Gamma-ray Burst 181027A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 27 Oct 18 01:49:59 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     868984,   Seg_Num: 0
GRB_RA:          225.383d {+15h 01m 32s} (J2000),
                 225.579d {+15h 02m 19s} (current),
                 224.861d {+14h 59m 27s} (1950)
GRB_DEC:         +30.891d {+30d 53' 28"} (J2000),
                 +30.818d {+30d 49' 04"} (current),
                 +31.088d {+31d 05' 15"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       17622 [cnts]    Image_Peak=399 [image_cnts]
TRIGGER_DUR:     8.192 [sec] 
TRIGGER_INDEX:   477     E_range: 25-100 keV
BKG_INTEN:       123053 [cnts]
BKG_TIME:        6450.18 SOD {01:47:30.18} UT
BKG_DUR:         64 [sec]
GRB_DATE:        18418 TJD;   300 DOY;   18/10/27
GRB_TIME:        6539.39 SOD {01:48:59.39} UT
GRB_PHI:         -12.77 [deg]
GRB_THETA:        23.49 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     6.63 [sigma]
IMAGE_SIGNIF:    7.88 [sigma]
MERIT_PARAMS:     +1  +0  +0  +3  +2  -2 -100  +0 -69  +0 
SUN_POSTN:       211.36d {+14h 05m 27s}  -12.71d {-12d 42' 46"}
SUN_DIST:         45.63 [deg]   Sun_angle= -0.9 [hr] (East of Sun)
MOON_POSTN:       62.30d {+04h 09m 11s}  +16.65d {+16d 38' 51"}
MOON_DIST:       129.89 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:       48.32, 61.41 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      210.58, 45.56 [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:        This trigger occurred at longitude,latitude = 172.84,-8.49 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(48.0<100sec) coincident with the FERMI_GBM event (trignum=562297792).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 27 Oct 18 01:50:11 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     562297792
GRB_RA:          234.400d {+15h 37m 36s} (J2000),
                 234.559d {+15h 38m 14s} (current),
                 233.976d {+15h 35m 54s} (1950)
GRB_DEC:         +43.783d {+43d 46' 60"} (J2000),
                 +43.722d {+43d 43' 21"} (current),
                 +43.946d {+43d 56' 46"} (1950)
GRB_ERROR:       30.43 [deg radius, statistical plus systematic]
GRB_INTEN:       149 [cnts/sec]
DATA_SIGNIF:     4.90 [sigma]
INTEG_TIME:      0.512 [sec]
GRB_DATE:        18418 TJD;   300 DOY;   18/10/27
GRB_TIME:        6587.31 SOD {01:49:47.31} UT
GRB_PHI:          66.00 [deg]
GRB_THETA:        65.00 [deg]
DATA_TIME_SCALE: 0.5120 [sec]
HARD_RATIO:      0.42
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      73%  GRB
2nd_MOST_LIKELY:  20%  Distant Particles
DETECTORS:       0,1,1, 0,0,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       211.36d {+14h 05m 27s}  -12.71d {-12d 42' 46"}
SUN_DIST:         60.27 [deg]   Sun_angle= -1.5 [hr] (East of Sun)
MOON_POSTN:       62.30d {+04h 09m 12s}  +16.65d {+16d 38' 53"}
MOON_DIST:       119.21 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:       70.58, 52.79 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      212.07, 60.27 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2018/bn181027076/quicklook/glg_lc_medres34_bn181027076.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 102.98,-21.40 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(48.0<100sec) coincident with the SWIFT_BAT event (trignum=868984).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 27 Oct 18 01:50:25 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     562297792
GRB_RA:          219.980d {+14h 39m 55s} (J2000),
                 220.182d {+14h 40m 44s} (current),
                 219.444d {+14h 37m 47s} (1950)
GRB_DEC:         +30.390d {+30d 23' 24"} (J2000),
                 +30.310d {+30d 18' 35"} (current),
                 +30.604d {+30d 36' 15"} (1950)
GRB_ERROR:       11.58 [deg radius, statistical only]
DATA_SIGNIF:     6.80 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        18418 TJD;   300 DOY;   18/10/27
GRB_TIME:        6587.31 SOD {01:49:47.31} UT
GRB_PHI:          48.00 [deg]
GRB_THETA:        57.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4153 (Gnd S/W Version number)
SUN_POSTN:       211.36d {+14h 05m 27s}  -12.71d {-12d 42' 47"}
SUN_DIST:         43.85 [deg]   Sun_angle= -0.6 [hr] (East of Sun)
MOON_POSTN:       62.30d {+04h 09m 12s}  +16.65d {+16d 38' 55"}
MOON_DIST:       128.44 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:       47.22, 66.06 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      204.93, 43.20 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2018/bn181027076/quicklook/glg_lc_medres34_bn181027076.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_562297792.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(48.0<100sec) coincident with the SWIFT_BAT event (trignum=868984).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sat 27 Oct 18 01:51:09 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     562297792
GRB_RA:          236.300d {+15h 45m 12s} (J2000),
                 236.487d {+15h 45m 57s} (current),
                 235.802d {+15h 43m 13s} (1950)
GRB_DEC:         +31.650d {+31d 38' 60"} (J2000),
                 +31.592d {+31d 35' 31"} (current),
                 +31.805d {+31d 48' 20"} (1950)
GRB_ERROR:       6.75 [deg radius, statistical only]
DATA_SIGNIF:     10.20 [sigma]
DATA_INTERVAL:   11.264 [sec]
GRB_DATE:        18418 TJD;   300 DOY;   18/10/27
GRB_TIME:        6587.31 SOD {01:49:47.31} UT
GRB_PHI:          54.00 [deg]
GRB_THETA:        70.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41531 (Gnd S/W Version number)
SUN_POSTN:       211.36d {+14h 05m 27s}  -12.71d {-12d 42' 47"}
SUN_DIST:         50.43 [deg]   Sun_angle= -1.7 [hr] (East of Sun)
MOON_POSTN:       62.31d {+04h 09m 14s}  +16.65d {+16d 39' 00"}
MOON_DIST:       131.44 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:       50.49, 52.13 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      223.04, 49.74 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2018/bn181027076/quicklook/glg_lc_medres34_bn181027076.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_562297792.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(48.0<100sec) coincident with the SWIFT_BAT event (trignum=868984).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 27 Oct 18 01:53:28 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     868984,   Seg_Num: 0
GRB_RA:          225.383d {+15h 01m 32s} (J2000),
                 225.579d {+15h 02m 19s} (current),
                 224.861d {+14h 59m 27s} (1950)
GRB_DEC:         +30.891d {+30d 53' 28"} (J2000),
                 +30.818d {+30d 49' 04"} (current),
                 +31.088d {+31d 05' 15"} (1950)
GRB_DATE:        18418 TJD;   300 DOY;   18/10/27
GRB_TIME:        6539.39 SOD {01:48:59.39} UT
TRIGGER_INDEX:   477
GRB_PHI:         -12.77 [deg]
GRB_THETA:        23.49 [deg]
DELTA_TIME:      38.00 [sec]
TRIGGER_DUR:     8.192 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     6.63 [sigma]
IMAGE_SIGNIF:    7.88 [sigma]
LC_URL:          sw00868984000msb.lc
SUN_POSTN:       211.36d {+14h 05m 27s}  -12.71d {-12d 42' 49"}
SUN_DIST:         45.63 [deg]   Sun_angle= -0.9 [hr] (East of Sun)
MOON_POSTN:       62.33d {+04h 09m 19s}  +16.66d {+16d 39' 19"}
MOON_DIST:       129.87 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:       48.32, 61.41 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      210.58, 45.56 [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:        This trigger occurred at longitude,latitude = 172.84,-8.49 [deg].

GCN Circular #23383
A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 01:48:59 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 181027A (trigger=868984). Swift could not slew to the burst due to an observing constraint. The BAT on-board calculated location is RA, Dec 225.383, +30.891 which is
```
   RA(J2000) = 15h 01m 32s
   Dec(J2000) = +30d 53' 28"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 80 sec. The peak count rate was ~1200 counts/sec (15-350 keV), at ~49 sec after the trigger.
Due to a Sun observing constraint, Swift cannot slew to the BAT position until 03:50 UT on 2018 November 06. There will thus be no XRT or UVOT data for this trigger before this time.
Burst Advocate for this burst is A. Y. Lien (amy.y.lien 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 #23384
S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 181027A (trigger #868984) (Lien, et al., GCN Circ. 23383). The BAT ground-calculated position is RA, Dec = 225.361, 30.937 deg which is
```
    RA(J2000)  =  15h 01m 26.7s
    Dec(J2000) = +30d 56' 12.6"
```
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 96%.
The mask-weighted light curve shows a weak emission followed by a bright peak. The emission starts at T-18.4 sec, peaks at T+47.5 sec and ends at T+85.4 sec. T90 (15-350 keV) is 81.16 +- 10.55 sec (estimated error including systematics).
The time-averaged spectrum from T-18.45 to T+85.44 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.42 +- 0.09. The fluence in the 15-150 keV band is 2.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+47.81 sec in the 15-150 keV band is 1.2 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/868984/BA/
GCN Circular #23385
P. Veres (UAH) and E. Bissaldi (Politecnico & INFN Bari) report on behalf of the Fermi GBM Team:
"At 01:49:47.31 UT on 27 October 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 181027A (trigger 56229779 / 181027076), which was also detected by the Swift/BAT (Lien et al. 2018, GCN 23383). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 61 degrees.
The GBM light curve consists of two pulses with a duration (T90) of about 90 s (50-300 keV). The time-averaged spectrum from T0-84.5 s to T0+44.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.10 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 183 +/- 27 keV.
The event fluence (10-1000 keV) in this time interval is (7.76 +/- 0.57)E-6 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.64 s in the 10-1000 keV band is 2.48 +/- 0.22 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."

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Jochen Greiner, last update: 27-Oct-2018 [Disclaimer]