[vsnet-alert 12290] (fwd) MAXI J1409-619

[Taichi Kato]

   Fwd, new MAXI X-ray transient MAXI J1409-619.  Accurate astrometry of
the IR (optical?) counterpart will be helpful in identifying the quiescent
counterpart.

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The Astronomer's Telegram                   http://www.astronomerstelegram.org 
==============================================================================
ATEL #2959							     ATEL #2959

Title:		MAXI/GSC detects an X-ray transient MAXI J1409-619 
Author:	K. Yamaoka, S. Nakahira (AGU), H. Negoro (Nihon U.), N. Kawai
		(Tokyo Tech), A. Uzawa, K. Yamazaki, T. Matsumura, Y. Tsuboi (Chuo
		U.), K. Kawasaki, S. Ueno, H. Tomida, M. Kohama, M. Ishikawa (JAXA),
		T. Mihara, M. Sugizaki, M. Serino, Y.E. Nakagawa, T. Yamamoto, T.
		Sootome, M. Matsuoka (RIKEN), M. Morii, K. Sugimori, R. Usui (Tokyo
		Tech), A. Yoshida (AGU), H. Tsunemi, M. Kimura (Osaka U.), M. Nakajima,
		H. Ozawa, F. Suwa (Nihon U.), Y. Ueda, N. Isobe, S. Eguchi, K. Hiroi
		(Kyoto U.), A. Daikyuji (Miyazaki U.), report on behalf of the MAXI
		team
Queries:	yamaoka at phys.aoyama.ac.jp
Posted:	20 Oct 2010;  11:06  UT
Subjects:	X-ray, Request for Observations, Transients

The MAXI/GSC has detected a faint X-ray transient source at a position:

(R.A., Dec) = (212.26, -61.95) = (14h09m02s.4, -61d57m00s.0) (J2000)  

with a statistical error of about 0.2 degrees.  The systematic error is
smaller because the position is calibrated using nearby bright sources
4U 1323-60 and 4U 1254-69. The 4-10 keV flux reached a peak at 41 +/- 7
mCrab on October 17, then decreased to 29 +/- 7 mCrab on October 18.  

We note that this position is marginally consistent with that of a RASS
source:       

1RXS J141108.2-615601 (R.A., Dec) = (212.79, -61.93) = (14h11h08s.7, -61d55m47s.0)
(J2000),      

which has been identified to a bright dMe star (Torres et al. 2006, A&A,
460, 695, Riaz, Gizis, and Harvin, 2006, AJ, 132, 866).      

Follow-up observations of this MAXI source are encouraged. The MAXI/GSC
will continue     to monitor the same sky region every day. The MAXI/GSC
light curve and image are available at the following URL: http://maxi.riken.jp/news/en/

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The Astronomer's Telegram                   http://www.astronomerstelegram.org 
==============================================================================
ATEL #2962							     ATEL #2962

Title:		MAXI J1409-619: Swift localization and identification as a
		new X-ray transient 
Author:	J. A. Kennea (PSU), H. Krimm (CRESST/GSFC/USRA), P. Romano,
		V. Mangano (INAF-IASFPA), P. Curran (CEA-Saclay) and P. Evans (U Leicester)
		
Queries:	kennea at astro.psu.edu
Posted:	20 Oct 2010;  22:31  UT
Subjects:	X-ray, Transients

At 15:14 UT on Oct 20th, 2010 Swift began a 1ks target of opportunity
observation of MAXI J1409-619 (Yamaoka et al, 2010, ATEL #2959). Utilizing
photon counting mode data we find a uncatalogued bright X-ray source inside
the MAXI error circle at the following UVOT enhanced location, RA, Dec(J2000)
= 212.01068, -61.98340, which is equivalent to :   

RA(J2000) = 14h 08m 02.56s,   
Dec(J2000) = -61d 59m 00.3s,   

with an estimated uncertainty of 1.9 arcseconds radius (90% confidence).
This source lies 7.3 arcseconds from the MAXI localization, inside the
0.2 degree error circle. We note that this position is inconsistent with
any catalogued X-ray source and lies ~0.4 degrees away from the Galactic
plane, and therefore conclude that MAXI J1409-619 is a new Galactic X-ray
Transient source. The nearest catalogued source is 2MASS 14080271-6159020,
a J=15.874 source 2.1 arcseconds from the center of the XRT error circle,
and is likely the IR counterpart of the transient.    

The photon counting spectrum, corrected for pile-up, is well fit by an
absorbed power-law model with an absorption of ~3 x 10^22 cm^-2, and a
photon index of -0.5 (+0.1/-0.6).  The average flux over the XRT observation
is 1.3 x 10^-10 erg/s/cm^-2 (0.3-10 keV), uncorrected for absorption. The
source shows significant variability over the short 1ks observation, with
the count rate varying between 0.8 and 0.3 XRT counts/s, the lightcurve
shows a possible sinusoidal variation with a period of ~720 seconds, although
we note that it is impossible to tell if this represents an actual source
periodicity given the length of the data.   

The BAT hard X-ray transient monitor confirms the detection of MAXI J1409-619
in the 15-50 keV band. Analysis of archival images at the XRT position
shows that the source was first detected on 18-Oct-2010 at a level of 0.0068
+/- 0.0013 ct/s/cm^2, or ~30 mCrab. The source rate appears to be rising,
although we do not yet have the transient monitor data from the past 24
hours. It was not detected on 17-October-2010 (1-sigma upper limit of
0.004 ct/s/cm^2), the date of the peak in the MAXI light curve (Yamaoka
et al, ATel #2959).   

Based on the shape of the light curve, the characteristics of the X-ray
spectrum (flux and hard photon index), the location close to the Galactic
plane, plus the presence of an IR counterpart close to the XRT error circle,
MAXI J1409-619 may be a good SFXT candidate.    

Further multi-wavelength observations of this transient are encouraged
to determine its nature.