2011A&A...534A..30G


Query : 2011A&A...534A..30G

2011A&A...534A..30G - Astronomy and Astrophysics, volume 534A, 30-30 (2011/10-1)

Long-term magnetic activity of a sample of M-dwarf stars from the HARPS program. I. Comparison of activity indices.

GOMES DA SILVA J., SANTOS N.C., BONFILS X., DELFOSSE X., FORVEILLE T. and UDRY S.

Abstract (from CDS):

The search for extra-solar planets similar to Earth is becoming a reality, but as the level of the measured radial-velocity reaches the sub-m/s, stellar intrinsic sources of noise capable of hiding the signal of these planets from scrutiny become more important. Other stars are known to have magnetic cycles similar to that of the Sun. The relationship between these activity variations and the observed radial-velocity is still not satisfactorily understood. Following our previous work, which studied the correlation between activity cycles and long-term velocity variations for K dwarfs, we now expand it to the lower end of the main sequence. In this first paper our aim is to assess the long-term activity variations in the low end of the main sequence, having in mind a planetary search perspective. We used a sample of 30 M0-M5.5 stars from the HARPS M-dwarf planet search program with a median timespan of observations of 5.2 years. We computed chromospheric activity indicators based on the CaII H and K, Hα, HeI D3, and NaI D1 and D2 lines. All data were binned to average out undesired effects such as rotationally modulated atmospheric inhomogeneities. We searched for long-term variability of each index and determined the correlations between them. While the SCaII, Hα, and NaI indices showed significant variability for a fraction of our stellar sample (39%, 33%, and 37%, respectively), only 10% of our stars presented significant variability in the HeI index. We therefore conclude that this index is a poor activity indicator at least for this type of stars. Although the Hα shows good correlation with SCaII for the most active stars, the correlation is lost when the activity level decreases. This result appears to indicate that the CaII-Hα correlation is dependent on the activity level of the star. The NaI lines correlate very well with the SCaII index for the stars with low activity levels we used, and are thus a good chromospheric activity proxy for early-M dwarfs. We therefore strongly recommend the use of the NaI activity index because the signal-to-noise ratio in the sodium lines spectral region is always higher than for the calcium lines.

Abstract Copyright:

Journal keyword(s): techniques: spectroscopic - stars: late-type - stars: activity

Simbad objects: 34

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Number of rows : 34
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 HD 225213 Er* 00 05 24.4278018131 -37 21 26.504223709 11.074 10.022 8.562 7.589 6.432 M2V 189 0
2 CD-23 1056 PM* 02 46 42.8866903919 -23 05 11.802472662 12.911 11.651 10.237 9.36 8.544 K5V 53 1
3 G 77-46 PM* 03 21 46.9231319786 -06 40 24.217353522   12.49 11.314 10.981 9.47 M2V 42 0
4 L 229-91 PM* 04 09 15.6684896752 -53 22 25.289691709 14.397 13.302 11.811 10.734 9.32 M3.5 80 2
5 HD 285968 PM* 04 42 55.7753203198 +18 57 29.394344631 12.668 11.49 9.951 8.931 7.702 M2.5V 275 2
6 HD 36395 PM* 05 31 27.3958475290 -03 40 38.021551815 10.626 9.443 7.968 6.996 5.913 M1.5Ve 448 0
7 HD 42581 Er* 06 10 34.6152510171 -21 51 52.658021185 10.801 9.607 8.125 7.164 6.121 M1V 417 0
8 CD-22 3005 PM* 06 21 53.8081068586 -22 43 24.070505873 13.218 12.061 10.693 9.804 8.843 M1Vk 41 0
9 BD+05 1668 PM* 07 27 24.4989685603 +05 13 32.841491057 12.558 11.443 9.872 8.699 7.161 M3.5V 358 0
10 CD-24 6144 PM* 07 54 10.8827709147 -25 18 11.420592819 12.286 11.107 9.715 8.845 8.029 M0 39 0
11 Ross 85 PM* 09 41 10.3603705950 +13 12 34.424857126 13.097 11.891 10.370 9.371 8.182 M2.5V 110 0
12 CD-45 5627 Er* 09 58 34.3230661116 -46 25 30.404116219 13.77 12.8 11.320 10.133 8.635 M3Ve 85 1
13 V* AN Sex RS* 10 12 17.6684359061 -03 44 44.393843397 11.941 10.757 9.264 8.258 7.066 M2V 199 0
14 BD+01 2447 PM* 10 28 55.5513010331 +00 50 27.601817738 12.389 11.151 9.650 8.617 7.389 dM2 269 0
15 HD 95735 Er* 11 03 20.1948195942 +35 58 11.576182057 10.030 8.960 7.520 5.99 4.79 M2+V 650 0
16 CD-31 9113 PM* 11 35 26.9474098036 -32 32 23.883014588 12.508 11.322 9.813 8.821 7.664 M2V 136 1
17 Ross 905 PM* 11 42 11.0933874353 +26 42 23.658083337   12.06 10.613 10.272 8.24 M3V 539 1
18 CD-51 6859 PM* 12 37 52.2156541938 -52 00 05.321462032 13.397 12.198 10.663 9.586 8.233 M3V(e) 99 0
19 HD 119850 Er* 13 45 43.7754528655 +14 53 29.473195472 10.989 9.894 8.50 7.465 6.363 M2V 304 0
20 NAME Proxima Centauri Er* 14 29 42.9451234609 -62 40 46.170818907 14.21 12.95 11.13 9.45 7.41 M5.5Ve 1065 0
21 BD-07 4003 BY* 15 19 26.8271336166 -07 43 20.190958776 13.403 11.76 10.560 9.461 8.911 M3V 562 2
22 CD-40 9712 PM* 15 32 12.9326267337 -41 16 32.131578815 11.918 10.815 9.311 8.265 6.947 M2.5V 121 0
23 HD 156384C PM* 17 18 58.8271844065 -34 59 48.612934284 12.96 11.79 10.22 10.05 8.82 M1.5V 180 1
24 CD-46 11540 LM* 17 28 39.9455601300 -46 53 42.693246243 12.177 10.973 9.407 8.337 7.006 M3V 220 1
25 CD-51 10924 PM* 17 30 11.2030058822 -51 38 13.139736838 12.317 11.028 9.585 8.675 8.60 M0V 90 1
26 CD-48 11837 PM* 17 35 13.6166681026 -48 40 51.124034671 12.875 11.673 10.127 9.101 7.871 M1.5V 59 0
27 NAME Barnard's star BY* 17 57 48.4997994034 +04 41 36.111354228 12.497 11.24 9.511 8.298 6.741 M4V 704 2
28 HD 180617 PM* 19 16 55.2565250393 +05 10 08.038856129 11.768 10.63 9.115 8.076 6.782 M3-V 368 0
29 HD 204961 PM* 21 33 33.9749932664 -49 00 32.403471949 11.359 10.176 8.672 7.665 6.479 M2/3V 230 1
30 BD-05 5715 PM* 22 09 40.3443754647 -04 38 26.651267098 13.006 11.868 10.366 9.279 7.877 M3.5V 237 1
31 BD-15 6290 BY* 22 53 16.7323107416 -14 15 49.303409936 12.928 11.749 10.192 9.013 7.462 M3.5V 892 1
32 L 49-19 PM* 22 55 45.5132862851 -75 27 31.205026497 13.004 11.873 10.377 9.312 7.958 M3V 63 0
33 HD 217987 PM* 23 05 52.0354545522 -35 51 11.058757520   8.83 7.39     M2V 233 0
34 V* BR Psc BY* 23 49 12.5251391270 +02 24 04.403044891 11.532 10.427 8.993 8.029 6.946 dM1 292 0

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2021.09.22-11:29:20

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