Atomic Clocks in Space: A Search for Rubidium and Cesium Masers in M- and L-Dwarfs

TL;DR

This study searched for atomic clock hyperfine transition masers of rubidium and cesium in M- and L-dwarfs to explore their potential as precise astrophysical tools, but found no evidence of such masers.

Contribution

First observational search for rubidium and cesium hyperfine masers in stellar atmospheres, testing their feasibility as natural atomic clocks in space.

Findings

No detection of Rb or Cs masers in 21 M- and L-dwarfs.

Previous surveys also found no Rb masers in giant stars.

Results suggest such masers are rare or absent in these environments.

Abstract

I searched for the ground state 6.8 and 9.2 GHz hyperfine transitions of rubidium and cesium toward M- and L-dwarfs that show Rb and Cs optical resonance lines. The optical lines can pump the hyperfine transitions, potentially forming masers. These spin-flip transitions of Rb and Cs are the principal transitions used in atomic clocks (the $^{133}$Cs hyperfine transition defines the second). If they are detected in stellar atmospheres, these transitions would provide exceptionally precise clocks that can be used as accelerometers, as exoplanet detectors, as probes of the predictions of general relativity, as probes of light propagation effects, and as a means to do fundamental physics with telescopes. Observations of 21 M- and L-dwarfs, however, show no evidence for Rb or Cs maser action, and a previous survey of giant stars made no Rb maser detections.