Supernovae

A major focus of LCOGT is studying supernovae and gamma-ray bursts. These are exploding stars so bright they can be seen from distant galaxies, hundreds of millions to billions of lightyears away. A certain type of supernovae (Type Ia) are used to map out the history of the expansion of the universe and have revealed that the universe is expanding at an ever-accelerating rate due to the presence of a mysterious source of energy. We are using the LCOGT network to study nearby supernovae in combination with more distant supernovae discovered by the Supernova Legacy Survey (SNLS) to determine the nature of this Dark Energy. We also study other types of supernovae (core-collapse supernovae), which tell us about the deaths of massive stars and the births of black holes.

LCOGT is a member of several collaborations studying stellar explosions from the nearby to distant universe. The Palomar Transient Factory (PTF) is set to begin in March 2009 and will monitor the sky on timescales from days to months, discovering novae, supernovae, and more exotic phenomena in relatively nearby (redshift [z] less than 0.1) galaxies at a rate of hundreds per year. The Supernova Legacy Survey (SNLS) is a recently-completed five year program involving the Canada-France-Hawaii Telescope, Keck, Gemini, and VLT. The SNLS discovered and obtained data on about 2000 distant (0.1<z<1.1) supernovae, the largest sample ever collected.  They are still being analyzed by astronomers at LCOGT. Finally, LCOGT is a member of the Pan-STARRS collaboration, a project using a newly built instrument and telescope in Hawaii to survey 3/4 of the sky in addition to a more focused region (70 square degrees) to medium depth.

 

The Rise-Time of Normal and Subluminous Type Ia Supernovae

We calculate the average stretch-corrected rise-time of type Ia supernovae (SNe Ia) in the Supernova Legacy Survey. We use the aggregate lightcurves of spectroscopic and photometrically identified SNe Ia to fit the rising part of the lightcurve with a simple quadratic model. We obtain a lightcurve shape corrected, i .e. stretch-corrected, fiducial rise-time of 17.02+0.18-0.28 (stat) days. The measured rise-time differs from an earlier finding by the SNLS (Conley et al. 2006) due to the use of different SN Ia templates.

arXiv:1109.5757, apj accepted

PTF 10bzf (SN 2010ah): a broad-line Ic supernova discovered by the Palomar Transient Factory

We present the discovery and follow-up observations of a broad-line type-Ic supernova (SN), PTF 10bzf (SN 2010ah), detected by the Palomar Transient Factory (PTF) on 2010 February 23. The SN distance is \cong 218 Mpc, greater than GRB 980425 / SN 1998bw and GRB 060218 / SN 2006aj, but smaller than the other SNe firmly associated with gamma-ray bursts (GRBs). We conducted a multi-wavelength follow-up campaign with Palomar-48 inch, Gemini-N, Keck, Wise, Swift, the Allen Telescope Array, CARMA, WSRT, and EVLA.

Corsi et al. 2011, ApJ, accepted

PTF10ops - a subluminous, normal-width lightcurve Type Ia supernova in the middle of nowhere

PTF10ops is a Type Ia supernova (SN Ia), whose lightcurve and spectral properties place it outside the current SN Ia subtype classifications. Its spectra display the characteristic lines of subluminous SNe Ia, but it has a normal-width lightcurve with a long rise-time, typical of normal luminosity SNe Ia. The early-time optical spectra of PTF10ops were modelled using a spectral fitting code and found to have all the lines typically seen in subluminous SNe Ia, without the need to invoke more uncommon elements.

Maguire et al. 2011, MNRAS, accepted

Constraining Type Ia Supernovae progenitors from three years of SNLS data

While it is generally accepted that Type Ia supernovae are the result of the explosion of a carbon-oxygen White Dwarf accreting mass in a binary system, the details of their genesis still elude us, and the nature of the binary companion is uncertain. Kasen (2010) points out that the presence of a non-degenerate companion in the progenitor system could leave an observable trace: a flux excess in the early rise portion of the lightcurve caused by the ejecta impact with the companion itself.

Astrophysical Journal -- accepted v738

SNLS3: Constraints on Dark Energy Combining the Supernova Legacy Survey Three Year Data with Other Probes

We present observational constraints on the nature of dark energy using the Supernova Legacy Survey three year sample (SNLS3) of Guy et al. (2010) and Conley et al. (2011). We use the 472 SNe Ia in this sample, accounting for recently discovered correlations between SN Ia luminosity and host galaxy properties, and include the effects of all identified systematic uncertainties directly in the cosmological fits.

Sullivan et al. 2011, ApJ, submitted

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