Optical short-time variability properties of AGN

25 Pages·2017·8.11 MB·English

Optical short-time variability properties of AGN
Ester Aranzana
E. Körding, P. Uttley, S. Scaringi
X-ray Universe 6-9 June 2017, Rome
AGN variability
• Characteristic time-scales (different physical mechanisms)
• Light crossing time-scale ~ hours
• Dynamical time-scale ~ days
• Thermal time-scale ~ years
• Viscous time-scale ~ tens of years
McHardy (2009)
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome
AGN variability
• Characteristic time-scales (different physical mechanisms)
• Light crossing time-scale ~ hours
• Dynamical time-scale ~ days
• Thermal time-scale ~ years
• Viscous time-scale ~ tens of years
2.17 0.90
t M L
�
b
BH bol
⇠
McHardy (2009)
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome
AGN variability
• Characteristic time-scales (different physical mechanisms)
• Light crossing time-scale ~ hours
• Dynamical time-scale ~ days
• Thermal time-scale ~ years
• Viscous time-scale ~ tens of years
2.17 0.90
t M L
• Amplitude of variability
�
b
BH bol
⇠
⌫
2
� (%) = P(⌫)d⌫
McHardy (2009)
s
⌫
Z 1
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome
Why studying optical variability of AGN?
• Long-term variability: • Short-term variability:
SDSS, Palomar Green handful of selected sources
Quasars, PanSTARRS with Kepler
Simm et al. 2015 Mushotzy et al. 2011
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome
Why studying optical variability of AGN?
Origin of rapid optical variability?
★ Jet
★ Reprocessing of X-rays
★ Disc instabilities
Is there a cosmological evolution on the variability properties of
the AGN?
Accretion states?
Variability properties associated to a certain BH mass or
luminosity?
Ester Aranzana E s t e r A r a n z a n aT h e o p t i c a l r m s - fl u x r e l aOtpiotinca: lf rvoamri aCbVilsit tyo p AroGpNesr t i e s o f A G N X - r a y U n i v e r s e 6 - 9 J u nNeA 2C0 2117s, tR oofm Meay 2015
Sample selection and observations with K2
275 AGN selected from the “Million Quasar Catalogue”
with R > 19
(Flesch 2013)
Duration: 80 days
Cadence: 29.4 min
Bandpass: 420-900 nm
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome
Monte Carlo simulations of power spectra
Uttley et al. 2002
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome
Monte Carlo simulations of power spectra
Uttley et al. 2002
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome
Monte Carlo simulations of power spectra
e
g l
r
a
c
S
m b - P
o
L obs
Uttley et al. 2002
Ester Aranzana Optical variability properties of AGN X-ray Universe 6-9 June 2017, Rome