TY - JOUR
T1 - Multiwavelength monitoring of the BL lacertae object PKS 2155-304 in 1994 MAY. I. The ground-based campaign
AU - Pesce, Joseph E.
AU - Urry, C. Megan
AU - Maraschi, Laura
AU - Treves, Aldo
AU - Grandi, Paola
AU - Kollgaard, Ronald I.
AU - Pian, Elena
AU - Smith, Paul S.
AU - Aller, Hugh D.
AU - Aller, Margo F.
AU - Barth, Aaron J.
AU - Bucklev, David A.H.
AU - Covino, Elvira
AU - Filippenko, Alexei V.
AU - Hooper, Eric J.
AU - Joner, Michael D.
AU - Kedziora-Chudczer, Lucyna
AU - Kilkenny, David
AU - Knee, Lewis B.G.
AU - Kunkel, Michael
AU - Layden, Andrew C.
AU - Magalhães, Antonio Mario
AU - Marang, Fred
AU - Margoniner, Vera E.
AU - Palma, Christopher
AU - Pereyra, Antonio
AU - Rodrigues, Claudia V.
AU - Schutte, Andries
AU - Sitko, Michael L.
AU - Tornikoski, Merja
AU - Van Der Walt, Johan Der
AU - Van Wyk, Francois
AU - Whitelock, Patricia A.
AU - Wolk, Scott J.
PY - 1997
Y1 - 1997
N2 - Optical, near-infrared, and radio observations of the BL Lac object PKS 2155-304 were obtained simultaneously with a continuous UV/EUV/X-ray monitoring campaign in 1994 May. Further optical observations were gathered throughout most of 1994. The radio, millimeter, and near-infrared data show no strong correlations with the higher energies. The optical light curves exhibit flickering of 0.2-0.3 mag on timescales of 1-2 days, superposed on longer timescale variations. Rapid variations of ∼0.01 mag minute-1, if real, are the fastest seen to date for any BL Lac object. Small (0.2-0.3 mag) increases in the V and R bands occur simultaneously with a flare seen at higher energies. All optical wave bands (UBVRI) track each other well over the period of observation, with no detectable delay. For most of the period the average colors remain relatively constant, although there is a tendency for the colors (in particular, B- V) to vary more when the source fades. In polarized light, PKS 2155 -304 showed strong color dependence (polarization increases toward the blue, Pv/PI = 1.31) and the highest optical polarization (U = 14.3%) ever observed for this source. The polarization variations trace the flares seen in the UV flux. For the fastest variability timescale observed, we estimate a central black hole mass of ≲1.5 × 109(δ/10) M⊙, consistent with UV and X-ray constraints and smaller than previously calculated for this object.
AB - Optical, near-infrared, and radio observations of the BL Lac object PKS 2155-304 were obtained simultaneously with a continuous UV/EUV/X-ray monitoring campaign in 1994 May. Further optical observations were gathered throughout most of 1994. The radio, millimeter, and near-infrared data show no strong correlations with the higher energies. The optical light curves exhibit flickering of 0.2-0.3 mag on timescales of 1-2 days, superposed on longer timescale variations. Rapid variations of ∼0.01 mag minute-1, if real, are the fastest seen to date for any BL Lac object. Small (0.2-0.3 mag) increases in the V and R bands occur simultaneously with a flare seen at higher energies. All optical wave bands (UBVRI) track each other well over the period of observation, with no detectable delay. For most of the period the average colors remain relatively constant, although there is a tendency for the colors (in particular, B- V) to vary more when the source fades. In polarized light, PKS 2155 -304 showed strong color dependence (polarization increases toward the blue, Pv/PI = 1.31) and the highest optical polarization (U = 14.3%) ever observed for this source. The polarization variations trace the flares seen in the UV flux. For the fastest variability timescale observed, we estimate a central black hole mass of ≲1.5 × 109(δ/10) M⊙, consistent with UV and X-ray constraints and smaller than previously calculated for this object.
KW - BL lacertae objects: individual (PKS 2155-304)
KW - Galaxies: active
KW - Galaxies: photometry
KW - Polarization
UR - http://www.scopus.com/inward/record.url?scp=21744455046&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=21744455046&partnerID=8YFLogxK
U2 - 10.1086/304538
DO - 10.1086/304538
M3 - Article
AN - SCOPUS:21744455046
SN - 0004-637X
VL - 486
SP - 770
EP - 783
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2 PART I
ER -