Extended period of High Activity of Mrk 421 measured by HAWC

ATel #13831; Jose Andres Garcia-Gonzalez (IF-UNAM, jagarcia@fisica. unam. mx, ITESM-EIC, anteus79@tec. mx) and Israel Martinez (UMD, imc@umd. edu) on behalf of the HAWC Collaboration
on 24 Jun 2020; 00:19 UT
Credential Certification: José Andrés García-González (jagarcia@fisica.unam.mx)

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Since June 14th, the HAWC gamma-ray observatory has observed an increased TeV gamma-ray emission from Markarian 421, with the highest flux happening the night of Jun 14th, reaching a flux above 1 TeV of (10.57 +/- 1.13) X 10^-11 (~ 6 equivalent Crab units) between 2020-06-15 20:47:56 and 2020-06-16 03:03:54 UTC.

The summary of this extended period is as follows:

Duration of each transit is 6.2 hr

MJD 59014 (2020-06-14 20:51:52 to 2020-06-15 03:07:50 UTC) Preliminary flux level: 6.26 +/- 1.09 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 3.5 CU)

MJD 59015 (2020-06-15 20:47:56 to 2020-06-16 03:03:54 UTC) Preliminary flux level: 10.57 +/- 1.13 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 6 CU)

MJD 59016 (2020-06-16 20:44:00 to 2020-06-17 02:59:58 UTC) Preliminary flux level: 5.48 +/- 1.00 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 3 CU)

MJD 59017 (2020-06-17 20:40:04 to 2020-06-18 02:56:02 UTC) Preliminary flux level: 5.43 +/- 1.00 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 3 CU)

MJD 59018 (2020-06-18 20:36:08 to 2020-06-19 02:52:06 UTC) Preliminary flux level: 2.99 +/- 1.00 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 1.69 CU)

MJD 59019 (2020-06-19 20:32:12 to 2020-06-20 02:48:10 UTC) Preliminary flux level: 3.08 +/- 0.98 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 1.75 CU)

MJD 59020 (2020-06-20 20:28:16 to 2020-06-21 02:44:14 UTC) Preliminary flux level: 7.06 +/- 1.08 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 4 CU)

MJD 59021 (2020-06-21 20:24:20 to 2020-06-22 02:40:18 UTC) Preliminary flux level: 5.38 +/- 1.03 X 10^-11 cm^-2s^-1 [>1 TeV] (~ 3 CU)

HAWC continuously monitors this source and will keep reporting in case that the enhance 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. A preliminary plot showing the source activity for the aforementioned period may be found at https://data.hawc-observatory.org/atels/2020-06-14to21_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.