Central Bureau for Astronomical Telegrams
IAUC 7254: GM Sgr, SAX J1819.3-2525 = XTE J1819-254; V1493 Aql
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Circular No. 7254
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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GM SAGITTARII AND SAX J1819.3-2525 = XTE J1819-254
K. Ayani, Bisei Astronomical Observatory (BAO); and T. C.
Peiris, Arthur C. Clarke Institute for Modern Technologies, Sri
Lanka, report: "A spectrogram (range 390-760 nm; resolution 0.7 nm
at H-alpha) of GM Sgr was obtained with the BAO 1.01-m telescope on
Sept. 15.50-15.52 UT, when the x-ray flux of SAX J1819.3-2525 was
rapidly increasing (IAUC 7253). Broad emission lines of the Balmer
series and of He II 468-nm are prominent. The H-alpha emission
line has a FWHM of about 2700 km/s and an equivalent width of 8 nm.
The He II 541-nm emission line is also present. This suggests that
GM Sgr is indeed the optical counterpart of SAX J1819.3-2525."
R. M. Hjellming and M. P. Rupen, National Radio Astronomy
Observatory; and A. J. Mioduszewski, Sydney University, report the
Very Large Array detection on Sept. 16.02 UT of a radio source at
R.A. = 18h19m21s.64, Decl. = -25o24'25".6 (equinox 2000.0;
uncertainty +/- 0".3) with preliminary fluxes of 0.35, 0.4, and
0.25 Jy at 1.46, 4.9, and 14.9 GHz, respectively. This is 0".8
from the 1"-uncertainty position of GM Sgr reported by Williams on
IAUC 7253. There was no radio source above 5 mJy at this position
in the 1.49-GHz NVSS image of the field in June 1996. This
confirms the identification of SAX J1819.3-2525 = XTE J1819-254
(IAUC 7119, 7120, 7253) with the 'cataclysmic variable' GM Sgr.
M. Tichy and J. Ticha, Klet Observatory, report that a CCD
image taken on Sept. 15.839 UT, with cirrus clouds and GM Sgr at
low altitude (limiting mag about 13), shows GM Sgr at mag about
11.5, indicating the star's apparent rapid fading from the peak
visual mag about 9 noted on IAUC 7253.
W. Liller, Vina del Mar, Chile, reports that a low-dispersion
spectrogram (about 0.7 nm/pixel at H-alpha) of GM Sgr taken with a
CCD on Sept. 16.158 UT shows a strong H-alpha emission line at
least 3.0 times the intensity of the neighboring continuum. (The
spectrum is partially blended with that of nearby faint star.)
Liller further reports that the broadband V magnitude on Sept.
16.131 was 13.27.
V1493 AQUILAE
CCD magnitude estimates by D. Hanzl at Brno, Czech Republic
(comparison star GSC 1048.863, assuming V = 8.40 +/- 0.02, B-V =
+0.311 +/- 0.02, from Tycho Catalogue): Aug. 19.864 UT, V = 12.20
+/- 0.05; 21.830, V = 11.51 +/- 0.02; 22.840, V = 11.90 +/- 0.01,
B-V = +1.03 +/- 0.01; Sept. 4.806, V = 13.92 +/- 0.01, B-V = +0.80
+/- 0.02; 9.788, V = 14.66 +/- 0.05, B-V = +0.65 +/- 0.05; 12.798,
V = 14.82 +/- 0.01, B-V = +0.64 +/- 0.04.
(C) Copyright 1999 CBAT
1999 September 16 (7254) Daniel W. E. Green
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