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J/A+A/369/758       VRI photometry of BL Lac (1997-1999)     (Fan+, 2001)
Optical observations of BL Lacertae from 1997 to 1999
     Fan J.H., Qian B.C., Tao J.
    <Astron. Astrophys. 369, 758 (2001)>
    =2001A&A...369..758F
ADC_Keywords: BL Lac objects ; Photometry, VRI

Keywords: galaxies: active - galaxies: photometry -
          BL Lacertae objects: individual: BL Lac (PKS 2200+420)

Abstract:
    We present the optical (V, R, and I) photometry for BL Lacertae, which
    was observed from 1997 through 1999, with the 1.56-m telescope at the
    Shanghai astronomical observatory (SHAO). After the 1997 outburst, it
    dimmed to a low state and then brightened again. During the period
    JD 2450701 to JD 2450701.5, variations of 0.40mag, 0.27mag, and
    0.21mag over a time scale of 100min were found for V, R, and I bands,
    suggesting that the variations were decreasing with wavelength. The
    correlation between V, R, and I is also analyzed using the DCF
    (Discrete Correlation Function) method. This shows that the
    variability in the V, R, and I bands are correlated with no time delay
    longer than 0.2day.
Objects:
    ----------------------------------------------------------
       RA   (2000)   DE      Designation(s)
    ----------------------------------------------------------
    22 02 43.3   +42 16 40   BL Lac = PKS 2200+420
    ----------------------------------------------------------

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table1.dat        50      369   Optical measurements of BL Lacertae in 1997-1999


See also:
  J/A+AS/143/357 : Tuorla Quasar Monitoring (Katajainen+ 2000)
  J/A+AS/136/455 : BVRI photometry of 3 BL Lac objects (Bai+, 1999)
  J/A+AS/120/89  : 408MHz observations (Bondi+ 1996)
  J/AZh/71/717   : Polarimetric Observations of BL Lac (Gagen-Torn+ 1994)


Byte-by-byte Description of file: table1.dat

   Bytes Format Units   Label     Explanations

   1- 12  F12.4 d       HJD       Heliocentric Julian date
  14- 18  F5.2  mag     Vmag      ? V magnitude
  20- 24  F5.3  mag     e_Vmag    ? rms uncertainty in Vmag
  26- 30  F5.2  mag     Rmag      ? R magnitude
  32- 36  F5.3  mag     e_Rmag    ? rms uncertainty in Rmag
  38- 42  F5.2  mag     Imag      ? I magnitude
  44- 48  F5.3  mag     e_Imag    ? rms uncertainty in Imag


Acknowledgements: Junhui Fan 

(End)                                        Patricia Bauer [CDS]    12-Apr-2001