Flaring activity period of Mrk 421 measured by HAWC

ATel #14113; 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 22 Oct 2020; 23:33 UT
Credential Certification: José Andrés García-González (jagarcia@fisica.unam.mx)

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In the last week the HAWC gamma-ray observatory has observed an increased TeV gamma-ray emission from Markarian 421, with a highest flux above 1 TeV of (12.46 +/- 1.16) X 10^-11 cm^-2s^-1 ( 7.04 equivalent Crab units) from 2020-10-22 12:20:45 to 2020-10-22 18:36:43 UTC.

A list of previous periods of high activity may be found in the following Telegrams: #Atel 13808, #Atel 13831, #Atel 13875, #Atel 13917 , #Atel 13993 and #Atel 14070

The summary of this new activity period is as follows:

Duration of a full transit is 6.2 hr:

MJD 59141 ( 2020-10-19 12:32:32 - 2020-10-19 18:48:30 UTC)
Preliminary flux level: (5.65 +/- 1.05) X 10^-11 cm^-2s^-1 [>1 TeV] (3.18 CU)

MJD 59142 ( 2020-10-20 12:28:36 - 2020-10-20 18:44:34 UTC)
Preliminary flux level: (2.58 +/- 0.91) X 10^-11 cm^-2s^-1 [>1 TeV] (1.45 CU)

MJD 59143 ( 2020-10-21 12:24:41 - 2020-10-21 18:40:39 UTC)
Preliminary flux level: (6.05 +/- 1.04) X 10^-11 cm^-2s^-1 [>1 TeV] (3.42 CU)

MJD 59144 ( 2020-10-22 12:20:45 - 2020-10-22 18:36:43 UTC)
Preliminary flux level: (12.46 +/- 1.16) X 10^-11 cm^-2s^-1 [>1 TeV] (7.04 CU)

HAWC continuously monitors this source and will keep reporting in case that the enhanced activity continues. 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. A preliminary plot showing the source activity from the beginning of the high activity to this ATel may be found at https://data.hawc-observatory.org/atels/2020-10-19to22_HAWC_Markarian421_halfTransits.png

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.