individual
What campus are you from?
Daytona Beach
Authors' Class Standing
Benjamin Katz, Sophomore
Lead Presenter's Name
Benjamin Katz
Faculty Mentor Name
Dr. Aufdenberg
Abstract
Only one A-type supergiant, Deneb, has a measured angular diameter from long-baseline interferometric measurements. The next two brightest A-type supergiants, η Leo and ν Cep, are expected to have angular diameters below 1 milliarcsecond, well matched for the angular resolution of intensity interferometry with Imaging Air Cherenkov Telescope (IACT) arrays, such as VERITAS. While VERITAS has measured stars in a wide (20 nm) band, measurements in a very narrow band containing only the Hδ line have not been made. To predict the expected squared visibility across this line, we constructed stellar atmosphere models for η Leo and ν Cep. Here we show models of center-to-limb variations for both stars. Model visibilities for both stars in a narrow (0.2 nm) band correspond to ~4.5% larger angular diameters relative to an adjacent wide (10 nm) band. The limb-darkening correction for ν Cep is higher than for η Leo: 11.9% vs. 9.4%, as expected from ν Cep’s surface gravity, which is over four times lower. The narrow band (0.2 nm) required to see a 4% difference in angular diameter between the line and continuum is 100 times narrower than currently used for IACT arrays doing intensity interferometry. Future instruments with higher sensitivity and larger apertures could enable direct tests of wavelength-dependent limb darkening across Balmer lines in A-type supergiants beyond Deneb.
Did this research project receive funding support from the Office of Undergraduate Research.
No
Interferometric Constraints on Balmer-Line Limb Darkening in A-type Supergiant Stars
Only one A-type supergiant, Deneb, has a measured angular diameter from long-baseline interferometric measurements. The next two brightest A-type supergiants, η Leo and ν Cep, are expected to have angular diameters below 1 milliarcsecond, well matched for the angular resolution of intensity interferometry with Imaging Air Cherenkov Telescope (IACT) arrays, such as VERITAS. While VERITAS has measured stars in a wide (20 nm) band, measurements in a very narrow band containing only the Hδ line have not been made. To predict the expected squared visibility across this line, we constructed stellar atmosphere models for η Leo and ν Cep. Here we show models of center-to-limb variations for both stars. Model visibilities for both stars in a narrow (0.2 nm) band correspond to ~4.5% larger angular diameters relative to an adjacent wide (10 nm) band. The limb-darkening correction for ν Cep is higher than for η Leo: 11.9% vs. 9.4%, as expected from ν Cep’s surface gravity, which is over four times lower. The narrow band (0.2 nm) required to see a 4% difference in angular diameter between the line and continuum is 100 times narrower than currently used for IACT arrays doing intensity interferometry. Future instruments with higher sensitivity and larger apertures could enable direct tests of wavelength-dependent limb darkening across Balmer lines in A-type supergiants beyond Deneb.