Gamma-ray Burst 180329A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 29 Mar 18 00:59:04 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     819301,   Seg_Num: 0
GRB_RA:          329.298d {+21h 57m 11s} (J2000),
                 329.545d {+21h 58m 11s} (current),
                 328.618d {+21h 54m 28s} (1950)
GRB_DEC:         -15.071d {-15d 04' 14"} (J2000),
                 -14.983d {-14d 58' 59"} (current),
                 -15.309d {-15d 18' 32"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       25245 [cnts]    Image_Peak=384 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   477     E_range: 25-100 keV
BKG_INTEN:       182024 [cnts]
BKG_TIME:        3387.30 SOD {00:56:27.30} UT
BKG_DUR:         64 [sec]
GRB_DATE:        18206 TJD;    88 DOY;   18/03/29
GRB_TIME:        3480.80 SOD {00:58:00.80} UT
GRB_PHI:         -48.25 [deg]
GRB_THETA:        23.11 [deg]
SOLN_STATUS:     0x83
RATE_SIGNIF:     9.59 [sigma]
IMAGE_SIGNIF:    6.90 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +2  -3 -100  +0 -74  +0 
SUN_POSTN:         7.62d {+00h 30m 29s}   +3.29d {+03d 17' 24"}
SUN_DIST:         41.90 [deg]   Sun_angle= 2.5 [hr] (West of Sun)
MOON_POSTN:      158.82d {+10h 35m 16s}  +11.13d {+11d 08' 01"}
MOON_DIST:       170.19 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:       40.44,-47.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      326.20, -2.43 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.  
COMMENTS:        This trigger occurred at longitude,latitude = 160.31,17.67 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Thu 29 Mar 18 01:02:20 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     819301,   Seg_Num: 0
GRB_RA:          329.298d {+21h 57m 11s} (J2000),
                 329.545d {+21h 58m 11s} (current),
                 328.618d {+21h 54m 28s} (1950)
GRB_DEC:         -15.071d {-15d 04' 14"} (J2000),
                 -14.983d {-14d 58' 59"} (current),
                 -15.309d {-15d 18' 32"} (1950)
GRB_DATE:        18206 TJD;    88 DOY;   18/03/29
GRB_TIME:        3480.80 SOD {00:58:00.80} UT
TRIGGER_INDEX:   477
GRB_PHI:         -48.25 [deg]
GRB_THETA:        23.11 [deg]
DELTA_TIME:      -70.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x83
RATE_SIGNIF:     9.59 [sigma]
IMAGE_SIGNIF:    6.90 [sigma]
LC_URL:          sw00819301000msb.lc
SUN_POSTN:         7.62d {+00h 30m 30s}   +3.29d {+03d 17' 28"}
SUN_DIST:         41.90 [deg]   Sun_angle= 2.5 [hr] (West of Sun)
MOON_POSTN:      158.85d {+10h 35m 23s}  +11.12d {+11d 07' 27"}
MOON_DIST:       170.15 [deg]
MOON_ILLUM:      92 [%]
GAL_COORDS:       40.44,-47.84 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      326.20, -2.43 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        Since the IMAGE_SIGNIF is less than 7 sigma, this is a questionable detection.  
COMMENTS:        This trigger occurred at longitude,latitude = 160.31,17.67 [deg].

GCN Circular #22556
J. L. Racusin (NASA/GSFC), A. Deich (PSU), J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 00:58:00 UT, the Swift Burst Alert Telescope (BAT) triggered and located a marginal-significance (6.9 sigma) image peak that may be GRB 180329A (trigger=819301). Swift could not slew to the location due to an observing constraint. The BAT on-board calculated location is RA, Dec 329.298, -15.071 which is
```
   RA(J2000) = 21h 57m 11s
   Dec(J2000) = -15d 04' 14"   
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows some variation consistent with a ~8 second long GRB, however this variation is also consistent with the presence of the currently-active black hole transient MAXI J1820+070 in the FOV. The peak count rate was ~1400 counts/sec (15-350 keV), at ~5 sec after the trigger.
Due to a Sun observing constraint, Swift cannot slew to the BAT position until 23:07 UT on 2018 April 02. There will thus be no XRT or UVOT data for this trigger before this time.
Due to the low significance of this detection, the presence of a bright variable X-ray source in the BAT Field of View, and the lack of follow-up observations from the XRT and UVOT, we cannot determine whether this is a GRB at this time. Further analysis of the full downlinked data will be required to decide if this is a GRB or a statistical fluctuation in the image plane.
Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular #22561
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), J. L. Racusin (NASA/GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180329A (trigger #819301) (Racusin et al., GCN Circ. 22556). The BAT ground-calculated position is RA, Dec = 329.314, -15.043 deg which is
```
  RA(J2000)  =  21h 57m 15.3s
  Dec(J2000) = -15d 02' 36.0"
```
with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 80%.
The mask-weighted light curve shows a weak pulse that starts at ~T0, peaks at ~T+1 s, and ends at ~T+10 s. T90 (15-350 keV) is 9.1 +- 1.8 sec (estimated error including systematics).
The time-averaged spectrum from T-0.30 to T+9.69 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.39 +- 0.31. The fluence in the 15-150 keV band is 2.3 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.14 sec in the 15-150 keV band is 0.5 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
Due to an observing constraint, there are no observations of this source with the Swift XRT or UVOT, and hence no confirmation of the nature of the source. However, because the image significance from the ground analysis of the BAT data is ~ 9 sigma, and the temporal and spectral properties are consistent with those from a BAT GRB, we conclude that this source is likely a real GRB.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/819301/BA/

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Jochen Greiner, last update: 30-Mar-2018 [Disclaimer]