MAXI/GSC is monitoring a peculiar X-ray activity of GRO J1008-57. The current long outburst started from August 2012. After the decay of the long outburst lasting for about 2 month, the flux turned into an increase again from MJD 56236 (2012-11-05). The flux reached 62 +- 7 mCrab (4-10 keV) on 2012-11-08 (MJD 56239) in 1-day bin. The latest 4-10 keV flux at 2012-11-09 03:00 UT reached 120 +- 9 mCrab in 4-hour bin. It is already as bright as the peak of the regular normal outburst at periastron. The Swift/BAT also detected the increase in 15-50 keV. According to the binary orbital parameters (Coe et al. 2007; Sootome et al. 2012), the present flare corresponds to ~0.3 orbital phase. Such a bright flare has not been recorded at this orbital phase.
Archive for the ‘compact source’ Category
We analyzed the MAXI/GSC light curve of an X-ray burst from EXO
1745-248 in Terzan 5 reported in Atel #3714, #3718, #3720 and found
that the initial peak at MJD 55858.53 decayed exponential with an
e-folding time of 10 hour.
If the emission is a blackbody radiation, the temperature can be estimated from the hardness of two energy bands.
MJD 4-10/2-4 keV kT [keV] 10-20/4-10 keV kT [keV]
55858.53 2.9 2.9 +- 0.8 0.32 2.4 +- 0.6
55858.59 1.5 1.7 +- 0.4 0.19 2.0 +- 0.8
55858.78 1.05 1.4 +- 0.4 0.50 2.8 +- 1.0
55858.84 1.24 1.58 +- 0.5 0.37 1.85 +- 0.8
55858.91 1.06 1.43 +- 0.5 0.19 1.83 +- 1.5
55858.97 1.03 1.40 +- 0.5 0.06 1.80 +- 3.9
(Errors are 1-sigma.)
The values derived from 4-10/2-4 keV and 10-20/4-10 keV
are consistent with each other. It showed a softening from 2.9 keV in the beginning to 1.5 keV in the end.
The fluence is 2.4 x 1042 erg in 2-10 keV assuming 8.7 kpc distance (Cohn et al. ApJ 571 818 (2002)). Using H burning energy of 6 x 1018 erg/g, the mass of H is 4.0 x 1023 g. Using the average flux of 10 mCrab (1.7 x 1036 erg/s, 9.0 x 1015 g/s), the reputation time is calculated to be 510 yr. (<- It was a mistale. Correctly 510 days. If we use C-burning energy it becomes 5100 days = 14 yrs. by TM 2011.11.16)
The sphere radius of the blackbody is 6.3 km with using 2 keV and 6.8 x 1037 erg/s at the peak.
These results (e-folding time, temperature, softening, fluence, and radius) are typical as a super-burst from low-mass X-ray binaries.
Archived light-curve data is available at
MAXI/GSC detected an X-ray burst at the scan transit centered at UT 2011-06-05T00:10:03.
The burst was detected at least for 30 seconds within the 62 seconds triangular transit response of MAXI/GSC.
The nominal location of the source, assuming that the source flux was constant over the transit
(which probably was not), is determined as
(R.A., Dec) = (+322.76 deg, +12.03 deg)
= (21 31 3, +12 01 44)(J2000)
with a rectangular 90% statistical error box with the following corners:
(R.A., Dec) = (+322.65 deg, +12.24 deg)
= (21 30 35, +12 14 7)(J2000)
(R.A., Dec) = (+322.93 deg, +12.19 deg)
= (21 31 42, +12 11 14)(J2000)
(R.A., Dec) = (+322.87 deg, +11.82 deg)
= (21 31 28, +11 49 28)(J2000)
(R.A., Dec) = (+322.59 deg, +11.87 deg)
= (21 30 21, +11 52 20)(J2000)
There is additional systematic uncertainty of 0.2 degree (90% containment radius).
This position is consistent with that of the globular cluster M15,
whose position is (R.A, Dec) = (322.49 deg, 12.17 deg).
The burst flux was 220 +-20 mCrab in the 4 – 10 keV band.
This burst is though to be the type I X-ray burst, because the softening of the spectrum was observed.
As reported in ATEL #3363, #3378, #3393, this source has been active recently.
MAXI/GSC has detected a new outburst from Be transient X-ray binary pulsar A0535+262 (Atel #3166). The figure shows the lightcurve folded with 110.2-day orbital period (Moritani 2010) in the 1.5 yr MAXI observations. Orbital phase zero corresponds to the periastron. The current light curve (orange) traces the previous giant outburst (blue) in December 2009 very well. (It may be a little smaller this time). The He I double line indicates a new gas-disk ejection from the Be star (Atel #3176). No strong precursor before MJD55601 (= Feb 9) may indicate that the gas was ejected very recently just before the “He I double line” observation (Feb 5). The short (1.2 yr) recurrent time shows that the Be star has become active.
We reported in ATEL#2873 (Negoro et al.) that MAXI/GSC detected a new X-ray transient, MAXI J1659-152 at (RA,Dec)=(264.79, -15.27) (J2000), whose position is consistent with the location of GRB100925A reported in GCN#11296 (Mangano et al.).
The GSC light curve since UT 2010-09-21 00:00 (MJD 55460.0) is shown in the below. The X-ray brightening seems to start around 2010-09-25 00:00 (MJD 55464.0) . The latest light-curve data will be updated on the data-product web page.
MAXI/GSC has detected X-ray brightening of the Be/X-ray binary system, A0535+26, since 2010 June 25 (UT). Its brightening has also been detected by the Fermi/GBM earth occultation, as reported in ATEL #2705.
The possible detection of the brightening by MAXI/GSC was first noticed on June 27 with a nova-search program involved in the ground pipeline data-reduction process. The source was observed by GSC #3 camera, which is now in a test operation at a reduced high voltage of 1550V. Since the response calibration at the 1550 V is just being developed, the data are not currently used in the light curve archived on the MAXI public-web page. Figure shows the light curve preliminarily obtained from the GSC #3 data. The brightening since 2010 June 25 (MJD=55372) is clearly seen. The source had been unobservable until June 23 for the sun-protection area. The fluxes preliminarily estimated in 4–10 keV band are 43+-6 mCrab on June 25, 75+-6 mCrab on June 28, and 65+-6 mCrab on June 29. The data of June 27 and June 28 are not ready at the moment because the download of telemetry data during these period is delayed.
Following our report “MAXI/GSC detects X-ray brightening of Cir X-1″ issued in Atel #2608, RXTE and Swift made follow-up observations, in which type-I X-ray bursts were detected at a position consistent with that of Cir X-1 (Atel #2643, #2650, #2651, #2653). We re-examined the data of the MAXI persistent/non-bursting source in the Cir X-1 region. We detected only one source at the position of (RA,DEC) = (230.04 +- 0.05, -57.27 +/- 0.03) (errors are statistical only). Considering the positional systematic error of 0.2 degree, the source location is consistent with that of Cir X-1. Furthermore, MAXI/GSC detected an X-ray burst at 2010-05-29 15:50:50, confirming the detections by RXTE and Swift. The two energy-band light curve is shown in the figure, which suggest spectral softening during the decay phase indicative of the type-I (thermonuclear) nature or the burst.
We thank Dr. Linares for encouraging this reanalysis.
MAXI/GSC detected an X-ray brightening of the X-ray source GX 304-1. The figure shows one day image of GX 304-1 on 22 March 2009, with pseudo-colors. The preliminary one-day average flux of the source in the 4-10 keV energy band was about 10 mCrab on 21 March and 30 mCrab on 22 March. We had reported the previous outburst of the source on 15 November 2009 (ATel #2297), which peaked around 19 November 2009. The interval between the previous and current outburst is consistent with known recurrence period of 132.5 days.
MAXI/GSC detected an X-ray brightening of the LMXB 4U 1608-522. The figure shows the light curve of this source in 4 – 10 keV band, which was made by image fitting method currently in development. Please be careful about data points before the detection of the flare on March 2 (MJD 55257), because the cause of the baseline offset is not completely understood. Nonetheless, the increase of the flux must be true. We have reported the news to Astronomers Telegram #2462.
To be frank with you, we made a mistook about author list, when we post the telegram. The author list should be as follows:
M. Morii (Tokyo Tech), H. Negoro (Nihon U.), M. Suzuki (JAXA), Y. Ueda (Kyoto U.), M. Matsuoka, K. Kawasaki, S. Ueno, H. Tomida, M. Ishikawa (JAXA), T. Mihara, M. Kohama, Y.E. Nakagawa, M. Sugizaki, T. Yamamoto, T. Saotome (RIKEN), N. Kawai, K. Sugimori (Tokyo Tech), A. Yoshida, K. Yamaoka, S. Nakahira (AGU), H. Tsunemi, M. Kimura (Osaka U.), M. Nakajima, S. Miyoshi, H. Ozawa, R. Ishiwata, (Nihon U.), N. Isobe, S. Eguchi, K. Hiroi (Kyoto U.), A. Daikyuji (Miyazaki U.), A. Uzawa, T. Matsumura, K. Yamazaki (Chuo U.) report on behalf of the MAXI team