CDROM/AJ/V111/P0439 Chromospheric Emission (Henry+ 1996) ================================================================================ A Survey of Ca II H and K Chromospheric Emission in Southern Solar-Type Stars Todd J. Henry, David R. Soderblom, Robert A. Donahue and Sallie L. Baliunas <1996, AJ, 111, 439> =1996AJ....111..439H ================================================================================ Abstract: More than 800 southern stars within 50 pc have been observed for chromospheric emission in the cores of the Ca II H and K lines. Most of the sample targets were selected to be G dwarfs on the basis of colors and spectral types. The bimodal distribution in stellar activity first noted in a sample of northern stars by Vaughan and Preston in 1980 is confirmed, and the percentage of active stars, about 30%, is remarkably consistent between the northern and southern surveys. This is especially compelling given that we have used an entirely different instrumental setup and stellar sample than used in the previous study. Comparisons to the Sun, a relatively inactive star, show that most nearby solar-type stars have a similar activity level, and presumably a similar age. We identify two additional subsamples of stars -- a very active group, and a very inactive group. The very active group may be made up of young stars near the Sun, accounting for only a few percent of the sample, and appears to be less than ~0.1 Gyr old. Included in this high-activity tail of the distribution, however, is a subset of very close binaries of the RS CVn or W UMa types. The remaining members of this population may be undetected close binaries or very young single stars. The very inactive group of stars, contributing ~5%-10% to the total sample, may be those caught during a Maunder Minimum type phase. If the observations of the survey stars are considered to be a sequence of snapshots of the Sun during its life, we might expect that the Sun will spend about 10% of the remainder of its main sequence life in a Maunder Minimum phase. File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table4.dat 125 1016 Chromospheric activity observations table4.not 70 177 Notes on individual objects in table 4 -------------------------------------------------------------------------------- Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1-11 A11 --- HD Henry Draper number 12-13 2X --- --- Blank 14-15 A2 --- Note *[0123*] Coded note 16-17 2X --- --- Blank 18-26 A9 --- Mult *Multiplicity information 27-28 2X --- --- Blank 29 A1 --- Ref *[BDGHIJW] Coded reference for Mult 30 1X --- --- Blank 31-34 A4 --- Sample *[BCNPSX] Coded sample information 35-41 F7.3 mag V V magnitude 42-48 F7.3 mag e_V Error in V 49-56 F8.3 mag B-V (B-V) color 57-63 F7.3 mag e_B-V Error in B-V 64-66 3X --- --- Blank 67-68 A2 --- MRef *Coded reference for V and B-V 69-70 2X --- --- Blank 71-76 A6 --- Date UT date of observation 77-79 3X --- --- Blank 80-82 A3 --- Flag *Flag indicating special status of obs. 83-90 F8.3 --- SCTIO []? S value from CTIO observation 91-98 F8.3 --- SMW []? S value converted to Mt. Wilson system 99-106 F8.2 --- RHK []? Log R'(HK) value 107-110 4X --- --- Blank 111 I1 --- Obs []? Number of observations 112-119 F8.3 --- MRHK []? Mean log R' value of observations 120-125 F6.3 --- e_MRHK []? Error in MRHK -------------------------------------------------------------------------------- Notes for file: table4.dat -------------------------------------------------------------------------------- Notes: 0 = target not listed in INCA (The Hipparcos Input Catalog) 1 = double target listed as A and B in INCA, but components have different HD numbers 2 = target listed as AB in INCA, but split in this survey 3 = target listed as single in INCA, but with orbits in references B, D or G (see Ref below) * = note given at end of table Mult: Multiplicity information P = period in d(ays) or y(ears) s = separation in arcseconds a = semimajor axis of orbit in arcseconds Ref: Reference for multiplicity information B = Batten, Fletcher & MacCarthy 1989, Eighth Catalogue of the Orbital Elements of Spectroscopic Binary Systems, Publications of the Dominion Astrophysical Observatory, v. XVII (BFM89) D = Duquennoy & Mayor 1991, A&A, 248, 485 G = Gliese 1969, Veroffentlichungen des Astronomischen Rechen- Instituts, Heidelburg, No. 22 (G69); Gliese & Jahreiss 1979, A&AS, 38, 423; 1991, Preliminary Version of the Third Catalog of Nearby Stars (GJ91) H = Heintz 1984, AJ, 89, 1068; 1994, AJ, 108, 2338 I = Hipparcos Input Catalog, Turon, C. et al. 1992, ESA Publication Division, c/o ESTEC, Noordwijk, The Netherlands (INCA) J = Jeffers, van den Bos & Greeby 1963, Index Catalogue of Visual Double Stars, 1961.0, Publications of the Lick Observatory, v. XXI (IDS) W = Worley & Heintz 1983, Fourth Catalog of Orbits of Visual Binary Stars, Publications of the United States Naval Observatory, v. XXIV, part VII (WH83) Sample: B = Best & Brightest C = Calibration N = Nearby P = Primary S = Secondary X = Extra MRef: Reference for magnitude and color information Ig = INCA, good data with (B-V) error <= 0.10 mag Ip = INCA, poor data with (B-V) error > 0.10 mag, only value available G = Gliese & Jahreiss 1991 S = SIMBAD blank = no value available Flag: Flag indicating special status of observation cal = calibration star con = contaminated spectrum hgh = very high SCTIO value (> 0.600) low = very low SCTIO value (< 0.180) noi = noisy spectrum off = minima of H and K lines out of dithering window pht = no (B-V) photometry available, or (B-V) out of sample range (0.50 to 1.00 for all samples) There are only 4 stars with (B-V) = 0.40 to 0.49: 1 Primary, 1 Calibration, 2 Extra targets. ray = cosmic ray in necessary window spc = special target str = strange spectrum -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.not -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1-70 A70 --- Note HD number followed by text of the note -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 07-Mar-1996