New 3 millimeter observations of interstellar HNO: Reinstating a discredited identification

HNO has been observed in six interstellar clouds via its I0i-00o transition at 3 mm wavelength. L134N, W33A, W51M, and DR 21 are new HNO sources. The excellent agreement between laboratory and astronomical rest frequency in L134N is important for establishing the correctness of the astronomical assignment of this line. With the exception of Ori A, every known NO source contains detectable HNO. The typical column density ratio Ariol(NO)/Ar,ot(HNO) appears to be 100-200, except for L134N ( ∼ 800) and DR 21(OH) ( ∼ 20). These new HNO results correct several misconceptions in the current literature.