Measurement of the photosphere oblateness of $?$ Cassiopeiae via Stellar Intensity Interferometry with the VERITAS Observatory
Year: 2025
Type: article
Abstract: We use the stellar intensity interferometry system implemented with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) at Fred Lawrence Whipple Observatory (FLWO) as a light collector to obtain measurements of the rapid rotator star $\gamma$ Cassiopeiae, at a wavelength of 416 nm. Using data from baselines sampling different position angles, we extract the size, oblateness, and projected orientation of the photosphere. Fitting the data with a uniform ellipse model yields a minor-axis angular diameter of $0.43\pm0.02$ mas, a major-to-minor-radius ratio of $1.28\pm0.04$, and a position angle of $116^\circ\pm5^\circ$ for the axis of rotation. A rapidly-rotating stellar atmosphere model that includes limb and gravity darkening describes the data well with a fitted angular diameter of $0.604^{+0.041}_{-0.034}$ mas corresponding to an equatorial radius of 10.9$^{+0.8}_{-0.6}~R_\odot$, a rotational velocity with a $1~\sigma$ lower limit at $97.7\%$ that of breakup velocity, and a position angle of $114.7^{+6.4}_{-5.7}$ degrees. These parameters are consistent with H$\alpha$ line spectroscopy and infrared-wavelength Michelson interferometric measurements of the star's decretion disk. This is the first measurement of an oblate photosphere using intensity interferometry.
DOI: 10.13016/m2kx38-mzr1
Authors: Archer, A., Aufdenberg, J. P., Bangale, P., Bartkoske, J. T., Benbow, W., Buckley, J. H., Chen, Y., Chin, N. B. Y., Christiansen, J. L., Chromey, A. J., Duerr, A., Godoy, M. Escobar, Feldman, S., Feng, Q., Filbert, S., Fortson, L., Furniss, A., Hanlon, W., Hervet, O., Hinrichs, C. E., Holder, J., Hughes, Z., Humensky, T. B., Jin, W., Johnson, M. N., Kertzman, M., Kherlakian, M., Kieda, D., Korzoun, N., LeBohec, T., Lisa, M. A., Lundy, M., Maier, G., Matthews, N., Moriarty, P., Mukherjee, R., Ning, W., Ong, R. A., Pandey, A., Pohl, M., Pueschel, E., Quinn, J., Rabinowitz, P. L., Ragan, K., Reynolds, P. T., Ribeiro, D., Roache, E., Rose, J. G., Sadeh, I., Saha, L., Santander, M., Scott, J., Sembroski, G. H., Shang, R., Tak, D., Tucci, J. V., Valverde, Janeth, Vassiliev, V. V., Williams, D. A., Wong, S. L., Collaboration, The VERITAS
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6903592668
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