J/MNRAS/476/2501 AGN short time-scale optical variability (Aranzana+, 2018)
Short time-scale optical variability properties of the largest AGN sample
observed with Kepler/K2.
Aranzana E., Kording E., Uttley P., Scaringi S., Bloemen S.
<Mon. Not. R. Astron. Soc., 476, 2501-2515 (2018)>
=2018MNRAS.476.2501A 2018MNRAS.476.2501A (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; QSOs ; Redshifts
Keywords: accretion, accretion discs - galaxies: active - quasars: general -
quasars: supermassive black holes
Abstract:
We present the first short time-scale (∼ hours to days) optical
variability study of a large sample of active galactic nuclei (AGNs)
observed with the Kepler/K2 mission. The sample contains 252 AGN
observed over four campaigns with ∼30 min cadence selected from
the Million Quasar Catalogue with R magnitude <19. We performed time
series analysis to determine their variability properties by means of
the power spectral densities (PSDs) and applied Monte Carlo techniques
to find the best model parameters that fit the observed power spectra.
A power-law model is sufficient to describe all the PSDs of our
sample. A variety of power-law slopes were found indicating that there
is not a universal slope for all AGNs. We find that the rest-frame
amplitude variability in the frequency range of 6x10-6-10-4Hz
varies from 1 to 10 per cent with an average of 1.7 per cent. We explore
correlations between the variability amplitude and key parameters of
the AGN, finding a significant correlation of rest-frame short-term
variability amplitude with redshift. We attribute this effect to the
known 'bluer when brighter' variability of quasars combined with the
fixed bandpass of Kepler data. This study also enables us to
distinguish between Seyferts and blazars and confirm AGN candidates.
For our study, we have compared results obtained from light curves
extracted using different aperture sizes and with and without
detrending. We find that limited detrending of the optimal photometric
precision light curve is the best approach, although some systematic
effects still remain present.
Description:
In this work, we presented a catalogue of the optical variability
properties in the high-frequency domain of a large sample of 252
sources. Using light curves of extremely high quality from Kepler/K2,
we studied their power spectra by using the PSRESP Monte Carlo method.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tableb1.dat 141 252 Parameters for all the MQ AGN analysed in this work
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See also:
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
VII/283 : The Million Quasars (Milliquas) catalog (6.3) (Flesch, 2019)
Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 9 I9 --- EPIC EPIC number
10 A1 --- n_EPIC [*] Note on EPIC (1)
12- 19 F8.4 deg RAdeg Right ascension (J2000)
21- 28 F8.4 deg DEdeg Declination (J2000)
30- 31 A2 --- Type Type of AGN (2)
33- 36 F4.1 mag b'mag b' magnitude (2)
38- 41 F4.1 mag r'mag r' magnitude (2)
43- 46 F4.2 --- z Redshift (2)
48- 51 F4.2 --- betaopt Negative power-law index of the simulated
PSD for the 'optimal' aperture
52 A1 --- --- [+]
53- 56 F4.2 --- E_betaopt Error on betaopt (upper value)
57 A1 --- --- [-]
58- 61 F4.2 --- e_betaopt Error on betaopt (lower value)
63- 66 F4.2 --- betaPRF9 Negative power-law index of the simulated
PSD for the PRF aperture
67 A1 --- --- [+]
68- 71 F4.2 --- E_betaPRF9 Error on betaPRF9 (upper value)
72 A1 --- --- [-]
73- 76 F4.2 --- e_betaPRF9 Error on betaPRF9 (lower value)
78- 81 F4.2 --- betadet Negative power-law index of the simulated
PSD for the 'optimal' detrended light
curves
82 A1 --- --- [+]
83- 86 F4.2 --- E_betadet Error on betadet (upper value)
87 A1 --- --- [-]
88- 91 F4.2 --- e_betadet Error on betadet (lower value)
93- 97 F5.2 --- Norm Best normalisation
99-104 F6.2 % Noise Poisson noise level obtained in the
minimisation
106-110 F5.1 % Prob Acceptance probability for the model
112-116 F5.2 % sigmaobs ?=- Fractional rms measured in the
observed power spectra
118-122 F5.2 % sigmalit Fractional rms measured in the
simulated power spectra
124-128 F5.2 % sigmarestfit Rest-frame fractional rms
130-133 F4.2 % e_sigmarestfit Rms uncertainty on sigmarestfit
135-141 F7.2 [10+8] Lbol Estimated bolometric luminosity
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Note (1): * for stars that could be affected by the Moire effect.
Note (2): extracted from the Million Quasar Catalogue catalogue
(Flesch, 2019, Cat. VII/283).
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 23-Apr-2021