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Up: A catalog of rotational stars


1 Introduction

The behaviour of the distribution of rotational velocities as a function of luminosity and color can provide important constraints for models of angular momentum as stars evolve through the HR diagram, as well as important information on the presence of external rotational brakes, tidal interactions in binary systems and the link between stellar activity and rotation.

For the rotating evolved stars, one of the best known properties is that these ones rotate slowly, but little is known in detail. Herbig & Spalding ([1953], [1955]) have shown that a cutoff in the distribution of rotational velocities seems to be present in subgiant and giant stars, near the spectral type G0. Essentially, these authors pointed out that rotation rates decrease from late F-type toward early G-type stars in those luminosity classes.

In general, the pioneering works could only predict upper limits for the rotation rates of evolved stars. Uesugi & Fukuda ([1982]) have compiled 102 sources of $v \sin i\ $data for 6472 stars. Although, among the stars quoted by these authors, there are for about 10% of G and K-type evolved stars with rotational velocity values, the vast majority of these measurements are unreliable, since the techniques used for these observations presented modest resolution, larger than what we know today to be the mean rotational velocities for these stars. In some cases, such as Herbig & Spalding ([1953], [1955]), Oke & Greenstein ([1954]), Huang ([1953]) and Alschuler ([1975]), the limits are typically near 20 km s-1. Kraft ([1965]) predicted limits to 6.0 km s-1 for the Hyades giants and to 10.0 km s-1 for the yellow giants of NGC 2281 and NGC 6633. Most recently, D. Gray and co-workers obtained rotational velocities for about 170 stars of luminosity classes IV through Ib, from high-resolution spectroscopic observations (Gray [1989]; Gray & Nagar [1985]; Gray & Toner [1986], [1987]), by using the Fourier deconvolution technique on single line profiles. These authors have obtained very accurate $v \sin i\ $values, with typical velocity resolution of about 0.5 to 2.0 km s-1. These observations concern mostly stars of spectral types G and K. Fekel (1997) has also obtained rotational velocity $v \sin i\ $for about 60 evolved stars into the luminosity classes IV, III and II. As one can see from the works by D. Gray and co-workers, M. Mayor and co-workers and F. Fekel, rotation rates of the large majority of G and K stars are actually several times smaller than the $\sim$ 20 kms-1 upper limits set by the early works.

Admittedly, extensive surveys of $v \sin i\ $at high resolution are needed for the best comprehension of the rotational behaviour of evolved stars because, up to the present, the paucity of the samples have prevented a complete statistical analysis.

   
Table 1: Comparison between CORAVEL and Gray's $v \sin i\ $measurements for stars of luminosity classes III and IV
HD $v \sin i\ $ $v \sin i\ $ remark
  (Gray) (COR)  
87 3.8 3.8 SB
2114 3.9 3.2  
2507 4.2 4.4  
3546 2.5 4.2 SB
3817 3.2 1.7  
7672 4.5 2.9 SB
10761 2.9 2.1  
12929 3.1 1.0 SB
17878 3.6 2.6 SB
20825 7.9 8.0  
21120 4.8 5.9 SB
27348 3.1 1.8  
27371 2.4 1.0  
27697 2.5 1.2 SB
28305 2.5 2.4  
28307 3.4 1.5  
51000 4.7 4.0  
62509 2.5 1.0  
65448 2.4 2.5 SB
71369 2.4 4.3 SB
72561 3.8 6.0  
74485 6.0 6.6  
79452 4.6 4.5  
82210 4.9 5.5  
82328 6.4 8.3 SB?
85945 6.2 6.2  
89485 2.7 1.1  
94481 3.9 2.8  
95689 2.6 1.6 SB
113994 1.8 1.0  
119445 6.0 6.9  
119458 4.9 4.0 SB
124850 15 14.8  
124897 2.4 1.0  
130259 5.6 4.9  
133208 3.4 2.5  
135722 1.1 1.2 SB
140573 0.0 1.6  
142980 1.1 1.0 SB
144608 3.5 1.4  
147266 2.5 1.2  
148387 2.2 1.6  
148856 3,4 4,8 SB
150997 2.2 1.7  
151627 4.7 4.1 SB
153751 24 23 SB
157910 3.6 4.1  
160781 4.5 4.5  
161096 1.6 1.0  
161239 5.4 5.9  
161797 1.2 1.7 SB?
163993 3.5 3.2  
165760 3.9 2.2  
167768 4.6 3.9  
168656 2.6 1.0  
173920 7.7 8.0  


 
Table 1: continued
HD $v \sin i\ $ $v \sin i\ $ remark
  (Gray) (COR)  
182572 2.3 1.7  
185758 5.8 7.1 SB
185958 9.1 9.9  
186675 3.1 1.7  
188119 1.1 1.2  
188512 1.8 1.2  
194577 4.7 3.3  
196524 40.0 49.8 SB
196755 3.3 3.3  
197964 2.8 1.0  
197989 3.0 1.4 SB
198149 1.5 1.4  
198809 5.9 4.7  
200039 2.8 1.0  
200253 4.7 3.0  
202109 3.4 1.0  
203574 2.4 1.0  
205435 2.7 1.9  
208110 4.0 3.3  
210220 3.4 1.8  
214558 4.1 1.4  
215665 7.8 7.5  
216131 2.6 1.2  
218658 4.7 5.5  
219615 0.0 1.6  
220858 2.6 1.0  
221115 3.1 1.5  
222404 0.0 1.0 SB?

Since March 1986 we have undertaken at Geneva Observatory a vast observational program to obtain rotational velocities for a well-defined sample of evolved stars of luminosity classes IV, III, II and Ib/Ib-II large enough to allow a reliable study of their rotational characteristics. This paper presents the results of the survey, concerning essentially the observations for the subgiant, giant and bright giant stars. The results for the supergiants Ib/Ib-II will be published in a forthcoming supplement catalog. Although the initial aim of the present work is the study of the rotational behaviour of evolved stars our observational procedure has produced about 4000 radial velocity measurements. When this survey was planned, there were still some 30% of class II giant and Ib supergiant stars from our selected sample for which no radial velocity measurements were available. The present paper brings such information for these stars.

This catalog is arranged as follows. Section 2 presents the definition of the sample, the observational procedure used throughout this survey, the calibration of rotation rate values, with a discussion of their probable errors and a comparison of our $v \sin i\ $measurements with those obtained by using other high resolution techniques. The list of the individual $v \sin i\ $measurements and the mean radial velocity values are presented in Sect. 3.



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Up: A catalog of rotational stars

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