The MAXI team reported one detection of the transient events to Astronomer’s Telegram (ATEL)
in November.
And MAXI team also reported one Gamma-ray burst event to GCN: The Gamma-ray bursts Coordinates Network.
This is an X-ray all-sky image from the MAXI GSC observations from
August 15 to October 29, 2009. The color indicates the hardness of the
X-ray sources: the red sources are “soft”, i.e. emit more low-energy
X-rays, while the blue sources are “hard”, i.e. emit more X-rays with
higher energies.
Press release:
http://www.jaxa.jp/press/2009/11/20091126_maxi_e.html
(Japanese) http://www.jaxa.jp/press/2009/11/20091126_maxi_j.html
The MAXI team reported three detections of the transient events to Astronomer’s Telegram (ATEL)
in October.
We had the second detection of a gamma-ray burst (GRB 090926B) with GSC. The raw light curve (not corrected for collimator response) and the raw source image is shown below. An interesting point is that the detection by MAXI is 17 seconds earlier than the Swift trigger, and the transit duration (~30 s) is shorter than normal (40-60 s for a steady source). Probably the GRB started in the middle of the transit, and the tail of the burst is truncated at the end of the transit. Therefore, the light curve and the source image are complicated products of triangular collimator response and the GRB time profile. (Link to the GCN Circular)
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).
We 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 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 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. 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. 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.