Monitor of All-sky X-ray Image (MAXI)

Launch Date: June 11, 2008

Extended Mission Lifetime: 2024+ (Pending JAXA Review)

End of Operations: Limited by ISS lifetime, currently 2030

Data Archive: JAXA

MAXI is a wide-field X-ray telescope designed to perform an all-sky survey. MAXI was developed by JAXA; data processing and operations are conducted by JAXA, Riken, Osaka University, Tokyo Institute of Technology, Aoyama Gakuin University, Nihon University, Kyoto University, Miyazaki University, and Chuo University.

GCN Notice Types in GCN Classic and GCN Classic Over Kafka: Detailed Descriptions and Examples

JSON-Serialized GCN Notices Types in GCN Kafka:

MAXI provides Notices for both known and unknown source detections by GSC. The known source Notice is used when the detected event is associated with a known X-ray source or cataloged object. The unknown source Notice is used when the detected event is not immediately associated with a known source and is reported as a new or unidentified transient candidate. Depending on the available localization information, an unknown source Notice may report no position uncertainty, a circular uncertainty region, an elliptical uncertainty region, or rectangular error-region corners.

Both Notice types provide basic alert metadata, event timing, sky position, flux information, and detection information.

Type	Contents	Latency
gcn.notices.maxi.gsc.known	Known source detections, including source/event identification, sky position, flux information, and detection information	200 minutes
gcn.notices.maxi.gsc.unknown	Unknown source detections or transient candidates, including sky position, flux information, detection information, and localization information when available	200 minutes

MAXI known source and unknown source schemas are available. Example JSON message files are available for known source Notices and for unknown source Notices with no position uncertainty, circular, elliptical, and rectangular localization information. See the Schema Browser for more information on the properties defined in the schemas.　Detailed description of the properties and examples of MAXI Notices are available in the GCN Schema GitHub project.

The MAXI team maintains an archive of their JSON Notices.

Additional Notes on MAXI/GSC Notice Fields

trigger_time

The trigger_time reported in MAXI Notices is a representative time associated with the MAXI analysis time interval for which the detection significance is highest. This time may not always be identical to the detection time reported later in GCN Circulars or other follow-up reports, where a different representative time may be used depending on the event and the details of the analysis.

flux and flux_error

The flux reported in MAXI Notices is given in units of erg cm-2 s-1 to be compatible with the core Spectral schema. It is not directly derived from spectral analysis. Instead, it is derived from the MAXI count rate of the source or event, normalized by the count rate measured from Crab observations, and converted to physical flux assuming a canonical Crab spectrum. The flux_error field gives the 1-sigma statistical uncertainty on this flux.

flux_spectral_band and flux_spectral_unit

The flux_spectral_band field specifies the energy band used for the reported flux. The flux_spectral_unit field specifies the unit of the energy band, typically keV.

detection_timescale and detection_timescale_units

The detection_timescale field gives the time scale used in the MAXI detection analysis. The unit is specified by detection_timescale_units, which may be s for seconds, scan for one MAXI/GSC camera scan, orbit for one ISS orbit, or d for days.

event_name

For MAXI known-source Notices, event_name gives the name of the detected known source. For MAXI unknown-source Notices, event_name gives the transient or GRB name when available.

Localization fields

The ra and dec fields give the source position in degrees in J2000 equatorial coordinates.

The ra_dec_error field gives the statistical localization uncertainty. When the localization is circular, this field is a single radius in degrees. When the localization is elliptical, this field is a three-element array giving the major radius, minor radius, and position angle of the error ellipse in degrees.

The rectangular_error_corners field gives the four corners of a rectangular error box. Each corner is represented as an [RA, Dec] pair in degrees in J2000 equatorial coordinates.

The containment_probability field gives the probability that the true source position is contained within the reported localization region.

The systematic_included field indicates whether the reported localization uncertainty includes systematic uncertainty.

band_flux_low, band_flux_med, and band_flux_high

For MAXI known-source Notices, these fields provide MAXI flux estimates in predefined energy bands. Each field is a two-element array containing [flux, flux_error], where the flux is given in erg cm-2 s-1 and the error is the 1-sigma statistical uncertainty.

• band_flux_low: 2-4 keV band
• band_flux_med: 4-10 keV band
• band_flux_high: 10-20 keV band

Common GCN Circular Types:

MAXI Yearly Trigger Rates: