Further optical brightening of the blazar PKS 1424-418

ATel #15552; F. Jankowsky, F. Ait-Benkhali, M. Zacharias, S. J. Wagner (LSW Heidelberg)
on 15 Aug 2022; 15:13 UT
Credential Certification: Felix Jankowsky (f.jankowsky@lsw.uni-heidelberg.de)

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Optical observations of PKS 1424-418 (z=1.522, White et al., ApJ, 327, 561 (1988)) with the Automatic Telescope for Optical Monitoring (ATOM) in Namibia indicate a further increase of the optical flux. Preliminary analysis of measurements performed on 14 August 2022 (MJD 59805.8) yield an R magnitude of 12.9. This is 0.5 magnitudes higher than the 13.4 magnitudes previously measured with ATOM on 23 July 2022 (reported in ATel #15525). After this previous report, PKS 1424-418 exhibited a flux decrease to levels of 14.2 magnitudes, but has begun to re-brighten again around 8 August.

Observations with the Fermi-LAT covering the 24h period around ATOM's latest measurement reveal a gamma-ray flux in the 100 MeV to 500 GeV band of (3.7 +/- 0.3) 10^6 cm^-2 s^-1. Since 7 August, gamma-ray flux has begun to show significant daily variability.

This current activity of PKS 1424-418 has been associated with a long-term increase in radio flux-density starting in late 2021 (ATel #15536). A re-brightening of this blazar has also previously been observed with AGILE (ATel #15533). Further multi-frequency observations of this outburst is encouraged.

ATOM is a 75cm optical telescope located at the H.E.S.S. site in Namibia.

Fermi-LAT fluxes are also available on the public LAT light curve page: http://fermi.gsfc.nasa.gov/ssc/data/access/lat/msl_lc