Prompt photometric identification of young SNe using the robotic Palomar 60" telescope







Early identification of young SNe, discovered shortly after explosion (i.e., a prompt determination of their type), is crucial to trigger the proper type-dependent follow-up programs undertaken by various research groups, in the radio, through ground and space-based NIR/optical/UV, to the X-ray band. SNe are routinely classified through the analysis of their optical spectra. The scarcity of spectroscopic resources, as well as the time required to secure, analyze and report such spectra, introduces a (sometimes substantial) delay between the discovery of SNe and their classification. Gal-Yam et al. 2004 have used the methods first introduced by Poznanski et al. 2002 and presented means for prompt classification of young SNe using their broad-band colors. We are now implementing these methods using the newly robotic 60" telescope at Palomar observatory. Our first results are presented here.


SN 2004cs (phototype Ia):
This SN was discovered by LOSS on June 23, 2004. Available photometry (the object was invisible 2 days prior to discovery) indicated it was a young SN. We have promptly (on June 24, 2004) obtained follow-up photometry with the newly robotic Palomar 60" telescope, in Johnson BVR and Gunn g-band. This combination of bands was shown by Gal-Yam et al. 2004 to be well suited to classifying such young SNe. Photometric classification was delayed by the lack of photometric calibration of sufficient quality. Such calibration has been secured, using the same telescope, on July 30, 2004. The measured magnitudes and their respective uncertainties (including both photometric errors and zero-point uncertainties) are: B=18.16(0.07) mag, V=18.06(0.07) mag, R=17.87(0.08) mag and g=18.23(0.05) mag on June 24, UT. The resulting color-color diagram indicates this event was a young (well before peak) SN Ia, at the time of discovery. These findings are reported in IAUC XXXX.


SN 2004dh:
This SN was discovered by LOSS on July 11, 2004, but announced only on July 21. Available photometry (the object was invisible ~12 days prior to discovery) indicated it was a young SN. We have promptly (on July 24, 2004) obtained follow-up photometry with the newly robotic Palomar 60" telescope, in Johnson BVRI bands. Prompt spectroscopy by Matheson et al. showed it was a young type II SN. We measured the following magnitudes and their respective uncertainties (including both photometric errors and zero-point uncertainties): B=18.36(0.04) mag, V=17.91(0.02) mag, R=17.58(0.03) mag and I=17.39(0.04) mag on July 25, UT. Applying the methods of Gal-Yam et al. 2004, the resulting color-color diagram is in good agreement with the available spectroscopy, indicating this is a young type II SN, perhaps a type II-P.


SN 2004dk:
This SN was discovered by LOSS on Aug. 1, 2004. Available photometry (the object was invisible ~2 days prior to discovery!) indicated it was a young SN. We have promptly (on the night of Aug 2, 2004) obtained follow-up photometry with the newly robotic Palomar 60" telescope, in Johnson BVR and Gunn g-band. Prompt spectroscopy by Patat et al. showed it was a young type Ic SN. We measured the following magnitudes and their respective uncertainties (including both photometric errors and zero-point uncertainties): B=17.79(0.05) mag, V=17.18(0.02) mag, R=16.79(0.02) mag and g=17.50(0.04) mag on Aug 3, UT. Applying the methods of Gal-Yam et al. 2004, the resulting color-color diagram is in good agreement with the available spectroscopy, indicating this is a young core-collpase SN, of either type Ib, Ic (the "right" answer) or possibly type II-P.


The SN phototyping team at P60:

Anne Rajala
Derek Fox
Avishay Gal-Yam




Constructed: June 2004, by: Avishay Gal-Yam , E-Mail: avishay@astro.caltech.edu