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THE ASTRONOMER Electronic Circular No 2299      2007 Jan 14 16.16UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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V2362 CYGNI
J. Rayner, Institute for Astronomy, University of Hawaii et. al., report 
on IAUC 8788 that 0.8- to 5-micron spectroscopy of V2362 Cyg was 
obtained from 2006 Nov. 30 and Dec. 20 UT using the SPEX instrument on 
the 3-m reflector of the Infrared Telescope Facility. The Nov. 30 data 
were obtained at the visual peak of the nova's second outburst. That 
outburst rejuvenated its spectrum, erasing the higher excitation lines 
and most of the He I emission features -- and replacing them with strong 
lines of neutral carbon, nitrogen, and oxygen and singly ionized iron. 
There were no signs of dust local to the nova.

In contrast, the Dec. 20 measurement revealed a spectrum completely 
transformed through the formation of hot dust. Beyond 2 microns, the 
spectrum is well fitted by a Planck function with the single temperature 
of 1410 K.  In retrospect, it is clear that the precipitous drop in the 
visible light curve beginning in early
December was due to dust formation, and that emission from this hot dust 
accounted for the unexpectedly bright fluxes between 3 and 13 microns 
measured on Dec. 12 and reported on IAUC 8785. The failure to recognize 
the dust at that time was a consequence of its high temperature, which 
placed the characteristic turnover of the Planck function outside of the 
measurement range.  The underlying emission-line spectrum also changed 
significantly since Nov. 30, showing both a narrowing of the lines and 
an increase in excitation marked by the appearance of He II emission.

David Boyd has reported to us that the significance of the faint star 
very close to the nova is growing during the present fade. He has 
decided to include the combined brightness of the two objects since, on 
nights of poor seeing, they may not be cleanly
resolvable. The following include some re-measures on this basis:

Date                   JD          V      dV    V-Ic   d(V-Ic)
2006 Dec  17.718   2454087.218   13.12   0.01   1.70   0.02
2006 Dec  19.735   2454089.235   13.25   0.02   1.79   0.03
2006 Dec  28.787   2454098.287   13.67   0.02   1.31   0.03
2007 Jan  10.751   2454111.251   13.71   0.01   0.54   0.03
2007 Jan  11.824   2454112.324   13.71   0.02   0.55   0.04

Guy M Hurst