General information

Name of the source: PG 1553+113
Brief description of the source:
- Object type : AGN
- Redshift (z) : 0.433 Dorigo Jones et al
- BL Lac
- RA: 15 5543.044 (hh mm ss), Dec: +11 11 24.365 (dd mm ss)
- RA, Dec in deg (ICRS): 238.92934976, 11.19010155

Analysis by Estelle Pons (LAPP - estelle.pons@lapp.in2p3.fr)

PG 1553+113 - 2023 ToO data analysis (Helena Luciani)

General analysis information

Source-independent analysis
lstchain version: lstchain-v0.10.9

Data selection configuration

Start observation time: 2023-04-26 01:09:52.000
End observation time: 2023-04-26 05:14:00.000

User input:

source coordinates: (238.92935002, 11.19010157) (ra, dec) in deg
date directory: 2023-04-25
telescope pointings from the source: min_angle = 0.35 deg, max_angle = 0.45 deg
zenith distance range: 0 deg < zenith < 50 deg
maximum diffuse NSB: 2.3

Total number of loaded subruns: 1674
Total number of loaded runs: 15

Number of runs (% is w.r.t. those in Sky region & zenith range):

   In the requested Sky region and range of dates:	 15
 + zenith in requested range:				 15
 + NSB in requested range:				 15 (100.0%)
 + FF and pedestal interleaved events are present:	 15 (100.0%)
 + Stable pointing:					 15 (100.0%)
 + dR/dI fit P-value ok:				 15 (100.0%)
 + dR/dI LS periodogram ok:				 15 (100.0%)
 + dR/dI index ok:					 15 (100.0%)
 + dR/dI rate ok:					 15 (100.0%)
 + intensity threshold ok:				 15 (100.0%)

Selected: 15 of 15 runs (in 1 night)
Total observation time: 3.87 hours

List of selected runs: [12859 12860 12861 12863 12864 12865 12866 12867 12868 12869 12870 12871 12872 12873 12874]

DL1 to DL2

Random Forest : /fefs/aswg/data/models/AllSky/20240131_allsky_v0.10.5_all_dec_base/dec_931/

Configuration file: /fefs/aswg/data/models/AllSky/20240131_allsky_v0.10.5_all_dec_base/dec_931/lstchain_config_2024-01-31.json

DL2 data:

dl2_LST-1.Run12859.h5
dl2_LST-1.Run12860.h5
dl2_LST-1.Run12861.h5
dl2_LST-1.Run12863.h5
dl2_LST-1.Run12864.h5
dl2_LST-1.Run12865.h5
dl2_LST-1.Run12866.h5
dl2_LST-1.Run12867.h5
dl2_LST-1.Run12868.h5
dl2_LST-1.Run12869.h5
dl2_LST-1.Run12870.h5
dl2_LST-1.Run12871.h5
dl2_LST-1.Run12872.h5
dl2_LST-1.Run12873.h5
dl2_LST-1.Run12874.h5

DL3 data and IRFs

Input gamma:

/fefs/aswg/data/mc/DL2/AllSky/20240131_allsky_v0.10.5_all_dec_base/TestingDataset/dec_931/node_theta_*

Config file :

../cta-lstchain/docs/examples/irf_dl3_tool_config.json

IRFs : GH_efficiency= 0.7, theta_containment= 0.7

--point-like --energy-dependent-gh --energy-dependent-theta --gh-efficiency=0.7 --theta-containment=0.7

DL3 creation using IRF nearest node

 "EventSelector": {
   "filters": {
     "intensity": [50, Infinity],
     "width": [0, Infinity],
     "length": [0, Infinity],
     "r": [0, 1],
     "wl": [0.01, 1],
     "leakage_intensity_width_2": [0, 1],
     "event_type": [32, 32]
   }
 },
 "DL3Cuts": {
   "min_event_p_en_bin": 100,
   "global_gh_cut": 0.7,
   "gh_efficiency": 0.7,
   "min_gh_cut": 0.1,
   "max_gh_cut": 0.98,
   "global_alpha_cut": 10,
   "global_theta_cut": 0.2,
   "theta_containment": 0.7,
   "alpha_containment": 0.7,
   "min_theta_cut": 0.1,
   "max_theta_cut": 0.32,
   "fill_theta_cut": 0.32,
   "min_alpha_cut": 1,
   "max_alpha_cut": 20,
   "fill_alpha_cut": 20,
   "allowed_tels": [1]

High-level analysis

Gammapy version: 1.1

1D analysis

Analysis Results

Livetime : 3.67 h

Significance : 15.68σ

Theta2 plot

Theta2 cut for signal extraction: 0.04 deg2

Energy range: 10 GeV - 10 TeV

Significance: 15.68σ

Light-curve

Energy threshold: 50 GeV

Time binning: 20 min

SED

Energy range: 10 GeV - 10 TeV

Best fit model: Log Parabola + EBL (Dominguez 2011)

600px

PG 1553+113 - 2023 ToO data analysis 2 (Arshia Ruina)

General analysis information

Source-independent analysis
lstchain version: lstchain-v0.10.9

Data selection configuration

Source coordinates (ra, dec): (238.92935002°, 11.19010157°)
Telescope pointings around source: [0.35°, 0.45°]
Zenith distance range: [0°, 52°]
Maximum diffuse NSB std: 2.3
first_date = 20191101
last_date = 20231231

Number of runs (% is w.r.t. those in Sky region & zenith range):

   In the requested Sky region and range of dates:	 125
 + zenith in requested range:				 120
 + NSB in requested range:				 116 (96.7%)
 + FF and pedestal interleaved events are present:	 116 (96.7%)
 + Stable pointing:					 116 (96.7%)
 + dR/dI fit P-value ok:				 116 (96.7%)
 + dR/dI LS periodogram ok:				 113 (94.2%)
 + dR/dI index ok:					 103 (85.8%)
 + dR/dI rate ok:					 90 (75.0%)
 + intensity threshold ok:				 90 (75.0%)

Selected: 90 of 8196 runs
Total observation time (elapsed time): 22.75 h
Total ontime 22.52 hrs
Total livetime 21.38 hrs

List of runs:

   * 20210321 [4207]
   * 20210407 [4335 4336]
   * 20210408 [4343 4344]
   * 20210410 [4363 4364 4365 4366 4367 4368 4369 4370]
   * 20210508 [4652 4653 4654]
   * 20210604 [4902 4903 4904 4905]
   * 20220228 [7153 7154]
   * 20220501 [8059 8060 8061 8062 8063 8064]
   * 20220520 [8377 8378 8379]
   * 20220523 [8424 8425]
   * 20220602 [8600 8601 8602]
   * 20230120   [11748 11749 11750 11751]
   * 20230123 [11809 11810 11811 11812 11813]
   * 20230126 [11903 11904 11906]
   * 20230224 [12080 12081 12082 12083 12084 12085]
   * 20230226 [12096 12097 12098 12099]
   * 20230317 [12234 12235 12236 12237]
   * 20230321 [12362 12363 12364 12365 12366]
   * 20230414 [12697 12698 12699 12700]
   * 20230418 [12755 12756 12757 12758]
   * 20230425 [12859 12860 12861 12863 12864 12865 12866 12867 12868 12869 12870 12871 12872 12873 12874] <<-- flare night

DL1 to DL2 conversion

RF Model: /fefs/aswg/data/models/AllSky/20240131_allsky_v0.10.5_all_dec_base/dec_931
Config file: Github link

File list: File:Dl2 filelist AR.pdf

Creating IRFs

lstchain_create_irf_files -g ${file} -c ${config_file} -o ${irf_file} --point-like --energy-dependent-gh --energy-dependent-theta

Config file: Github link
gh_efficiency= 0.7, theta_containment= 0.7

DL2 to DL3

lstchain_create_dl3_file --overwrite --use-nearest-irf-node --config ${config_file} --input-dl2 ${file} --input-irf-path ${irfs}  --source-name=PG1553+113 --source-ra=238.92935002deg --source-dec=11.19010157deg --output-dl3-path ${OUTPUT_DIR}/

Config file: Github link
gh_efficiency= 0.7, theta_containment= 0.7

The default version of the analysis used "nearest node IRF". Later, I also tried using "interpolation IRF".

lstchain_create_dl3_file --overwrite --config ${config_file} --input-dl2 ${file} --input-irf-path ${irfs}  --source-name=PG1553+113 --source-ra=238.92935002deg --source-dec=11.19010157deg --output-dl3-path ${OUTPUT_DIR}/

High level analysis

Selecting runs only for the flaring night

For PG1553+113, intra-night variability is looked for using the longest data collection period available i.e. data from the night of 26-04-2023 (nearly 4 hours of data).

Number of runs selected: 15
Run list (flare night): [12859 12860 12861 12863 12864 12865 12866 12867 12868 12869 12870 12871 12872 12873 12874]
Start observation time: 2023-04-26 01:09:56.663
End observation time: 2023-04-26 05:13:44.526
Total ontime of flare night observations: 3.86 hrs
Total livetime of flare night observations: 3.67 hrs

Note: Only observations with a minimum livetime of 30 seconds were selected.

Theta-squared plot

Excess counts plot

600px

Light curve

LC is estimated from 50 GeV to 10 TeV
Energy binning:

e_reco_min = 10 * u.GeV
e_reco_max = 10 * u.TeV
e_true_min = 10 * u.GeV
e_true_max = 100 * u.TeV
e_reco_bin_p_dec = 5
e_true_bin_p_dec = 100

The LC is made in varying time bins, ranging from 5 min to 40 min

LCs with nearest node IRFs (default)

LC with 20 min time bins, and energy threshold 50 GeV

LC with 20 min time bins, and energy threshold 150 GeV

Cross-check of LC with Helena Luciani

LCs with interpolation IRFs

LC with 20 min time bins, and energy threshold 50 GeV

LC with 20 min time bins, and energy threshold 150 GeV

SED

Energy range: 10 GeV - 10 TeV Best fit model: Log Parabola + EBL (Dominguez 2011)

It is a match with Helena Luciani (see above). We will upload a comparison plot with both SEDs overlayed on one another soon.

Differential Spectrum

It is a match with Helena Luciani (see above). We will upload a comparison plot with both spectra overlayed on one another soon.

Constraints on the emitting region radius

We characterise the variations in the flux by using the normalised RMS variability amplitude, F_var, defined as

F_{\text{var}} = \sqrt{\frac{S^{2}- \langle \sigma^{2}_{\text{err}} \rangle }   {{\langle F \rangle}^{2} } }

where S^2 is the sample variance, σ^2 is the mean square error (MSE) and <F> is the mean flux. We obtain S^2 > MSE and F_var (%) = 24.04 ± 6.93 (3.47σ significance) which hints towards the presence of IDV.

Method: Gammapy compute_fvar

We compute the shortest variability timescale using the flux halving/doubling timescales as follows

F(t_{1}) = F(t_{2}) 2^{(t_{1}-t_{2})/\tau}

where τ is a characteristic halving/doubling time-scale and F(t1) and F(t2) are the fluxes of the LC at times t1 and t2, respectively.

Method 1: Gammapy compute_lightcurve_doublingtime

Method 2: Gammapy compute_flux_doubling

Both methods give same results.

Using this shortest variability timescale, we compute an upper limit on the radius of the emission region using the formula

R \leq \frac{c t_{\text{var}} \delta}{1+z}

where the Doppler factor, δ, ranges from 11 to 35.

The procedure followed here is inspired from sections 3.1 and 3.2 of the XMM paper by Dhiman et al. 2021

Results:

PG 1553 - 2023 ToO data analysis

Contents

General information

PG 1553+113 - 2023 ToO data analysis (Helena Luciani)

General analysis information

Data selection configuration

DL1 to DL2

DL3 data and IRFs

High-level analysis

Analysis Results

Theta2 plot

Light-curve

SED

PG 1553+113 - 2023 ToO data analysis 2 (Arshia Ruina)

General analysis information

Data selection configuration

DL1 to DL2 conversion

Creating IRFs

DL2 to DL3

High level analysis

Theta-squared plot

Excess counts plot

Light curve

SED

Differential Spectrum

Constraints on the emitting region radius

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