[vsnet-chat 3983] (fwd) Re: Nc's and other peculiar variables (Bedient)

[Taichi Kato <tkato>]

(fwd) Re: Nc's and other peculiar variables (Bedient)

J. Bedient wrote:

> There is a 2MASS point source very close to the position reported in IAUC
> 7556 by Platais et al. for V445 Pup (R.A. = 7h37m56s.882, Decl. =
> -25o56'58".88 (J2000)).  2MASSI J0737568-255658 is listed at R.A. = 07h 37m
> 56m.881, Decl. = -25o 56' 58".85 (J2000) in the Two Micron All Sky Survey
> (2MASS) Second Incremental Data Release Point Source Catalog.
> 
> Assuming the two objects are one and the same, the following photometric
> magnitudes from the 2MASS Second Incremental Data Release Point Source
> Catalog represent pre-outburst observations of V445 Pup (epoch 1999 Feb.
> 2.236): J = 12.270 +/- 0.031, H = 11.933 +/- 0.036, K = 11.515 +/- 0.030.

   See also my discussion in [vsnet-campaign-nova 104].

    The accurate position provided by H. Abe agrees the position of a 14-th
mag USNO star within 1-2 arcsec.  If this star is indeed the progenitor
of the erupting object, the color from the comparison between the visual
and 2MASS magnitudes becomes V-J = +2.  The color is not particularly red
in this field.  Even assuming that the object is not significantly
reddened, the color is still bluer than most of symbiotic stars, which
have V-J colors of +3 to +5 or even larger.  If the object is a nova, the
color suggests either a) usual cataclysmic variable with moderate reddening
or b) cataclysmic-type binary with a relatively evolved secondary.
[e.g. U Sco (Porb=1.2d) has a V-J color of +1.5].

[vsnet-campaign-nova 112]:

   These stars are the same.  I used USNO A1.0.  If we adopt the USNO A2.0
magnitudes, the V-J color is even more bluer (closer to a slightly reddened
cataclysmic variable).  I wonder how accurate A2.0 photometric calibration
in this field.

  ***

[New comment]

   The object being likely hydrogen-deficient, all colors should be treated
with caution.  Simple comparisons with hydrogen-rich systems could be
misleading.

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