2. New HAEBE candidates
Almost all HAEBEs known before the IRAS mission were identified as IRAS PSC sources (Thé et al. 1994) except for a few stars, which are located in crowded areas with a complicated background (Weaver & Jones 1992). Therefore, one can expect to find new HAEBE candidates among the sources detected by IRAS . Such a search was performed by Dong & Hu (1991), who positionally cross-correlated the IRAS PSC and the catalogue of galactic early-type emission-line stars by Wackerling (1970). Dong & Hu (1991) have found more than 100 essentially unstudied stars, which could potentially become members of different stellar groups with IR excesses. These objects are listed in Table 4b of Thé et al. (1994). A disadvantage of such a cross-correlation procedure is the low precision of the optical positions listed in the Wackerling (1970) catalogue. It may lead either to optical misidentification of an IR source or to complete loss of the optical counterpart due to the positional difference. The position of the IR source may also be incorrect because of the potential presence of several nearby radiation sources, which is not unusual in the large IRAS diaphragms. In order to emphasize these situations Thé et al. (1994) gave a separate list of stars with such offsets larger than 30".
However, in some cases, inaccurate optical positions can be improved by identification of a source in catalogues with higher positional precision (such as the Guide Star Catalogue (GSC) or the AC 2000 Catalogue) and new stars with IR excesses can be found. For this reason we have completed a new cross-correlation analysis of the IRAS PSC and the Wackerling catalogue allowing the maximum offset between the optical and IR positions to be 60". This search resulted in the identification of nearly 40 objects not listed by Dong & Hu (1991). They include a number of well-known bright stars (e.g., Sgr) and planetary nebulae (e.g., LS III +54o46) as well as nearly 20 mostly unstudied objects from the lists of Wray (1966) and Henize (1976). Properties of these objects, which may be considered as additions to early-type emission-line objects listed in Tables 4a and 4b by Thé et al. (1994), will be described in a forthcoming paper. Here we present a study of two stars from our list of newly found stars with IR excesses, MQ Cas and BD+11o829.
The optical position of MQ Cas listed in Wackerling (1970) has an offset of 58" with respect to that of IRAS 00070+5756, which was found by us as its possible IR counterpart. In SIMBAD MQ Cas is listed as a counterpart of this IRAS source, however its optical position is given according to Wackerling (1970). Comparison of the finding chart given by Wenzel (1955) for MQ Cas and the same area in the GSC allowed us to identify the variable with the star GSC 3664-0126. The position of this star coincides with that of the IR source within the IRAS error box (15"). Thus we improved the optical position of MQ Cas, which turned out to be as follows (GSC): R.A. , Dec. , (2000.0). This star is known as an irregular Orion variable (Wenzel 1956) with an amplitude of nearly 2m (117 - 136, pg). Dolidze (1975) detected a moderate H emission in its spectrum, although the spectral type has not yet been determined. The presence of the H line in emission along with the obvious IR excess leads us to suspect that MQ Cas is a PMS candidate.
The same suggestion can be made about BD+11o829, whose optical position is within the IRAS error box of the source IRAS 05275+1118. This star attracted no attention in the past. However, its location close to a number of PMS stars (HAEBEs HK Ori, HDE 244604, HDE 245185, and T Tau stars CO Ori and GW Ori) in addition to the IR excess pointed to its possible PMS nature. We identified BD+11o829 with the star GSC 0709-1217.
© European Southern Observatory (ESO) 1999
Online publication: June 18, 1999