RADIAL VELOCITIES AND SPECTRAL TYPES FOR FOURTEEN STARS *

Transcription

1 RADIAL VELOCITIES AND SPECTRAL TYPES FOR FOURTEEN STARS * NANCY G. ROMAN National Aeronautics and Space Administration Washington, D.C. Kitt Peak National Observatoryt Tucson, Arizona Received December 12,1966 Radial velocities and spectral types are given for thirteen stars between 8 and 12 m vq. Photoelectric magnitudes and colors are listed for six of these stars. The stars include a Ban star, a weak-line G8 IV star, two F-type subdwarfs and two emission-line stars near AO. Some years ago, the writer initiated a program of spectroscopic and photometric observations of stars in the Kapteyn Selected Areas brighter than 12.0 m pg. The original plan of obtaining space motions for these stars has, so far, proved impractical. However, a recent visit to the Kitt Peak National Observatory provided an opportunity to obtain radial velocities for a few of the stars that appeared par- ticularly interesting either spectroscopically or photometrically. In addition, several stars for which slit spectrograms were not pre- viously available were added to the program. One plate of each star was obtained with the 400 line/mm grating in the spectrograph on the 36-inch telescope which gives a dis- persion of approximately 127 A/mm. Measurements of four stan- dard velocity stars indicate that the mean error of an observation is =t=10km/sec. For comparison, the internal mean error of the mea- surements is 5 km/sec, and the average difference between the direct and reversed measurements is 7 km/sec. Although the single plate per star gives no indication of a possible variable velocity, the velocities (last column of Table I) should be useful statistically. The spectral types, in the fourth column of Table I, were esti- mated from the same plates. Although several key standards were * Contributions from the Kitt Peak National Observatory, No foperated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science Foundation. 168

2 VELOCITIES AND SPECTRAL TYPES 169 O «< N lo CO > I (N (M ^ 00 a io io CO o tf CM i l CM I I IO 00 N CO (N cq co ^ + + cd oo io oq co io ^ io H O O o o o o o o o CD CO IO cm o cm co O O O Q o o o o CO CD O i I CM CM CO O O I I o o o o Radial Velocities and Spectral Types CQ a <d o & C/3 O IO 05) 5h 4-> Cj (73 ^F oo ^ CO cq Tf 05 oo 1-Î l~h l-h r I Q-l )-H *~h M > > > > a Oí CD O Q ÉL, w CM OO 00 CM CM cq co io ^ ^ ^ ^ CM CM CM ' I i l N OO CO D io oq D ^ oo CD CD o- 0 t i > > > a IO O CM 05) 05) < pq pq pq ^ CO 05 CO IO ID ^ i l CM O IO o o o I + I I I 05 O CO ^ 05 CO CD ^ S CO ID CD CM CM H N CD 05 (M T I i-h (M H Tf Tf) i-h i-h i-h CO CO IO CD CD CD 00 05) # ss 05 * «9 N ^ «Iß IO I S 8 7 ^ Q I I Pi 9 0 Q û QJ B ffi pq pq t>* oo i l CM CO i-h IO ^F CO xf 05) 4 # T I H 03 t> o O CO O CM CO O L- IO i~h OÛQÛO a as cq a sc IO Tjn cq ^F ^F i l o 00 i I > > > > a CD o 0 00 m fe O O N ^ 05 OO r I IO CO O IO CO o co + + N N 00 0^0 IO i-h i-h TF 05) CM CO CO 1 1 CM CM CM CD Ä CD K?n IO 00 cd 52 io i H o r-h IO i03 3 < " i l i 4 CM CD _ <3 û Q Q co pq a pq * See following notes. fthese spectroscopic parallaxes have been corrected for interstellar absorption.

3 170 NANCY G. ROMAN NOTES TO TABLE I HD 6724 Wayman (1961) has published the radial velocity of this star as +1.4 ±1.6 km/sec. BD Ban star (see Bidelman and Keenan 1951). The photometry is based on a single observation. HD This relatively bright star was observed by mistake in place of a nearby standard velocity star. As it does not appear in the General Catalogue of Stellar Radial Velocities, the measurement is included here. The spectral type and magnitude are from the Henry Draper Catalogue. HD = MWC 159 H/2, and possibly Hy, appear to have slightly red-shifted emission cores. However, the measurement of the displacement of these cores proved inconsistent. The hydrogen absorption lines are broad and possibly asymmetric. Dr. Garrison has examined a Mount Wilson plate of this star and finds strong emission at Hß and some at Hy (private communication). The published velocity for this star is +4 km/sec. HD = MWC 956 Dr. Bidelman, in a private communication, has noticed an absorption reversal in the Ha emission and suggests that this is apparently a shell star. The published velocity for this star is 18.2 km/sec. SA The magnitude may be slightly variable. HD The lines are much weaker than those in a normal subgiant of the same type. unavailable, the types should be reasonably accurate. They agree well with those the writer estimated on McDonald plates of a similar dispersion. In Table I the SA number is from Harvard Annals, Volume 101. Roman numeral VI is used to denote the F-type subdwarfs. The two-decimal magnitudes are photoelectric measures on the UBV system obtained by the writer at the McDonald Observatory; those in italics are from the Potsdam catalog of spectral types and the Harvard-Groningen photometry in southern and northern Selected Areas. The spectroscopic parallaxes are based on the calibration compiled by Blaauw ( 1963 ). The color indices on the UBV system measured by the writer are

4 VELOCITIES AND SPECTRAL TYPES 171 given in Table II. This table also contains proper motions from the 1966 Smithsonian Astrophysical Observatory Star Catalogue or The Radcliffe Catalogue (Knox-Shaw and Barrett 1934). The latter proper motions are given in parentheses and have been reduced to absolute motions by means of the catalog s table of mean motions of the comparison stars. If the computed tangential motions are TABLE II Additional Information Star B-V Proper Motion fi a COS ô Space Vel. U-B C'/yr) ("/yr) (km/sec) HD 6724 HD 6868 BD *11 HD BD HD HD SA HD BD (-0.009) ( +.009) +0* (+0.001) (-0.042) (+0.025) 35 ( ) (-0.006) (-0.040) 96 meaningful, total space velocities have been computed and are given in the last column of this table. Three of the stars appear to have well-established motions larger than 60km/sec: the Ban star BD , the weak-line subgiant, HD , and the apparently normal subgiant, BD The last star, placed on the program because of the high tangential velocity, was classified as G8IV on McDonald and Kitt Peak spectrograms independently. The stars HD 44128, 50209, and are brighter in the ultraviolet than is normal for their spectral types. Although they were included in the program primarily to check the spectral types obtained from McDonald plates ( since a reddened early B star would have similar colors ) there is no question that the types are near A0. The ( B V) color indices of HD and , which are essentially unreddened, appear normal. HD has weaker

5 172 NANCY G. ROMAN hydrogen lines than normal for B9 V and possibly even for B9 III, but it does not show the additional lines visible at B9II on this dispersion. Although HD may have very slightly weakened hydrogen lines, it is not obviously unlike a normal AO V star. Dr. Garrison has examined Mount Wilson plates of HD and HD and finds that both stars show hydrogen emission lines ( private communication ). In a study of the stars in the Scorpio-Centaurus association, Garrison ( 1967 ) classified several late B-type stars which, at prism dispersion of 86 A/mm at HS, are spectroscopically later than the B3-5 types implied by the color indices on several photometric systems. He suggests that similar stars probably occur in other clusters. It is possible that HD is also related to those observed by Garrison, although it is more likely that it is also an emission star. The writer is grateful to the staff of the Kitt Peak National Observatory not only for the use of the telescope and Grant measuring engine and for their hospitality during her visit, but particularly for their helpful advice, their sincere concern for the success of her work, and their loan of plates of spectroscopic standards. She also thanks Dr. Garrison for his informative letter about his observations. REFERENCES Bidelman, W. P., and Keenan, P. C. 1951, Ap. J. 114, 473. Blaauw, A. 1963, in Basic Astronomical Data, K. Aa. Strand, ed. (Chicago: University of Chicago Press ) 5 p Garrison, R. F. 1967, Ap. J. 147, Knox-Shaw, H., and Barrett, H. G. S. 1934, The Radcliffe Catalogue of Proper Motions in the Selected Areas, (Oxford University Press, London: Humphrey Milford). Wayman, P. A. 1961, Roy. Obs. Bull. No. 36. Wilson R. E. 1963, General Catalogue of Stellar Radial Velocities (Washington, D.C.: Carnegie Institution of Washington Pub. No. 601).