The upgraded MIRC-X beam combiner at the CHARA array combines the light from all six telescopes simultaneously. It disperses light across several spectral channels and operates in the near infrared J and H-bands. MIRC-X can be used to create images of stellar surfaces and circumstellar emission. The precision closure phases are well suited to detecting faint binary companions.
MIRC-X injects the light from each telescope into optical fibers for spatial filtering.The fiber outputs from the six beams are arranged in a linear non-redundant pattern to spatially encode the fringes from each pair of telescopes. The combined light passes through a spectrograph and is imaged onto the detector.
Three spectral modes are currently available in the H-band: prism R=50 (8 spectral channels), prism R=102, and grism R=190. A higher resolution grism with R=1170 is available with approval from the instrument team.
The simultaneous J+H mode using 4 telescopes is under development.
The instrumentation development of the new MIRC-X combiner was led by the University of Exeter and the University of Michigan. The beam combiner is equipped with an ultra-low read-noise detector system and extended the wavelength range to the J and H-band. The first phase of the MIRC-X commissioning was successfully completed in June 2017.
The original Michigan Infrared Beam Combiner (MIRC) was developed by John Monnier and his optical interferometry group in the Astronomy Department at the University of Michigan. It dispersed light across 8 spectral channels in the near infrared H-band (1.6 microns). MIRC produced the first images of a main sequence star other than the sun, measured the oblateness and gravity darkening of rapid rotators, imaged starpots on the surface of magnetically active stars, and detected faint binary companions at small separations.
Observing and Data Reduction
Instrument Papers for MIRC-X (Commissioned in June 2017):
MIRC-X: a highly-sensitive six telescope interferometric imager at the CHARA Array - Anugu et al. 2020, AJ, 160, 158
The MIRC-X 6-telescope imager: Key science drivers, instrument design and operation - Kraus et al. 2018, SPIE, 10701, 23
MIRC-X/CHARA: sensitivity improvements with an ultra-low noise SAPHIRA detector - Anugu et al. 2018, SPIE, 10701, 24
Instrument Papers for MIRC (Operational from 2006 to April 2017):
The Michigan Infrared Combiner (MIRC): Infrared imaging with the CHARA Array - Monnier et al. 2004, SPIE, 5491, 1370 (pdf)
Michigan Infrared Combiner (MIRC): Commissioning Results at the CHARA Array - Monnier et al. 2006, SPIE, 6268, 1 (pdf)
High precision interferometer: MIRC with photometric channels - Che et al. 2010, SPIE, 7734, 2
Imaging from the first 6-beam infrared combiner - Che et al. 2012, SPIE, 8445, 0