Joining forces: 30 years of optical monitoring of the Einstein Cross

Abstract

We present an extended optical monitoring of the quadruply-imaged gravitationally lensed quasar QSO 2237+0305, the Einstein Cross, including observations from different observatories in both hemispheres and using a new photometric technique. This technique uses a region far enough from the lens system to determine accurately the sky background level, and minimises contamination from the lensing galaxy by combining analytical and numerical modeling of its structure. The resulting light curves of the four quasar images describe variations across practically the entire optical spectrum and span about 9000 days in the $VRI$ bands. The multi-band microlensing variability is captured with an unprecedented level of detail, and a preliminary microlensing analysis reveals an almost linear scaling of source radius with wavelength, providing direct evidence for the wavelength-dependent structure of the region contributing to optical passband fluxes. Specifically, assuming a mean microlens mass $⟨M⟩$ = 0.3 ${\mathrm{M}}_{\odot }$ and concentric Gaussian sources that move according to the velocity distribution peaks (speed and direction) reported in a previous microlensing analysis, we find that the half-light radius of the $g$-band source is 9.6 $\pm$ 2.7 lt-day and the size of the sources grows with wavelength with a power-law index of $\alpha$ = 0.94 $\pm$ 0.05. We conclude that these long-term light curves set stringent empirical constraints on models of quasar emission and microlensing physics.

arXiv commentAccepted to A&A; 18 pages, 6 long tables (Tables C.1-C.6) are available at the CDS [minor change to the title]

References in corpus (32)

• Magnetic Stress at the Marginally Stable Orbit: Altered Disk Structure, Radiation, and Black Hole Spin Evolution
• Quantitative Interpretation of Quasar Microlensing Light Curves
• Sizes and Temperature Profiles of Quasar Accretion Disks from Chromatic Microlensing
• Measuring the Remnant Mass Function of the Galactic Bulge
• The Variable Diffuse Continuum Emission of Broad Line Clouds
• Microlensing variability in the gravitationally lensed quasar QSO 2237+0305 = the Einstein Cross. II. Energy profile of the accretion disk
• The multiple quasar Q2237+0305 under a microlensing caustic
• Chandra Observations of QSO 2237+0305
• Imaging a Quasar Accretion Disk with Microlensing
• Microlensing Evidence That A Type 1 Quasar Is Viewed Face On
• The Optical Gravitational Lensing Experiment. A Hunt for Caustic Crossings in QSO 2237+0305
• The Transverse Peculiar Velocity of the Q2237+0305 Lens Galaxy and the Mean Mass of Its Stars
• Microlensing variability in the gravitationally lensed quasar Q2237+0305 = the Einstein Cross, I. Spectrophotometric monitoring with the VLT
• The Einstein Cross: constraint on dark matter from stellar dynamics and gravitational lensing
• The gravitational lens MG0414+0534: a link between red galaxies and dust
• QSO 2237+0305 VR light curves from Gravitational Lenses International Time Project optical monitoring
• An X-Ray Microlensing Test of AU-Scale Accretion Disk Structure in Q2237+0305
• Stars and dark matter in the spiral gravitational lens 2237+0305
• Quasar Microlensing Variability Studies Favor Shallow Accretion Disk Temperature Profiles
• Observational determination of the time delays in gravitational lens system Q2237+030
• Structure of the Accretion Disk in the Lensed Quasar Q2237+0305 from Multi-Epoch and Multi-Wavelength Narrow Band Photometry
• Color Effects Associated with the 1999 Microlensing Brightness Peaks in Gravitationally Lensed Quasar Q2237+0305
• New database for a sample of optically bright lensed quasars in the northern hemisphere
• Gravitational Microlensing by Random Motion of Stars: Analysis of Light Curves
• Fast simulations of extragalactic microlensing
• Liverpool-Maidanak monitoring of the Einstein Cross in 2006$-$2019. I. Light curves in the $gVrRI$ optical bands and microlensing signatures
• Diffuse emission in microlensed quasars and its implications for accretion-disk physics
• Resolving the Vicinity of Supermassive Black Holes with Gravitational Microlensing
• A Second-Order Moment of Microlensing Variability as a Novel Tool in Extragalactic Research
• Free-floating "planets'' in the macrolensed quasar Q2237+0305
• Primordial black holes in the main lensing galaxy of FBQ 0951+2635
• Detection of colour variations from gravitational microlensing observations in the quadruple quasar HE0435-1223: Implications for the accretion disk