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arXiv · 1511.01515

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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Abstract

The optical light curve of the quasar PG 1302-102 at $z = 0.278$ shows a strong, smooth 5.2 yr periodic signal, detectable over a period of $\sim 20$ yr. 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 $\sim 10^{5}$ yr due to gravitational wave emission alone. Here we report the rest-frame near-infrared time lags for PG 1302-102. Compiling data from {\it WISE} and {\it Akari}, we confirm that the periodic behavior reported in the optical light curve from Graham et al. (2015) is reproduced at infrared wavelengths, with best-fit observed-frame 3.4 and $4.6 μ$m time lags of $(2219 \pm 153, 2408 \pm 148)$ days for a near face-on orientation of the torus, or $(4103\pm 153, 4292 \pm 148)$ 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 further out dusty regions. The implied distance of this dusty, assumed toroidal region is $\sim$ 1.5 pc for a near face-on geometry, or $\sim$1.1 pc for the relativistic Doppler boosted case.

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Hyunsung D. Jun, Daniel Stern, Matthew J. Graham, S. G. Djorgovski, Amy Mainzer, Roc M. Cutri, Andrew J. Drake, Ashish A. Mahabal. 2015-11-04. Infrared Time Lags for the Periodic Quasar PG 1302-102. https://arxiv.org/abs/1511.01515

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