CDROM/APJS/V85/P315 F, G, and K Dwarfs of Pleiades (Soderblom+ 1993) ================================================================================ Rotation and Chromospheric Emission Among F, G, and K Dwarfs of the Pleiades David R. Soderblom, John R. Stauffer, J. Daniel Hudon, & Burton F. Jones <1993, ApJS, 85, 315> =1993ApJS...85..315S ================================================================================ Abstract: We report and discuss high-resolution echelle spectra of more than 100 F, G, and K dwarfs in the Pleiades. Comparisons of the profiles of Halpha and the Ca II infrared triplet to chromospherically inactive field stars allow us to measure chromospheric activity in these stars, and we have determined v sin i values to a limit of 7 km/s. We have combined these new observations with published data and have conducted a census to assess the state of our knowledge of Pleiades solar-type stars. After allowing for a patch of heavy reddening in the southwest part of the cluster, consistent dereddened colors are determined from the available photometry and temperatures are derived. Rotation is fully resolved in the Pleiades for stars more massive than the Sun, but for less massive stars there are still too many upper limits to v sin i to determine the underlying, intrinsic distribution of rotation. Over the entire mass range we consider (1.4 >~ M/M(sun) >~ 0.6), no single value can characterize rotation at any one mass because the spread is too large. Most G and K dwarfs in the Pleiades rotate slowly (v sin i <~ 10 km/s), but ~20% of the stars are ultrafast rotators (UFRs) with v sin i >~ 30 km/s. That fraction of UFRs is independent of color, and the highest rotation rates are found among the K dwarfs. The surfaces of the many slowly rotating solar-type stars in the Pleiades are already rotating at or near the rate of stars of the same mass in the Hyades. That means that the dominant aspect of the evolution of rotation from the age of the Pleiades to the Hyades is convergence on rotation. Among the F dwarfs, the degree of convergence is about a factor of 5, but among the K stars it is at least a factor of 20. We argue that this convergence, as well as the large number of slow rotators at 1.0 M(sun), suggests that the convective envelopes and radiative cores of these Pleiads are rotationally decoupled, with later replenishment of angular momentum to the envelope. The Pleiades also shows a broad range in the strength of chromospheric emission (CE) at any one color. CE depends on both mass and rotation, but, once the rotation is normalized to an index akin to the Rossby number, rotation and activity are well correlated. Most G and K dwarfs in the Pleiades show Halpha and the infrared triplet in absorption, with filling in of the line cores. Some stars show overt Halpha emission comparable in strength and profile to the weaker T Tauri stars, and a few even show overt emission at the infrared triplet. We have also found three G dwarfs with peculiar Halpha profiles whose rotation rates substantially exceed those seen previously in the Pleiades among stars of their color. These stars show very broad wings to their Halpha emission profiles, suggesting that the emission arises over a broad range of height in the stars' atmospheres. Keywords: open clusters and associations: individual (Pleiades) -- stars: chromospheres -- stars: late-type -- stars:rotation File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table1.dat 78 113 Lick Observations table7a.dat 80 200 A Census of F, G, and K Dwarf Members of the Pleiades table7b.dat 22 80 Pleiades Members from Pels' List -------------------------------------------------------------------------------- Comments for file: table1.dat -------------------------------------------------------------------------------- Table 1 presents the results of observations obtained at Lick Observatory with the Hamilton coude echelle spectrograph fed by the Shane 3 m telescope. Use of a TI 800x800 CCD enabled the authors to record the central portions of orders from near Hbeta to the Ca II infrared triplet, including Halpha and the lithium 6708 A feature. To determine radial and rotational velocities the authors used the two echelle orders centered at 6010 and 6140 A, each containing ~40 A of spectrum; those regions contain many stellar absorption features yet few telluric lines. The standard deviation of the radial velocities of the nonbinaries on the Pleaides sample is 1.3 km/s. Only ~0.4 km/s of that is due to a real velocity dispersion within the cluster. The remainder of the scatter is due to observational error and to the presence of unknown binaries among the stars thought to be single. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- HII H II (Hertzsprung) number 5- 6 2X --- --- Blank 7-10 A4 --- fgk Id. no. as cross-reference to TABLE7A.DAT 11-20 F10.3 d HJD Heliocentric Julian date minus 2440000 21-26 F6.1 km/s vrad []? Rad. vel. wrt cluster mean=+4.8 km/s 27 A1 --- u_vrad Qualifier ':' (one case only, star 1136) 28 A1 --- l_vsini Limiting character for vsini 29-31 F3.1 km/s vsini []? v sin i 32 A1 --- u_vsini Qualifier ':' (one case only, star 1136) 33-37 F5.2 0.1nm WHa *[]? Equivalent width, core of H-alpha 38-43 F6.2 0.1nm W8498 *[]? Equivalent width, core of Ca II 8498A 44 A1 u_W8498 Qualifier ':' for W8498 45-49 F5.2 0.1nm W8542 *Equivalent width, core of Ca II 8542A 50-55 F6.2 0.1nm W8662 *[]? Equivalent width, core of Ca II 8662A 56-61 F6.2 Mergs/cm2/s FHa []? Chromospheric flux, H-alpha 62-66 F5.2 Mergs/cm2/s F8542 []? Chromospheric flux, Ca II 8542A line 67-72 F6.2 --- RHa []? log FHa/(stellar bolometric flux) 73-78 F6.2 --- R8542 []? log F8542/(stellar bolometric flux) -------------------------------------------------------------------------------- Notes for file: table1.dat -------------------------------------------------------------------------------- WHa, W8498, W8542, W8662: Values are measured by subtracting the profile of a chromospherically inactive star. Units are Angstroms relative to the continuum. -------------------------------------------------------------------------------- Comments for file: table7a.dat -------------------------------------------------------------------------------- Table 7A presents a list of Pleiades members that have intrinsic colors appropriate to spectral types F, G, and K. See Section 4 of the printed paper for a detailed discussion of the entries in this list. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table7a.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- fgk *Running number 5- 6 2X --- --- Blank 7-13 A7 --- Name *Star name 14-19 F6.3 mag B-V *[]? Mean observed (B-V) value 20 A1 --- q_B-V *(B-V) quality flag 21 1X --- --- Blank 22 A1 --- n_B-V *Number of values used to calculate (B-V) 23-28 F6.2 mag V-R_J *[]? Johnson (V-R) color 29-33 F5.2 mag V-I_J *[]? Johnson (V-I) color 34-39 F6.2 mag V-R_K *[]? Kron (V-R) color from Stauffer (1980, 1982, 1984) 40 1X --- --- Blank 41 A1 --- f_V-I_K *[(] Means V-I_K contains the Stromgren (b-y) 42-46 F5.3 mag V-I_K *[]? Kron (V-I) color or Stromgren (b-y) index 47 1X --- --- [)] Matching right parenthesis, ')', or blank 48-54 F7.3 mag V-B_W *[]? Walraven (V-B)_W color 55-56 2X --- --- Blank 57-62 A6 --- Sp *Spectral type 63-69 F7.3 mag B-V_0 *Adopted unreddened color, (B-V)_0. 70 A1 --- u_B-V_0 ':' in one case, HII 2281 = k212 71-75 I5 --- Teff *Adopted value of the effective temperature 76 A1 --- u_Teff ':' in one case, HII 2281 = k212 77 1X --- --- Blank 78-80 A3 km/s vsini *Rotational velocity, v sin i (in km/s) -------------------------------------------------------------------------------- Notes for file: table7a.dat -------------------------------------------------------------------------------- fgk: Running number, grouped in intervals of 0.1 in (B-V)_0 [dereddened (B-V) color] and with a prefix roughly indicative of spectral class. These numbers are continued for the Pels stars in TABLE7B.DAT. Name: Star name: No prefix: H II number of Hertzsprung (1947, Ann Leiden Obs., 19, Part 1A). 'R', 'S' : Trumpler (1922, Lick Obs. Bull 10, 110) (sometimes denoted as TR or TS). 'sk' : Stauffer et al. 1991, AJ, 101, 980. 'Ton' : Tonantzintla number from Haro et al. (1982, Bol. Inst. Tonantzintla, 3, 1). These are the numbers in column (1) of their Table I, and should not be confused with the `T' designations there. B-V: Mean observed (B-V) value, taken from the compilation of Mermilliod (1986, Bull. d'Inf. du CDS, No. 31, 175), except that any Johnson & Mitchell (1958, ApJ, 128, 31) observation with (B-V) > 1.00 was rejected as being too inaccurate unless no other was available. q_B-V: (B-V) quality flag. A colon, ':' indicates a poor-quality observation of Johnson & Mitchell (1958, ApJ, 128, 31) (indicated by a `J' in n_B-V) or that the (B-V) values for that star show greater than average variance. n_B-V: Number of independent (B-V) values used to calculate (B-V). A `J' indicates that the only available datum was a photographic (B-V) from Johnson & Mitchell 1958, ApJ, 128, 31. V-R_J, V-I_J: Johnson colors from Mendoza (1967, Bol. Obs. Tonantzintla y Tacubaya, 4, 149) and Landolt (1979, ApJ, 231, 468) V-R_K: Kron (V-R) color from Stauffer (1980, AJ, 85, 1341; 1982, AJ, 87, 1507; 1984, ApJ, 280, 189) f_V-I_K: Left parenthesis, '(', for the hottest stars, meaning V-I_K contains the Stromgren (b-y) index from Crawford and Perry (1976, AJ, 81, 419) V-I_K: Kron (V-I) color from Stauffer (1980, AJ, 85, 1341; 1982, AJ, 87, 1507; 1984, ApJ, 280, 189), or the Stromgren (b-y) index if f_V-I_K = '(' V-B_W: Walraven (V-B)_W color, from van Leeuwen et al. (1986, A&AS, 65, 309) Sp: Spectral type, from Mermilliod (1986, Bull. d'Inf. du CDS, No. 31, 175), Kraft & Greenstein (1969, in Low-Luminosity Stars, ed. S. S. Kumar (New York: Gordon & Breach), 65), Wilson (1963, ApJ, 138, 832), Herbig (1962, ApJ, 135, 736), Breger (1984, A&AS, 57, 217), and Breger (1986, ApJ, 309, 311). B-V_0: Adopted unreddened color, (B-V)_0. Except for the few stars with unusual reddening (see Table 9 of the printed paper), these were all calculated using E(B-V) = 0.04 magnitude, but all available colors were used as input, using mean relations. These colors are not, of course, precise to 0.001 magnitude but the authors have preserved an extra decimal place to reduce round-off error. Teff: Adopted value of the effective temperature, calculated from (B-V)_0 as described in the printed paper, and rounded to the nearest 20 K vsini: Rotational velocity, v sin i (in km/s), from the present study, SH, Stauffer et al. (1984, ApJ, 280, 202), Anderson et al. (1966, ApJ, 143, 299), and Kraft (1967, ApJ, 150, 551). A note of 'SB2' indicates a double-lined spectroscopic binary whose v sin i values are given in Table 2 of the printed paper. A few other recent determinations of v sin i for some of these stars are mentioned in the text. -------------------------------------------------------------------------------- Comments for file: table7b.dat -------------------------------------------------------------------------------- Table 7B lists the Pels stars [Pels, Oort, & Pels Kluyver 1975, A&A, 43, 423] with running numbers that continue from TABLE7A.DAT, because at present only Walraven photometry is available for most of them. -------------------------------------------------------------------------------- Byte-by-byte Description of file: table7b.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- fgk Running fgk number, contd. from TABLE7A.DAT 5- 9 I5 --- Pels Pels number 10-16 F7.3 mag V-B_W *Walraven (V-B)_W color 17-22 F6.2 mag B-V_0 *Adopted unreddened color, (B-V)_0 -------------------------------------------------------------------------------- Notes for file: table7b.dat -------------------------------------------------------------------------------- V-B_W: Walraven (V-B)_W color, from van Leeuwen et al. 1986, A&AS, 65, 309 B-V_0: Adopted unreddened color, (B-V)_0. The authors used the (V-B)_W color to estimate this value in the way described in section 4.1 of the printed paper so that the Pels stars can be compared to the others. -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 23-Mar-1995