission-line profiles of Type Ib/c supernovae - Probing the ejecta asphericity , 2009, 0904.4632.

[34]  W. M. Wood-Vasey,et al.  SN 2008ha: AN EXTREMELY LOW LUMINOSITY AND EXCEPTIONALLY LOW ENERGY SUPERNOVA , 2009, 0902.2794.

[35]  Ricardo Covarrubias,et al.  THE HE-RICH CORE-COLLAPSE SUPERNOVA 2007Y: OBSERVATIONS FROM X-RAY TO RADIO WAVELENGTHS , 2009, 0902.0609.

[36]  A. Pastorello,et al.  A low-energy core-collapse supernova without a hydrogen envelope , 2009, Nature.

[37]  B. Metzger,et al.  Nickel-rich outflows from accretion discs formed by the accretion-induced collapse of white dwarfs , 2008, 0812.3656.

[38]  A. J. Drake,et al.  FIRST RESULTS FROM THE CATALINA REAL-TIME TRANSIENT SURVEY , 2008, 0809.1394.

[39]  K. Schawinski,et al.  The radial distribution of Type Ia supernovae in early-type galaxies: implications for progenitor scenarios , 2008, 0804.4690.

[40]  A. Pastorello,et al.  ESC* supernova spectroscopy of non-ESC targets , 2008, 0804.1939.

[41]  A. Pastorello,et al.  The Carbon-rich Type Ic SN 2007gr: The Photospheric Phase , 2007, 0712.1899.

[42]  R. Kirshner,et al.  Long γ-Ray Bursts and Type Ic Core-Collapse Supernovae Have Similar Locations in Hosts , 2007, 0712.0430.

[43]  E. L. Robinson,et al.  A CATALOG OF NEAR-INFRARED SPECTRA FROM TYPE Ia SUPERNOVAE , 2007, 0906.4085.

[44]  S. E. Persson,et al.  The underluminous Type Ia supernova 2005bl and the class of objects similar to SN 1991bg , 2007, 0711.4548.

[45]  W. Hillebrandt,et al.  Double-detonation supernovae of sub-Chandrasekhar mass white dwarfs , 2007, 0710.5486.

[46]  E. O. Ofek,et al.  The Broad-lined Type Ic SN 2003jd , 2007, 0710.5173.

[47]  R. Foley,et al.  The Aspherical Properties of the Energetic Type Ic SN 2002ap as Inferred from Its Nebular Spectra , 2007, 0708.0966.

[48]  Gijs Nelemans,et al.  Faint Thermonuclear Supernovae from AM Canum Venaticorum Binaries , 2007, astro-ph/0703578.

[49]  R. Kotak,et al.  ESC and KAIT observations of the transitional type Ia SN 2004eo , 2007, astro-ph/0702565.

[50]  R. Kotak,et al.  ESC observations of SN 2005cf – I. Photometric evolution of a normal type Ia supernova , 2007, astro-ph/0702566.

[51]  Tokyo,et al.  The properties of the 'standard' type Ic supernova 1994I from spectral models , 2006, astro-ph/0604293.

[52]  S. E. Persson,et al.  Optical and Infrared Photometry of the Type Ia Supernovae 1991T, 1991bg, 1999ek, 2001bt, 2001cn, 2001cz, and 2002bo , 2004, astro-ph/0409036.

[53]  P. Prugniel,et al.  Hyperleda. I. Identification and designation of galaxies , 2003 .

[54]  M. Turatto,et al.  Low‐luminosity Type II supernovae: spectroscopic and photometric evolution , 2003, astro-ph/0309264.

[55]  M. Turatto,et al.  Photometry and Spectroscopy of the Type IIP SN 1999em from Outburst to Dust Formation , 2003 .

[56]  J. Anthony Tyson,et al.  Survey and Other Telescope Technologies and Discoveries , 2002 .

[57]  Robert Jedicke,et al.  Pan-STARRS: A Large Synoptic Survey Telescope Array , 2002, SPIE Astronomical Telescopes + Instrumentation.

[58]  J. Cuby,et al.  Optical and Infrared Spectroscopy of SN 1999ee and SN 1999ex , 2002, astro-ph/0203491.

[59]  Thomas Matheson,et al.  Optical Spectroscopy of Type Ib/c Supernovae , 2001, astro-ph/0101119.

[60]  D. Schlegel,et al.  Maps of Dust Infrared Emission for Use in Estimation of Reddening and Cosmic Microwave Background Radiation Foregrounds , 1998 .

[61]  Jr.,et al.  The Global Schmidt law in star forming galaxies , 1997, astro-ph/9712213.

[62]  D. Schlegel,et al.  Maps of Dust IR Emission for Use in Estimation of Reddening and CMBR Foregrounds , 1997, astro-ph/9710327.

[63]  C. Gouiffes,et al.  The properties of the peculiar type Ia supernova 1991bg — I. Analysis and discussion of two years of observations , 1996, astro-ph/9605178.

[64]  Shiomi Kumagai,et al.  Theoretical light curves for the type IC supernova SN 1994I , 1994 .

[65]  R. Chevalier,et al.  Late emission from supernovae - A window on stellar nucleosynthesis , 1989 .

[66]  K. Nomoto,et al.  Accreting white dwarf models for type I supernovae. III. Carbon deflagration supernovae , 1984 .

[67]  W. Arnett.  Type I supernovae. I. Analytic solutions for the early part of the light curve , 1982 .

[68]  P. Murdin.  MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY , 2005 .

[69]  Chien Y. Peng,et al.  UBVRI Photometry of the Type IC SN 1994I in M51 , 1996 .

[70]  A. Filippenko.  Early-time spectra of type IC supernovae - Further evidence for the presence of hydrogen , 1992 .