AGN Variability interest group

Back to the eROSITA AGN working group

The purpose of this page is to serve as a data exchange for a loose groups of people interested in AGN variability, both spectral and flux.

For non-AGN & TDE, see TDA Science Projects.

People interested

• Johannes Buchner
• Mirko Krumpe
• Gabriele Ponti (TBC)
• Joern Wilms (TBC)

Please add your name!

Ideas for projects & papers

Add ideas, information and names where you are interested, so we can communicate and work together. This is still all in the pre-WG approval phase, so nothing is set in stone (e.g., w.r.t. leading projects). Mostly this is a collection of ideas.

• Blazar luminosity variability:

  • Science goals: Constraining jet models TDA_Projects_Wilms-blazarJets

  • People interested: Joern Wilms (TBC), ...
  • Data requirements: needs ...?
• Occultation on 6m-year timescales (absorption/spectral variability)
  • Science goals: listed below
  • People interested:

    • JohannesBuchner (statistical inference on torus/BLR granularity)

    • MirkoKrumpe (statistical inference on torus/BLR granularity, follow-up of behaviour of individual events for in-depth understanding, ...)

  • Data requirements:
    • needs second all-sky survey
    • possibly first results can be done comparing to archives (RASS, 3XMM, CSC)

    • needs >10,000 sources, so small areas (<10 square degrees) are not effective.

• Occultation on day timescales (scanning stripe overlaps)
  • Science goals:
  • People interested:

    • MirkoKrumpe

    • ...
  • Data requirements: eRASS, eFEDS also ok?
• Extreme increases in AGN luminosity
  • Science goals: a factor of 100x luminosity increase ("turn-on") enables dust reverberation mapping, i.e. constraining the torus geometry if followed up with infrared campaigns
  • People interested:
    • ...
  • Data requirements:
    • needs second all-sky survey, possibly first results can be done comparing to archives (RASS, 3XMM, CSC)
• Extreme decreases in AGN luminosity
  • Science goals: a factor of 100x luminosity decreases ("turn-off") allow constraining the torus geometry through a clean view of the X-ray reflection spectrum. Requires follow-up with hard X-rays (NuSTAR), thus limited to (previously) bright sources.
  • People interested:

    • JohannesBuchner

    • MirkoKrumpe

    • ...
  • Data requirements:
    • probably needs second all-sky survey to identify rapid decreases
• Tidal Disruption Events

  • see eroTDA_ScienceProjects

• flux variability as Black hole mass estimator & as standard candles

  • see AGN_flux_variability

  • People interested:
    • Gabriele Ponti
    • Andrea Merloni
    • Kirpal Nandra

    • Barbara DeMarco

    • ...

There is also eRosita/AGN_spectral_variability, feel free to integrate that here as specific science projects.

Work Products

• Johannes Buchner: MC Proposal for constraining torus granularity with 180d-2y eROSITA cadences (bright AGN) and CDF-S with advanced statistical methods (faint AGN). Feasibility calculations and predictions for eRASS begin at the bottom of page 3:

  • 13,000 hard-band detected AGN in the extragalactic sky
  • measure NH in soft band (more sensitive), every 6 months
  • expect 120-1,200 of the 13,000 AGN to show eclipse events after waiting 6 months
  • with that, can constrain obscurer granularity (see figure);
  • redshifts/BHM not needed initially, but will be useful later to divide by source type
  • Further divisions by strength of NH variation
• Mirko Krumpe: ...