Thursday, October 30, 2014

Possible Supernova in M61 (NGC 4303)

Following the posting on the Central Bureau's Transient Object Confirmation Page about a possible Supernova in the barred spiral galaxy Messier 61 (or NGC 4303 - TOCP Designation: PSN J12215757+0428185) we performed some follow-up of this object through a 0.10-m f/5.0 astrograph + CCD from MPC Code H06 (iTelescope, New Mexico). 

On our images taken on October 30.5, 2014 we can confirm the presence of an optical counterpart with unfiltered CCD magnitude 13.2 and at coordinates:

R.A. = 12 21 57.61, Decl.= +04 28 17.8

(equinox 2000.0; UCAC-3 catalogue reference stars).
 Our confirmation image (click on it for a bigger version)

An animation showing a comparison between our confirmation image and the archive POSS2/UKSTU plate (IR Filter - 1991). Click on the thumbnail below for a bigger version:

UPDATE - October 31, 2014

ATel #6648 issued on 31 Oct 2014 confirms PSN J12215757+0428185 as a Type Ia-pec Supernova. Spectroscopic classification has been obtained by "The Asiago Transient Classification Program" with the Asiago 1.82 m Copernico Telescope (+AFOSC; range 340-1000 nm; resolution 1.2 nm) and 1.22 m Galileo Telescope (+Boller&Chivens; range 360-790 nm; resolution 0.8 nm). According to the Asiago team: "Heliocentric radial velocity of the host galaxy M61 from Bingelli et al. 1985, AJ 90, 1681 via NED. Distance modulus (Virgo + GA + Shapley) m-M = 30.67[0.15] mag, suggesting an absolute mag M~-17.4. The spectrum shows a blue continuum with relatively weak and narrow Si II 635.5-nm absorption. Fe III lines at 430 and 500 nm are visible, suggesting that the object might be a member of the Type-Iax class of supernovae". Click on the image below to see a bigger version of spectrum obtained at Asiago.

Credit: The Asiago Transient Classification Program

This SN will have an official designation as soon as CBAT will issue its circular. Including this one, the total number of supernovae observed in M61 arrives to 7.

UPDATE - November 01, 2014

Cbet 4011 with the official designation for the SN in M61 has been issued: SUPERNOVA 2014dt IN M61 = PSN J12215757+0428185. Below you can see our confirmation image updated with official designation in the caption. Click on it for a bigger version. 

by Ernesto Guido, Martino Nicolini & Nick Howes

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