DISCOVERY OF A ∼5 DAY CHARACTERISTIC TIMESCALE IN THE<i>KEPLER</i>POWER SPECTRUM OF Zw 229–15

Edelson, R.; Vaughan, S.; Malkan, M.; Kelly, Brandon C.; Smith, Krista Lynne; Boyd, Padi; Mushotzky, R. F.

doi:10.1088/0004-637x/795/1/2

Cited by 73 publications

(117 citation statements)

References 33 publications

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“…This work, as well as several others (Mushotzky et al 2011, Edelson et al 2014, Koz lowski 2016 have highlighted observational shortcomings in the damped random walk model of quasar variability, in which a random walk at short timescales flattens at longer timescales in the damped part. In particular, there is now rather good evidence that a non-negligible fraction of quasars exhibit variability which have significantly redder PDSs at low frequencies than expected from the random walk, with this fraction depending on the black hole mass.…”

Section: Discussionsupporting

confidence: 56%

OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

Čaplar

Lilly

Trakhtenbrot

2017

ApJ

114

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We characterize the optical variability of quasars in the intermediate Palomar Transient Factory (iPTF) and Palomar Transient Factory (PTF) surveys. We re-calibrate the r-band light curves for ∼28,000 luminous, broad-line AGNs from the SDSS, producing a total of ∼2.4 million photometric data points. We utilize both the structure function (SF) and power spectrum density (PSD) formalisms to search for links between the optical variability and the physical parameters of the accreting supermassive black holes that power the quasars. The excess variance (SF 2 ) of the quasar sample tends to zero at very short time separations, validating our re-calibration of the time-series data. We find that the the amplitude of variability at a given time-interval, or equivalently the time-scale of variability to reach a certain amplitude, is most strongly correlated with luminosity with weak or no dependence on black hole mass and redshift. For a variability level of SF(τ )=0.07 mag, the time-scale has a dependency of τ ∝ L 0.4 . This is broadly consistent with the expectation from a simple Keplerian accretion disk model, which provides τ ∝ L 0.5 . The PSD analysis also reveals that many quasar light curves are steeper than a damped random walk. We find a correlation between the steepness of the PSD slopes, specifically the fraction of slopes steeper than 2.5, and black hole mass, although we cannot exclude the possibility that luminosity or Eddington ratio are the drivers of this effect. This effect is also seen in the SF analysis of the (i)PTF data, and in a PSD analysis of quasars in the SDSS Stripe 82.

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Section: Discussionsupporting

confidence: 56%

OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

Čaplar

Lilly

Trakhtenbrot

2017

ApJ

114

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“…We ran simulations assuming PSD slopes of −3, −2.5, and −2 to cover most of the observed range of AGN behavior (e.g., Gonzalez-Martin & Vaughan 2012;Edelson et al 2014). Only pure power-law PSD slopes were assumed in this initial analysis; no broken or bending power laws were used.…”

Section: Ccf Significance Testingmentioning

confidence: 99%

Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing

Edelson

Gelbord

Cackett

et al. 2017

ApJ

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130

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Swift monitoring of NGC 4151 with an∼6hr sampling over a total of 69 days in early 2016 is used to construct light curves covering five bands in the X-rays (0.3-50keV) and six in the ultraviolet (UV)/optical (1900-5500Å). The three hardest X-ray bands (>2.5keV) are all strongly correlated with no measurable interband lag,while the two softer bands show lower variability and weaker correlations. The UV/optical bands are significantly correlated with the X-rays, lagging ∼3-4days behind the hard X-rays. The variability within the UV/optical bands is also strongly correlated, with the UV appearing to lead the optical by ∼0.5-1days. This combination of 3day lags between the X-rays and UV and 1day lags within the UV/optical appears to rule out the "lamp-post" reprocessing model in which a hot, X-ray emitting corona directly illuminates the accretion disk, which then reprocesses the energy in the UV/optical. Instead, these results appear consistent with the Gardner & Done picture in which two separate reprocessings occur: first, emission from the corona illuminates an extreme-UV-emitting toroidal component that shields the disk from the corona; this then heats the extreme-UV component,which illuminates the disk and drives its variability.

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“…Detailed modeling of quasar light curves has shown that the broadband variability is well-described to first approximation by a first-order continuous autoregressive process (i.e., a damped random walk; e.g., Kelly et al 2009Kelly et al , 2011MacLeod et al 2010), although small deviations from this behavior have been observed at short timescales using well-sampled light curves (e.g., Mushotzky et al 2011;Zu et al 2013;Edelson et al 2014;Graham et al 2014). This variable quasar continuum emission is believed to originate from their accretion disks, but the cause of Figure 2.…”

Section: Quasars In Tdssmentioning

confidence: 99%

The Time-Domain Spectroscopic Survey: Understanding the Optically Variable Sky With Sequels in SDSS-Iii

Ruan

Anderson

Green

et al. 2016

ApJ

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The Time-Domain Spectroscopic Survey (TDSS) is an SDSS-IV eBOSS subproject primarily aimed at obtaining identification spectra of ∼220,000 optically variable objects systematically selected from SDSS/Pan-STARRS1 multi-epoch imaging. We present a preview of the science enabled by TDSS, based on TDSS spectra taken over ∼320 deg 2 of sky as part of the SEQUELS survey in SDSS-III, which is in part a pilot survey for eBOSS in SDSS-IV. Using the 15,746 TDSS-selected single-epoch spectra of photometrically variable objects in SEQUELS, we determine the demographics of our variability-selected sample and investigate the unique spectral characteristics inherent in samples selected by variability. We show that variability-based selection of quasars complements colorbased selection by selecting additional redder quasars and mitigates redshift biases to produce a smooth quasar redshift distribution over a wide range of redshifts. The resulting quasar sample contains systematically higher fractions of blazars and broad absorption line quasars than from color-selected samples. Similarly, we show that M dwarfs in the TDSS-selected stellar sample have systematically higher chromospheric active fractions than the underlying M-dwarf population based on their Hα emission. TDSS also contains a large number of RR Lyrae and eclipsing binary stars with main-sequence colors, including a few composite-spectrum binaries. Finally, our visual inspection of TDSS spectra uncovers a significant number of peculiar spectra, and we highlight a few cases of these interesting objects. With a factor of ∼15 more spectra, the main TDSS survey in SDSS-IV will leverage the lessons learned from these early results for a variety of time-domain science applications.

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DISCOVERY OF A ∼5 DAY CHARACTERISTIC TIMESCALE IN THEKEPLERPOWER SPECTRUM OF Zw 229–15

Cited by 73 publications

References 33 publications

OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

OPTICAL VARIABILITY OF AGNs IN THE PTF/iPTF SURVEY

Swift Monitoring of NGC 4151: Evidence for a Second X-Ray/UV Reprocessing

The Time-Domain Spectroscopic Survey: Understanding the Optically Variable Sky With Sequels in SDSS-Iii

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