Understanding Quasar Variability through Kepler

Details Understanding Quasar Variability through Kepler Understanding Quasar Variability through Kepler

Jan 2012

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21915417s&link_type=abstract

American Astronomical Society, AAS Meeting #219, #154.17

Astronomy and Astrophysics

Astrophysics

Scientific paper

We are monitoring four flat spectrum radio quasars (blazars) and one powerful radio galaxy, Cygnus A, to search for variability on timescales comparable to the light crossing time of the accretion disk around the central supermassive black hole and the base of the relativistic jet. Kepler's essentially continuous monitoring at 1 min and 30 min cadences allows us to obtain high quality light curves extending for months, something not possible from even semi-dedicated collections of ground based optical telescopes. We can characterize the variability on timescales ranging from several minutes through many days to see if some optical variability in quasars might be due to a bright feature in the accretion disk as it approaches the last stable orbit, or, more likely for blazars, nearly coherent inhomogeneities in the jet, possibly in a helical structure or temporarily dominant turbulent cell. We have analyzed both the raw and "corrected” Kepler data to determine the power spectral densities of the four blazars as well as their structure functions. The principal challenge to our Kepler data analysis is that the automatic pipeline removal of day-to-week-scale drifts also removes real astrophysical brightness variations and so we have concentrated so far on the raw data while we work on better removal of only the instrumental drifts. Our preliminary results on short timescale variations indicate that three of the four blazars showed modest ( 15%) variations and relatively slow variability during three months of monitoring, but the fourth also shows many flares ( 3%) on several-day timescales, particularly during one quarter. While a visual inspection of this light curve gives a hint of a quasi-period, this is not borne out by the structure function and PDS analyses.
This work is supported by NASA/Kepler grant GO20018.

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