A&A manuscript no. ASTRONOMY (will be inserted by hand later) AND Your thesaurus codes are: ASTROPHYSICS 20(04.01.1; 11.01.2; 11.17.4 3C 273; 13.18.1; 13.21.1; 13.25.2) March 27, 2018 30 years of multi-wavelength observations of 3C273⋆ M. T¨urler1,2, S. Paltani1,2, T.J.-L. Courvoisier1,2, M.F. Aller3, H.D. Aller3, A. Blecha1, P. Bouchet4,5, M. Lainela6, I.M. McHardy7, E.I. Robson8,9, J.A. Stevens9,10, H. Terasranta¨ 11, M. Tornikoski11, M.-H. Ulrich12, E.B. Waltman13, W. Wamsteker14, and M.C.H. Wright15 1 Geneva Observatory, ch. des Maillettes 51, CH-1290 Sauverny, Switzerland 2 INTEGRAL Science Data Centre, ch. d’Ecogia´ 16, CH-1290 Versoix, Switzerland 3 University of Michigan, Department of Astronomy, 817 Dennison Building, Ann Arbor, MI 48 109, USA 4 European Southern Observatory, Casilla 19 001, Santiago 19, Chile 5 Cerro Tololo Inter-American Observatory, Casilla 603 – La Serena, Chile 6 Tuorla Observatory, V¨ais¨al¨antie 20, FIN-21 500 Piikki¨o, Finland 7 Department of Physics, University of Southampton, Southampton SO9 5NH, United Kingdom 8 Centre for Astrophysics, University of Central Lancashire, Preston, PR1 2HE, United Kingdom 9 Joint Astronomy Centre, 660 North A‘oh¯ok¯u Place, University Park, Hilo, Hawaii 96 720, USA 10 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, United Kingdom 11 Mets¨ahovi Radio Observatory, Mets¨ahovintie, FIN-02 540 Kylm¨al¨a, Finland 12 European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85 748 Garching bei M¨unchen, Germany 13 Remote Sensing Division, Naval Research Laboratory, Washington, DC 20 375-5351, USA 14 ESA-Vilspa, P.O. Box 50 727, E-28 080 Madrid, Spain 15 Department of Astronomy, University of California, Berkeley, CA 94 720, USA Received date / Accepted date Abstract. We present a wide multi-wavelength database of 1. Introduction most observations of the quasar 3C273 obtained during the last 30 years. This database is the most complete set of obser- 3C273 is the brightest quasar on the sky, with a mean V vations available for an active galactic nucleus (AGN). It con- band magnitude of 12.9. It can be easily observed from both hemispheres, thanks to its position very close to the celestial tains nearly 20000 observations grouped together into 70 light h m s ◦ ′ ′′ curves covering 16 orders of magnitude in frequency from the equator: α =12 29 06.70 , δ = +02 03 08.6 (J2000.0) and at high galactic latitude: = 289.95, = 64.36. The redshift radio to the γ-ray domain. l b + of 3C273 is z =0.158, which corresponds to an effective dis- The database is constituted of many previously unpublished −1 tance of 440 h Mpc, with a Hubble constant defined as H0 = observations and of most publicly available data gathered in −1 −1 100 h km s Mpc and a deceleration parameter of q0 = 0.05. the literature and on the World Wide Web (WWW). It is com- 7 arXiv:astro-ph/9807283v1 28 Jul 1998 The mean bolometric flux received from 3C273 between 10 plete to the best of our knowledge, except in the optical (UBV) and 1025 Hz (see Fig. 6) is 1.910−9 ergcm−2 s−1. If the whole domain where we chose not to add all observations from the spectrum of 3C 273 is emitted isotropically, this flux would literature. In addition to the photometric data, we present the correspond to a bolometric luminosity of 6.01046 −2 erg s−1. spectra of 3C273 obtained by the International Ultraviolet Ex- h The host galaxy of 3C273 is an elliptical (E4) galaxy, which plorer (IUE) satellite. In the X-ray domain,we used the spectral has an outer radius of about 15′′ and a V band magnitude of fit parameters from the literature to construct the light curves. 16.4 (Bahcall et al. 1997). Apart from describing the data, we show the most repre- 3C273 has a jet with apparent superluminal motion that sentative light curves and the average spectrum of 3C273. The ends with a hot spot called 3C273A. It is among the few ac- database is available on the WWW in a homogeneousand clear tive galactic nuclei (AGN) detected at energies above 100MeV form and we wish to update it regularly by adding new obser- by the Energetic Gamma-Ray Experiment Telescope (EGRET) vations. on board the Compton Gamma-Ray Observatory (CGRO) and is thus often classified as a blazar despite its prominent blue- Key words: astronomical data bases: miscellaneous – galax- bump and its strong emission-lines. This coexistence of blazar- ies: active – quasars: individual: 3C 273 – radio continuum: and Seyfert-like properties makes 3C273 be a very interesting galaxies – ultraviolet: galaxies – X-rays: galaxies but complex object. The detection of strong ultraviolet variability in 1982 Send offprint requests to: M. T¨urler (ISDC) (Courvoisier & Ulrich 1985) was at the origin of the multi- ⋆ Data available at: http://obswww.unige.ch/3c273/ wavelength monitoring campaign that started in 1983. This ob- Correspondence to: [email protected] servation effort, which is still going on, led to several publi- 2 M. T¨urler et al.: 30 years of multi-wavelength observations of 3C 273 Fig. 1. Time versus frequency distribution of all observations of 3C273 presently in the database. This figure summarizes more than 30years of observations in the spectral range from 10MHz to 1GeV, covering 16 orders of magnitude in frequency. The relative intensity of the observed flux (log(ν Fν )) is given by a greyscale cations on the multi-wavelength properties of 3C273 (Cour- AGN in general. The detailed studies of the blue-bumpvariabil- voisier et al. 1987, 1990; Lichti et al. 1995; von Montigny et al. ity (Paltani et al. 1998) and of the millimetre-to-radio flaring 1997). More detailed variability studies in specific spectral do- behaviour (T¨urler et al. in preparation) are examples of what mains were also possible with these observations (e.g. Turner can be done with these data and we hope that this analysis ef- et al. 1990; Cappi et al. 1998 (X-rays); Ulrich et al. 1988 (ultra- fort will continue elsewhere, thanks to this database. violet); Courvoisier et al. 1988 (optical and infrared); Robson et al. 1993 (infrared to radio); Stevens et al. 1998 (millimetre 2. Radio observations to radio)). We grouped together all radio measurements into 17 light The end of the IUE operations and the writing of a review curves from 15MHz to 37GHz (see Table 1). The 8.0GHz paper on 3C273 (Courvoisier 1998) is a good opportunity to light curve obtained with the 26m radio telescope of the make all these data available. The aim of this contribution is University of Michigan Radio Astronomy Observatory (UM- to present and to maintain a high quality publicly available RAO) is the most complete light curve of 3C273 obtained database of most observations of 3C273. Publishing such a by a single observatory during more than 30years (see Fig. wide database is not a goal in itself, but has the purposeto stim- 2). It is therefore given alone in the database, whereas other ulate variability analyses by a large community of astronomers. observations around 8GHz are included in the 10GHz light The huge effort of observing 3C273 during more than 30 years curve. The UMRAO monitoring of 3C273 at 14.5GHz and should lead to a better understandingof this object and henceof 4.8GHz started respectively in 1974 and in 1978. The 5GHz M. T¨urler et al.: 30 years of multi-wavelength observations of 3C 273 3 and the 15GHz light curves contain mainly these obser- Radio Astronomical Observatory (NRAO) at Kitt Peak (Dent vations. Details on the instrumentation and the calibration & Hobbs 1973). used at the UMRAO are given by Aller et al. (1985) to- We did not include all the isolated observations from early gether with the data obtained until 1984. We do not include radio catalogues. We added only the flux measurements re- here the polarization observations, which are publicly avail- ported by K¨uhr et al. (1981), since they are all recalibrated to able at the UMRAO Database Interface on the WWW at the scale of Baars et al. (1977), and the total flux densities (core http://www.astro.lsa.umich.edu/obs/radiotel/umrao.html. plus jet) reported by Conway et al. (1993). At very low fre- Shorter wavelengths radio observations at 22.2 and quency (< 30MHz), we added the observations from Braude et 36.8GHz were performed since 1980 both with the 14m tele- al. (1979), but multiplied by the scaling factor of 1.23 used for scope of the Mets¨ahovi Radio Observatory, Finland and with other objects by K¨uhr et al. (1981). In the 100–1000MHz range the 22m telescope of the Crimean Astrophysical Observatory, other isolated observations are from Artyukh (1984), Denni- Ukraine. The 22GHz and 37GHz light curves are very well son et al. (1981), Fanti et al. (1979, 1981), Fisher & Erickson sampled since 1986 except for a gap in the summer of 1994 (1980) and Hunstead (1972). Above 1GHz, some isolated ra- due to the replacement of the Mets¨ahovi antenna (see Fig. 2). dio observations were found in Jones et al. (1981), Landau et The observations during 1980–85 and during 1985–90 are re- al. (1983) and Lichti et al. (1995). All these data were included spectively published in Salonen et al. (1987) and in Ter¨asranta in the respective light curves. et al. (1992), together with details on the measurementmethods The radio light curves of 3C273 at 8.0GHz, 15GHz and and the calibrations.