Access to Astronomical Catalogues

Search catalogue
obsoleted
in preparation
catalog without ftp or VizieR link
J/ApJ/414/846    X-ray emission at the low-mass end   (Barbera+ 1993)

X-ray emission at the low-mass end: results from an extensive "Einstein Observatory" survey Barbera M., Micela G., Sciortino S., Harden F.R. Jr, Rosner R. <Astrophys. J. 414, 846 (1993)> =1993ApJ...414..846B
ADC_Keywords: Stars, late-type ; X-ray sources Keywords: stars: late-type - X-ray: stars Mission_Name: Einstein Abstract: We have used all tha available data from the Einstein Observatory Imaging Proportional Counter (IPC), and a critical compilation of catalogued optical data, to measure the 0.16-3.5 keV X-ray emission from 88 K and 169 M stars of luminosity classes IV, V and VI within 25 pc from the Sun. The IPC detected 54 out of the 88 K stars, 70 out of the 138 M stars with Mv less than 13.4 (corresponding approximatively to M5), and 15 out of the 31 fainter M stars. We have identified a subsample of surveyed stars that is statistically representative of the population of K and M stars in the solar neighborhood. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 104 257 Surveyed K and M stars
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
2- 10 A9 --- Gliese Designation from Gliese (1969), Gliese + Jahreiss (1979), cat. V/35, or Wooley et al. (1970), cat. V/32 12- 13 I2 h RAh Right Ascension 1950 (hours) 15- 16 I2 min RAm Right Ascension 1950 (minutes) 18- 19 I2 s RAs [0/60] Right Ascension 1950 (seconds) 21 A1 - DE- Declination 1950 (sign) 22- 23 I2 deg DEd Declination 1950 (degrees) 25- 26 I2 arcmin DEm Declination 1950 (minutes) 28- 29 I2 arcsec DEs [0/60] Declination 1950 (seconds) 31- 35 F5.2 mag mv Apparent magnitude 37- 40 F4.2 mag B-V []? Colour index 42- 46 F5.2 mag Mv Absolute magnitude 48- 53 A6 -- Sp Spectral class 55- 58 F4.1 pc Distance of star 60- 63 I4 km/s U []? Velocity component 65- 68 I4 km/s V []? Velocity component 70- 73 I4 km/s W []? Velocity component 75 A1 --- AgeFlag [YOH] Y = young disk star, O = old disk star, H = halo population star. 77 A1 --- l_rate [<] Limit flag on rate 78- 82 F5.3 ct/s rate X-ray Count rate (see also column n_rate) 84- 88 F5.3 ct/s e_rate []? Mean error on rate 90 A1 --- l_log(Lx) [<] Limit flag on log(Lx) 91- 95 F5.2 [10-7W] log(Lx) X-ray flux in broad band (0.16-3.5keV) 97- 98 A2 --- n_rate [ML ] Method for count rate evaluation (1) 100 A1 --- Pflag [SP] Pointed flag: S for stars observed serendipitously P for pointed stars. 102-104 A3 --- Notes [vh,] Notes (2)
Note (1): the methods are: L = REV-1 Local method, M = REV-1 Map method, ML = Maximum Likelihood method Note (2): the following symbols are used: v = stars with evidence of long term X-ray variability according to the Maximum Likelihood method adopted (Sciortino and Micela 1992), h = stars observed also with the HRI on board the Einstein Observatory.
Table 2: Distribution of K and M stars in Young disk (Y), Old disk (O), Halo population (H), and stars with unknown space velocities (U) for the optical sample (row 1), X-ray subsample made of the stars with angular distance from the centre of any IPC field greater than 3' (row 2), redefined X-ray serendipitous sample (row 3) and, X-ray representative sample (row 4). The fractions of stars in each age group are given in parenthesis. ------------------------------------------------------------------------------- | K stars | M stars Sample | Y O H U | Y O H U ------------------------------------------------------------------------------- Optical |191(30%) 308(48%) 16(2%) 131(20%)|157(15%) 241(23%) 21(2%) 616(60%) Offax > 3' | 21(44%) 18(37%) 1(2%) 8(17%)| 15(18%) 25(30%) 2(2%) 41(50%) Serendipit.| 14(36%) 16(41%) 1(3%) 8(20%)| 14(20%) 17(24%) 2(3%) 38(53%) Represent. | 23(35%) 33(50%) 2(3%) 8(12%)| 32(25%) 47(37%) 5(4%) 43(34%) ------------------------------------------------------------------------------- Table 3: Results of the K-S test for the rejection of the hypothesis that the distribution of Mv(mv) for the stars of the optical and X-ray subsamples are extracted from the same parent population. Three different subsamples are considered: the stars within the entire volume of 25 pc radius, within 12 pc (only for the K stars) and within 8 pc (only for the M stars). ----------------------------------- K stars M stars Mv mv Mv mv ----------------------------------- R ≤25 pc 0.133 0.997 0.978 0.870 R ≤12 pc 0.188 0.696 R ≤ 8 pc 0.396 0.031 ----------------------------------- Table 4.a: Expectations for late M detections --------------------------------------------------- log(Lx) Expected Observed Confidence erg/s detections detections level --------------------------------------------------- 27.5 9 2 0.995 28.0 7 0 0.999 28.5 3 0 0.950 --------------------------------------------------- statistical results testing the working hypothesis that late M stars follow the same cumulative X-ray luminosity function of early M stars. Column 1 gives the chosen X-ray luminosity threshold, column 2 gives the number of late M detections expected over the X-ray luminosity threshold, column 3 gives the actual number of detected late M stars over the same threshold and, column 4 is the confidence level for the rejection of the hypothesis that the actual number of detections is extracted from a Poisson distribution with mean equal to the expected number. Table 4.b: Expectations for late M detections ---------------------------------------------------- log(Fx) Expected Observed Confidence (erg/s/cm2=mW/m2) detections detections level ---------------------------------------------------- 6.4 5 1 0.966 6.6 5 0 0.993 6.8 3 0 0.950 ---------------------------------------------------- Analogous to Table 4.a but using stellar X-ray surface flux thresholds instead of X-ray luminosity. Table 5: X-ray luminosity of young and old disk populations Means and 1.sigma confidence level uncertainties derived from the X-ray luminosity functions of the young-disk and old-disk star subsamples, of the three spectral types, K, early M and late M, respectively. ------------------------------------ Spectral Log(Lx) (erg/s) Type young-disk old-disk ------------------------------------ K 28.0 ±0.1 27.5 ±0.1 early M 27.7 ±0.1 27.0 ±0.2 late M 27.3 ±0.1 26.9 ±0.2 ------------------------------------ Table 6: Comparison among three different stellar age-classification methods Wilcoxon two-sample test results for the comparison of young and old disk stars according to three different methods of age classification: the Eggen (U-V polygon), the |W|, and the V(pec) methods (section 4.4). ------------------------------- Method K early M late M ------------------------------- Eggen 0.998 0.999 0.799 V_pec 0.995 0.999 0.833 |W| 0.828 0.943 0.853 ------------------------------- Courtesy: Marco Barbera
(End) Francois Ochsenbein [CDS] 12-Jul-1994
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

catalogue service

© UDS/CNRS

Contact