TABLE OF CONTENTS:
INTRODUCTION AND BACKGROUND:
This was the second notice type that was distributed,
by the then called BACODINE system.
It is called the BATSE-MAXBC Notice.
The motivation for creating this notice type was to reclaim some
of the lost BATSE triggers
that were unaccessable to the GCN system (1) because the initial trigger
occured inside a telemetry gap, or (2) because the GRB had a slow rise
time and there were never enough counts within the first 10 sec of the burst
that the program could not produce a valid direction..
THE "MAXBC" NOTICE TYPE:
MAXBC stands for the MAXimum Burst Channels count rate information.
There are 16 count rates and they are determined by the on-board software
scanning the count rates at the 64-msec sampling in the 8 LADs
in two energy bands (20-50keV and 50-300keV)
for the 10 minutes after the initial trigger.
Whenever any of the 16 rates is greater than the previous maximum count rate
for that trigger, those 16 values are saved and become the new maximum (peak)
count rates.
This scanning process operates for 10 minutes after the initial trigger.
After that the scanning stops and those 16 peak count rates values
are inserted in the telemetry stream.
As usch, these 16 rates are an independent data set from the 1-sec sample
DISCLA rates used for the Original, FInal & LOCBURST Notices.
The GCN program always scans for these 16 MAXBC rates and then uses them in a process very similar to the main DISCLA rates for the Original Notices. The 3 brightest detectors are found and those rates plus the normal vectors for those 3 detectors are used to solve for the unknown burst direction vector (see the Original Notices for more details on this processing). The same "ideal physics response function" is assumed with the same caveats about the systematics in the location error due to scattering and non-cos(theta) distortions.
Sites can elect to receive these MAXBC Notices (by any of the distribution methods) in addition to the regular notices.
The TRIGGER_ID typing (see below) is not currently available for MAXBC notices. Because these MAXBC locations are based only on the 16 MAXBC numbers, which is significantly less than the countrate vs and vs energy information available for the Original/Final/LOCBURST Notices, it is not possible to make the trigger-type identification.
IMPORTANCE OF THIS MAXBC NOTICE:
Because there are gaps in the telemetry coverage by the three TDRS satellites
(coverage is about 85%), GCN misses some BATSE triggers as they first happen.
However, most of these can be recovered at the cost of increased time delay
by using these MAXBC count rates that are inserted into the telemetry
stream by the BASTE flight software, albeit at a delay of 10 minutes.
The MAXBC notices are also useful for situations where the burst had a slow risetime and there were never enough source-only rates withing the first 10 seconds of scanning after the trigger to have enough signal to yield a valid direction solution.
So if the initial trigger happened in a telemetry gap, GCN does not have access to the initial count rates during the trigger. But when telemetry resumes, GCN can use this alternate set of data to calculate a GRB direction. Since the transmission of the 16 MAXBC values continues all during the "burst readout period" (anywhere from 30 to ~200 minutes after the trigger), GCN can always collect these MAXBC values and calculate a direction (typical telemetry gap durations are 2 to 15 minutes). The penalty paid for reclaiming these otherwise lost triggers via this MAXBC (type=11) notification is that they occur with a much longer time delay than the normal BATSE-Original notices (type=1).
LOCATION ERROR:
The location errors (statistical and systematic) are very similar to thos
for the Original Notice type (which see).
In short, the brighter the burst the smaller the location error.
Bright bursts have typical errors of 5 degrees radius and the
burst right at threshold have errors of 10-15 degrees radius.
More information is available here.
DISTRIBUTION METHODS & FILTER FUNCTIONS:
As with all the GCN notice types, these BATSE-MAXBC Notices
are available to the GCN community via the Internet socket, e-mail,
alpha-numeric pager (long & short versions), phone/modem, and cell-phone
distribution methods.
The available filter functions are: ALL, VISIBLE, NIGHT, and various
custom filters.
See for more details on the filter capabilities.
FORMATS:
The format of the e-mail form (attached below) is very similar to the
BATSE-MAXBC. It is based on a "TOKEN: value" scheme to allow for
both the easy reading by humans and the easy parsing by computer daemons.
The details of the format and content of this form are described in
E-mail Definition Document.
Examples of the pager, short_pager & subject-only forms are also attached below.
The packing format and content of the socket packet method is also very
similar to that used in the Original packets. Those GCN sites using the
Internet socket method should refer to the
socket definition document
to get the details (this is packet_type=11).
RECOGNITION:
Sites are encouraged to include Scott D. Barthelmy and Paul Butterworth
in the author list of IAU Circulars, journal papers and conference
presentations
based on observations using these GCN/BATSE-MAXBC locations.
FURTHER HELP:
For more information, please contact me:
Phone: 301-286-3106
E-mail: scott@lheamail.gsfc.nasa.gov
TITLE: BACODINE MAXBC BURST POSITION NOTICE
NOTICE_DATE: Sat 11 Oct 97 12:01:22 UT
NOTICE_TYPE: MAXBC
TRIGGER_NUM: 6425
GRB_RA: 210.80d {+14h 03m 12s} (J2000),
210.76d {+14h 03m 02s} (current),
209.92d {+13h 59m 42s} (1950)
GRB_DEC: -59.05d {-59d 03' 01"} (J2000),
-59.04d {-59d 02' 23"} (current),
-58.81d {-58d 48' 36"} (1950)
GRB_ERROR: 13.3 [deg radius, statistical only]
GRB_INTEN: 2544 [cnts] Peak=2544 [cnts/sec]
GRB_TIME: 42652.32 SOD {11:50:52.32} UT
GRB_DATE: 10732 TJD; 284 DOY; 97/10/11
GRB_SC_AZ: 330.25 [deg] {XScan=-5.37}
GRB_SC_EL: 79.13 [deg] {Zenith_angle=10.87} {Scan=9.47}
SC_X_RA: 185.91 [deg] (J2000)
SC_X_DEC: 18.88 [deg]
SC_Z_RA: 207.31 [deg]
SC_Z_DEC: -69.82 [deg]
SUN_POSTN: 196.79d {+13h 07m 10s} -7.14d {-07d 08' 16"}
SUN_DIST: 52.99 [deg]
MOON_POSTN: 315.35d {+21h 01m 23s} -13.89d {-13d 53' 25"}
MOON_DIST: 85.41 [deg]
PROG_VERSION: 5.16
PROG_LEVEL: 1
COMMENTS: MAXBC Determination.
MAXC1/BC Values:
C1: 30 1 34 -1 19 0 21 5
BC: 90 4 106 -1 56 2 78 4
BACODINE MAXBC GRB RA=210.76d DEC=-59.04d TIME: 11:50:52.32 UT I=2544
MAXBC RA=209.92 DEC=-58.81d
MAXBC RA=210.76 DEC=-59.04d