[vsnet-newvar 1651] (fwd) Re: Position of Lillers nova suspect in SMC

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

(fwd) Re: Position of Lillers nova suspect in SMC

Date: Mon, 21 Oct 2002 12:23:48 +0200
From: "Berto Monard" <LAGMonar@csir.co.za>

Hi Bill, \Brian, Mati and other interestees,

last night I succeeded in imaging the fading nova in SMC. I would have
loved to do it earlier but the moon probably wasn't full enough ;-).

The image and the derived astrometry show that the bright object is
very closely coincident to the discussed star. 
My derived position with reference to the UCAC1 frame is : 00 56 30.49
-72 36 29.1 . 

The progenitor (or at least the eventual very close optical neighbour)
is not in the UCAC1 data, despite its isolation and relative brightness.
Possibly it was variable like most SMC stars that I ever monitored
(visually). More likely it is just a foreground star, omitted in the
UCAC1 database and very much in line with the nova far behind it... not
so Brian? 

Since the nova is still bright, the light of the 'eventual' very close
neighbour didn't affect the astrometry significantly. 

My observation (unfiltered CCD) vs the photometry of Vigneau et al:
Nova SMC 021020.825   138CR   MLF

the image .fts can be made available

Regards,

Berto Monard  /  MLF
Bronberg Observatory / CBA Pretoria



>>> Brian Skiff <Brian.Skiff@lowell.edu> 10/19/02 10:12AM >>>
     Mati wrote:
>>   I note that Bill Liller's nova suspect in the SMC is virtually
coincident
>>   with a USNO-A2.0 star (r=16.2, b=17.7, V= 16.8) at
>>   0 56 30.26 -72 36 29.4  [non-ASCII characters deleted]

     This star also appears in three CCD-based photometric surveys of
the SMC:

source              V    B-V   U-B   V-R   V-I    citation
Massey et al.     15.60 -0.12 -0.73  0.10         2002ApJS..141...81M
Zaritsky et al.   15.74  0.02 -0.99        0.06   2002AJ....123..855Z
OGLE BVI maps     15.84 -0.04              0.15   1998AcA....48..147U

The discordance among the results is surely from the
crowding---Zaritsky shows
12 additional stars within 10" radius, while the OGLE data show more
than 
two dozen!  Despite this, the colors are indicative of a hot star near
type
B0 or B1, and the V magnitude is consistent with the absolute magnitude
of such
a star (Mv about -3.5 or -4.0).  (I assume the Zaritsky U-B is wrong,
since it
leads to unphysical results.)  The USNO-A2.0 photometry is two
magnitudes in
error in blue, and the interpolated V (maybe better written as 'v') is
a full
magnitude too faint.  GSC-2.2 has similar problems.
     Coordinates from the various sources:

0 56 30.47   -72 36 28.5   (2MASS, probably 'best' at the moment)
0 56 30.41   -72 36 28.3   (OGLE)
0 56 30.43   -72 36 28.3   (Zaritsky)
0 56 30.43   -72 36 28.6   (GSC-2.2)
0 56 30.49   -72 36 28.3   (Massey)
0 56 30.49   -72 36 29.0   (DENIS)
0 56 30.26   -72 36 29.4   (USNO-A2.0)

     Only the A2.0 position is noticeably out, the others being within
0".3
(0".6 for DENIS).
     It is easy to find all this given the accurate position by doing
a
"search everything" query with the Strasbourg VizieR utility:

http://vizier.u-strasbg.fr/cgi-bin/VizieR 

     Anyway, though this star almost certainly has nothing to do with
the
nova, it could complicate things as the nova fades.

\Brian

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