MSc. Thesis Defense: AHMED ABDULLAH ABBASI
THROUGH DUST AND LIGHT: CONSTRAINING THE DISTANCE TO THE GBHT 4U 1630-47 THROUGH HIGH RESOLUTION MM AND X-RAY OBSERVATIONS
AHMED ABDULLAH ABBASI
Physics, MSc. Thesis, 2025
Thesis Jury
Prof.Dr. Emrah Kalemci (Thesis Advisor)
Prof.Dr. Unal Ertan
Prof.Dr. Tolga Guver
Date & Time: June 18th, 2025 – 12:00 PM
Place: Fens2019
Zoom Link: https://sabanciuniv.zoom.us/j/
Meeting ID: 948 550 7409
Keywords: Blackhole X-ray Binary, 4U 1630-47, Dust Scattering Halo, Molecular
Clouds, X-ray astronomy
Abstract
Accurately determining the distance to Galactic blackhole X-ray binaries is critical for understanding their intrinsic luminosities, accretion physics, and jet properties. However, for sources which are highly obscured by dust, traditional distance estimation methods often fail. In this thesis, we present a novel imaging-based methodology which utilizes high-resolution millimeter observations from the Atacama Pathfinder Experiment APEX combined with X-ray data from Chandra to constrain the distance to the galactic blackhole transient (GBHT) 4U 1630-47 through the modeling of its dust scattering halo (DSH). We identify 15 molecular clouds from the 12CO data and generate synthetic DSH images for all possible near/far configurations of these clouds across a grid of candidate source distances and subsequently fit the images both radially and azimuthally. Our analysis favors a source distance of 11.5 kpc, with strong constraints on several molecular clouds. We perform Monte Carlo analysis to quantify uncertainties and find a robust peak in best-fit distances at 11.5 kpc. While 13.6 kpc also yielded good statistical fits, it is ultimately discarded due to observational inconsistencies. This thesis demonstrates the power of combining high-resolution mm observations with X-ray imaging to resolve kinematic distance ambiguities and constrain the source distance. The methodology developed here builds upon the foundation laid in Kalemci et al. (2018), and is also presented in E. Kalemci (2025).