Giant outburst of V4641 Sgr (previous GM Sgr) = SAX J1819.3-2525
CCD images on 1999 Sep. 5 (before giant outburst) and Sep. 15 (during outburst). Images were taken at Kyoto University. South is approximately up.
GM Sgr rapid variation
GM Sgr, an outbursting object of unknown type, is reported to show remarkable short-term variation. Frequent observations are strongly urged.
YYMMDD(UT) mag observer 990829.424 127 (R. Stubbings) 990831.478 <131 (T. Watanabe) 990831.496 130 (R. Stubbings) 990909.462 112 (R. Stubbings) 990910.414 112 (R. Stubbings) 990910.474 112 (R. Stubbings) 990911.599 119 (R. Stubbings) 990912.409 111 (R. Stubbings) 990912.460 115 (T. Watanabe) 990912.476 112 (R. Stubbings) 990913.397 119 (R. Stubbings) 990913.730 123 (B. Monard) 990914.715 117 (B. Monard) 990914.749 114 (B. Monard) 990914.776 111 (B. Monard) 990914.787 111 (B. Monard)
GM Sgr very bright!
GM Sgr is undergoing a very bright outburst after rapid variations.
GM Sgr 990914 11:47UT 11.4 GM Sgr 990915 9:29UT 9.8 GM SGR 990915 9:47 9.8Star used for comparison is GSC 68483326
(Maximum magnitude later corrected to 8.8)
I was just writing an alert! The extreme bright outburst has been independently confirmed by CCD observation at Kyoto.
Can anyone take a spectrum?
The object presently looks as bright as GSC6848.3882 (Tycho V=9.30, B-V=0.49) on unfiltered CCD images.
According to IAUC 7119, GM Sgr was listed as a flaring X-ray transient SAX J1819.3-2525. The present outburst may be a reccurence of this event. Optical, X-ray, and radio (and more) follow-up observations are extremely strongly urged.
The X-ray outburst has been confirmed by subsequent observations by Smith et al. (IAUC 7253).
We obtained the optical spectra of GM Sgr using Bisei Astronomical Observatory 1.01-m telescope.
The following report has posted to CBAT.
K. Ayani, Bisei Astronomical Observatory, Japan, and T. C. Peiris, Arthur C. Clarke Inst. for Modern Technologies, Sri Lanka, report the following observation of GM Sgr.
The optical spectra (range 390-760 nm; resolution 0.7nm at H alpha) of
GM Sgr were obtained with Bisei Astronomical Observatory 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 Balmer series and of He II 468nm are prominent. H-alpha emission
line has a FWHM of about 2700 km/s and an equivalent width of 8nm. He
II 541nm emission line is also present. These facts indicate that GM
Sgr is the opitcal counterpart of SAX J1819.3-2525.
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The earliest detection of the current active state was made by Tsutomu Watanabe (VSOLJ) as:
GM Sgr outburst?
The possible novalike variable GM Sgr is reported by T. Watanabe to be possibly in outburst. His observation refers to the VSNET chart of GM Sgr. Confirmation of this field is urgently requested.
YYMMDD(UT) mag observer 990808.610 129 (T. Watanabe)Regards,
The outburst detection was published in VSOLJ Variable Star Bulletin:
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