Observations of the ^{2}∏_{3/2} J = 5/2 State of Interstellar OH

A high-sensitivity OH 5-cm line survey in late-type stars

“…For NML Cyg, we reached the sensitivity of 20 mJy (at 3σ level) over the observing LSR velocity range. The 0.8 K (2.2Jy) signal reported by Zuckerman et al (1972) and lying close to +5 km s −1 , would have been easily detected by us. However, we can not exclude that the emission varies with time.…”

“…The latter work was the most sensitive search for excited OH from stars yet performed. Zuckerman et al (1972) reported weak 6035 MHz ( 2 Π 3/2 , J = 5/2) emission from NML Cyg and Claussen & Fix (1981) reported weak 4751 MHz ( 2 Π 1/2 , J = 1/2) emission from AU Gem. However, both detections were not confirmed by Jewell et al (1985).…”

“…As far as we are aware only a few searches for J = 1/2 and 5/2 OH emission at 4.7 and 6 GHz from stars have been undertaken (see Thacker et al 1970;Zuckerman et al 1972;Baudry 1974;Claussen & Fix 1981;Jewell et al 1985). The latter work was the most sensitive search for excited OH from stars yet performed.…”

Observations of the 6 cm Lines of OH in Evolved (OH/IR) Stars

“…Nevertheless, excited-state emission has been detected in two evolved stars. Zuckerman et al (1972) report on 6035 MHz (and possibly 6030 MHz) maser emission in the red supergiant NML Cyg, although not at the same velocity as the 1612 MHz masers. Likewise, Claussen & Fix (1981) report on 4750 MHz emission from the Mira AU Gem; again, the velocities are not the same as in ground-state emission, although the authors note that the spectrum of the 4750 MHz emission appears to be centered at the same velocity, with peaks nearer the central velocity than at 1667 MHz.…”

“…The authors suggest that 53 mm absorption may play a role in pumping 1612 MHz masers in evolved stars, consistent with Gray et al (2005 Detections of OH lines beyond the ground-state transitions could provide useful constraints to clarify the modeling picture. There have been several searches for maser emission in the 4.7 GHz ( 2 P 1/2 , ) and 6.0 GHz ( 2 P 3/2 , ) tran-J p 1/2 J p 5/2 sitions of OH (Thacker et al 1970;Zuckerman et al 1972;Baudry 1974;Rickard et al 1975;Claussen & Fix 1981;Jewell et al 1985;Desmurs et al 2002). All searches failed to detect excited-state emission from OH/IR stars, with the exception of 6035 MHz emission in NML Cyg (Zuckerman et al 1972) and 4750 MHz emission in AU Gem (Claussen & Fix 1981), neither of which was confirmed in subsequent observations by Jewell et al (1985).…”