Supernova SUPERNOVA 2013ga (=PSN J22042153+3944340) in UGC 11895: image and spectroscopy
Updates: on 11 Nov. 2013, the Central Bureau for Astronomical Telegrams issued the CBET 3704, reporting that to this SN was given the official designation SN 2013 ga. This thanks to our spectroscopy. Here is an extract from that CBET: “Additional CCD magnitudes for 2013 ga: Oct. 21.745, 15.8 (G. Masi, F. Nocentini, and P. Schmeer; remotely using a 43-cm robotic telescope near Ceccano, Italy; position end figures 21s.51, 34″.1); Masi et al. add that spectra obtained with a 0.36-m reflector on Oct. 21.85 (100 lines/mm grating; dispersion 3.47 nm/pixel) show very clearly an Si II absorption around 615.0 nm, suggesting that this is a type-Ia supernova“.
On 21 Oct 2013, the Virtual Telescope imaged a supernova candidate, PSN J22042153+3944340, in the UGC 11895 galaxy. Optical images with the PlaneWave 17″ robotic unit easily located the transient, visible in the image above: it comes from the average of 4, 120-seconds exposures, taken with a bright moon. The source was found at mag. 15.8.
While the Moon was a great interference, we tried to do spectroscopy, to understand if this one was a true supernova and, if yes, of what type. For this, we used the Celestron C14 robotic unit, equipped with a 100 lines/mm diffraction grating. After averaging four, 300-seconds spectra, we firmly detected the evidence of absorption at about 6150 angstroms, that is Si II. This is the clear signature of a type Ia supernova. Spectrum is shown below, plotted with RSpec.
So we discovered that the previously reported transient is a type Ia supernova, reporting all this to the Central Bureau for Astronomical Telegrams. Observations were performed by G. Masi, F. Nocentini and P. Schmeer.
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