Analysis BLLac July 2021

BL Lacertae flare July 2021

General information

• Name of the source: BL Lacertae
• Brief description of the source:
  • IBL / LBL
  • highly variable
  • z = 0.069
  • RA: 22 02 43.3 (hh mm ss), Dec: +42 16 40 (dd mm ss)
  • RA, Dec in deg (ICRS): 330.68038, 42.277772

• Analysis by Daniel Morcuende (UCM, Madrid - dmorcuen@ucm.es)

Data-taking information

• Dates of data-taking:
  • 2021-07-09 (0.41 h)
    • ZD: 23 - 26 deg
    • Transmission9km: ~90%
    • Runs: 5219, 5220
    • Joint observations with MAGIC

• • 2021-07-10 (1.56 h)
    • ZD: 20 - 40 deg
    • Transmission9km: 50% - 60%
    • Runs: 5229 - 5235
    • Joint observations with MAGIC (runs 5229, 5230)

• • 2021-07-12 (0.49 h)
    • ZD: 43 - 47 deg
    • Transmission9km: < 50%
    • Runs: 5251 - 5252
    • Joint observations with MAGIC

• • 2021-07-15 (TBC h)
    • ZD: 14 - 21 deg
    • Transmission9km: > 80 %
    • Runs: 5273 - 5276

DL2 data

Standard run-wise data files produced by LSTOSA.

• lstchain v0.7.3
• tailcut 8-4 (with cleaning based on pedestal RMS)

/fefs/aswg/data/real/DL2/20210709/v0.7.3/tailcut84/dl2_LST-1.Run05219.h5
/fefs/aswg/data/real/DL2/20210709/v0.7.3/tailcut84/dl2_LST-1.Run05220.h5
/fefs/aswg/data/real/DL2/20210710/v0.7.3/tailcut84/dl2_LST-1.Run05229.h5
/fefs/aswg/data/real/DL2/20210710/v0.7.3/tailcut84/dl2_LST-1.Run05230.h5
/fefs/aswg/data/real/DL2/20210710/v0.7.3/tailcut84/dl2_LST-1.Run05231.h5
/fefs/aswg/data/real/DL2/20210710/v0.7.3/tailcut84/dl2_LST-1.Run05232.h5
/fefs/aswg/data/real/DL2/20210710/v0.7.3/tailcut84/dl2_LST-1.Run05233.h5
/fefs/aswg/data/real/DL2/20210710/v0.7.3/tailcut84/dl2_LST-1.Run05234.h5
/fefs/aswg/data/real/DL2/20210710/v0.7.3/tailcut84/dl2_LST-1.Run05235.h5
/fefs/aswg/data/real/DL2/20210712/v0.7.3/tailcut84/dl2_LST-1.Run05251.h5
/fefs/aswg/data/real/DL2/20210712/v0.7.3/tailcut84/dl2_LST-1.Run05252.h5

DL3 data selection

• intensity > 30
• r: [0, 1 ]
• wl: [0.05, 1]
• leakage_intensity_width_2: [0, 0.2 ]
• fixed_gh_cut: 0.7
• fixed_theta_cut: 0.2

High-level analysis

• Science Tool: gammapy 0.18.2 (+ bugfix https://github.com/gammapy/gammapy/pull/3374)

Significance of the detection

1 Off reflected position
Theta2 cut: 0.04 deg

• Squares: Background
• Circles: Signal events

Date: 2021-07-09

• List of runs: [5219, 5220]
• Observation time: 0.41 h
• Number of ON events: 257
• Number of OFF events: 234 +/- 15
• Excess: 23 +/- 22
• Li&Ma significance: 1.0 sigma

Date: 2021-07-10

• List of runs: [5229, 5230, 5231, 5232, 5233, 5234, 5235]
• Observation time: 1.56 h
• Number of ON events: 598
• Number of OFF events: 351 +/- 19
• Excess: 247 +/- 31
• Li&Ma significance: 8.1 sigma

Date: 2021-07-12

• List of runs: [5251, 5252]
• Observation time: 0.49 h
• Number of ON events: 26
• Number of OFF events: 31 +/- 6
• Excess: -5 +/- 8
• Li&Ma significance: -0.7 sigma

Date: 2021-07-15

500px

Stacked

• List of runs: [5219, 5220, 5229, 5230, 5231, 5232, 5233, 5234, 5235, 5251, 5252]
• Observation time: 2.46 h
• Number of ON events: 881
• Number of OFF events: 616 +/- 25
• Excess: 265 +/- 39
• Li&Ma significance: 6.9 sigma

Spectral analysis

Effective area

Migration Matrix and exposure

• 2021-07-10

• PowerLaw fit:
  • index: 3.5 +/- 0.2
  • E_ref: 0.1 TeV
  • amplitude: 1.3 +/- 0.2 10^-9 cm-2 s-1 TeV-1

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