Optical spectroscopic and 2MASS measurements of Stephenson H_α stars^*

Indian Institute of Astrophysics, Bangalore 560 034, India e-mail: manoj@iiap.ernet.in, hcbhatt@iiap.ernet.in

Corresponding author: G. Maheswar, maheswar@iiap.ernet.in

Received: 12 November 2002
Accepted: 25 February 2003

Abstract

We present the results of spectroscopic observations for 52 objects from the list of H_α emission stars of Stephenson (1986). Out of six known T Tauri stars observed, five showed H_α in emission and in one (StHa 40), H_α changed from being in absorption to emission over a period of two years, accompanied by photometric and spectral type variability. We confirm the T Tauri nature of one Stephenson object (StHa 48) on the basis of the presence of H_α and H in emission, Li I in absorption, infrared excess and X-ray emission. Among the 52 objects observed, there were other emission line objects: 1 Ke star, 1 BQ[ ] star, 2 galaxies and 2 Be stars. We present a higher-resolution spectrum of StHa 62 showing permitted and forbidden lines in emission typical of BQ[ ] stars. Twenty five out of 30 newly observed objects failed to show H_α in emission. We also present 2MASS observations for 112 StHa objects. We suggest three Stephenson objects (StHa 52, 125 and 129) to be YSOs on the basis of 2MASS, IRAS and ROSAT observations. These and all other known YSOs amongst StHa stars are found in regions of star-forming clouds in Taurus, Orion and Ophiuchus. YSOs at high galactic latitudes in other parts of the sky are therefore rare.