We had the first detection of a gamma-ray burst (GRB 090831) with GSC. The discovery sky image is attached below. The pale blue dot near the upper-left edge is the GRB. The transit light curve taken with a GSC Camera is also shown in the right. We reported the detection to GCN (Gamma-ray burst Coordinate Network) at NASA (link to the message).
Archive for August, 2009
Gamma-ray burst (GRB 090831) detected
Monday, August 31st, 2009MAXI detect the first tansient event
Friday, August 21st, 2009We had the first detection of a transient event with MAXI. In the nova search screen, we noticed a blue (i.e. hard) source that was not present before. With the close examination of the data, we find that a bright source was present only during a single scan at around 2009-08-20 18:37 UT. The transient event lasted at least for the full transit duration of 40 seconds, during which we noticed an indication of spectral softening. Based on its location, we tentatively identify this transient as a type-1 X-ray burst from X1724-307 in globular cluster Terzan 2. The peak flux is about 1.5 Crab. The figures below present the comparison of the sky maps that led to the detection of this burst: 4-orbit overage until 08-20 11h UT (left), one day average until 08-21 2h UT (right).
The “First Light” image of MAXI
Tuesday, August 18th, 2009The “First Light” image of MAXI has been released. It is shown at the top page of this site. In the first light image of MAXI, accumulated with the GSC for one ISS orbit, we can easily recognize about 20 bright Galactic sources. A preliminary analysis suggests that GSC achieved about 20-30 mCrab sensitivity in one orbit, mostly consistent with the pre-flight estimation (Matsuoka et al 2009, accepted for PASJ, http://arxiv.org/abs/0906.0631).
We will spend about two month to understand the instrument characteristics in orbit, the flight operations, and data processing before we start public release of the images and light curves.
The RBM map on earth
Thursday, August 6th, 2009The RBM count rate measured for a day is mapped on earth as shown below. We are surprised with the large difference of the count rates and the geographical distribution between the two RBM sensors.
RBM-H (horizontal) sensor: The SAA (South Atrantic Anomaly) is not so strong in ISS altitude (350km high). There is a higher background region in south of SAA. Auroral regions (North America, South Paciffic Ocean, South Indean Ocean) are also in high count rates. We defined the “High background region” for MAXI as black lines. The high voltage of the GSC cameras are turned off for safety within these regions.
RBM-Z(zenithal) sensor: The count rate is one-two order smaller than the horizontal sensor. The “south of SAA” is not so strong. The SAA is visible in zenithal sensor.
RBM (Radiation Belt Monitor) sensors were turned on.
Wednesday, August 5th, 2009RBM (Radiation Belt Monitor) sensors were turned on. There are two RBM sensors in MAXI. One of them (RBM-H) is placed at the center of GSC A-1 with its field of viewn in the horizontal (ram) direction. The other is placed at the center detector of GSC B-4 with its field of in the zenith. We will collect the count rate for a day to monitor the radiation environment in the ISS.
Power on MAXI.
Monday, August 3rd, 2009Power on MAXI. The main power to MAXI was turned on at 0:41 UT, and we established the communication to the MAXI data processor. The various subsystems (components) of MAXI were subsequently turned on in series: VSC (Visual Star Camera), RLG (Ring Laser Gyro), GSPR (GPS Receiver), GSCE-A, GSCE-B (Gas Slit Camera Electronics A/B), SSCE (Solid-state Slit Camera Electronics), PEL0, PEL1 (SSC Peltier Cooling System 0/1). We confirmed the electric currents, temperatures are within the expected range. We then initialized the ADS (attitude determination system), and confirmed the functions of ADS and RLG.