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J/AJ/132/1256       eim BATC photometry of OJ 287            (Wu+, 2006)

Optical monitoring of BL Lacertae object OJ 287: a 40 day period? Wu J., Zhou X., Wu X.-B., Liu F.-K., Peng B., Ma J., Wu Z., Jiang Z., Chen J. <Astron. J., 132, 1256-1266 (2006)> =2006AJ....132.1256W
ADC_Keywords: BL Lac objects ; Photometry Keywords: black hole physics - BL Lacertae objects: individual (OJ 287) - galaxies: active - galaxies: jets - galaxies: photometry Abstract: We present the results of our optical monitoring of the BL Lacertae object OJ 287 during the first half of 2005. The source did not show large-amplitude variations during this period and was in a relatively quiescent state. A possible period of 40 days was derived from its light curves in three BATC wave bands. A bluer-when-brighter chromatism was discovered, which is different from the extremely stable color during the outburst in 1994-1996. The different color behaviors imply different variation mechanisms in the two states. We then revisited the optical data on OJ 287 from the OJ-94 project and also found a probable period of 40 days in its optical variability during the late 1994 outburst. The results suggest that two components contribute to the variability of OJ 287 during its outburst state. The first component is the normal blazar variation. This component has an amplitude similar to that of the quiescent state and also may share a similar periodicity. The second component can be taken as a "low-frequency modulation" to the first component. It may be induced by the interaction of the assumed binary black holes in the center of this object. The 40 day period may be related to the helical structure of the magnetic field at the base of the jet or to the orbital motion close to the central primary black hole. Description: Our optical monitoring of OJ 287 was carried out on a 60/90cm Schmidt telescope located at the Xinglong Station of the National Astronomical Observatories of China (NAOC). The monitoring covered the time from 2005 January 29 to April 28. Objects: ------------------------------------------- RA (2000) DE Designation(s) ------------------------------------------- 08 54 48.9 +20 06 31 OJ 287 = OHIO J 287 ------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 52 61 Observational log and results in the BATC e band table2.dat 52 60 Observational log and results in the BATC i band table3.dat 52 57 Observational log and results in the BATC m band
See also: II/262 : BATC Data Release One - BATC DR1 (Zhou+ 1995-2005) J/A+AS/136/455 : BVRI photometry of 3 BL Lac objects (Bai+, 1999) J/A+AS/129/569 : BVRI photometry of OJ 287 (Jia Guibin+ 1998) J/A+A/450/39 : BVRI photometry of 8 red blazars (Gu+, 2006) Byte-by-byte Description of file: table1.dat table2.dat table3.dat
Bytes Format Units Label Explanations
1- 10 A10 "YYYY/DD/MM" Obs.Date UT date of the Observation (1) 12- 21 A10 "h:m:s" Obs.Time UT time of the Observation (1) 23- 33 F11.3 d JD Julian Date of the Observation (1) 35- 37 I3 s Exp Exposure time 39 A1 --- Band [eim] BATC band (2) 41- 46 F6.3 mag mag BATC band magnitude 48- 52 F5.3 mag e_mag Error in mag
Note (1): We took part in the multiwavelength campaign on OJ 287 coordinated by Stefano Ciprini during 2005 April 13-15 (JD2453473-475), so we do not present the data in these days in Tables 1-3 but give a point (the mean) per night in each light curve in Fig. 1. Note (2): the filter characteristics are (see Cat. II/262): --------------------------------- Filter Code cw(nm) FWHM(nm) --------------------------------- e 492.5 39 i 666.0 48 m 802.0 26 ---------------------------------
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 25-Apr-2008
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