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Laboratory Astrophysics Activities IAU Commission B5 2022 GA
Abstract
This paper gives an overview of the IAU B5 commission session on “Laboratory Astrophysics Activities” at the 2022 IAU General Assembly (GA). It provides a brief overview of the talks that were given in that session. The IAU 2022 GA B5 commission meeting was organised to present Laboratory Astrophysics activities in various parts of the world in an attempt to provide a first step towards a “Global Network of Laboratory Astrophysics Network of Activities and Data”. The program (10.5281/zenodo.7051332) and the presentations can be found in the ZENODO “cb5-labastro” community ( https://zenodo.org/communities/cb5-labastro ).
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Light from thermal black body radiators such as stars exhibits photon
bunching behaviour at sufficiently short timescales. However, with available
detector bandwidths, this bunching signal is difficult to be directly used for
intensity interferometry with sufficient statistics in astronomy. Here we
present an experimental technique to increase the photon bunching signal in
blackbody radiation via spectral filtering of the light source. Our
measurements reveal strong temporal photon bunching in light from blackbody
radiation, including the Sun. Such filtering techniques may revive the interest
in intensity interferometry as a tool in astronomy.
Context: Some stellar objects exhibit very narrow spectral lines in the visible range additional to their blackbody radiation. Natural lasing has been suggested as a mechanism to explain narrow lines in Wolf-Rayet stars. However, the spectral resolution of conventional astronomical spectrographs is still about two orders of magnitude too low to test this hypothesis. Aims: We want to resolve the linewidth of narrow spectral emissions in starlight. Methods: A combination of spectral filtering with single-photon-level temporal correlation measurements breaks the resolution limit of wavelength-dispersing spectrographs by moving the linewidth measurement into the time domain. Results: We demonstrate in a laboratory experiment that temporal intensity interferometry can determine a 20 MHz wide linewidth of Doppler-broadened laser light, and identify a coherent laser light contribution in a blackbody radiation background.