J/MNRAS/373/209 BATC eim photometry of BL Lac (Hu+, 2006) ================================================================================ Optical multiband observations of BL Lacertae during the outburst of 2005. Hu S.M., Wu J.H., Zhao G., Zhou X. =2006MNRAS.373..209H ================================================================================ ADC_Keywords: BL Lac objects ; Photometry Keywords: BL Lacertae objects: general - BL Lacertae objects: individual: BL Lacertae - galaxies: photometry Abstract: The aim of our observations is to investigate the intra-night variability properties and the spectral variability of BL Lacertae. 799 optical multiband observations were intensively made with the Beijing-Arizona-Taiwan-Connecticut (BATC) 60/90cm Schmidt telescope during the outburst composed of two subsequent flares in 2005. The second flare, whose rising phase lasted at least 44d, was observed with amplitudes of more than 1.1mag in three BATC optical bands. In general, on intra-night time-scale the amplitude of variability and the variation rate are larger at the shorter wavelength, and the variation rate is comparable in the rising and decaying phases within each band. A possible time-lag between the light curves in bands e and m, around 11.6min, was obtained. Based on the analysis of the colour index variation with the source brightness, the variability of BL Lacertae can be interpreted as having two components: a 'strongly chromatic' intra-night component and a 'mildly chromatic' inter-night component, which may be the results of both intrinsic physical mechanism and geometric effects. Description: Our observations were carried out with a 60/90cm f/3 Schmidt telescope, which is located at the Xinglong Station of the National Astronomical Observatories of China. We performed optical observations in the BATC e, i and m bands in a cyclic mode. Their central wavelengths are 4885, 6685 and 8013{AA}, respectively. BL Lac was observed on 26 nights during the period from 2005 July 5 to November 18. Objects: ------------------------------------------------ RA (2000) DE Designation(s) ------------------------------------------------ 22 02 43.3 +42 16 40 BL Lac = QSO B2200+420 ------------------------------------------------ File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 57 268 BATC e magnitudes of BL Lac table3.dat 57 267 BATC i magnitudes of BL Lac table4.dat 57 264 BATC m magnitudes of BL Lac -------------------------------------------------------------------------------- See also: II/262 : BATC Data Release One - BATC DR1 (Zhou+ 1995-2005) J/A+A/369/758 : VRI photometry of BL Lac (1997-1999) (Fan+, 2001) J/A+A/385/55 : Long-Term Polarization of BL Lac (Hagen-Thorn+ 2002) J/AZh/71/717 : Polarimetric Observations of BL Lac (Gagen-Torn+ 1994) J/PAZh/30/243 : BL Lac BV(RI)c-JHK photometry in 1999-2001 (Hagen-Thorn+,2004) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 "YYYY/MM/DD" Obs.Date UT date of observation 12- 13 I2 h Obs.h UT time of observation (hours) 14 A1 --- --- [:] 15- 16 I2 min Obs.m UT time of observation (minutes) 17 A1 --- --- [:] 18- 19 I2 s Obs.s UT time of observation (seconds) 21- 33 F13.5 d JD Julian date of observation 35- 37 I3 s ExpTime Exposure Time 39- 44 F6.3 mag emag BATC e magnitude 46- 50 F5.3 mag e_emag rms uncertainty on emag 52- 57 F6.3 mag demag Magnitude difference (G1) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 "YYYY/MM/DD" Obs.Date UT date of observation 12- 13 I2 h Obs.h UT time of observation (hours) 14 A1 --- --- [:] 15- 16 I2 min Obs.m UT time of observation (minutes) 17 A1 --- --- [:] 18- 19 I2 s Obs.s UT time of observation (seconds) 21- 33 F13.5 d JD Julian date of observation 35- 37 I3 s ExpTime Exposure Time 39- 44 F6.3 mag imag BATC i magnitude 46- 50 F5.3 mag e_imag rms uncertainty on imag 52- 57 F6.3 mag dimag Magnitude difference (G1) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 10 A10 "YYYY/MM/DD" Obs.Date UT date of observation 12- 13 I2 h Obs.h UT time of observation (hours) 14 A1 --- --- [:] 15- 16 I2 min Obs.m UT time of observation (minutes) 17 A1 --- --- [:] 18- 19 I2 s Obs.s UT time of observation (seconds) 21- 33 F13.5 d JD Julian date of observation 35- 37 I3 s ExpTime Exposure Time 39- 44 F6.3 mag mmag BATC m magnitude 46- 50 F5.3 mag e_mmag rms uncertainty on mmag 52- 57 F6.3 mag dmmag Magnitude difference (G1) -------------------------------------------------------------------------------- Global notes: Note (G1): Difference between the differential magnitude of comparison stars B, C (Bx-Cx), and the average of (Bx-Cx); x indicates the BATC band e, i or m. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 08-Jun-2007