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The Hubble Deep Field reveals a Supernova at z~0.95

F. Mannucci and A. Ferrara

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We report the discovery of a variable object in the Hubble Deep Field North (HDF-N) which has brightened, during the 8.5 days sampled by the data, by more than 0.9 mag in I and about 0.7 mag in V, remaining stable in B. Subsequent observations of the HDF-N show that two years later this object has dimmed back to about its original brightness in I.
The colors of this object, its brightness, its time behavior in the various filters and the evolution of its morphology are consistent with being a Type Ib supernova in a faint galaxy at z~0.95.

Full paper (Postscript, 5 pages including 2 figures, gzipped, 150 KB)
accepted for publication in MNRAS.

Composite (V+I) smoothed images of the exploding star with two different look-up tables

Location of the object in the HDF

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Figures of the paper with the the evolution of supernova the photometry and its images in the three bands

Photometry of the supernova in B, V, and I as a function of the (observer) time; day=0 corresponds to the first observation. Each point shows the 1 sigma photometric errors and the time span covered by the data; the dotted lines are the 3 sigma limits of each image. The the arrows in the I panels show the 3 sigma upper limits. The solid thick lines are a fit obtained from a K-corrected, time-dilated SNIb light curve at z= 0.95 with tmax=34.0, E(B-V)=0.04 and omega=0.1. The spectrum and the time evolution of a SNIb simultaneously fit the magnitudes of the variable object and its evolution in the three filters. The underlying galaxy results to have B=28.70, V=29.10 and I=29.15. Also shown are the curves for a SNIa at z~1.3 (short dashed) and a SNII at z~1.1 (long dashed) which do not provide an acceptable match.

Images of 2-584.2 in the B, V and I bands. The three images on the left are the total HDF-N images by Williams et al. 1996 with a pixel scale of 0.04 arcsec/pixel. On the right the time sequence in each filter with pixel scale of 0.05 arcsec/pixel showing the brightening of the object in V and I and its following dimming. Each image is labelled by the filter and the time range of the observations in days. The size of the central squares is 1 arcsec.

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