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Astron. Astrophys. 347, 137-150 (1999)

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1. Introduction

Herbig Ae/Be stars (HAEBEs) are pre-main-sequence (PMS) objects of intermediate masses (2 [FORMULA] M/M[FORMULA] [FORMULA] 10). Herbig (1960) proposed the first list of 26 such objects with emission-line spectra and spectral types earlier than F0 associated with dark or reflection nebulosities. Infrared (IR) excesses discovered in HAEBEs in the early 1970's (e.g., Geisel 1970) prompted Finkenzeller & Mundt (1984) to extend this list to 57 stars, including those without visible nebulae and not closely connected to star formation regions. The latter objects are called isolated HAEBEs (e.g., Grinin et al. 1991). Based on a long-term photometric monitoring of a large sample of young stars, Shevchenko (1989) proposed a new list of HAEBEs containing 87 stars.

A number of new HAEBE candidates were found in the IRAS Point Source Catalogue (PSC) after the release of the IRAS mission results (e.g., Dong & Hu 1991, Oudmaijer et al. 1992). Summarizing these and other new results, Thé et al. (1994) published a catalog of 287 early-type stars which exhibit characteristics which suggest that they are possible PMS stars. The authors called this sample "The Herbig Ae/Be stellar group". From a study of the observational characteristics of HAEBEs and related objects they concluded that there was no unique set of observational characteristics which could help to unambiguously distinguish a PMS star of intermediate mass, and presented the sample in five separate tables. Table 1 of that paper contains a list of 108 HAEBE members and candidate members. This list does not include HAEBE candidates found during a photometric and spectroscopic survey of southern IRAS sources with T Tau star-like IR properties (Gregorio-Hetem et al. 1992). A number of new HAEBE candidates have been found after publication of the Thé et al. catalogue (Torres et al. 1995, van den Ancker, Thé, & de Winter 1996). Thus the list of HAEBEs continues to grow. At the same time, the PMS nature of some of the recent HAEBE candidates has been demonstrated in a number of the follow-up studies (e.g., Miroshnichenko et al. 1997; Meeus, Waelkens, & Malfait 1998). Nevertheless, other such objects still remain poorly-studied and their evolutionary states are undetermined.

In this paper we present the results of multicolour photometric and classification-resolution ([FORMULA] 1300) spectroscopic observations of 7 recently recognized HAEBE candidates by Gregorio-Hetem et al. (1992) and Thé et al. (1994) and of 2 other stars, which we suggest, for the first time, to be pre-main-sequence candidates. The list of the observed objects is presented in Table 1.


[TABLE]

Table 1. List of the observed objects.
Notes:
a) the source coordinates are given on epoch 1950.0,
b) J denotes the Johnson photometric system,
c) C denotes the Cousins photometric system.


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© European Southern Observatory (ESO) 1999

Online publication: June 18, 1999
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