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Stellar intensity interferometry: Prospects for sub-milliarcsecond optical imaging

Dravins, Dainis LU ; LeBohec, Stephan; Jensen, Hannes and Nunez, Paul D. (2012) In New Astronomy Reviews 56(5). p.143-167
Abstract
Using kilometric arrays of air Cherenkov telescopes at short wavelengths, intensity interferometry may increase the spatial resolution achieved in optical astronomy by an order of magnitude, enabling images of rapidly rotating hot stars with structures in their circumstellar disks and winds, or mapping out patterns of nonradial pulsations across stellar surfaces. Intensity interferometry (once pioneered by Hanbury Brown and Twiss) connects telescopes only electronically, and is practically insensitive to atmospheric turbulence and optical imperfections, permitting observations over long baselines and through large air-masses, also at short optical wavelengths. The required large telescopes (similar to 10 m) with very fast detectors... (More)
Using kilometric arrays of air Cherenkov telescopes at short wavelengths, intensity interferometry may increase the spatial resolution achieved in optical astronomy by an order of magnitude, enabling images of rapidly rotating hot stars with structures in their circumstellar disks and winds, or mapping out patterns of nonradial pulsations across stellar surfaces. Intensity interferometry (once pioneered by Hanbury Brown and Twiss) connects telescopes only electronically, and is practically insensitive to atmospheric turbulence and optical imperfections, permitting observations over long baselines and through large air-masses, also at short optical wavelengths. The required large telescopes (similar to 10 m) with very fast detectors (similar to ns) are becoming available as the arrays primarily erected to measure Cherenkov light emitted in air by particle cascades initiated by energetic gamma rays. Planned facilities (e.g., CTA, Cherenkov Telescope Array) envision many tens of telescopes distributed over a few square km. Digital signal handling enables very many baselines (from tens of meters to over a kilometer) to be simultaneously synthesized between many pairs of telescopes, while stars may be tracked across the sky with electronic time delays, in effect synthesizing an optical interferometer in software. Simulated observations indicate limiting magnitudes around m(v) = 8, reaching angular resolutions similar to 30 mu arcsec in the violet. The signal-to-noise ratio favors high-temperature sources and emission-line structures, and is independent of the optical passband, be it a single spectral line or the broad spectral continuum. Intensity interferometry directly provides the modulus (but not phase) of any spatial frequency component of the source image; for this reason a full image reconstruction requires phase retrieval techniques. This is feasible if sufficient coverage of the interferometric (u, v)-plane is available, as was verified through numerical simulations. Laboratory and field experiments are in progress; test telescopes have been erected, intensity interferometry has been achieved in the laboratory, and first full-scale tests of connecting large Cherenkov telescopes have been carried out. This paper reviews this interferometric method in view of the new possibilities offered by arrays of air Cherenkov telescopes, and outlines observational programs that should become realistic already in the rather near future. (C) 2012 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
New Astronomy Reviews
volume
56
issue
5
pages
143 - 167
publisher
Elsevier
external identifiers
  • wos:000311768700001
  • scopus:84868360307
ISSN
1872-9630
DOI
10.1016/j.newar.2012.06.001
language
English
LU publication?
yes
id
0d2f7d0e-2309-468a-adc2-c2ccf2c25660 (old id 3373267)
date added to LUP
2013-01-31 11:12:19
date last changed
2017-08-20 03:23:16
@article{0d2f7d0e-2309-468a-adc2-c2ccf2c25660,
  abstract     = {Using kilometric arrays of air Cherenkov telescopes at short wavelengths, intensity interferometry may increase the spatial resolution achieved in optical astronomy by an order of magnitude, enabling images of rapidly rotating hot stars with structures in their circumstellar disks and winds, or mapping out patterns of nonradial pulsations across stellar surfaces. Intensity interferometry (once pioneered by Hanbury Brown and Twiss) connects telescopes only electronically, and is practically insensitive to atmospheric turbulence and optical imperfections, permitting observations over long baselines and through large air-masses, also at short optical wavelengths. The required large telescopes (similar to 10 m) with very fast detectors (similar to ns) are becoming available as the arrays primarily erected to measure Cherenkov light emitted in air by particle cascades initiated by energetic gamma rays. Planned facilities (e.g., CTA, Cherenkov Telescope Array) envision many tens of telescopes distributed over a few square km. Digital signal handling enables very many baselines (from tens of meters to over a kilometer) to be simultaneously synthesized between many pairs of telescopes, while stars may be tracked across the sky with electronic time delays, in effect synthesizing an optical interferometer in software. Simulated observations indicate limiting magnitudes around m(v) = 8, reaching angular resolutions similar to 30 mu arcsec in the violet. The signal-to-noise ratio favors high-temperature sources and emission-line structures, and is independent of the optical passband, be it a single spectral line or the broad spectral continuum. Intensity interferometry directly provides the modulus (but not phase) of any spatial frequency component of the source image; for this reason a full image reconstruction requires phase retrieval techniques. This is feasible if sufficient coverage of the interferometric (u, v)-plane is available, as was verified through numerical simulations. Laboratory and field experiments are in progress; test telescopes have been erected, intensity interferometry has been achieved in the laboratory, and first full-scale tests of connecting large Cherenkov telescopes have been carried out. This paper reviews this interferometric method in view of the new possibilities offered by arrays of air Cherenkov telescopes, and outlines observational programs that should become realistic already in the rather near future. (C) 2012 Elsevier B.V. All rights reserved.},
  author       = {Dravins, Dainis and LeBohec, Stephan and Jensen, Hannes and Nunez, Paul D.},
  issn         = {1872-9630},
  language     = {eng},
  number       = {5},
  pages        = {143--167},
  publisher    = {Elsevier},
  series       = {New Astronomy Reviews},
  title        = {Stellar intensity interferometry: Prospects for sub-milliarcsecond optical imaging},
  url          = {http://dx.doi.org/10.1016/j.newar.2012.06.001},
  volume       = {56},
  year         = {2012},
}