Be it unresolved: Extracting time delays from unresolved light curves

Speaker

Satadru Bag
Korea Astronomy and Space Science Institute (Republic of Korea)

Abstract

Gravitationally (strong) lensed transients, like supernovae (SNe), quasars, have become important in cosmology. Since the light corresponding to multiple images traverses different paths it has cosmological information. By measuring the time delay between images one can obtain independent constraints on the Hubble constant, the evolution of dark energy, spatial curvature etc. The light curves of SNe and quasars have different properties, however, lensed SNe and quasars have their own advantages. For example, the detection of lensed SNe are extremely rare as compared to that of lensed quasars but the formers have much better understood light curves. The upcoming time-domain surveys will observe a lot of lensed systems of both kinds of sources. However, many will have the images spatially unresolved, with the observed lightcurve a superposition of time-delayed image fluxes. We investigate whether unresolved images can be recognized as lensed sources given only lightcurve information and whether time delays can be extracted robustly.
In this talk, I will discuss a few such interesting methods that can identify the unresolved lensed systems of both source kinds, namely SN and quasar. Most importantly, these techniques are very much generic and, hence, do not assume any particular property of the sub-classes of the sources, such as the type of SNe, the flux variability of quasars etc. These techniques can be very useful in detecting the lensed systems in future optical surveys and measuring the time delays at the same time to improve our understanding of the cosmos.

Date and Time

April 29 2021
4pm KST (= 7am UTC)

Recording

Link to the recording on Youtube