Supernova 2000B in NGC 2320

SN 2000B was discovered by Pierre Antonini, Avignon, France on Jan. 11.0 2000 UT and confirmed by François Colas and Eric Frappa at Pic du Midi Observatory on Jan. 13.85. See IUAC 7347.

Part one: imagery

SN2000B image on January 14, 2000 - 20H40 UT. Stack by the drizzling method of 26 unfiltered KAF-0401E CCD exposures (60 seconds integration time each). Enlargement of 4x relative to the original image. FSQ-106 Takahashi refractror on Vixen GP mount + Audine CCD camera and IRIS processing. UAI site: 959 (Toulouse - France)

Standard co-adding of 3 images to an effective 3 minutes exposure. Notice that a supernova of this type can be detected with a very brief exposure time (2 or 3 minutes), no shutter, a small instrument (4 inch), a bad seeing and a severe polluted sky by the urban parasitic light of Toulouse (magnitude 2.5 eye limit for the night of the observation!). Besides, the CCD cooling was not on the way (ambiant temperature was around 7¨C). Click here to see a dramatic raw one minute exposure in this condition and compare to the processed result (NGC 2320 is at the center).

Left, the co-added 26 minutes supernova image obtained with the Takahashi FSQ-106 refractor. Right, a reference image extracted from the Buil-Thouvenot Atlas  (Takahashi CN-212 telescope). Botton, subtraction of the previous images after precise registration and blur in the same way. The galaxy was erased. The supernova is clearly visible and can be now easily measured.

Wavelet analysis of NGC 2320 galaxy. From left to right, wavelet coefficients 1, 2, 3 , 4, 5 and the residual image.

Co-adding of wavelet coefficients 2, 3 and 4 + clip at the zero value of the sky level). The supernova is correctly separated from the galaxy halo: This is essential for a precise determination of the background level and for precise photometry (aperture photometry for exemple).

R magnitude of SN2000B for the 2000/01/14.86

Reference star

Method: reference image substraction

Method: Wavelet analysis

Star 1



Star 2



Star 3



Star 4



Mean R magnitude




Part two: spectrography

Supernova 2000B spectra obtained by Francois Colas, Agnès Fienga and Christian Buil with the one-meter telescope of the Pic du Midi observatory on January 22.8, 2000 (left) and January 25.8, 2000 (right). Rainbow Optics grating (200 line/mm) in the focal reducer for a 24 A/pixel dispersion spectrum. Relative flux calibrated with the AOV star HD45105 (VisualSpec software). Note the presence of  the Si II signature at 6200 A (type Ia supernova).

The January 22.8, 2000 spectrum.

The January 25.8 spectrum.

Comparison of January 22.8 and 25.8 January spectra.