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.

(vsnet-alert 3475)

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)

(vsnet-alert 3477)

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       9.8
Star used for comparison is GSC 68483326

Rod Stubbings.

(Maximum magnitude later corrected to 8.8)

(vsnet-alert 3478)

I was just writing an alert! The extreme bright outburst has been independently confirmed by CCD observation at Kyoto.

Can anyone take a spectrum?

Taichi Kato

(vsnet-alert 3481)

The object presently looks as bright as GSC6848.3882 (Tycho V=9.30, B-V=0.49) on unfiltered CCD images.

Taichi Kato

(vsnet-alert 3482)

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.

Taichi Kato

The X-ray outburst has been confirmed by subsequent observations by Smith et al. (IAUC 7253).

Spectroscopy at Bisei Observatory

(vsnet-alert 3489)

Dear colleagues,

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.

Best regards,
Kazuya Ayani

RXTE observation etc.

RXTE observation page page

Astronomy Picture of the Day

Discovery channel news

The earliest detection of the current active state was made by Tsutomu Watanabe (VSOLJ) as:

(vsnet-alert 3345)

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)
Taichi Kato

The outburst detection was published in VSOLJ Variable Star Bulletin:

Watanabe's paper

Light curve (requires Java 1.1)

Light curve

VSNET data search


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