TeV flaring activity of the AGN PKS 0625–354 in November 2018

Abstract

Most γ-ray detected active galactic nuclei are blazars with one of their relativistic jets pointing towards the Earth. Only a few objects belong to the class of radio galaxies or misaligned blazars. Here, we investigate the nature of the object PKS 0625−354, its γ-ray flux and spectral variability and its broad-band spectral emission with observations from H.E.S.S., Fermi-LAT, Swift-XRT, and UVOT taken in November 2018. The H.E.S.S. light curve above 200 GeV shows an outburst in the first night of observations followed by a declining flux with a halving time scale of 5.9 h. The γγ-opacity constrains the upper limit of the angle between the jet and the line of sight to ∼10°. The broad-band spectral energy distribution shows two humps and can be well fitted with a single-zone synchrotron self Compton emission model. We conclude that PKS 0625−354, as an object showing clear features of both blazars and radio galaxies, can be classified as an intermediate active galactic nuclei. Multi-wavelength studies of such intermediate objects exhibiting features of both blazars and radio galaxies are sparse but crucial for the understanding of the broad-band emission of γ-ray detected active galactic nuclei in general.

Astronomy & Astrophysics 683, A70 (2024)
ArXiv pre-print

Auxiliary informations

Fig. 1. Nightly-binned light curve above 200 GeV measured with the H.E.S.S. telescopes in November 2018.

MJD dMJD Flux[cm^-2 s^-1] dFlux_low[cm^-2 s^-1] dFlux_high[cm^-2 s^-1]
58424.0057655 0.01646567531861 2.4335e-11 4.5547e-12 4.9419e-12
58424.99445876 0.06292619765736 4.9132e-12 1.8745e-12 2.0405e-12
58426.02857409 0.05806286400184 6.6102e-12 1.6346e-12 1.7496e-12
58426.99709292 0.06911130272783 5.1797e-12 1.6764e-12 1.8048e-12
58428.04207649 0.0681616992224 9.8331e-12 2.0399e-12 2.1868e-12
58429.02785259 0.06724617839791 1.5966e-12 1.2612e-12 1.3488e-12
58430.02852523 0.08380158059299 7.051e-13 2.0845e-12 2.4048e-12
58431.01608481 0.09050669288263 -9.4647e-13 1.6689e-12 1.879e-12
58432.02925955 0.05418581864797 3.5764e-14 1.3375e-12 1.4671e-12
58432.96819997 0.01974438712932 -2.3588e-12 2.2796e-12 2.6551e-12

Fig. 2. Spectral energy distributions measured with the H.E.S.S. telescopes in 2018 – spectral points.

average spectrum:

Energy ErrHigh ErrLow Flux ErrHigh ErrLow
[TeV] [TeV] [TeV] [TeV cm-2 s-1] [TeV cm-2 s-1] [TeV cm-2 s-1]
1.864e-01 2.908e-02 3.958e-02 8.180e-11 3.177e-11 2.959e-11
2.675e-01 4.875e-02 5.203e-02 2.035e-11 6.812e-12 6.476e-12
3.821e-01 8.206e-02 6.587e-02 8.943e-12 2.398e-12 2.274e-12
5.601e-01 1.212e-01 9.592e-02 3.042e-12 8.887e-13 8.292e-13
8.890e-01 3.225e-01 2.077e-01 8.078e-13 2.502e-13 2.316e-13

high state spectrum:

Energy ErrHigh ErrLow Flux ErrHigh ErrLow
[TeV] [TeV] [TeV] [TeV cm-2 s-1] [TeV cm-2 s-1] [TeV cm-2 s-1]
2.946e-01 5.348e-02 5.745e-02 1.063e-10 3.302e-11 2.881e-11
4.183e-01 9.256e-02 7.027e-02 1.633e-11 9.813e-12 8.075e-12
6.139e-01 1.360e-01 1.030e-01 1.020e-11 4.742e-12 3.855e-12
9.383e-01 2.732e-01 1.884e-01 2.481e-12 1.600e-12 1.226e-12

low state spectrum:

Energy ErrHigh ErrLow Flux ErrHigh ErrLow
[TeV] [TeV] [TeV] [TeV cm-2 s-1] [TeV cm-2 s-1] [TeV cm-2 s-1]
1.862e-01 2.920e-02 3.947e-02 8.168e-11 3.172e-11 2.954e-11
2.667e-01 4.957e-02 5.121e-02 1.511e-11 6.812e-12 6.459e-12
3.819e-01 8.229e-02 6.564e-02 7.652e-12 2.419e-12 2.288e-12
5.597e-01 1.216e-01 9.555e-02 2.517e-12 8.878e-13 8.248e-13
8.876e-01 3.239e-01 2.063e-01 6.505e-13 2.483e-13 2.287e-13

Fig. 3. Light curve and flux upper limits measured with Fermi-LAT in 2018 between 100 MeV and 500 GeV.

flux flux_err flux_ul95 ts index index_err tmin tmax mjd mjd_err ul
[10^{-8} cm^-2 s^-1] [10^{-8} cm^-2 s^-1] [10^{-8} cm^-2 s^-1]
0.8537752822032689 0.44505843347723945 1.3695223262807579 26.481889000016963 1.7113146217395143 0.20638695622286465 536457605 541641605 58149.00005787037 30.0 False
0.17124793677983757 0.174864437727625 0.36011420233229263 23.446717752551194 1.3489649039945335 0.34547458209063175 541641605 546825605 58209.00005787037 30.0 False
0.2748783954202438 0.28158456350901223 0.6329587801908849 6.843677279219264 1.7307330912484375 0.3799767273830494 546825605 552009605 58269.00005787037 30.0 True
4.256063117203727 1.5815111629255765 6.221240318428374 19.301459140937368 2.5768772556613095 0.3083197560608138 552009605 554601605 58314.00005787037 15.0 False
0.9480846609293854 1.3215388031394082 2.9031823900059837 0.865886400169984 2.605490427496777 1.1738437374880684 554601605 557193605 58344.00005787037 15.0 True
0.00023153601529587382 0.14740589150259994 2.9142569927978856 -4.25938269472681e-05 2.7980219294640407 133.95702718984808 557193605 559785605 58374.00005787037 15.0 True
1.0972184964957834 0.5421040808080724 1.7266803916744518 49.892373907598085 1.5935819141665024 0.18716842661882488 559785605 562377605 58404.00005787037 15.0 False
6.915169982498934 2.3094518704724734 9.908693187896207 21.507781770822476 2.6304073390348974 0.27049134005013675 562377605 564969605 58434.00005787037 15.0 False
1.6065263027049193 2.013324567037071 4.47064412289045 0.8782508037766092 2.75213764807652 0.7418847863492646 564969605 567561605 58464.00005787037 15.0 True

 

All of the information above are also available in this text file: [PKS0625m354_datapoints.txt]

Table of Contents