Micro-arcsec imaging from the ground with intensity interferometers

Abstract

Stellar amplitude interferometry is limited by the need to have optical distances known to a fraction of the wavelength. We suggest reviving intensity interferometry, which requires far less accurate hardware (~1cm mechanical precision) at the cost of more limited sensitivity. We present an algorithm that uses the very high redundancy of a uniform linear array to increase the sensitivity of the instrument by more than a hundredfold. An array of a hundred ~100m diameter elements can achieve a limiting magnitude of m b =14.4. Off-line processing of the data will enable such a ground-based facility to transform a two-dimensional field of point-like sources to a three-dimensional distribution of micro-arcsec resolved systems, each imaged in several optical bands. Each system will also have its high resolution residual timing, high quality (inside each band) spectra and light curve, emergent flux, effective temperature, polarization effects and perhaps some thermodynamic properties, all directly measured in a single observation run of such a dedicated facility. Coronagraphy, selectively suppressing large scale structures of the sources, can also be achieved by specific aperture shapes. We conclude that after three decades of abandonment optical intensity interferometry deserves another review, also as a ground-based alternative to the science goals of space interferometers.

Optical intensity interferometry through atmospheric turbulence

“…There has been a growing interest in recent years to revive the Hanbury-Brown-Twiss method (Ofir & Ribak 2006;Millour 2008;Foellmi 2009;Borra 2013;Dravins et al 2015), which has the potential to map the spatial structure of stellar formations (Millour 2010;Dravins et al 2013), detect exoplanets (Hyland 2005;Strekalov et al 2013) and for kilometric baseline arrays to achieve micro-arcsecond resolution Borra 2013;Capraro et al 2009;LeBohec et al 2008;Nuñez 2012).…”

Measuring Temporal Photon Bunching in Blackbody Radiation

“…Current atomic clock technology should even allow for the development of very large scale optical intensity interferometers with kilometric baselines, leading to micro-arcsecond resolution. With this, one could investigate stellar limb darkening coefficients, resolve spectroscopic binaries, measure stellar oblateness to better understand the internal dynamics, and also determine the pulsations of cepheid variables to better derive the Hubble constant Borra 2013;Dravins & LeBohec 2007;Dravins et al 2013;Foellmi 2009;LeBohec et al 2008;Naletto et al 2009;Nuñez 2012;Ofir & Ribak 2006;Rou et al 2012;Wittkowski et al 2004).…”

Toward a revival of stellar intensity interferometry

“…Conversely, it was recently shown that if, indeed, higher order correlations could be measured, then the sensitivity of the instrument can be improved (Ofir &Ribak 2006A and2006B). In their analysis, Ofir and Ribak at the Technion assume a full recording and off-line processing of all of the data.…”