Constraints on the origin of the first light from SN2014J

We study the very early lightcurve of supernova 2014J (SN 2014J) using the high-cadence broad-band imaging data obtained by the Kilodegree Extremely Little Telescope (KELT), which fortuitously observed M 82 around the time of the explosion, starting more than two months prior to detection, with up to 20 observations per night. These observations are complemented by observations in two narrow-band filters used in an H$alpha$ survey of nearby galaxies by the intermediate Palomar Transient Factory (iPTF) that also captured the first days of the brightening of the sn. The evolution of the lightcurves is consistent with the expected signal from the cooling of shock heated material of large scale dimensions, $gsim 1 R_{odot}$. This could be due to heated material of the progenitor, a companion star or pre-existing circumstellar environment, e.g., in the form of an accretion disk. Structure seen in the lightcurves during the first days after explosion could also originate from radioactive material in the outer parts of an exploding white dwarf, as suggested from the early detection of gamma-rays. The model degeneracy translates into a systematic uncertainty of $pm 0.3$ days on the estimate of the first light from SN 2014J.

The rise of SN2014J in the nearby galaxy M82

We report on the discovery of SN2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova over a wide range of the electromagnetic spectrum. The first set of optical, near-IR and mid-IR observations of SN2014J, orchestrated by the intermediate Palomar Transient Factory (iPTF), show that SN2014J is a spectroscopically normal Type Ia supernova, albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the lightcurve rise. Similarly to other highly reddened Type Ia supernovae, a low value of total-to-selective extinction, Rv < 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from HST with special emphasis on the sources nearest to the SN location.

Near-IR Search for Lensed Supernovae Behind Galaxy Clusters - II. First Detection and Future Prospects

Powerful gravitational telescopes in the form of massive galaxy clusters can be used to enhance the light collecting power over a limited field of view by about an order of magnitude in flux. This effect is exploited here to increase the depth of a survey for lensed supernovae at near-IR wavelengths. A pilot SN search program conducted with the ISAAC camera at VLT is presented. Lensed galaxies behind the massive clusters A1689, A1835 and AC114 were observed for a total of 20 hours split into 2, 3 and 4 epochs respectively, separated by approximately one month to a limiting magnitude J<24 (Vega). Image subtractions including another 20 hours worth of archival ISAAC/VLT data were used to search for transients with lightcurve properties consistent with redshifted supernovae, both in the new and reference data. The feasibility of finding lensed supernovae in our survey was investigated using synthetic lightcurves of supernovae and several models of the volumetric Type Ia and core-collapse supernova rates as a function of redshift. We also estimate the number of supernova discoveries expected from the inferred star formation rate in the observed galaxies. The methods consistently predict a Poisson mean value for the expected number of SNe in the survey between N_SN=0.8 and 1.6 for all supernova types, evenly distributed between core collapse and Type Ia SN. One transient object was found behind A1689, 0.5 from a galaxy with photometric redshift z_gal=0.6 +- 0.15. The lightcurve and colors of the transient are consistent with being a reddened Type IIP SN at z_SN=0.59. The lensing model predicts 1.4 magnitudes of magnification at the location of the transient, without which this object would not have been detected in the near-IR ground based search described in this paper (unlensed magnitude J~25). (abridged)