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 * Johannes Buchner: MC Proposal for constraining torus granularity with 180d-2y eROSITA cadences (bright AGN) and CDF-S with advanced statistical methods (faint AGN)  * Johannes Buchner: [[EroAGN_Var/JohannesBuchner_occultation_proposal | 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
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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:
  • 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:
    • 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:
    • Data requirements:
      • probably needs second all-sky survey to identify rapid decreases
  • Tidal Disruption Events

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

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: ...