PI''''8Z''•Srdv^^GI The Astrophysical Journal Supplement Series, No. 252, 28:1-18 © 1974. The American Astronomical Society. All rights reserved. Printed in U.S.A. SPECTRAL TYPES OF M DWARF STARS Alfred H. Joy Hale Observatories, Carnegie Institution of Washington, California Institute of Technology, Pasadena AND Helmut A. Abt Kitt Peak National Observatory,* Tucson, Arizona Received 1973 December 10 ABSTRACT Spectral types on a uniform system based on primarily TiO band strengths are given for 426 M dwarf stars. It is found that the frequency of emission-line stars increases steadily from ~ 5 percent among the early M’s through ~50 percent at M4.5 to 100 percent for M5.5 and later. The absolute magnitudes of emission-line (dMe) and normal (dM) dwarfs average the same within 0.07 mag at a given spectral type. A new calibration of absolute magnitudes, based on trigonometric parallaxes, is given. The measured width of the main-sequence band can be accounted for mostly in terms of the errors in classification, parallaxes, and photometry and to some duplicity; the cosmic dispersion is less than 0.3 mag. The R — / colors of dMe stars are larger by 0.08 ± 0.02(p.e.) mag than for dM stars, although the B — V colors do not show this effect. Subject headings: late-type stars — luminosities — spectral classification I. SPECTRAL CLASSIFICATION stars with hydrogen emission lines ; stars with emission lines due to calcium only are called “dM.” Since the previous publication (Joy 1947) of spectral A long-standing frustration regarding M dwarfs has types of late-type dwarfs, a considerable number of been the usage of names from a wide variety of additional stars have been observed. The resulting catalogs. In table 1 we have compiled most of the spectral types, combined with the recent additional designations used; further ones are given by Woolley parallaxes and photoelectric photometry, present a et al (1970). The designations include numbers from somewhat different view of the relation of absorption Cincinnati (Publications of the Cincinnati Observa- (dM) and emission-line (dMe) dwarfs. tory, No. 18 and 20), Furuhjelm [Frjm] (1917), Gliese Spectrograms of M dwarfs have been obtained [GLS] (1969), Groombridge [Grmb], (Dyson and systematically at the Hale Observatories during an Thackeray 1905), Luyten [LFT] (1955) and other interval of 50 years. Most of those dwarfs were dis- catalogs, McCormick [McC] (Vyssotsky 1943, 1956; covered by their large proper motions except for the Vyssotsky et al. 1946; Vyssotsky and Mateer 1952), McCormick (Vyssotsky) stars. The stars observed Ross (1925-1939), Weisse-Bessel [WB] (Weisse 1846, spectroscopically included most of the northern M 1863), Wolf (1914-1929), Yale (Jenkins 1952, 1963), dwarfs brighter than F = 11 mag and many fainter and the standard Aitken [ADS], Henry Draper, ones. The observations were made with the Mount Lalande, variable star, and constellation names. The Wilson 60-inch (1.5-m) and 100-inch (2.5-m) telescopes last three columns of table 1 give the apparent visual and Cassegrain spectrographs at dispersions of 100 Â magnitude from Gliese or other sources, the trigonom- mm ~1 or higher ; a few stars were observed at 220 Â etric absolute magnitude as given by Gliese, and the mm-1 and their resulting types of lower quality are spectral type. enclosed in brackets in table 1. Most of the spectrog- rams were obtained by Drs. W. S. Adams, E. R. Dyer, II. DISCUSSION Jr., M. L. Humason, and A. H. Joy. Meaningful statistics on the relative numbers of The spectral types given in table 1 for 426 M dwarfs emission- and absorption-type stars can be compiled are based mostly on the strengths of TiO bands in the from these data but not results concerning the blue. All the stars, including the ones reported on luminosity function among M dwarfs because the previously (Joy 1947), have been reclassified on a observational limit of the program was by apparent uniform system. Thus it is possible to consider the magnitude. Column (4) of table 2, which does not relative properties of dMe and dM stars because neither include the Taurus cloud and Orion Nebula stars, the selection of stars observed nor the spectral types shows that there are very few field emission stars determined were dependent on the presence or absence through M2, that roughly half of the M2.5-M5 stars of emission lines. The designation “dMe” refers to are dMe’s, and that all of the stars of types dM5.5 or later are dMe’s. The frequency of subdwarfs seems to show no strong dependence on type. * Operated by the Association of Universities for Research in Astronomy, Inc., under contract with the National Science A question of importance is whether the absolute Foundation. magnitudes of the dMe stars are different from those 1 © American Astronomical Society • Provided by the NASA Astrophysics Data System PI''''8Z''•Srdv^^GI Table 1 Identifications, Magnitudes, and Spectral Types R.A. Dec!. Identifications M. Spectral (1900) Type 0:00.4 +45°161 ADS 48B, BD+45°4408B, 18C 2, 20C 6s, GIS 4B, 8.97 8.84 B dM0.5 HD 38B, LFT 9, McC 217B, Yale 4 0:08.0 +19 49 BD+19°20, McC 83, Yale 32.1 10.1 dMO 0:11.8 +40 23 BD+40°45, 20C 16, GLS 14, LFT 28, McC 84 9.00 8.0 F dMO.5 Ross 5, Yale 45 0:12.7 +43 27 ADS 246A, BD+43°44, 18C 25A, 20C 19A, GLS 15A, 8.07 10.32 A dM2.5 Grmb 34A, LFT 31, McC 85, Yale 49A 0:12.7 +43 27 ADS 246B, 18C 25B, GLS 15B, Grmb 34B, LFT 32, 11.04 13.29 A dM4.5e Yale 49B 0:26.3 +66 42 ADS 433A, ADS 440A, BD+66°34, 20C 34, GLS 22A, 10.51 10.42 B dM2.5 LFT 47, Yale 86 0:27.7 +41 28 AC+42°23-87 , AC+41019-173 , GLS 22.1, McC 218, 11.0 9.8 E dMl Wolf 4, Yale 92.1 0:33.5 +30 04 AC+31°719, 20C 40, GLS 26, LFT 57, Wolf 1056, 11.02 10.54 C dM3.5 Yale 107 0:35.7 - 7 47 ADS 566B, BD-80117B, Yale 119B 10.02 dMl 0:36.4 -13 44 BD-13°116, McC 86, Yale 120.1 10.7 dMO 0:37.3 +35 00 FF And, BD+34°106, GLS 29.1, McC 87, Yale 125 10.38 8.7 E dMle 0:39.5 -1 9 29 BD-19°m, GLS 31.2, McC 88, Yale 140 10.6 9.4 E dMl.5 0:43.0 +57 17 ADS 671B, BD+57°150B, 20C 56B, n Cas B, GLS 34B, 7.51 8.66 B dMO LFT 75, Yale 155B 0:45.3 +57 45 AC+58°5535, AC+57°5559, 20C 60, GLS 38, LFT 80, 11.0 10.0 E dMl Wolf 33, Yale 169 0:55.1 +60 50 AC+61°3275, AC+60°3496, 20C 65, GLS 47, LFT 90A, 10.7 10.2 D dM2.5 Wolf 44, Yale 201 0:55.3 +71 09 AC+71°532, 20C 66, GLS 48, LFT 93, McC 364, 10.06 10.34 A dM3.5 Ross 318, Yale 202 0:56.3 +61 48 BD+61°195, 20C 68, GLS 49, LFT 94, McC 2, 9.57 9.72 C dM2 Wolf 46, Yale 204 0:57.0 +61 50 20C 70, GLS 51, LFT 95, Wolf 47, Yale 205 13.66 13.81 C dM5e 0:57.2 +46 31 McC 90A, Yale 205.2 10.9 dMO 0:57.4 -10 57 BD-11°192, McC 3, Yale 208 9.7 dMO. 5 1:00.4 +63 24 BD+63°137, 18C 142, 20C 74, GLS 52, LFT 104, 9.00 8.29 C dMl McC 365, Yale 217 1:03.4 +16 44 BD+16°120, 20C 82, GLS 53.2, LFT 114, Wolf 1515, 11.2 9.5 PF dMO Yale 231 1:07.5 -17 32 GLS 54.1, LFT 118, LPM 63, L725-32 11.6 12.4 F dM5.5e 1:12.1 +79 38 BD+79°38, GLS 56.4, McC 91, Yale 263 9.66 7.7 E dMO 1:25.5 +77 34 AC+77°742, McC 92, Yale 312.1 10.6 dMO 1:34.0 -18 28 GLS 65A, LFT 144, L726-8A, Yale 343.1A 12.45 15.27 B dM5.5e 1:34.0 -18 28 GLS 65B, LFT 145, L726-8B, UV Cet, Yale 343.IB 12.95 15.8 C dM6e 1:36.8 +63° 201 BD + 63°229 , 1 8C 238, 20C 121, GLS 69, HD 1 0436 , 8.40 7.78 B dMO.5 LFT 155, McC 381 , Yale 354 2 © American Astronomical Society • Provided by the NASA Astrophysics Data System PI''''8Z''•Srdv^^GI Table! (cont.) R.A. Dec!. Identifications M. Spectral (1900) Type 1:38.2 + 3°481 AC + 4° 2595-239 , AC + 3° 2259-31 , GLS 70, LFT 1851, 10.95 11.2 D dM 2 McC 93, Yale 363.1 1:48.0 -22 56 CD-23°693, 20C 132, GLS 79, HD 11507, LFT 168, 8.8 8.4 D dM1.5 McC 4, Yale 392 1:51.0 +29 20 AC+29°4398, McC 94, Yale 398 10.7 dM 1 1:52.5 +58 14 AC+59°13164, AC+58°13565, GLS 82, Ross 15, 12.1 11.7 D dM4e Yale 408 2:00.6 +44 43 AC+45°84-347, AC+45°91-61, 20C 146, GLS 84.2, 11.1 10.1 E dMO LFT 181 , Yale 433 2:07.4 + 3 10 BD+2°348, 20C 153, GLS 87, LFT 187, McC 95, 10.03 10.03 B dM2.5 Wolf 124, Yale 450 2:15.7 +47 24 BD+47°612, GLS 96, McC 96, Yale 481 9.41 9.3 C dM1.5 2:18.5 +49 21 AC+49°2493-285, McC 5, Yale 489.1 11.2 dMO 2:22.5 + 3 59 ADS 1865AB, BD+3°339, 18C 319, GLS 98AB, r9.38 8.41 B dMl .