Effelsberg Observations of Excited-State (6.0 GHz) OH in Supernova Remnants and W3(OH)

Abstract

While masers in the 1720 MHz transition of OH are detected toward many supernova remnants (SNRs), no other OH transition is seen as a maser in SNRs. We present a search for masers at 6049 MHz, which has recently been predicted to produce masers by pure collisional excitation at conditions similar to that required for 1720 MHz masing. The Effelsberg 100 m telescope was used to observe the excited-state 6016, 6030, 6035, and 6049 MHz lines of OH toward selected SNRs, most of which have previously-detected bright 1720 MHz masers. No excited-state masers are found toward SNRs, consistent with previous observations of the 6049 MHz and other excited-state transitions. We do not see clear evidence of absorption toward SNR target positions, although we do see evidence of absorption in the molecular cloud at +50 km/s near Sgr A East. Weak absorption is detected at 6016 MHz toward W3(OH), while stronger, narrower emission is seen at 6049 MHz, suggesting that the 6049 MHz emission is a low-gain maser. We conclude that conditions in SNRs are not conducive to excited-state maser emission, especially in excited-state satellite lines.

4 pages using emulateapj.cls including 2 tables and 1 figure, accepted to ApJL

References in corpus (4)

• GBT Observations of IC 443: the Nature of OH(1720 MHz) Masers and OH Absorption
• Structure of W3(OH) from Very High Spectral Resolution Observations of 5 Centimeter OH Masers
• Enhanced density and magnetic fields in interstellar OH masers
• Excited-state OH Mainline Masers in AU Geminorum and NML Cygni

Cited by in corpus (6)

• A Survey of Hydroxyl Toward Supernova Remnants: Evidence for Extended 1720 MHz Maser Emission
• Excited-state OH Masers and Supernova Remnants
• A search for OH 6 GHz maser emission towards supernova remnants
• High-Sensitivity Observations of Molecular Lines with the Arecibo Telescope
• Collisional Pumping of OH Masers near Supernova Remnants
• A 95 GHz Methanol Emission Survey Toward Eight Small Supernova Remnants