December January paper

This page is devoted to the first paper on OP313 following the LST detection and the ATel

The aim is to focus on the December 2023 and January 2024 data set and publish this data set in a quick paper

Fermi analysis

The Fermi LAT analysis has been performed on a large time scale to derive a long-term light curve and run a Bayesian block analysis to defined bocks of observation

Parameters

RA      =        197.6324  degrees
Dec     =        32.3547  degrees
Start   =        715617241.0   MET (s)
Stop    =        727281241.0   MET (s)
ROI     =        10.0  degrees
E min   =        100.0  MeV
E max   =        300000.0  MeV
E min ext       =        50.11872336272722  MeV
E max ext       =        598578.6944906638  MeV
IRFs    =        P8R3_SOURCE_V3
evclass =        128
evtype  =        3

Long term Fermi-LAT Light curve

For more information, see https://www.lst1.iac.es/wiki/index.php/Fermi_LAT_Main_OP313

This plot is the Fermi-LAT LC with the final bayesian block description.

The SEDs corresponding to each block is given here :

Focus on the December / January data

The Fermi analysis has been run on the LST GTI and lead to a detection at TS=485.58. Power-law and logparabola model were tested and the later is prefered at a TS 0f 8.

LST analysis

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]

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
• Energy threshold: ~ 40 GeV
• Selection cuts IRF and DL3: 70% efficiency in both gammaness and theta gamma-ray selection cuts. Intensity > 50 p.e.

Gammapy settings

• Gammapy version: v1.1
• Energy binning
• Safe mask: 5% of max. Aeff
• Energy range for spectral fitting: 70 GeV to 1 TeV
• EBL model: Saldaña-Lopez 2021

Conference plots

For 2024 conferences, we decided to have a common set of plots to be shown, including theta2 plots, high and low state lightcures and SEDs showing the LST-1 spectrum, LAT spectrum, and joint fit butterfly shape (but no parameters or spectral points from the joint fit).

December Data set

Fermi-LAT and LST results. Not corrected for EBL.

Fermi-LAT and LST results together with the joint fit on top. Not corrected for EBL.

January Data set

Fermi-LAT and LST results together with the joint fit on top. Not corrected for EBL.