GRB230512A

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Alert Information

• Name/type of the alert: Name
• GCN notice: https://gcn.nasa.gov/circulars/33778
• Triggered by: Fermi GBM (but alert from TH by Fermi-LAT)
• Alert coordinates (From Fermi-LAT):
  • RA: 19 41 36.00 (hh mm ss), Dec: +38 24 00.00 (dd mm ss)
  • RA, Dec in deg (ICRS): 295.4, 38.4
• Alert arrival time: 06:27:45 UT
• Other relevant information:
  • Redshift (z): n/a

Multi-wavelength Observations

Timeline

T0+	Instrument	Outcome	Outcome specific value (flux/UL/...)	Comment	Link
0-300 s after the GBM trigger	Fermi-LAT	Detection	(1.0 ± 0.3) E-05 ph/cm2/s	The highest-energy photon is a 1.7 GeV	https://gcn.nasa.gov/circulars/33780
45.5 - 57.3 ks	Swift-XRT	No aparent detection	Nine uncatalogued X-ray sources have been detected	However none of them is above the RASS limit or shows definitive signs of fading.	https://gcn.nasa.gov/circulars/33789
2 hours	Zwicky Transient Facility	No aparent detection	Two sources were found within the 95% localization region	These are likely unrelated as they fall outside the LAT localization	https://gcn.nasa.gov/circulars/33784
0.57624 d, 1.64044 d	Kitab	aparent detection	19.43, n/d (UL at 20)	A source disappeared from May 12 to May 13 in the XRT #5 error circle	https://gcn.nasa.gov/circulars/33796
14.22 hours	GIT	No detection	>20.39 (r), >21.08 (g')	2x400s exposures in the r' and g' band	https://gcn.nasa.gov/circulars/33797
~7.5 h	Liverpool Telescope	No detection	3-sigma limit of r’ > 22.15	We detect no source at the position of the candidate optical counterpart reported by Kitab	https://gcn.nasa.gov/circulars/33798
1.003 d, 0.998 d	Zwicky Transient Facility	No detection	r , 21.02 mag; g , 20.83 mag	no sources were found up in the candidate optical counterpart reported by Kitab	https://gcn.nasa.gov/circulars/33799
0.537 d, 1.543 d, 1.563 d	Nanshan/NEXT	No detection	r , 20.7 mag; r , 21.8 mag; z, 20.0 mag	No optical source is detected in our stacked images at the XRT source 5 position, it doesn't reveal the Kitab candidate although it is deeper.	https://gcn.nasa.gov/circulars/33800

In the end no counterpart was detected. No counterpart was in the improved IPN triangulation (https://gcn.nasa.gov/circulars/33808)

LST Observations

• * Dates of data-taking: 2023-05-12
  • 2023-05-12 (4.1 h)
    • Zenith range (deg): 62 - 15
    • Transmission9km: n/a
    • Observation condition: dark, moonlight, high level of dust, moderate cloudiness
    • Observation mode: std wobbles
    • Runs: 12962 - 12973
    • Joint observations with MAGIC? : Yes
    • ELOG link: [1]
    • Important comments: '

Analysis by Arnau Aguasca-Cabot (UB - arnau.aguasca@fqa.ub.edu)

Data-taking information

• Overall selected observation time: ~ 4 h
• Selected runs: 12962 - 12973
• Position analyzed: 295.4, 38.4

I divided the analysis between the dark analysis (12962 - 12968) and moon analysis (12969-12973) because the number of surviving pedestal for latter runs was higher than the threshold (4%) for the standard analysis. The moon raised more or less during run 12967. However, the standard cleaning seems OK until 12968.

DL1 data

Used DL1ab files produced by LSTOSA

/fefs/aswg/data/real/DL1/20230512/v0.9/tailcut84/

For the moon analysis, I applied tighter cuts (tail cut 11, 5). Path to DL1b files for moon analysis:

/fefs/aswg/workspace/arnau.aguasca/Analysis/results/real/DL2/20230512/srcind/v0.9.13/tailcut115_dynclg/AllSky_20230127_v0.9.12_base_prod_az_tel_dec_3476/

The config file is here:

/fefs/aswg/workspace/arnau.aguasca/scripts/_configs/GRB230512A/real_config_lstchain_belong_v0.9.13_tailcut115.json

DL2 data

• Random forest:

/fefs/aswg/data/models/AllSky/20230127_v0.9.12_base_prod_az_tel/dec_3476/

• lstchain config file

/fefs/aswg/data/models/AllSky/20230127_v0.9.12_base_prod_az_tel/dec_3476/lstchain_config.json

Theta2 plot from DL2

Dark analysis

• Cuts and parameters used:
  • intensity > 50
  • gammaness > 0.7
  • Theta2_global_cut=0.09 (the uncertainty error of the Fermi-LAT position)
  • leakage < 0.2

Moon analysis

• Cuts and parameters used:
  • intensity > 150
  • gammaness > 0.7
  • Theta2_global_cut=0.09 (the uncertainty error of the Fermi-LAT position)
  • leakage < 0.2

The intensity cut value is chosen close to the peak of the intensity distribution for all run in moon conditions.

Theta2 plot for all runs:

Theta2 plot for GRB230512A.

Appling BKG normalisation between

• • norm_range_theta2_min=0.3
  • norm_range_theta2_max=0.5

The significance is 0.23 sigma.

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