Cherenkov Telescopes as Optical Telescopes for Bright Sources: Today's Specialised Thirty Metre Telescopes?

TL;DR

Cherenkov telescopes, with large apertures and rapid imaging capabilities, are highly suitable for optical observations of bright sources, offering advantages in studying phenomena like exoplanets and gamma-ray bursts, especially on short timescales.

Contribution

This paper explores the potential of Cherenkov telescopes as optical instruments for bright sources, highlighting their advantages and limitations compared to traditional telescopes.

Findings

IACTs can achieve millimagnitude photometry for bright sources with second-long exposures.

Their large photon collection rate enables potential for precise polarimetry.

Poor angular resolution limits high spectral resolution spectroscopy with IACTs.

Abstract

Imaging Atmospheric Cherenkov Telescopes (IACTs) use large-aperture (~ 10 - 30 m) optical telescopes with arcminute angular resolution to detect TeV gamma-rays in the atmosphere. I show that IACTs are well-suited for optical observations of bright sources (V <= 8 - 10), because these sources are brighter than the sky background. Their advantages are especially great on rapid time-scales. Thus, IACTs are ideal for studying many phenomena optically, including transiting exoplanets and the brightest gamma-ray bursts. In principle, an IACT could achieve millimagnitude photometry of these objects with second-long exposures. I also consider the potential for optical spectroscopy with IACTs, finding that their poor angular resolution limits their usefulness for high spectral resolutions, unless complex instruments are developed. The high photon collection rate of IACTs is potentially useful for precise polarimetry. Finally, I briefly discuss the broader possibilities of extremely large, low resolution telescopes, including a 10" resolution telescope and spaceborne telescopes.