J/ApJS/269/60 Optical monitoring from 2020-2022 of BL Lac (Yuan+, 2023) ================================================================================ Optical monitoring and intraday variabilities of BL Lacertae. Yuan Y.H., Du G.J., Fan J.H., Liu Y., Yang J.H., Ding G.Z., Pei Z.Y. =2023ApJS..269...60Y ================================================================================ ADC_Keywords: BL Lac objects; Photometry, SDSS Keywords: Galaxies ; Blazars ; CCD photometry Abstract: BL Lacertae is a key monitoring target of the 1.26m National Astronomical Observatory-Guangzhou University Infrared/Optical telescope. Within the monitored duration from 2020 September 4 to 2022 September 28, we report 13,948 observations at the g, r, and i bands (g band: 4498, r band: 4866, i band: 4584). (1) In the monitored duration, this source is located in a very bright and variable state. The maximum variabilities are {Delta}m_g_=2.013+/-0.073mag at g band, {Delta}m_r_=1.900+/-0.049mag at r band, and {Delta}m_i_=2.279+/-0.089mag at i band. (2) Among the gri intraday lightcurves, there are 104 portions of data sets displaying intraday variabilities (IDVs), with the IDV timescales ({Delta}T) being in the range of 15.84-375.84 minutes and the biggest variable value {Delta}m=0.430+/-0.041mag. (3) The distributions of {Delta}T show frequency-dependent behavior, and with the frequency increasing, {Delta}T tend to be shorter. The variable rates (V={Delta}m}/{Delta}T) from the g band are more intense than the values (V_r_) from the r band, but are more stable than the values (V_i_) from the i band. (4) On three days (2020-September-7, 2020-September-19, and 2022-September-7), we find the intraday periodic oscillations, whose periods are around 150 minutes, 232 minutes, and 150 minutes, respectively, and which might come from the source "flickering." (5) Based on the distributions between flux densities (F_gri_) and spectral indices ({alpha}), they show the bluer-when-brighter behaviors and some uneven locations, which should come from the ministructures of the jet, the shock-induced particle acceleration, or magnetic reconnection in the jet. Description: We used the 1.26m National Astronomical Observatory-Guangzhou University Infrared/Optical telescope (NGT), located at Xinglong station, National Astronomical Observatories, Chinese Academy of Sciences, to monitor the object BL Lacertae. The filters adopt standard Sloan Digital Sky Survey (SDSS) g, r, and i bands. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 22 02 43.29 +42 16 39.9 BL Lac = 1ES 2200+420 ---------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table2.dat 62 4865 gri observations of BL Lacertae (1ES 2200+420) -------------------------------------------------------------------------------- See also: J/ApJ/430/467 : Superluminal motions for extragal. sources (Vermeulen+, 1994) J/ApJ/833/77 : gamma-ray bright blazars optical polarization (Itoh+, 2016) J/ApJ/837/45 : 2006-2012 Rc-band & 4.8GHz obs. of AO 0235+164 (Fan+, 2017) J/ApJS/229/21 : VRI monitoring of the QSO 3C 273 in 2005-2016 (Xiong+, 2017) J/AJ/155/31 : 2005-2012 BVRI obs. of blazar S5 0716+714 (Hong+, 2018) J/A+A/620/A185 : Long-term optical monitoring of TeV Blazars (Nilsson+, 2018) J/ApJS/262/43 : NGT gri monitoring of the FSRQ 3C 454.3 (Yuan+, 2022) Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 7 F7.3 d gJD [97.69/851.9]? Julian date of g-band observation, gJD-2459000 9- 14 F6.3 mag gmag [12.6/14.7]? Observed SDSS g-band AB magnitude 16- 20 F5.3 mag e_gmag [0.005/0.2]? Uncertainty in gmag 22- 28 F7.3 d rJD [97.69/851.9] Julian date of r-band observation, rJD-2459000 30- 35 F6.3 mag rmag [11.7/13.7] Observed SDSS r-band AB magnitude 37- 41 F5.3 mag e_rmag [0.006/0.2] Uncertainty in rmag 43- 49 F7.3 d iJD [97.69/851.9]? Julian date of i-band observation, iJD-2459000 51- 56 F6.3 mag imag [10.7/13.1]? Observed SDSS i-band AB magnitude 58- 62 F5.3 mag e_imag [0.003/0.1]? Uncertainty in imag -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 15-Feb-2024