2007A&A...469..503D


C.D.S. - SIMBAD4 rel 1.7 - 2021.03.03CET04:26:43

2007A&A...469..503D - Astronomy and Astrophysics, volume 469, 503-510 (2007/7-2)

REM near-IR and optical multiband observations of PKS 2155-304 in 2005.

DOLCINI A., FARFANELLI F., CIPRINI S., TREVES A., COVINO S., TOSTI G., PIAN E., SBARUFATTI B., MOLINARI E., CHINCARINI G., ZERBI F.M., MALASPINA G., CONCONI P., NICASTRO L., PALAZZI E., TESTA V., VITALI F., ANTONELLI L.A., DANZIGER J., TAGLIAFERRI G., MEURS E., VERGANI S., FERNANDEZ-SOTO A., DISTEFANO E., CUTISPOTO G. and D'ALESSIO F.

Abstract (from CDS):

Spectral variability is the main tool for constraining emission models of BL Lac objects. By means of systematic observations of the BL Lac prototype PKS 2155-304 in the infrared-optical band, we explore variability on scales of months, days, and hours. We made our observations with the robotic 60 cm telescope REM located at La Silla, Chile, and VRIJHK filters were used. PKS 2155-304 was observed from May to December 2005. The wavelength interval explored, the total number of photometric points, and the short integration time render our photometry substantially superior to previous ones for this source. On the basis of the intensity and colour, we distinguish three different states of the source, each lasting months, which include all those described in the literature. In particular, we report the highest state ever detected in the H band. The source varied by a factor of 4 in this band, much more than in the V band (a factor ≃2). The source softened with increasing intensity, in contrast to the general pattern observed in the UV-X-ray bands. On five nights in November we had nearly continuous monitoring for 2-3h. A variability episode on a time scale of τ≃24h is well-documented, and a much more rapid flare with τ=1-2h, is also apparent, but is supported by relatively few points. The overall spectral energy distribution of PKS 2155-304 is commonly described by a synchrotron-self-Compton model. The optical infrared emission is in excess of the expectation of the model in its original formulation. This can be explained by a variation in the frequency of the synchrotron peak, which is not unprecedented in BL Lacs.

Abstract Copyright:

Journal keyword(s): galaxies: active - galaxies: BL Lacertae objects: individual: PKS 2155-304

VizieR on-line data: <Available at CDS (J/A+A/469/503): tablea1.dat>

Errata: erratum vol. 476, p. 1219 (2007)

CDS comments: Table 2 : ref. stars A,B and C are in SIMBAD with their 2MASS identifications.

Simbad objects: 10

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Number of rows : 10

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 3C 66A BLL 02 22 39.6111630878 +43 02 07.797284539   15.71 15.21 14.5   ~ 807 1
2 QSO B0537-441 BLL 05 38 50.36155219 -44 05 08.9389165   15.77 16.48 16   ~ 804 2
3 3C 279 Bla 12 56 11.1664521013 -05 47 21.531840471   18.01 17.75 15.87   ~ 2752 2
4 4C 39.49 BLL 16 53 52.21668494 +39 45 36.6089458 14.09 14.15 13.29 8.26   ~ 1954 2
5 2MASS J21584233-3010274 * 21 58 42.3391094811 -30 10 27.390143741     13.899     ~ 1 0
6 2MASS J21584380-3017157 * 21 58 43.8067143221 -30 17 15.772180095     13.822     ~ 1 0
7 [DAT2004] PKS 2155-304 C4 * 21 58 46.5032659934 -30 17 51.335310498     13.179     ~ 2 0
8 QSO B2155-304 BLL 21 58 52.0651817803 -30 13 32.120657891   13.36 13.09 12.62   ~ 1591 1
9 V* EZ Aqr Er* 22 38 33.576000 -15 17 59.75700 15.762 14.33 12.38 12.12 8.677 M5V 287 1
10 3C 454.3 Bla 22 53 57.74798 +16 08 53.5611   16.57 16.10 15.22   ~ 2557 2

    Equat.    Gal    SGal    Ecl

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