XTE J1720-318: X-ray nova

Alert from the RXTE team

Date: Tue, 14 Jan 2003 22:24:57 -0500 (EST)
From: Ron Remillard 
Subject: New X-ray Transient, XTE J1720-318

New X-ray Transient, XTE J1720-318

R. A. Remillard, A. M. Levine, and E. H. Morgan (M.I.T.), and E. Smith, and J. Swank (NASA GSFC), for the RXTE All Sky Monitor Team at M.I.T. and NASA's Goddard Space Flight Center, report the discovery of a transient X-ray source at R.A. = 17h19m58s, Decl. = -31 46'.8 (equinox J2000.0; estimated 3' uncertainty at 90% confidence). The source was first detected on 2003 January 9 when the average flux (2-12 keV) was 130 +- 20 mCrab. The intensity increased to 430 +- 40 mCrab on Jan. 10 and 400 +- 20 mCrab on Jan. 13. A brief observation of the ASM position on January 14 with the RXTE PCA confirms the presence of a bright transient. More extensive observations with the PCA and HEXTE, including raster scans to improve the source position, are planned starting Jan. 15. The error circle does not contain any noteworthy sources in the Simbad catalogs. The ASM hardness ratios indicate that the spectrum was moderately hard Jan. 9-10 and relatively soft on Jan. 13. These results resemble the early spectral evolution of X-ray transients known to contain an accreting black hole. We encourage optical and radio observations of this new transient.

-----

Ron Remillard
MIT

Look for counterparts!!

(CCD image of the field of the X-ray nova taken by Berto Monard on 2003 Jan. 16.)

(vsnet-campaign-xray 178)

Date: Fri, 17 Jan 2003 17:43:51 +0900 (JST)
From: Taichi Kato 
To: vsnet-campaign-xray@ooruri.kusastro.kyoto-u.ac.jp,
	vsnet-newvar@ooruri.kusastro.kyoto-u.ac.jp
Subject: [vsnet-campaign-xray 178] XTE J1720-318 refined position

XTE J1720-318 refined position

   According to ATEL #115, the RXTE PCA refined position is reported to be
R.A. = 17h 20m 00s, Decl. = -31o 44'.8 (J2000.0), with error radius of
0.5-1 arcmin.  The object is suggested to be a black hole candidate
in the so-called "high" state.

Radio Counterpart

(vsnet-campaign-xray 181)

Date: Tue, 21 Jan 2003 09:30:09 +0900 (JST)
From: Taichi Kato 
Subject: [vsnet-campaign-xray 181] XTE J1720-318 radio counterpart

XTE J1720-318 radio counterpart

According to IAUC 8054, Rupen et al. reports the discovery of a new radio source, which is likely the counterpart of XTE J1720-318.

   The J2000.0 position of the new source is

   17h 19m 59s.062 (+/-0s.087)
   -31o 44' 59".7 (+/-1".10)

   The position is 1'.4 from the original X-ray position.

Regards,
Taichi Kato

Infrared counterpart

(Left: Infrared image taken by D. Kato, the IRSF/SIRIUS team. Right: 2MASS image (provided by H. Yamaoka))

(vsnet-campaign-xray 183)

Date: Tue, 21 Jan 2003 19:10:29 +0900 (JST)
From: Taichi Kato 
Subject: [vsnet-campaign-xray 183] XTE J1720-318 likely infrared counterpart

XTE J1720-318 likely infrared counterpart

Dear Colleagues,

Daisuke Kato-san, Nagoya University, has just submitted the following article to IAUC. The referred URL is already accesible. A reference page on VSNET will be coming soon.

Rehards,
Taichi Kato

===

D. Kato, T. Nagata (Nagoya U.) on behalf of the IRSF/SIRIUS team (Nagoya U., NAOJ), T. Kato, M. Uemura (Kyoto U), and H. Yamaoka (Kyushu U.) report: "We performed near-infrared (J, H, Ks) imaging of the field of the X-ray transient XTE J1720-318 (IAUC 8050) with the Simultaneous three-color InfraRed Imager for Unbiased Survey (SIRIUS) on the Nagoya-SAAO 1.4m (IRSF) telescope at Sutherland, South Africa on 2003 Jan. 18.1 and 19.1 UT. We detected a likely infrared counterpart at 17h 19m 59s.00, -31o 45' 01".2 (J2000.0, about 150 2MASS position reference stars, error 0".2), located within 1".7 of the proposed radio counterpart (IAUC 8054). The new object is invisible on public 2MASS images, although definite identification would require further follow-up observations since the brightness of the new object is close to the limiting magnitudes of the 2MASS survey. The J, H, Ks magnitudes of the object are 16.73 +/- 0.02, 15.91 +/- 0.03, 15.31 +/- 0.03 (Jan. 18.1) and 16.68 +/- 0.02, 15.80 +/- 0.03, 15.27 +/- 0.05 (Jan. 19.1). The finding chart is available at http://www.z.phys.nagoya-u.ac.jp/~kato/irsf3.gif ".

Letter

Nagata, T.; Kato, D.; Baba, D.; Nishiyama, S.; Nagayama, T.; Nagashima, C.; Kurita, M.; Sato, M.; Kato, T.; Uemura, M.; Yamaoka, H.; Monard, B.; Ita, Y.; Matsunaga, N.; Nakajima, Y.; Tamura, M.; Nakaya, H.; Sugitani, K.
The Infrared Counterpart of the X-Ray Nova XTE J1720-318
PASJ (Letters), in press

[VSNET preprint] [PDF file]

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