The Astrophysical Journal (Jan 2024)

An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory

  • A. Acharyya,
  • J. P. Aufdenberg,
  • P. Bangale,
  • J. T. Bartkoske,
  • P. Batista,
  • W. Benbow,
  • A. J. Chromey,
  • J. D. Davis,
  • Q. Feng,
  • G. M. Foote,
  • A. Furniss,
  • W. Hanlon,
  • C. E. Hinrichs,
  • J. Holder,
  • W. Jin,
  • P. Kaaret,
  • M. Kertzman,
  • D. Kieda,
  • T. K. Kleiner,
  • N. Korzoun,
  • T. LeBohec,
  • M. A. Lisa,
  • M. Lundy,
  • N. Matthews,
  • C. E McGrath,
  • M. J. Millard,
  • P. Moriarty,
  • S. Nikkhah,
  • S. O’Brien,
  • R. A. Ong,
  • M. Pohl,
  • E. Pueschel,
  • J. Quinn,
  • P. L. Rabinowitz,
  • K. Ragan,
  • E. Roache,
  • J. G. Rose,
  • J. L. Sackrider,
  • I. Sadeh,
  • L. Saha,
  • G. H. Sembroski,
  • R. Shang,
  • D. Tak,
  • M. Ticoras,
  • J. V. Tucci,
  • D. A. Williams,
  • S. L. Wong,
  • The VERITAS Collaboration

DOI
https://doi.org/10.3847/1538-4357/ad2b68
Journal volume & issue
Vol. 966, no. 1
p. 28

Abstract

Read online

We use the Very Energetic Radiation Imaging telescope Array System (VERITAS) imaging air Cherenkov telescope array to obtain the first measured angular diameter of β UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angular diameter. The age of the Ursa Major moving group has been assessed from the ages of its members, including nuclear member Merak ( β UMa), an A1-type subgiant, by comparing effective temperature and luminosity constraints to model stellar evolution tracks. Previous interferometric limb-darkened angular-diameter measurements of β UMa in the near-infrared (Center for High Angular Resolution Astronomy (CHARA) Array, 1.149 ± 0.014 mas) and mid-infrared (Keck Nuller, 1.08 ± 0.07 mas), together with the measured parallax and bolometric flux, have constrained the effective temperature. This paper presents current VERITAS-SII observation and analysis procedures to derive squared visibilities from correlation functions. We fit the resulting squared visibilities to find a limb-darkened angular diameter of 1.07 ± 0.04 (stat) ± 0.05 (sys) mas, using synthetic visibilities from a stellar atmosphere model that provides a good match to the spectrum of β UMa in the optical wave band. The VERITAS-SII limb-darkened angular diameter yields an effective temperature of 9700 ± 200 ± 200 K, consistent with ultraviolet spectrophotometry, and an age of 390 ± 29 ± 32 Myr, using MESA Isochrones and Stellar Tracks. This age is consistent with 408 ± 6 Myr from the CHARA Array angular diameter.

Keywords