Flux and color variations of the quadruply imaged quasar HE 0435-1223^⋆

¹ Département d’Astrophysique, Géophysique et Océanographie, Bât. B5C, Sart Tilman, Université de Liège, 4000 Liège 1, Belgique
e-mail: ricci@astro.ulg.ac.be
² Main Astronomical Observatory, Academy of Sciences of Ukraine, Zabolotnoho 27, 03680 Kyiv, Ukraine
³ Centro de Astro-Ingeniería, Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago, Chile
⁴ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
⁵ Dipartimento di Fisica “E.R. Caianiello”, Università degli Studi di Salerno, via Ponte Don Melillo, 84085 Fisciano (SA), Italy
⁶ Instituto Nazionale di Fisica Nucleare, Sezione di Napoli, Italy
⁷ SUPA, University of St Andrews, School of Physics & Astronomy, North Haugh, St Andrews, KY16 9SS, UK
⁸ Deutsches SOFIA Institut, Universitaet Stuttgart, Pfaffenwaldring 31, 70569 Stuttgart, Germany
⁹ Istituto Internazionale per gli Alti Studi Scientifici (IIASS), Vietri Sul Mare (SA), Italy
¹⁰ Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
¹¹ Department of Physics & Astronomy, Aarhus University, Ny Munkegade, 8000 Aarhus C, Denmark
¹² Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, 2100 Copenhagen Ø, Denmark
¹³ KASI – Korea Astronomy and Space Science Institute, 61-1 Hwaam-dong, Yuseong-gu, Daejeon 305-348, Republic of Korea
¹⁴ National Space Institute, Technical University of Denmark, 2800 Lyngby, Denmark
¹⁵ Astronomisches Rechen-Institut, Zentrum für Astronomie, Universität Heidelberg, Mönchhofstraße 12-14, 69120 Heidelberg, Germany
¹⁶ Dipartimento di Ingegneria, Università del Sannio, Corso Garibaldi 107, 82100 Benevento, Italy
¹⁷ Bellatrix Astronomical Observatory, Center for Backyard Astrophysics, Ceccano (FR), Italy
¹⁸ Physics Department, Sharif University of Technology, Tehran, Iran
¹⁹ European Southern Observatory, Casilla 19001, Santiago 19, Chile
²⁰ Max Planck Institute for Solar System Research, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
²¹ Astrophysics Group, Keele University, Newcastle-under Lyme, ST5 5BG, UK
²² Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
²³ INAF – Osservatorio Astronomico di Brera, 23807 Merate, Italy
²⁴ SOFIA Science Center, NASA Ames Research Center, Mail Stop N211-3, Moffett Field CA 94035, USA
²⁵ Centre for Star and Planet Formation, Geological Museum, Øster Voldgade 5, 1350 Copenhagen, Denmark

Received: 23 November 2010
Accepted: 10 January 2011

Abstract

Aims. We present VRi photometric observations of the quadruply imaged quasarHE0435-1223, carried out with the Danish 1.54 m telescope at the La Silla Observatory. Our aim was to monitor and study the magnitudes and colors of each lensed component as a function of time.

Methods. We monitored the object during two seasons (2008 and 2009) in the VRi spectral bands, and reduced the data with two independent techniques: difference imaging and point spread function (PSF) fitting.

Results. Between these two seasons, our results show an evident decrease in flux by  ≈ 0.2–0.4 magnitudes of the four lensed components in the three filters. We also found a significant increase ( ≈ 0.05–0.015) in their V − R and R − i color indices.

Conclusions. These flux and color variations are very likely caused by intrinsic variations of the quasar between the observed epochs. Microlensing effects probably also affect the brightest “A” lensed component.