2025ApJ...995..191A

Query : 2025ApJ...995..191A

2025ApJ...995..191A - Astrophys. J., 995, 191 (2025/December-3)

Measurement of the Photosphere Oblateness of γ Cassiopeiae via Stellar Intensity Interferometry with the VERITAS Observatory.

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., ESCOBAR GODOY M., 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 J., VASSILIEV V.V., WILLIAMS D.A., WONG S.L. (The VERITAS Collaboration)

Abstract (from CDS):

We use the stellar intensity interferometry system implemented with the Very Energetic Radiation Imaging Telescope Array System at Fred Lawrence Whipple Observatory as a light collector to obtain measurements of the rapid rotator star γ 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 ± 0.02 mas, a major-to-minor-radius ratio of 1.28 ± 0.04, and a position angle of 116° ± 5° 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 $0.60{4}_{-0.034}^{+0.041}$ mas corresponding to an equatorial radius of ${10.9}_{-0.6}^{+0.8}\,{R}_{\odot }$, a rotational velocity with a 1σ lower limit at 97.7% of breakup velocity, and a position angle of $114\mathop{.}\limits^{{\rm{^\circ }}}{7}_{-5.7}^{+6.4}$. These parameters are consistent with Hα 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.

Abstract Copyright: © 2025. The Author(s). Published by the American Astronomical Society.

Journal keyword(s): Astronomy data modeling - High angular resolution - Long baseline interferometry - Nonclassical interferometry - Stellar radii - Stellar rotation

Status at CDS : Large table(s) will be appraised for possible ingestion in VizieR.

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 * gam Cas HXB 00 56 42.5310945 +60 43 00.264089 1.18 2.29 2.39 2.32 2.40 B0.5IVpe 1253 0
2 * bet UMa PM* 11 01 50.4797515135 +56 22 56.761138187 2.35 2.35 2.37 2.31 2.35 A1IVps 462 0

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