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Special Notice #103: V2491 Cygni (Nova in Cygnus) [Nova Cyg 2008 No. 2]

April 11, 2008

IAU Circular No. 8934 (D. Green, Ed., Central Bureau for Astronomical Telegrams) announces the discovery of a nova in Cygnus by Koichi Nishiyama, Kurume, Fukuoka-ken, Japan, and Fujio Kabashima, Miyaki-cho, Saga-ken, Japan, on unfiltered CCD images taken April 10.728 UT at magnitude 7.7. Nothing is visible at this position on their past survey frames taken on  Apr. 3.717 (limiting mag 12.5) and 7.727 (limiting mag 12.7).  

An apparent independent discovery of this nova at mag ~8.0 by was made by Z.-w. Jin and X. Gao on images taken by Gao on Apr. 10.831 UT at Xingming Observatory, Mt. Nanshan, China (position end figures measured by J. Beize, Beijing, 02.00s, 10.1"; nothing was visible at this position on Xingming images taken on Apr. 8.831 (limiting mag about 14). 

K. Haseda (Toyohashi, Aichi, Japan) finds nothing brighter than mag 12.3 on patrol images taken Apr. 4.774 UT.

N. N. Samus, Institute of Astronomy, Moscow, reports that this nova is being assigned the name V2491 Cyg.

Coordinates from Nishiyama and Kabashima:

R.A. = 19:43:01.96  Decl. = +32:19:13.8 (equinox 2000.0)

Confirming images by E. Guido and G. Sostero, Remanzacco, Italy, taken April 11 remotely with a 0.25-m reflector near Mayhill, NM, show the nova at position end figures 01.98s, 13.5".  They report that a Palomar Oschin Schmidt telescope plate from 1995 Aug. 3 shows an apparent star with red mag ~18 at this location; they also provide the following photometry: (uncertainty +/- 0.05 mag in each color):  Apr. 11.36, B = 8.06, V = 7.54, R = 7.04; 11.46, 8.20, 7.77, 7.15.  G. Klingenberg, Mo i Rana, Norway, reports the following photometry from CCD images taken with a 25-cm reflector near Mayhill, NM:  Apr. 11.333, V = 7.63; 11.335, B = 8.06; 11.440, V = 7.74; 11.443, B = 8.15.  

An image by K. Kadota, Ageo, Saitama-ken, Japan, on Apr. 11.741 UT yields mag 7.4 and position end figures 01.98s, 14.1". Kadota notes that a USNO-B1.0-catalogue star has position end figures 02.039s, 13.84" and red magnitudes 15.5 and 16.3 (different epochs from Palomar Sky Survey plates).

CBET 1334 (D. Green, Ed., Central Bureau for Astronomical Telegrams) announces that K. Ayani, Bisei Astronomical Observatory and K. Matsumoto, Osaka Kyoiku University, Japan, write that low-resolution spectra of V2491 Cyg obtained Apr. 11.72 UT indicate that the object is a nova in its early phase of outburst. Fe II emission may be present.  

V2491 Cyg has been added to VSX (pending approval) and has been assigned the identifier VSX J194301.9+321913. It has also been assigned the AAVSO unique ID 000-BFT-191.

A finder chart for the V2491 Cyg field may be generated using VSP: http://www.aavso.org/observing/charts/vsp/ and entering the coordinates. The name V2491 CYG should shortly generate a finder chart as well. A comparison star sequence has not yet been established for V2491 Cyg. Please be sure to indicate all comparison stars used when submitting data.

Visual and photometric observations are requested. Please report your observations to the AAVSO as 'V2491 CYG' (AUID 000-BFT-191).

Congratulations to the discovers of V2491 Cyg!

This AAVSO Special Notice was prepared by Elizabeth O. Waagen.

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