OP313 Dec2023 Jan2024 LST1 analysis details
Contents
- 1 LST analysis OP313 Dec 2023 and Jan 2024
- 1.1 Links to presentation of the LST-1 analysis in several analysis and OP313 meetings
- 1.2 Data-taking information
- 1.3 Good-quality selected dataset
- 1.4 lstchain settings
- 1.5 Gammapy settings
- 1.6 Analysis cross-check
- 1.7 Test on background normalization systematics
- 1.8 Test varying the efficiency of gamma-ray selection cuts
- 1.9 Test on MAGIC vs LST-1 with the same common GTIs
LST analysis OP313 Dec 2023 and Jan 2024
Wiki page with general information on all results for the paper: December_January_paper
LST-1 analyzers:
- Seiya Nozaki (MPP)
- Jorge Otero-Santos (IAA-CSIC)
- Mireia Nievas-Rosillo (IAC)
- Daniel Morcuende (IAA-CSIC)
Links to presentation of the LST-1 analysis in several analysis and OP313 meetings
- 2023-12-20 | LST EGAL meeting: https://indico.cta-observatory.org/event/4778/contributions/43117/attachments/24993/36374/OP313_Dec_flare-2.pdf
- 2024-01-18 | LST EGAL meeting: https://indico.cta-observatory.org/event/4779/contributions/43526/attachments/25079/36510/OP313_EgalMeeting_20240118%20(1).pdf
- 2024-01-19 | OP 313 Kick-off meeting: https://indico.cta-observatory.org/event/5330/contributions/43423/attachments/25097/36541/OP313_LST_Jan2024.pdf
- 2024-01-30 | LST analysis call: https://indico.cta-observatory.org/event/5377/contributions/43825/attachments/25187/36697/OP313_LST_analysis_20230130.pdf
- 2024-02-02 | OP 313 meeting: https://indico.cta-observatory.org/event/5379/contributions/43829/attachments/25221/36786/OP313_LST_20240202.pdf
- 2024-02-16 | OP 313 meeting: https://indico.cta-observatory.org/event/5412/contributions/44159/attachments/25331/37045/20240216_OP313_LST_srcdep.pdf
- 2024-02-16 | OP 313 meeting: https://indico.cta-observatory.org/event/5412/contributions/44159/attachments/25331/37042/OP313_LST_20240215.pdf
- 2024-02-19 | LST analysis call: https://indico.cta-observatory.org/event/5418/contributions/44198/attachments/25346/37068/OP313_LSTreco_20240219-1.pdf
Data-taking information
- NSB level: all data was taken in dark NSB conditions
- Zenith angles: 15-54 deg (December 2023 data have zenith angle > 30 deg)
Good-quality selected dataset
The list of data runs below was obtained using the notebook https://github.com/cta-observatory/cta-lstchain/blob/main/notebooks/data_quality.ipynb.
We used default settings, but min_drdi_at_422pe = 1.2 instead of the default 1.5 to recover 1.7 h from January 2024 where low statistics limit us. Still, the data selected have a relative light yield above ~80%.
Also, short data runs (< 5 min) were excluded, because usually short runs are a symptom of problems during data acquisition.
'2023-12-09': [15942, 15943, 15944, 15945], '2023-12-10': [15975, 15976, 15977, 15978], '2023-12-11': [16007, 16008, 16009, 16010], '2023-12-12': [16042, 16043, 16044, 16045], '2023-12-13': [16079, 16080, 16081, 16082, 16083], '2023-12-14': [16114, 16116, 16117, 16118, 16119], '2023-12-15': [16150, 16151, 16152, 16153, 16154, 16155, 16156], '2023-12-16': [16188, 16189, 16191, 16192, 16193], '2023-12-17': [16220, 16221, 16222, 16223, 16224, 16225], '2023-12-18': [16240, 16241, 16242, 16243, 16244, 16246], '2024-01-09': [16293, 16294, 16295], '2024-01-13': [16350, 16351, 16352, 16353, 16354, 16356, 16357, 16358, 16359], '2024-01-17': [16391, 16392], '2024-01-19': [16412, 16413, 16414, 16415], '2024-01-21': [16418, 16419, 16420]
In total, there are 19.8 hours effective time.
- Relative light yield of the selected data:
Number of runs (% is w.r.t. those in Sky region & zenith range): In the requested Sky region and range of dates: 90 + zenith in requested range: 90 + NSB in requested range: 90 (100.0%) + FF and pedestal interleaved events are present: 90 (100.0%) + Stable pointing: 90 (100.0%) + dR/dI fit P-value ok: 90 (100.0%) + dR/dI LS periodogram ok: 87 (96.7%) + dR/dI index ok: 85 (94.4%) + dR/dI rate ok: 83 (92.2%) + intensity threshold ok: 82 (92.2%)
lstchain settings
- lstchain version: v0.10.7
- MC production: 20230901_v0.10.4_allsky_base_prod
- RF models: /fefs/aswg/data/models/AllSky/20230901_v0.10.4_allsky_base_prod/dec_3476/
- DL2 MC for IRF calculation: /fefs/aswg/data/mc/DL2/AllSky/20230901_v0.10.4_allsky_base_prod/TestingDataset/dec_3476
- Used IRF interpolation
- Selection cuts IRF and DL3: 70% efficiency in both gammaness and theta gamma-ray selection cuts (Mireia used 68% theta containment instead). Intensity > 50 p.e.
- Energy threshold: ~ 40 GeV. Calculated from DL2 testing gamma MC (several nodes with similar zenith as the bulk of the telescope pointing positions: 32.059_az_102.217, 37.814_az_90, 43.197_az_87.604, 47.952_az_90, 52.374_az_110.312), weighting the default MC spectrum by a log parabola calculated from OP313 (alpha: -3.7, beta: -1.1, amplitude: 3.0e-09 TeV s-1 cm-2, E_0: 100 GeV) and assuming the same selection cuts as in the DL3 files (intensity>50 p.e., 70% efficiency in gammaness cut, and 70% efficiency in theta cut). Treatment of the DL2 MC was done using functions from
lstchain.mcmodule
Gammapy settings
- Gammapy version: v1.1
- Energy binning:
reco energy axis: 5 GeV - 10 TeV, 5 bins per decade true energy axis: 1 GeV - 20 TeV, 10 bins per decade
- 3 off positions for SED and LC calculation
- Safe mask: 5% of max. Aeff
- Energy range for spectral fitting: 70 GeV - 1 TeV (In Mireia's analysis, the fit range starts at around 60 GeV, because uses a slightly different reconstructed energy binning)
- redshift: 0.997
Analysis cross-check
Cross-checks of different LST-1 analysis results.
Cross-check of LST-1 SED from OP313 during high-flux period (Dec 2023):
Cross-check of LST-1 LC from OP313 (Dec 9th 2023 to Jan 21th 2024):
| Analyzer | Analysis method | Spectral model | EBL model | Index | Amplitude [x 10-8 TeV-1 s-1 cm-2] | E_ref [GeV] | alpha_norm |
|---|---|---|---|---|---|---|---|
| Seiya | source-dependent | PWL+EBL | Saldana-Lopez 2021 | 2.37 ± 0.88 | 0.82 ± 0.14 | 100 | 1.0 |
| Jorge | source-independent | PWL+EBL | Saldana-Lopez 2021 | 2.07 ± 0.51 | 1.15 ± 0.13 | 100 | 1.0 |
| Mireia | source-independent | PWL+EBL | Dominguez 2011 | 1.86 ± 0.50 | 0.93 ± 0.11 | 100 | 1.0 |
| Daniel | source-independent | PWL+EBL | Saldana-Lopez 2021 | 2.00 ± 0.45 | 1.14 ± 0.13 | 100 | 1.0 |
Test on background normalization systematics
The relative difference between the background counts in two off-source regions at the same distance from the center of the field of view (0.4 deg), and equidistant from the OP313 location is 0.31% ± 0.14% (counts in the OFF region at 90 deg: 487702 ± 698, and in the OFF region at 270 deg: 486203 ± 697). Therefore we tested the effect that a factor ±0.5% in the background normalization has in the SED calculation (see best-fit model spectral parameters calculated after considering the change in background normalization for source-independent analysis, assuming PWL+EBL Saldana-Lopez 2021 model).
| Background normalization | Index | Amplitude [x 10-8 TeV-1 s-1 cm-2] | E_ref [GeV] | alpha_norm |
|---|---|---|---|---|
| +0.5% | 2.12 ± 0.58 | 0.89 ± 0.14 | 100 | 1.0 |
| -0.5% | 1.86 ± 0.37 | 1.39 ± 0.14 | 100 | 1.0 |
Test varying the efficiency of gamma-ray selection cuts
We tested the effect of using several efficiencies in selection cuts. Gammaness (50%-90%) and theta (70%-90%). The hatched band in the plot below encompasses all statistical uncertainty bands of the best-fit model for each combination of efficiencies.
Test on MAGIC vs LST-1 with the same common GTIs
Test made with MAGIC (Axel's) DL3 files and LST-1 (Mireia's) DL3 files, cutting them to a common GTI selection. In total around 7.4 hours (a bit less of livetime for LST). Except at the lowest energies, the agreement is good within uncertainties and the individual bins match well.
