ASM Alert Number | Date (UT) | R.A. (J2000) | Decl. (J2000) | Comments/ID |
Number 24 | 03/02/14 | 285.841 | +3.283 | No comment yet. |
Number 23 | 01/09/07 | 252.137 | -50.047 | XTE J1650-500 |
Number 22 | 01/03/25 | 107.768 | +20.099 | No comment yet. |
Number 21 | 01/01/10 | 154.575 | +68.666 | No comment yet. |
Number 20 | 00/12/27 | 113.395 | -15.101 | No comment yet. |
Number 19 | 00/12/22 | 88.530 | +16.657 | No comment yet. |
Number 18 | 00/09/18 | 7.861 | +55.820 | No comment yet. |
Number 17 | 00/09/12 | 251.151 | -44.897 | No comment yet. |
Number 16 | 00/09/11 | 83.559 | +21.528 | No comment yet. |
Number 15 | 00/09/11 | 256.125 | -35.922 | No comment yet. |
Number 14 | 00/09/10 | 19.897 | +63.431 | No comment yet. |
Number 13 | 00/09/10 | 351.279 | +58.698 | No comment yet. |
Number 12 | 00/09/09 | 279.900 | +5.312 | False alarm due to bad calibration. |
Number 11 | 99/10/09 | 284.634 | +22.640 | XTE J1859+226 |
Number 10 | 99/02/15 | 298.222 | +54.664 | Most likely solar contamination. |
Number 9 | 98/09/15 | 296.590 | +27.333 | XTE J1946+274 (= 3A 1942+274) |
Number 8 | 98/09/07 | 237.866 | -56.539 | XTE J1550-564 |
Number 7 | 98/08/27 | 286.658 | +9.424 | SGR 1900+14 |
Number 6 | 98/07/03 | 359.775 | +8.561 | GRB 980703 |
Number 5 | 98/06/27 | 320.734 | -5.907 | XTE J2123-058 |
Number 4 | 98/06/09 | 82.106 | -65.442 | AB Dor |
Number 3 | 98/06/04 | 266.956 | -28.344 | XTE J1744-288 |
Number 2 | 98/05/26 | 303.431 | +38.166 | XTE J2012+381 |
Number 1 | 98/03/31 | 64.859 | +55.959 | XTE J0421+560 ( = CI Cam) |
The All-Sky Monitor scans the
sky continuously in the 2-12 keV band, measuring the states of known
X-ray sources and searching for the emergence of new Novae and other
transients. Full-time telemetry connection to the satellite enables
the data to arrive at MIT within 5 to 60 minutes of the observations.
A single detection of a new X-ray source yields a line of position a
few arcminutes wide. Multiple detections provide crossed lines of
position, which constrain the location to a region of a few tens of
square arcminutes. We maintain
a catalog of known x-ray sources and recurrent transients. An
alert is generated only if two positions overlap within a 300 s
interval, and if this overlap region is inconsistent with any source
in our catalog.
These alerts will report detections of both new X-ray Novae and GRBs.
To aid users in distinguishing between the two, the alert system will
check for a contemporaneous BATSE GRB
detection. Since BATSE does not detect all GRBs, a lack of a
corresponding BATSE burst should not be taken as proof that the event
is not a GRB. The system also checks and reports on the ASM
time-series data for evidence of variability on time-scales between
1/8-s and 90-s. GRBs tend to be highly variable at those timescales,
while X-ray Novae vary much more slowly.
For each ASM alert, a web page that displays a sky map of the area
around the crossed boxes, copies of alert messages, and plots of the
time-series data is generated here. (See the list below.) As further
data related to each event are accumulated, the web pages here are
updated. No additional alerts are sent (remember on return visits to
press RELOAD on your browser to make sure you have the most recent
update). The web page will also provide a link to the DSS web site to generate a
FITS-format image of the region around the ASM error box. A second
link will query the SIMBAD database for
a list of nearby catalogued sources. These links are provided for
your convenience, and we have no offical connection to the groups that
maintain these sites; see the external sites for their conditions of
use.
Test runs on thirteen months of ASM data yielded nine alerts: five NEW
transient X-ray sources, the re-emergence of a transient last detected
in 1976, one GRB, one Soft Gamma-ray Repeater, and one nearby flare
star. Two false alarms generated web pages (Numbers 2 and 8), but did
not match the filter criteria used to generate email alerts to
external sites. We are less strict for internal alerts, so that we
can check borderline cases manually. Only observations that pass
strict believability criteria will generate external email alerts. We
are therefore confident, under the assumption that the ASM will
continue to perform at its current ability, that even if an alert from
this program is not generated by a GRB, there will be something
new of Astronomical interest within the reported error box.
The alerts are produced in a standardized format, and they will be
distributed via the
Gamma-ray burst Coordinate Network (GCN), as well as direct emails
to whomever requests them. This format is easily parsed by software
to either alert the current working observer at your site or activate
the automatic response of your instrument. The goal is to provide an
accurate counterpart identification as soon as possible to enable
spectroscopic measurements and broad-band monitoring of the event
decay. Results should be reported via the
GCN Circulars and any additional means of distribution you see fit
to use. Please contact Scott Barthelmy for more
information about the GCN. Please note that for security reasons,
only registered users can submit GCN Circulars. It is trivial to join
that list, merely contact Scott. If, however, it is the middle of the
night and you wish to report a result, you may wish to try the
Astronomer's Telegram
for rapid result dissemination.