Infrared time lags for the periodic quasar PG 1302-102

Hyunsung D. Jun, Daniel Stern, Matthew J. Graham, S. G. Djorgovski, Amy Mainzer, Roc M. Cutri, Andrew J. Drake, Ashish A. Mahabal

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20 Scopus citations


The optical light curve of the quasar PG 1302-102 at z 0.278 = shows a strong, smooth 5.2 year periodic signal, detectable over a period of ∼20 years. Although the interpretation of this phenomenon is still uncertain, the most plausible mechanisms involve a binary system of two supermassive black holes with a subparsec separation. At this close separation, the nuclear black holes in PG 1302-102 will likely merge within 105 ∼ years due to gravitational wave emission alone. Here, we report the rest-frame near-infrared time lags for PG 1302-102. Compiling data from WISE and Akari, we confirm that the periodic behavior reported in the optical light curve from Graham et al. is reproduced at infrared wavelengths, with best-fit observed-frame 3.4 and 4.6 m m time lags of (2219 ± 153, 2408 ± 148) days for a near face-on orientation of the torus, or (4103 ± 153, 4292 ± 148) days for an inclined system with relativistic Doppler boosting in effect. The periodicity in the infrared light curves and the light-travel time of the accretion disk photons to reach the dust glowing regions support that a source within the accretion disk is responsible for the optical variability of PG 1302-102, echoed at the farther out dusty regions. The implied distance of this dusty, assumed toroidal region is .1.5 pc for a near face-on geometry or .1.1 pc for the relativistic Doppler-boosted case.

Original languageEnglish (US)
Article numberL12
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Nov 20 2015
Externally publishedYes


  • galaxies: active
  • quasars: individual (PG 1302-102)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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