Статья

Optical and radio variability of the BL Lacertae object AO 0235+16: A possible 5-6 year periodicity

C. M. RaiteriOsservatorio Astronomico di Torino, Via Osservatorio 20, 10025 Pino Torinese, ItalyM. VillataOsservatorio Astronomico di Torino, Via Osservatorio 20, 10025 Pino Torinese, ItalyH. D. AllerDept. of Astronomy, Dennison Bldg., U. Michigan, Ann Arbor, MI 48109, USAM. F. AllerDept. of Astronomy, Dennison Bldg., U. Michigan, Ann Arbor, MI 48109, USAJ. HeidtO. M. KurtanidzeAbastumani Astrophysical Observatory, GeorgiaL. LanteriOsservatorio Astronomico di Torino, Via Osservatorio 20, 10025 Pino Torinese, ItalyM. MaesanoDipartimento di Fisica, Università La Sapienza, Roma, P.le A. Moro 2, 00185 Roma, ItalyE. MassaroDipartimento di Fisica, Università La Sapienza, Roma, P.le A. Moro 2, 00185 Roma, ItalyF. MontagniDipartimento di Fisica, Università La Sapienza, Roma, P.le A. Moro 2, 00185 Roma, ItalyR. NesciDipartimento di Fisica, Università La Sapienza, Roma, P.le A. Moro 2, 00185 Roma, ItalyK. NilssonM. G. NikolashviliAbastumani Astrophysical Observatory, GeorgiaP. NurmiL. OstoreroDipartimento di Fisica Generale, Università di Torino, Via P. Giuria 1, 10125 Torino, ItalyT. PursimoR. RekolaA. SillanpääL. O. TakaloH. TeräsrantaMetsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, FinlandG. TostiCattedra di Astrofisica, Università di Perugia, Via B. Bonfigli, 06126 Perugia, ItalyT. J. BalonekFoggy Bottom Observatory, Colgate University, Hamilton, NY, USAM. FeldtMax-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, GermanyA. HeinesC. A. HeislerMount Stromlo and Siding Spring Observatories, Canberra, AustraliaJ. Y. HuBeijing Astronomical Observatory, Beijing, ChinaM. KidgerTeide Observatory, Tenerife, SpainJ. R. MattoxDept. of Chemistry, Physics, & Astronomy, Francis Marion University, PO Box 100547, Florence, SC 29501-0547, USAElizabeth J. McGrathFoggy Bottom Observatory, Colgate University, Hamilton, NY, USAA. K. PatiVainu Bappu Observatory, Indian Institute of Astrophysics, Dept. of Science & Technology, Kavalur, IndiaR. M. RobbDept. of Physics and Astronomy, University of Victoria, British Columbia, CanadaA. C. SadunDept. of Physics, University of Colorado at Denver, PO Box 173364, Denver, CO 80217-3364, USAP. ShastriVainu Bappu Observatory, Indian Institute of Astrophysics, Dept. of Science & Technology, Kavalur, IndiaS. J. WagnerJianyan WeiBeijing Astronomical Observatory, Beijing, ChinaXue-Bing WuBeijing Astronomical Observatory, Beijing, China

2001en

ABI

Аннотация

The BL Lacertae object AO 0235+16 is well known for its extreme optical and radio variability. New optical and radio data have been collected in the last four years by a wide international collaboration, which confirm the intense activity of this source: on the long term, overall variations of in the R band and up to a factor 18 in the radio fluxes were detected, while short-term variability up to in a few hours and in one day was observed in the optical band. The optical data also include the results of the Whole Earth Blazar Telescope (WEBT) first-light campaign organized in November 1997, involving a dozen optical observatories. The optical spectrum is observed to basically steepen when the source gets fainter. We have investigated the existence of typical variability time scales and of possible correlations between the optical and radio emissions by means of visual inspection and Discrete Correlation Function (DCF) analysis. On the long term, the autocorrelation function of the optical data shows a double-peaked maximum at 4100-4200 days (11.2-11.5 years), while a double-peaked maximum at 3900-4200 days (10.7-11.5 years) is visible in the radio autocorrelation functions. The existence of this similar characteristic time scale of variability in the two bands is by itself an indication of optical-radio correlation. A further analysis by means of Discrete Fourier Transform (DFT) technique and folded light curves reveals that the major radio outbursts repeat quasi-regularly with a periodicity of ~5.7 years, i.e. half the above time scale. This period is also in agreement with the occurrence of some of the major optical outbursts, but not all of them. Visual inspection and DCF analysis of the optical and radio light curves then reveal that in some cases optical outbursts seem to be simultaneous with radio ones, but in other cases they lead the radio events. Moreover, a deep inspection of the radio light curves suggests that in at least two occasions (the 1992-1993 and 1998 outbursts) flux variations at the higher frequencies may have led those at the lower ones.

Перевод пока недоступен

Идентификаторы

DOI: 10.1051/0004-6361:20011112

Цитирования и источники

Цитирований: 13Использованных источников: 0

Показатели — AkademScholar