TO: All GCN Sites 14 Feb 05 RE: Swift-BAT Notices go Real-Time, and Non-GRB Filtering INTRO: This is the 3rd announcement in the series of getting the Swift burst information into the GCN system; ref: 2nd, 21dec04 http://gcn.gsfc.nasa.gov/gcn/admin/gcn_swift2.txt 1st, 06nov04 http://gcn.gsfc.nasa.gov/gcn/admin/gcn_swift1.txt SWIFT-BAT NOTICES DISTRIBUTED IN REAL-TIME: The Swift-BAT Instrument team has completed the initial phase of their on-orbit verification and is now ready to distribute the BAT Notices in real-time, ie no humans-in-the-loop delays. This automatic distribution will start Tuesday, 15 Feb 05. This includes the following Notice types: SWIFT_BAT_GRB_ALERT // BAT GRB ALERT SWIFT_BAT_GRB_POSITION // BAT GRB Position SWIFT_BAT_GRB_NACK_POSITION // BAT GRB No Position SWIFT_BAT_TRANS // BAT Transient Position SWIFT_BAT_GRB_LIGHTCURVE // BAT GRB Lightcurve SWIFT_FOM_OBSERVE // FOM decision about the merit check SWIFT_SC_SLEW // S/C decision about slewing or not BAT POSITION ERRORS: The initial alignment measurement of the BAT Coded-Aperture Mask to the Detector Array has been completed, and the BAT bore-sight to the s/c Star Trackers has been completed. The initial alignment correction matrices have been uploaded. Using steady-state sources that are near the BAT detection threshold (just like nearly all burst detections will be at threshold), the positional accuracy has been shown to be 3 arcmin at 90% containment (this is a conservative specification and will be improved as the BAT team acquires more experience). TRIGGER-ID FILTERING: Because the Swift-BAT instrument triggers on things other than GRBs, recipients can elect to have Trigger_ID filtering enabled if they do not want to receive BAT Notices that come from non-GRB sources. Currently, there are 3 methods used to identify/filter-against non-GRB sources: a) Known Sources: Those sources are: variable/flaring sources like Cyg X-1, steady-state sources that are just at the BAT detection threshold, AGN, X-Ray Bursters, etc). These sources are identified by both on-board catalog comparisons and ground-based catalog comparisons. About one third of the BAT POSITION Notices are due to objects contained in the catalogs. The catalogs are based on detections already made by BAT, the INTEGRAL catalog, a few other instruments, some literature searches, and other miscellaneous sources. These two catalogs are not exhaustive in their content; and as such, there will be some otherwise known sources detected by BAT that will still be reported as GRBs. The BAT Team estimates this false-positive rate to be less than 1 in 10. (Triggers that satisfy this catalog match will be reclassified as hard x-ray Transients (see below).) b) Hi-Background Rate Triggers: Triggers that occur near the SAA (on the edges) have a high background rate, and, more importantly, occur when the background rate is changing (ie a slope that the one-bkg-interval trigger criteria have difficulty with). The BAT Team estimates that the false-positive occurance will be less than 2 per month. c) At-Threshold Detections: Triggers that yield a lo-significance peak in the image domain are also of questionable GRB-identity. The nominal threshold in the image plane is 6 sigma. Triggers with an image significance less than 7 sigma will be identified as such (another flag bit). The BAT Team estimates that the false-positive occurance will be 1 per week. Full-format email recipients will receive Notices with comments indicating one or more of these 3 conditions. Socket-sites can access the appropriate flag-bits in the "soln_status" field of the packet (see the sock_pkt_def_doc.html). Historical Note: The CGRO-BATSE Notices had Trigger_ID filtering capability, but this field (column) in the "sites.cfg" file has been a No-Op since 1999. It is now being re-activated for use with Swift-BAT Notices. Sites that have the Trigger_ID filter enabled will NOT receive the BAT_GRB_POSITION Notices that satify any of the above conditions. Nor will they receive the BAT_GRB_LIGHTCURVE, FOM_OBSERVE, and SC_SLEW Notices (that result from that initial BAT_GRB_POSITION Notice). BAT TRANSIENT NOTICES: There is a new GCN/Swift-BAT Notice type: SWIFT_BAT_TRANS. As mentioned in the above discussion about trigger_id filtering, those triggers determined to not be a GRB because of a positional match with an entry in either the flight or ground catalogs, then the trigger is reclassified (from a burst) to a hard-x-ray transient source. It is identical in structure and field-content to the SWIFT_BAT_GRB_POSITION Notice, but the type number is changed from 61 to 84. GCN recipients can elect to receive this new Notice type. (If a recipient already receives BAT_GRB_POSITION Notice and does NOT have Trigger_ID filtering enabled, then he/she will get these non-GRB transients as part of the stream of type=61 Notices. And they will be clearly identified in the Comments-section of the full-email format and the long-pager format. The reason for creating this SWIFT_BAT_TRANS type is if the recipient is interested ONLY in the hard x-ray transients (and not any GRBs). (Some day there may be dis/enable filtering on each sub-type of this BAT_TRANS (x-ray burster vs AGN vs whatever), but for now there is only the dis/enable for the BAT_TRANS type.) SIGN-UP and REQUESTS FOR CONFIG CHANGES: >From previous announcements, many GCN recipients have already signed up for the various Swift Notices. However, many have not. (Your configuration is appended below.) Sites should take this opportunity to request that they receive which Swift-based Notices they want. And as always, requests for changes in any part of a site's configuration are always welcomed; now, or any time in the future. Send those requests to: scott@milkyway.gsfc.nasa.gov (Replies to this announcement email go to another place and may not be noticed for many days.) And when requesting a change to your confiuration, please include your sitename (or some specific identifying information). There are over 410 entries in the list, and I can not remember all of you. When I get a terse email like "Hi, this is Bob. Send me the Swift Notices.", it gets difficult to sort out. A marked-up version of your configuration (appended below) is always an excellant way to communicate. NOTICE TYPES: There are 24 different types of information from the Swift mission. Since some of these Notices are of a sufficiently different type of content than previous missions (ie images, spectra, etc), people may need to study the web pages (see below) carefully to determine which types are suitable for their specific operation. Please note that 3 types are not yet available. Note that there 3 groups of messages: Flight-Generated: SWIFT_BAT_GRB_ALERT // BAT GRB ALERT SWIFT_BAT_GRB_POSITION // BAT GRB Position SWIFT_BAT_GRB_NACK_POSITION // BAT GRB No Position SWIFT_BAT_TRANS // BAT Transient Position SWIFT_BAT_GRB_LIGHTCURVE // BAT GRB Lightcurve SWIFT_FOM_OBSERVE // FOM decision about the merit check SWIFT_SC_SLEW // S/C decision about slewing or not SWIFT_XRT_POSITION // XRT Position of afterglow SWIFT_XRT_SPECTRUM // XRT Spectruma of afterglow SWIFT_XRT_IMAGE // XRT Image of afterglow SWIFT_XRT_LIGHTCURVE // XRT Lightcurve of afterglow SWIFT_XRT_NACK_POSITION // XRT did not find a position SWIFT_UVOT_DARKBURST // UVOT full-pixel image SWIFT_UVOT_FINDCHART // UVOT sifted-pixel image Ground Re-Processed: SWIFT_BAT_GRB_LIGHTCURVE_PROC // Ground processed version SWIFT_XRT_SPECTRUM_PROC // Ground processed version SWIFT_XRT_IMAGE_PROC // Ground processed version SWIFT_UVOT_DARKBURST_PROC // Ground processed version SWIFT_UVOT_FINDCHART_PROC // Ground processed version SWIFT_UVOT_POSITION // UVOT afterglow position Misc: SWIFT_BAT_GRB_POS_TEST // BAT GRB Position Test message SWIFT_POINT_DIR [NOT YET AVAILABLE] // Pointing Direction message SWIFT_FULL_DATA_INIT [NOT YET AVAILABLE] // Is the initial data set available SWIFT_FULL_DATA_UPDATE [NOT YET AVAILABLE] // Has the initial data set been updated CONTENTS and FORMATS: A detailed description of all the Swift Notices is contained in: http://gcn.gsfc.nasa.gov/gcn/swift.html and for the socket sites, the packets are defined in: http://gcn.gsfc.nasa.gov/gcn/sock_pkt_def_doc.html The Swift mission has packet types 60 through 84. The email/pager/cell sites are encouraged to also read the sock_pkt_def_doc web page, because the same fields that are in the socket packets also appear as the various "TOKEN: value" lines in the email-based distribution formats. Socket sites are also encouraged to look at the socket_demo program to understand the socket packet formats and the content -- there are generic packet unpacking routines therein. http://gcn.gsfc.nasa.gov/gcn/socket_demo.c Please note that both the sock_pkt_def_doc and the socket_demo.c have been updated to (a) the new Notice type, (b) the new flag bits, and (c) modified/improved interpretations of the flags bits. ATTACHMENTS: 1) For the full_email-based recipients, they can also select if they want to receive the various lightcurves, images, and spectra as attachments. There are only two choices: a) you select no attachments, or b) you get all the attachments (currently, there is no option to get the UVOT_DARKBURST Notice with the actual image attached, and get, say, get the XRT_SPECTRUM Notice without its spectrum attachment). These attachments are not big, so getting a couple of the Notice types with attachments that you do not particularly want will not be a burden on your email inbox. You also have to specify which format you want: FITS, GIF, JPEG, Postscript. 2) The BAT_LIGHTCURVE Notice type does not have all the formats implemented; only the FITS format is currently available. All the other Notice types have the full compliment of attachment formats available. SCHEDULE: The original plan for the 3 phases of availability is listed below. This announcement introduces the transition from phase 2 to phase 3. 1) Delayed Circulars: Even though Swift launched on 20 Nov 2004, the fully automated phase of the GCN/Swift Notices (positions, images, spectra, & lightcurves) will not be immediately available. The Swift team will be performing an on-orbit check-out, during which the positions will not be made available to the public in real time (delays of 1-3 hrs). The positions will be distributed with some delay through the GCN Circulars. There are numerous cross-checks and calibrations that must be performed to guarantee the safety of the spacecraft & instruments and the accuracy of the burst Notices. (This phase is already happening.) 2) Delayed Notices: After some of the check-out period has happened, the positions (& the other information types) will be available and distributed through GCN Notices, also with some delay (0.3-2 hrs). (The official check-out interval is 135 days, however the distribution of positions may happen sooner if the various instrument teams develop confidence in their instruments sooner.) During the check-out period, if a burst is determined by the instrument teams to be of high enough confidence, then it will be distributed with some delay. (This phase is already happening.) 3) Real-Time Distribution: And then full automatic distribution will start. Full-auto means from Swift, through TDRSS, to GCN, out to the world; with no human intervention/inspection/processing in the loop. This announcement is for the start of this phase for the BAT-based Notices only. The full-auto (no delay) distribution for XRT and UVOT will start within 1-3 weeks. Sincerely, Scott Barthelmy NASA-GSFC, Code 661, Greenbelt, MD 20771 PHONE: 301-286-3106 (office) PHONE: 301-346-3733 (cell) FAX: 301-286-1684 (1st choice, -1682 2nd choice) EMAIL: scott@lheamail.gsfc.nasa.gov PAGER: 3013463733@mobile.att.net (by email, 200 characters max per message) WEB: http://gcn.gsfc.nasa.gov/gcn ///////////////////////// your current configuration ////////////////////////////