TO: All GCN sites 04 Dec 99 RE: SAX to GCN goes FULL AUTO INTRODUCTION The processing of the GRB locations detected by SAX-WFC/-NFI has been made completely automated so that the delay is now minimized. The GCN system has been distributing the SAX WFC and NFI burst locations in a semi-manual procedure since late 1997. This semi-manual procedure incurred some extra delay time, but now (as of 25 Nov 99) the procedure is fully automated (from the SAX Ops center in Italy all the way through to the outgoing portion of GCN) so the delay times are as small as possible. About 6-15 times a year, there is a GRB in the FOV of the WFC instrument that is bright enough for the WFC to produce a location. Some of the detected GRBs are followed-up with a ToO observation with the NFI (MECS & LECS) instruments. ACTION ITEM Like all the other sources of GRB locations within the GCN system, users can elect to receive (or not) this SAX source as well. Many sites have already elected to receive SAX Notices from during the semi-auto phase of operations. Other sites may want to review their burst follow-up strategies now that the SAX Notices are end-to-end fully automated. After reviewing this announcement and description document, those sites wanting to receive this new source of GRB locations should send an email or call requesting that the enable flag be turned on for their site. (Note: Currently, 40% of the sites have SAX Notices enabled.) SEQUENCE OF EVENTS The sequence of activities for a typical burst follows: 1) SAX Science Operations (SSO) continuously analyzes the GRBM and WFC data and BATSE triggers looking for a burst. 2) When there is a trigger, the SSO does a quick-look in the WFC data (at T+2-3 hrs): If the WFC detected the burst, then SSO sends a SAX_WFC_SRC to GCN: This would be an Initial "saw" something subtype. This would be an "~10 arcmin" (diameter) location. The SSO also decides if the burst can be follow-up with an NFI observation. 3) In the meantime, the SSO will probably continue to analyze the WFC detection and issue an improved location notice (2-5 hrs): SSO sends a SAX_WFC_SRC to GCN with Subtype "Updated". This would be a "~6 arcmin" (diameter) location. There could be more than one of these "Updated" notices, or there could be none, and the sequence jumps from the "Initial" to the "Final" notice. 4) SSO does a quick-look on the NFI data when it becomes available (10-24 hrs). If the NFI detected the burst, then SSO sends a SAX_NFI_SRC to GCN: This would be an "Initial" "saw" subtype. If nothing was detected, then SSO sends a SAX_NFI_SRC to GCN: This might be the end of the sequence of events (unless there was more processing of the WFC data to improve that location). It is also possible that no notice will be generated and sent; however, a GCN Circular may be generated and sent. 5) The SSO continues to analyze the NFI detection and issues an improved location notice (24-48 hrs): SSO sends a SAX_NFI_SRC to GCN with Subtype "Updated". There could be more than one of these "Updated" notices, or there could be none, and the sequence jumps from the "Initial" to the "Final" notice. The total time delay is 2-3 hours for the WFC Initial and ~5 hours for the WFC Updated/Final, and ~12-24 hours for an NFI Initial location. NOTICE TYPES For each the WFC and the NFI Notice types there can be Initial, Updated, and Final subtypes. The SAX-WFC Initial Position, Update, and Final Position Notices come out 2 to 5 hours after the burst. Given the vagaries of s/c operations and burst scenarios, some subtypes may be missing from the sequence of Notices issued. FORMATS Samples of the E-mail, Pager, Short-form Pager, etc distribution methods of the two GCN/SAX-WFC and -NFI Notice types are attached below. The format is very similar to the other spacecraft/instrument sources of GRB locations. Many of the fields are the same. Note that if the intensity is not determined at the time of the Notice (particularly true for Initial Notices), then the intensity field will contain the string "unknown" instead of a numerical value. The socket packet contents and format is similar to the other packet types and are described in detail in the socket definition document (see the GCN web site). The Position Notices are type=34 & 36. FILTERING Sites can elect to receive either the WFC Notices or the NFI Notices or both types. There is a separate dis/enable bit for each type. This filtering applies to the full set of distribution methods/media. Currently, there is no filter bits for the "saw" vs "no_saw" scenarios, because the rate of issuance of no_saw Notices is so low. ERROR BOXES The uncertainty in the location will depend on (a) the burst intensity, (b) its position relative to the WFC FOV, and (c) the relative locations and intensities of other sources in the FOV. The typical error for the Initial Notice is ~10 arcmin and ~6 arcmin (diameter) for the Update and Final Notices. Systematic uncertainty depends on satellite attitude (whether startrackers or gyros or sun sensor are in use) and varies from 0 arcmin to 1 degree in the worst situations. The errors quoted in the position Notices include both the statistical and the systematic contributions. The confidence level for that error is also specified in the Notice (it is typically 1-sigma). The errors for the x-ray afterglow counterparts detected by the NFI instruments are typically 2 arcmin (diameter). RECOGNITION Sites are encouraged to acknowledge SAX and GCN in their publications based on follow-up observations using these GCN/SAX-WFC/-NFI locations. FURTHER HELP For further information on this, please contact: Luigi Piro (for SAX issues) piro@ias.rm.cnr.it John Heise (for WFC issues) J.Heise@sron.nl Scott Barthelmy (for GCN issues) scott.barthelmy@gsfc.nasa.gov or see the SAX-GRB web page (http://www.ias.rm.cnr.it/ias-home/sax/grb1.html), SAX-WFC web page (http://www.sdc.asi.it/wfc.html), GCN web page (http://gcn.gsfc.nasa.gov/gcn), GCN/SAX GRBs table (http://gcn.gsfc.nasa.gov/gcn/sax_grbs.html). E-MAIL EXAMPLES Examples of the two notice types of the e-mail formats are shown below. The "/////" divider bars are NOT part of the messages. The RA,Dec listed for the POSITION Notices is the SAX-WFC or -NFI RA,Dec position. For those sites/people that use daemons and/or incoming e-mail filters, the "Subject" lines for the two notices are fixed, and the strings are: 1) GCN/SAX_WFC_POSITION 2) GCN/SAX_NFI_POSITION /////////////////////////////////////////////////////////////////////////////// TITLE: GCN/SAX_WFC BURST POSITION NOTICE NOTICE_DATE: Sun 05 Jan 98 21:23:00 UT NOTICE_TYPE: SAX-WFC Initial {or Updated or Final} GRB_DATE: 10576 TJD; 128 DOY; 97/05/08 GRB_TIME: 78060.00 SOD {21:41:00.00} UT GRB_SAX_RA: 102.950d {+06h 51m 48s} (J2000), 102.840d {+06h 51m 22s} (current), 100.867d {+06h 43m 28s} (1950) GRB_SAX_DEC: +79.280d {+79d 16' 48"} (J2000), +79.283d {+79d 16' 60"} (current), +79.337d {+79d 20' 15"} (1950) GRB_SAX_ERROR: 0.170 [deg radius (stat+sys), 1-sigma] GRB_SAX_INTEN: 2000.00 [mCrab] SUN_POSTN: 45.86d {+03h 03m 27s} +17.28d {+17d 17' 01"} SUN_DIST: 67.13 [deg] MOON_POSTN: 73.70d {+04h 54m 48s} +17.58d {+17d 34' 51"} MOON_DIST: 63.15 [deg] COMMENTS: SAX-WFC GRB Coordinates. COMMENTS: COMMENTS: On May 8, around 21.41 UT the GRBM instrument aboard BEPPOSAX COMMENTS: detected a gamma-ray burst that was simultaneously seen COMMENTS: in the WFC. COMMENTS: COMMENTS: Preliminary coordinates, as derived by the analysis carried COMMENTS: out by the PI of the program (E. Costa) and the team COMMENTS: of the Science Operation Center are: COMMENTS: alpha(2000)=102.95 deg COMMENTS: delta= +79.28 COMMENTS: (error radius about 10 arcmin) COMMENTS: COMMENTS: We will circulate a refined position (estimated error radius of COMMENTS: about 3 arcmin) as soon as it will available from the off-line COMMENTS: analysis of the data carried out by the PI team. COMMENTS: COMMENTS: Observations in all wavelenghts are urged. /////////////////////////////////////////////////////////////////////////////// TITLE: GCN/SAX_NFI BURST POSITION NOTICE NOTICE_DATE: Sun 05 Jan 98 21:23:00 UT NOTICE_TYPE: SAX-NFI Initial GRB_DATE: 10576 TJD; 128 DOY; 97/05/08 GRB_TIME: 78060.00 SOD {21:41:00.00} UT GRB_SAX_RA: 102.950d {+06h 51m 48s} (J2000), 102.840d {+06h 51m 22s} (current), 100.867d {+06h 43m 28s} (1950) GRB_SAX_DEC: +79.280d {+79d 16' 48"} (J2000), +79.283d {+79d 16' 60"} (current), +79.337d {+79d 20' 15"} (1950) GRB_SAX_ERROR: 0.017 [deg radius (stat+sys), 1-sigma] GRB_SAX_INTEN: 150.00 [mCrab] SUN_POSTN: 45.86d {+03h 03m 27s} +17.28d {+17d 17' 01"} SUN_DIST: 67.13 [deg] MOON_POSTN: 73.70d {+04h 54m 48s} +17.58d {+17d 34' 51"} MOON_DIST: 63.15 [deg] COMMENTS: SAX-NFI GRB Coordinates. COMMENTS: COMMENTS: On May 8, around 21.41 UT the GRBM instrument aboard BEPPOSAX COMMENTS: detected a gamma-ray burst that was simultaneously seen COMMENTS: in the WFC. It was decided to perform an NFI follow-up COMMENTS: observation on this burst (starting at T+8 hrs). COMMENTS: COMMENTS: The data analysis is continuing and a refined location COMMENTS: may be forthcoming. ////////////////////////////////////////////////////////////////////////////// PAGER EXAMPLES Examples of the two types of the (regular) pager formats are shown below. There are no "Subject" lines for these e-mails sent to the pager companies because the Subject line would use up valuable character counts from the maximum displayable for the body of the message. ////////////////////////////////////////////////////////////////////////////// GCN/SAX_WFC GRB Initial RA=102.840d DEC=+79.283d TIME: 21:41:00.00 UT I=2000.00 mCrab SAX-WFC GRB Coordinates. ////////////////////////////////////////////////////////////////////////////// GCN/SAX_NFI GRB Initial RA=102.843d DEC=+79.238d TIME: 21:41:00.00 UT I=2400.00 mCrab SAX-NFI GRB Coordinates. ////////////////////////////////////////////////////////////////////////////// SHORT-FORM PAGER EXAMPLES Examples of the four types of the short-form pager format are shown below. There are no "Subject" lines for these e-mails sent to the pager companies, because the Subject line would use up valuable character counts from the maximum displayable for the body of the message. And it was the very limited display character count of some companies that motivated the short-form pager method in the first place. ////////////////////////////////////////////////////////////////////////////// SAX-WFC RA=100.867 DEC=+79.337d ////////////////////////////////////////////////////////////////////////////// SAX-NFI RA=100.931 DEC=+79.310d ////////////////////////////////////////////////////////////////////////////// SUBJECT-ONLY FORMAT The two forms of the Subject-only format exist for the SAX-WFC/-NFI Notices. --end