Astrophysics Research
Dr. Parshati Patel has always been fascinated by the formation of planets and stars! She always found a way to bring those topics into her research as she pursued her undergraduate and graduate studies! You can check out her research projects and thesis below:
PhD Thesis - Investigating Gaseous Disks around Herbig Be Stars
Supervisors: Dr. Aaron Sigut and Dr. John Landstreet
Herbig Be stars are massive, pre-main sequence (young) stars that inherit a circumstellar disk of dust and gas from the star formation phase. The region close to the star is gaseous as dust is thought to have evaporated due to high temperatures, and this region is currently poorly understood. Using the non-LTE circumstellar disk codes BEDISK and BERAY, as well as observed spectra (3700 to 10,500 \AA ) from the ESPaDOnS instrument on Canada France Hawaii Telescope, we attempted to constrain the physical properties of this inner, gaseous region. By comparing synthetic line profiles of hydrogen and ionized metals with the observed line profiles, we hoped to understand the geometry, density structure, and kinematics of the gaseous disk.
Thesis: "The Inner Gaseous Disks of Herbig Be Stars"
Papers:
If interested, you can watch my Ph.D. Public Lecture on Youtube!
This is a theoretical image of a Be star seen at the infrared wavelength band (5 microns) as computed by my Ph.D. supervisor’s BERAY code.
Image Credit: Aaron Sigut (2011)
Masters Project: Modelling the Hα-UBV Signature of Disk Growth and Dissipation in Classical Be Stars
Supervisors: Dr. Aaron Sigut and Dr. John Landstreet
Be stars show short and long-term variations in their spectra due to the presence of the circumstellar disk and it is the long-term variations that are attributed to the formation and dissipation of the circumstellar disk. Be stars show a correlation between Hα emission, which is produced in the disk, and UBV colours. These correlations are likely determined by the viewing angle of the observer, and these correlations can be useful to constraint the scale height of the circumstellar disks and the extent of gravitational darkening of the central star. In this report, we investigate these correlations by using BEDISK and BERAY codes to reproduce the emission and colours at different viewing angles for a simple model. These models are shown to be consistent with the observed correlations showing both positive and negative correlations between Hα emission and UBV colours. To further investigate the effect of the disk scale height on these correlations, the emission and colours were produced for a disk with an enhanced scale height. For higher inclinations, the enhanced scale height models show a large change in brightness compared to the basic model, suggesting that the scale height of the disk is important at such inclinations. Be stars, being rapid rotators, are darker at the equator and this can affect UBV colours. Gravitationally darkened models show a reduced change in colours at higher rotation rates which are close to the critical velocity.
Paper:
Hα equivalent width (Å, top panel) and change in V-magnitude (bottom panel) as a function of time for the B1V (solid lines) and B5V (dashed lines) models seen nearly pole-on at i = 15°. All of the models assumed a thin, hydrostatic disk with H set by Equation (2) in the paper, and gravitational darkening of the central B star was not included. The disk grows for one year and then dissipates over one year.
If you are looking for information on Parshati’s STEM Engagement Research, please have a look at the STEM Engagement Research page!