NGC 5128, J.L. Sersic, Atlas de Galaxias Australes, 1968
NGC 253, J.L. Sersic, Atlas de Galaxias Australes, 1968
1st Extragalactic Astronomy Meeting, 1975, J.L. Sersic, T.G. Catellanos, P. Kaufman
NGC 2442, J.L. Sersic, Atlas de Galaxias Australes, 1968
2nd Extragalactic Astronomy Meeting, 1987
NGC 2997, J.L. Sersic, Atlas de Galaxias Australes, 1968
3rd Extragalactic Astronomy Meeting, 1996
NGC 55, J.L. Sersic, Atlas de Galaxias Australes, 1968

Weiss, Joaquin

Argentina Facultad de Ciencias Astronomicas y Geofisicas, La Plata (FCAGLP)

The color behavior of the Blazar PKS 2155-304: analysis of two decades of data taken at Argentine facilities

Blazars are a subclass of Active Galactic Nuclei (AGNs). Based on their emission and absorption line features at the optical range, they are divided into BL Lac and Flat Spectrum Radio Quasars (FSRQ).  One of the main features of blazars is the presence of temporal variability in their flux across the entire electromagnetic spectrum. According to the color-brightness behavior, BL Lac objects tend to become bluer as the source’s brightness increases (Bluer when brighter, BWB), while FSRQs are more like redder when brighter (RBW). However, recent results have shown that both BWB and RBW objects tend to stabilize their color as their brightness increases even further, calling them Bluer-stable when brighter (BSWB) and Redder-stable when brighter (RSWB). Through the detailed study of the optical flux behavior in blazars it is possible to infer the conditions under which the observed emission is generated in the source.

In this work, we present the results obtained for the blazar PKS 2155-304, a BL Lac at z = 0.116. This object has been detected from Radio to TeV energies, being one of the brightest in the southern hemisphere. Our research group has observed this source at different Argentine astronomical facilities (e.g., CASLEO, Bosque Alegre), with data spanning over more than two decades. Using these photometric data, in this work we present the results of a detailed analysis of the V- and R-band behavior of PKS 2155-304, with emphasis on the spectral index changes. These results are compared with those reported in the literature.

PROGRAM