Discovery of Pulsed OH Maser Emission Stimulated by a Pulsar

Abstract

Stimulated emission of radiation has not been directly observed in astrophysical situations up to this time. Here we demonstrate that photons from pulsar B1641-45 stimulate pulses of excess 1720 MHz line emission in an interstellar OH cloud. As this stimulated emission is driven by the pulsar, it varies on a few millisecond timescale, orders of magnitude shorter than the quickest OH maser variations previously detected. Our 1612 MHz spectra are inverted copies of the 1720 MHz spectra. This "conjugate line" phenomenon enables us to constrain the properties of the interstellar OH line-producing gas. We also show that pulsar signals suffer significantly deeper OH absorption than do other background sources; confirming earlier tentative findings that OH clouds are clumpier on small scales than neutral hydrogen clouds.

Accepted by Science

References in corpus (5)

• The Southern Galactic Plane Survey: HI Observations and Analysis
• OH 1720 MHz Masers in Supernova Remnants --- C-Shock Indicators
• Ground-state OH observations towards NGC 6334
• Detection of OH absorption against PSR B1849+00
• HI line measurements of pulsars towards the Galactic Centre and the electron density in the inner Galaxy

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