PKS 1302-102 is a quasar in the Virgo constellation, located at a distance of approximately 1.1 Gpc (around 3.5 billion light-years).[1] It has an apparent magnitude of about 14.9 mag in the V band with a redshift of 0.2784.[1] The quasar is hosted by a bright elliptical galaxy,[3] with two neighboring companions at distances of 3 kpc and 6 kpc. The light curve of PKS 1302-102 appears to be sinusoidal with an amplitude of 0.14 mag and a period of 1,884 ± 88 days, which suggests evidence of a supermassive black hole binary.[4]
PKS 1302-102 was selected from the Catalina Real-Time Transient Survey as one of 20 quasars with apparent periodic variations in the light curve. Of these quasars, PKS 1302-102 appeared to be the best candidate in terms of sinusoidal behavior and other selection criteria, such as data coverage of more than 1.5 cycles in the measured period.[4] One plausible interpretation of the apparent periodic behavior is the possibility of two supermassive black holes (SMBH) orbiting each other with a separation of approximately 0.1 pc in the final stages of a 3.3 billion year old galaxy merger. If this turns out to be the case, it would make PKS 1302-102 an important object of study to various areas of research, including gravitational wave studies and the unsolved final parsec problem in a merger of black holes.
Other explanations, of lesser likelihood, to the observed sinusoidal periodicity include a hot spot on the inner part of the black hole's accretion disk and the possibility of a warped accretion disk which partially eclipses in the orbit around a single SMBH.[4] However, it also remains possible that the periodic behavior in PKS 1302-102 is indeed just a random occurrence in the light curve of an ordinary quasar, as spurious nearly-periodic variations can occur over limited time periods as part of stochastic quasar variability.[5] Further observations of the quasar could either promote true periodicity or rule out a binary interpretation, especially if the measured light curve randomly diverges from the sinusoidal model.[5]
^Disney, M. J.; Boyce, P. J.; Blades, J. C.; Boksenberg, A.; Crane, P.; Deharveng, J. M.; Macchetto, F.; Mackay, C. D.; Sparks, W. B. (1995-07-13). "Interacting elliptical galaxies as hosts of intermediate-redshift quasars". Nature. 376 (6536): 150–153. Bibcode:1995Natur.376..150D. doi:10.1038/376150a0. S2CID4346547.
^ abVaughan, S.; Uttley, P.; Markowitz, A. G.; Huppenkothen, D.; Middleton, M. J.; Alston, W. N.; Scargle, J. D.; Farr, W. M. (2016-09-01). "False periodicities in quasar time-domain surveys". Monthly Notices of the Royal Astronomical Society. 461 (3): 3145–3152. arXiv:1606.02620. Bibcode:2016MNRAS.461.3145V. doi:10.1093/mnras/stw1412. ISSN0035-8711.
13h05m33.01498s, −10° 33′ 19.4266″
