Figure 2: [12-25] vs. K-L diagram for the 199 observed
stars in the K and L bands. The triangles represent the 8 new infrared
stars confirmed by spectroscopic measurements, the dots,
the 12 other new carbon star candidates, the open squares the stars previously
known as carbon stars through their optical spectra (GCCCS) or their IRAS
low resolution spectra, the filled squares, the 2 objects which might be
contaminated by a nearby star, and the crosses, the other stars.
The black-body line, the areas defined by Epchtein et al. (1987)
and the reddening vector corresponding to are also drawn
Figure 3: Red spectra of 10 objects (03118+6144, 04256+5054,
04391+4904, 04469+3228, 05391+4757, 05581+2232, 05592+4627, 06175+2347,
07152+1228, 19580+2552). The spectrum of
06175+2347 is represented to illustrate the typical features
of a carbon star obtained with the same instrumentation.
Some of the CN band heads as well as the NaD doublet and H
are indicated. Some of the band heads of TiO characteristics of M type star
are indicated on the spectrum of 05581+2232
Table 4: The number of observed stars according to
various classifications: LRS, VH, Epchtein et al. (1987),
GCCCS
The colours of the observed objects have been plotted in a
[12-25] vs. K-L diagram (Fig. 2), in order to discriminate between
oxygen and carbon rich stars. Following our classification method
(Epchtein et al. 1987),
the objects can be roughly splitted into
3 main groups. One group is located along a vertical strip at low K-L and
corresponds to O-rich stars surrounded by a thin dust shell,
a second group follows a sequence located above the blackbody line and
corresponds to C-rich stars (region c),
finally, a few objects with larger colour indices
correspond to oxygen stars with thick dust shells (region o2 and
o3).
The numbers of objects that belong to each of these classes are given in
Table 4.
The brightest stars in our sample have a thin CDS (K-L<0.7).
It is among them that the percentage of carbon stars is the lowest.
Most of them are listed in the GSC, and their range approximately
between 3 and 5.
The 8 stars that were not observed in the L band are unlikely to be
IRCS according to their location in other two-colour diagrams
such as [12-25] vs. J-K. They are likely to be M stars with thin CDS.
The complete list of the 20 new IRCS candidates that we propose
is given in Table 5.
All of them were discovered by IRAS, but were, so far, of unknown nature, i.e.
not already identified as carbon stars (not in the GCCCS, not LRS "4n").
Flag "C" in Col. 3 indicates that their carbon rich nature
has been confirmed by optical spectroscopic observations (see Sect. 4).
The 3 objects with LRS "0n" or "1n" included in this list have LRS of
too poor quality to identify their chemical type.
The 17 others have no LRS. Only, 06000+3445 has a GSC counterpart.
According to our previous studies, since these objects have
(Fouqué et al. 1992) and are not located at the edge of the class c
area, their probability of being IRCS is very high (Paper I).
Two IRCS 18240+2326 and 21489+5301 have a K-L slightly larger than 4
in the "4n" samples. 21489+5301 has been already pointed
out as a candidate of extreme carbon star (Volk et al. 1992b,
and Omont et al. 1993).
Table 5: List of the 20 new infrared carbon star candidates