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Possible Nova in Sgr
IAUC No. 8113 reports the discovery of a possible nova in Sgr by
Hideo Nishimura (Kakegawa, Shizuoka, Japan). The approximate position
reported by Nishimura is:
18h 07m 19s
-27o 24' 20"
(J2000.0)
The magnitude were as follows (using the tentative object's notation):
SGRnova2003 20030325.81 <110p Nmh
SGRnova2003 20030327.81 109p Nmh
SGRnova2003 20030330.80 <110p Nmh 120?
SGRnova2003 20030405.80 104p Nmh
SGRnova2003 20030408.792 98p Nmh
According to the same IAUC, Kushida and Kushida reported astrometry
of a bright object on an unfiltered CCD image: 18h 07m 20s.38, -27o 24' 31".6
(J2000.0). However, this position almost perfectly coincides with a
bright 2MASS star (likely a very red star) located at
2MASS 180720.388 -272432.27 (2000.0) 6.039 0.000 0.000
= MSX5C_G003.7266-03.3729 at 180720.6 -272431
(This 2MASS identification has been also independently communicated by
John Greaves).
This identification indicates that either the object was misidentified
by Kushida and Kushida, or that the object is less likely a nova, if
the identification was correct. [There is still a small possibility that
a red star underwent an unusual outburst, though.]
It would be interesting to note that there are a number of variable
objects near the original position reported by Nishimura. Many of them
are OGLE2 variable stars, which have been classified as "transient-type"
variables. These objects are, however, very faint.
180718.9 -272420 (2000.0) OGLE2-BUL-SC18-V1565 16.692I (0.304) trans
180719.1 -272425 (2000.0) OGLE2-BUL-SC18-V1566 14.877I (0.114) trans
180719.2 -272413 (2000.0) OGLE2-BUL-SC18-V1769 12.733I (0.017) trans
180719.2 -272420 (2000.0) OGLE2-BUL-SC18-V1567 13.576I (0.046) trans
180719.3 -272426 (2000.0) OGLE2-BUL-SC18-V1569 15.320I (0.200) trans
180719.4 -272417 (2000.0) OGLE2-BUL-SC18-V1593 14.018I (0.081) trans
180719.5 -272422 (2000.0) OGLE2-BUL-SC18-V1595 14.496I (0.138) trans
There are also 2MASS stars, but not as bright as the above object
most likely measured by Kushida and Kushida. The brightest one near the
Nishimura's position is:
2MASS 180719.244 -272420.37 (2000.0) 11.924 10.492 10.299
(= GSC 6850.4355)
There is also a GCVS (position still uncertain) star V4006 Sgr
180715.3 -272535 (2000.0) SGRV4006 M 11.6 <14.4 P 37846 281 -
This Mira star is sufficiently bright, but has not been yet properly
identified (although the discovery finding chart would suggest the
GCVS location is correct) with a very conspicuous 2MASS counterpart
at the reported position (either on 2MASS public images and catalogs).
The brightest 2MASS object in this field is the star measured by Kushida
and Kushida. It may have been possible that the original paper
(by L. Lukas) somehow provided an incorrect chart, or the original
type classification was wrong. If V4006 Sgr was truly a Mira-star,
it may have been possible that Nishimura "recovered" this variable.
It would be still worth persuiting for the exact location of this supposed
Mira-star, too.
Precise measurement of Nishimura's photograph, other comteporaneously
taken photographs and images, and further examination of the identity
are strongly encouraged.
Regards,
Taichi Kato
Return to the Powerful Daisaku
vsnet-adm@kusastro.kyoto-u.ac.jp
