Q2237+0305 source structure and dimensions from light-curve simulation

Abstract

Assuming a two-component quasar structure model consisting of a central compact source and an extended outer feature, we produce microlensing simulations for a population of compact masses in the lensing galaxy of Q2237+0305. Such a model is a simplified version of that adopted to explain the brightness variations observed in Q0957. The microlensing light curves generated for a range of source parameters were compared to the light curves obtained in the framework of the Optical Gravitational Lensing Experiment program. With a large number of trials, we built, in the domain of the source structure parameters, probability distributions to find 'good' realizations of light curves. The values of the source parameters which provide the maximum of the joint probability distribution calculated for all the image components have been accepted as estimates for the source structure parameters. The results favour the twocomponent model of the quasar brightness structure over a single compact central source model, and in general the simulations confirm the Schild-Vakulik model that previously described successfully the microlensing and other properties of Q0957. Adopting 3300 km s −1 for the transverse velocity of the source, the effective size of the central source was determined to be about 2 × 10 15 cm, and ε ≈ 2 was obtained for the ratio of the integral luminosity of the outer feature to that of the central source.

Discovery of universal outflow structures above and below the accretion disc plane in radio-quiet quasars

“…The S‐S model calculations do not incorporate any influence from the dusty torus region and cannot therefore naturally reproduce the amplitude of the variability or the rapidity. The results of the study with unbiased calculations and unrestricted accretion disc sizes and allowing for the fractional contribution from dusty torus emission/reflection (Vakulik et al 2007) quite naturally match the amplitudes, durations and lensed fractions of the luminosity. The detection of reverberation between the luminous inner structure, presumably the inner edge of the accretion disc as in the S‐S model, and a large outer region would strongly favour limiting the S‐S model to the description of the inner luminosity only.…”

“…An initiating pulse with a characteristic duration of 50 proper days is followed by successive brightness features having longer durations, as would be expected if the reverberation region were of size comparable to or somewhat larger than the initiating region. The general pattern of four pulses sequenced as expected for the Elvis surface geometry is normally observed, and it is therefore unsurprising that studies of quasar microlensing have already shown that an inner structure having size scale expected for the accretion disc inner edge gives a microlensing pulse of only one‐third of the expected amplitude, which has already been interpreted to imply that outer luminous structure must contribute to the quasar’s continuum emission (Schild 1996; Vakulik et al 2007).…”

Analytical Methods in Gravitational Microlensing

“…), and this model will agree with the available data provided that an appropriate source size is chosen. On the other hand, a number of authors [4,16,[33][34][35][36][37][38][39] discussed delicate questions concerning determination a fine quasar structure from HAE. For example, the authors of [36] wrote that the GLITP data [28] on Q2237+0305 admit only accretion disc models (see also [4,39]).…”

“…We note that since the work by Kochanek [37], followed by a number of authors [4,35,[38][39][40][41][42], statistical methods dealing with the complete light curves of the GLS images have been developed. This approach is very attractive because it allows to take into account the whole aggregate of observational data on image brightness variations yielding estimates of the microlens masses and source model parameters.…”

“…Amplification for the Gaussian Source. Formula (38) has been used [5] to derive the amplification of a Gaussian source with the brightness distribution (42), the limbdarkening source, and the power-law source (see the next subsections).…”