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Observations with the Southern Connecticut Stellar Interferometer. II. First Three-Telescope Observations and a New Diameter Measurement of Arcturus

Elliott P. Horch, Sebastian M. Lucero, Max Martone, Riley C. Barrett, Ana I. Baculima Durán, Fiona T. Powers Özyurt, Gage Posick, Alexander Petroski, James W. Davidson,, Steven R. Majewski, Richard A. Pellegrino, Paul M. Klaucke, Xavier Lesley-Saldaña, Torrie Sutherland, Olivia S. Weiss

TL;DR

This study demonstrates the viability of stellar intensity interferometry (SII) with a three-telescope setup by achieving a significant Hanbury Brown–Twiss photon-bunching signal for Vega and updating the unresolved-source correlation efficiency. It also delivers a new limb-darkened diameter for Arcturus by combining SCSI data with differential speckle imaging (DSSI) from APO, yielding $\theta_{LD} = 21.5 \pm 1.8$ mas and showing consistency with historical interferometric measurements. By extending spatial-frequency coverage through speckle data and validating SII on small-aperture baselines, the work highlights a complementary pathway to long-baseline interferometry for precise stellar diameters. Overall, the results establish SII's practicality on modest infrastructure and its potential to augment traditional optical interferometry across multiple wavelengths.

Abstract

We discuss the most recent observations made with the Southern Connecticut Stellar Interferometer (SCSI), which is a three-station stellar intensity interferometer located on the campus of Southern Connecticut State University, in New Haven, Connecticut. Two different kinds of observations are presented. We first analyze observations of Vega taken in a three-telescope mode. (Previously, the instrument had only two operational stations.) We show that, while the efficiency remains nearly identical to that reported in our last paper, the addition of the third station allows more photon data to be recorded simultaneously, and therefore we can build up the photon-bunching peak in the data stream in fewer hours on sky for an unresolved source. In the second part of the paper, we report our observations to date of the nearby red giant star, Arcturus, most of which occurred in the first half of 2025. These show that, as a partially resolved source at the baselines we used, we detect fewercorrelations in the photon-bunching peak than for an unresolved source of comparable brightness. Combining the data with speckle imaging observations taken at Apache Point Observatory, we derive a new measurement of Arcturus' diameter that extends the time baseline of interferometric observations of the star and is consistent with previous analyses made by other investigators.

Observations with the Southern Connecticut Stellar Interferometer. II. First Three-Telescope Observations and a New Diameter Measurement of Arcturus

TL;DR

This study demonstrates the viability of stellar intensity interferometry (SII) with a three-telescope setup by achieving a significant Hanbury Brown–Twiss photon-bunching signal for Vega and updating the unresolved-source correlation efficiency. It also delivers a new limb-darkened diameter for Arcturus by combining SCSI data with differential speckle imaging (DSSI) from APO, yielding mas and showing consistency with historical interferometric measurements. By extending spatial-frequency coverage through speckle data and validating SII on small-aperture baselines, the work highlights a complementary pathway to long-baseline interferometry for precise stellar diameters. Overall, the results establish SII's practicality on modest infrastructure and its potential to augment traditional optical interferometry across multiple wavelengths.

Abstract

We discuss the most recent observations made with the Southern Connecticut Stellar Interferometer (SCSI), which is a three-station stellar intensity interferometer located on the campus of Southern Connecticut State University, in New Haven, Connecticut. Two different kinds of observations are presented. We first analyze observations of Vega taken in a three-telescope mode. (Previously, the instrument had only two operational stations.) We show that, while the efficiency remains nearly identical to that reported in our last paper, the addition of the third station allows more photon data to be recorded simultaneously, and therefore we can build up the photon-bunching peak in the data stream in fewer hours on sky for an unresolved source. In the second part of the paper, we report our observations to date of the nearby red giant star, Arcturus, most of which occurred in the first half of 2025. These show that, as a partially resolved source at the baselines we used, we detect fewercorrelations in the photon-bunching peak than for an unresolved source of comparable brightness. Combining the data with speckle imaging observations taken at Apache Point Observatory, we derive a new measurement of Arcturus' diameter that extends the time baseline of interferometric observations of the star and is consistent with previous analyses made by other investigators.
Paper Structure (11 sections, 2 equations, 7 figures)

This paper contains 11 sections, 2 equations, 7 figures.

Table of Contents

  1. Introduction
  2. Three-Telescope Operations
  3. Instrumentation and Observing Method
  4. Data Reduction Methodology
  5. Three-Telescope Observations and Results
  6. Observations of Arcturus
  7. Observations with SCSI
  8. Speckle Imaging of Arcturus
  9. A New Measurement of the Diameter of Arcturus
  10. Discussion
  11. Conclusions

Figures (7)

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