Spectral classifications in the near infrared of stars with composite spectra - II. Study of a sample of 180 stars
Astron. Astrophys. Suppl. Ser.
Spectral classi cations in the near infrared of stars with composite spectra
N. Ginestet 1
J.M. Carquillat 1
C. Jaschek 0
M. Jaschek 0
0 Observatoire de Strasbourg, URA 1280 (CNRS), 11 Rue de l'Universite , 67000 Strasbourg , France
1 Observatoire Midi-Pyrenees, UMR No. 5572 (CNRS) , 14 Avenue Edouard Belin, 31400 Toulouse , France
A sample of 180 supposedly compositespectrum stars has been studied on the basis of spectra obtained in the near infrared (8370 − 8780 A) at a dispersion of 33 A/mm. The objective was to study the cooler components of the systems. Of our sample, 120 are true composite spectra, 35 are hot spectra of types B, F and 25 are Am stars. We nd a strong concentration of the cooler components of the composite spectra around G8III. In view of the di culty of classifying composite spectra, because of the superposition of an early type dwarf and a late type giant or supergiant spectrum, we have made several tests to control the classi cation based upon the infrared region. Since all tests gave positive results, we conclude that our classi cations can be considered as being both reliable and homogeneous.1
stars; classi cation | infrared; stars | binaries; spectroscopic
1. Introduction
In a preceding paper
(Ginestet et al. 1994)
we have shown
that the near infrared region (8370−8780 A) is interesting
for classifying the cooler components of composite
spectra. This is essentially due to the fact that whereas in the
blue spectral region (3800 − 4800 A) the magnitude
difference between both components is about zero (i.e. both
spectra are hopelessly intermingled), in the near infrared
region the magnitude di erence is more favorable to the
Send o print requests to: J.M. Carquillat
? based upon observations carried out at Observatoire de
Haute-Provence (CNRS).
1 Table 1 is also available electronically at the CDS via
anonymous ftp 130.79.128.5 or
http://cdsweb.u-strasbg.fr/Abstracts.html
cooler component. Very frequently the traces of the early
type companion can only be perceived faintly through the
presence of weak hydrogen lines of the Paschen series.
Let us recall here briefly that we shall call composite
spectra all those resulting from the combination of the
spectra of a hot early type dwarf (type B or A) and that
of a late type subgiant, giant or even supergiant object
(types G, K or M).
The rst paper (Paper I) was devoted to the study of a
sample of 92 MK standards, which permitted to establish
the classi cation criteria for this region, using the
equivalent widths of certain lines or blends of lines. For early
type spectra we have used essentially the Paschen lines
P12 and P14 of hydrogen, the CaII lines 8498, 8542 and
the OI line 8446. For the late type spectra we have used
mainly the CaII triplet lines (8498, 8542, 8662 A), the FeI
(8621, 8688 A), TiI (8426, 8435 A) lines and the blend
8468. The latter is constituted by a blend of lines of iron
and titanium but contains also some faint lines of CN, Mg
and Zr.
In the present paper (Paper II) we apply the results of
Paper I to a sample of stars with composite spectra.
We have provided in Paper I a list of papers written
on both the near infrared spectral region and on
composite spectra. We shall not repeat here these references, but
complete the list given with some papers published
recently. The most important additions are four new atlases
covering the near infrared. The rst is by Torres-Dodgen
& Weaver (1993) which covers the 5800 − 8900 A region
at a resolution of about 15 A. The second atlas is the one
by Danks & Dennefeld (1994) covering the region 5800−
10200 A at a dispersion of 171 A/mm. The third atlas
(Andrillat et al. 1995) covers the 8400 − 8800 A region of
early type stars at a dispersion of 33 A/mm and the fourth
is by ourselves (Carquillat et al. 1997). It covers the same
region as the third atlas and uses the same dispersion but
deals only with late type stars. We mention also a recent
136 N. Ginestet et al.: Spectral classi cations in the near infrared of stars with composite spectra. II.
Table 1. Classi cations of the cool components, SP(IR), of stars with composite spectra
138 N. Ginestet et al.: Spectral classi cations in the near infrared of stars with composite spectra. II.
Table 1. continued
paper by Weaver & Torres-Dodgen (1995) on an
automated classi cation of A type stars in the near infrared.
reduced and measured with the IHAP software available
at the OHP.
2. Observations, treatment of spectra and measure of equivalent widths
Our sample is composed by 180 stars and was selected
essentially from the list
of Hynek (1938
). Additional
obThe spectra used for classifying the stars of our s
am- jects come from Markowitz (1969
), Cowley (1973, 1976),
ple were obtained with the same instrument as the MK Ho eit & Jaschek (1982)
and Stickland (1988
). Our
samstandards of Paper I. The stars were observed with the ple is contained essentially within the observational limits
(...truncated)