Analysis of microlensing events with latest generation telescopes.
| dc.contributor.author | Shah, Sarang | |
| dc.date.accessioned | 2020-02-27T22:50:38Z | |
| dc.date.available | 2020-02-27T22:50:38Z | |
| dc.date.issued | 2019 | en |
| dc.description.abstract | Gravitational microlensing is an astronomical phenomenon where the gravity of a foreground massive object bends the rays of light of a background source into images. Effectively, the background source appears to be magnified with respect to time. Since this does not require detection of light from the lens, gravitational microlensing can be used to study different populations of objects in the galaxy, even the extra-solar planets. This phenomenon was practically formulated and investigated since the last decade of 20th century by a few observing groups. Today gravitational microlensing is observed and monitored by fourth generation telescopes towards high density stellar fields like the Galactic Bulge, Large and Small Magellanic clouds. With the increased capabilities there are numerous microlensing events that are detected but not yet analysed. Analysing these events, especially formed by a binary lens is not only challenging but tedious task. However with a suitable model that explains the light curve, we can estimate the mass and distance to the objects that are unlikely to be detected by other methods like direct imaging, transit and radial velocity. In this thesis, I have shown how the microlensing data analysis can be done which not only includes filtering of the photometric data but also fitting of the appropriate microlensing model to the data. I also show how the prior knowledge about the nature of galaxy towards galactic bulge, the galactic model and higher order effects in microlensing can be used to constrain the lens mass and distance. I have analysed five microlensing events in this thesis. OGLE-2017-BLG-0192 and OGLE-2017-BLG-0103 are single lens single source events. The light curve of these events are explained by the orbital parallax effect. This galactic model analysis for these events gives the lens as a low mass star in the galactic disc. OGLE-2017-BLG-1170 is a microlensing event where the asymmetry in the peak of the light curve is caused by a secondary companion to the lens. This event was also observed due to Spitzer telescope which enabled us to measure the space parallax for this event. This galactic model analysis gives a pair of super-Jupiters located in the galactic bulge. OGLE-2018-BLG-1647 is a cusp approach microlensing event with a spike in the light curve close to the peak. The galactic model analysis of this event shows that the lens is a system of a high mass brown dwarf host and a Jupiter mass companion. The light curve of OGLE-2017-BLG-0380 needs a heuristic analysis and the small bump on the decreasing side can be explained by binary lens orbital motion of two masses in the galactic bulge where the primary is a dwarf star and the secondary companion is a brown dwarf. The analysis of these binary lens events show that there are pair of low mass objects in the galaxy which can be detected by only by gravitational microlensing. Unfortunately these events cannot be studied further by other methods because of the faintness and large distance to the lens. Nevertheless, growing samples of such low mass binaries suggest that there is a big population of such objects or even isolated low mass objects present in the galaxy. Overall, in this thesis, I show how helpful the latest generation microlensing survey telescopes are proving to characterise the gravitational micro-lenses. | en |
| dc.identifier.uri | http://hdl.handle.net/10092/18619 | |
| dc.identifier.uri | http://dx.doi.org/10.26021/7066 | |
| dc.language | English | |
| dc.language.iso | en | |
| dc.publisher | University of Canterbury | en |
| dc.rights | All Rights Reserved | en |
| dc.rights.uri | https://canterbury.libguides.com/rights/theses | en |
| dc.title | Analysis of microlensing events with latest generation telescopes. | en |
| dc.type | Theses / Dissertations | en |
| thesis.degree.discipline | Physics | en |
| thesis.degree.grantor | University of Canterbury | en |
| thesis.degree.level | Doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |
| uc.bibnumber | 2829881 | |
| uc.college | Faculty of Science | en |