Latest increased Activity of Mrk 421 measured by HAWC

ATel #14070; Jose Andres Garcia-Gonzalez (IF-UNAM, jagarcia@fisica. unam. mx, ITESM-EIC, anteus79@tec. mx), Israel Martinez (UMD, imc@umd. edu) on behalf of the HAWC Collaboration
on 7 Oct 2020; 15:31 UT
Credential Certification: José Andrés García-González (jagarcia@fisica.unam.mx)

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In the past day the HAWC gamma-ray observatory has observed an increased TeV gamma-ray emission from Markarian 421, with a highest flux above 1 TeV of (11.01 +/- 1.64) X 10^-11 cm^-2s^-1 ( 6.22 equivalent Crab units) from 2020-10-06 13:23:39 to 2020-10-06 16:31:38 UTC.

This new increase in the integrated flux has been preceded by an extended period of high activity with some interruptions (see for ref. #Atel 13808, #Atel 13831, #Atel 13875, #Atel 13917 and #Atel 13993).

The summary of this new activity period is as follows:

Duration of a full transit is 6.2 hr, we are separating the transit in two parts of ~ 3.1 hr each:

MJD 59128 (2020-10-06 13:23:39 - 2020-10-06 16:31:38 UTC) (rising)
Preliminary flux level: 11.01 +/- 1.64 X 10^-11 cm^-2s^-1 [>1 TeV] (6.22 CU)

MJD 59128 (2020-10-06 16:31:38 - 2020-10-06 19:39:37 UTC) (setting)
Preliminary flux level: 9.49 +/- 1.59 X 10^-11 cm^-2s^-1 [>1 TeV] (5.36 CU)

HAWC continuously monitors this source and will keep reporting in case that the enhanced activity follows. Follow-up observations are encouraged. All flux values are obtained from a maximum likelihood fit under the assumption of a fixed spectral shape with power law index of 2.2 and exponential cut-off at 5 TeV.

The HAWC contact people for this analysis are Jose Andres Garcia-Gonzalez (IF-UNAM, jagarcia@fisica.unam.mx, ITESM-EIC, anteus79@tec.mx) and Israel Martinez (UMD, imc@umd.edu). HAWC is a TeV gamma-ray water Cherenkov array located in the state of Puebla, Mexico, that monitors two thirds of the sky every day with an instantaneous field of view of ~2 sr.