2022A&A...661A..24F


Query : 2022A&A...661A..24F

2022A&A...661A..24F - Astronomy and Astrophysics, volume 661A, 24-24 (2022/5-1)

The corona - chromosphere connection studied with simultaneous eROSITA and TIGRE observations.

FUHRMEISTER B., CZESLA S., ROBRADE J., GONZALEZ-PEREZ J.N., SCHNEIDER C., MITTAG M. and SCHMITT J.H.M.M.

Abstract (from CDS):

Stellar activity manifests itself in a variety of different phenomena, some of which we can measure as activity tracers from different atmospheric layers of the star, typically at different wavelengths. Stellar activity is furthermore inherently time variable, therefore simultaneous measurements are necessary to study the correlation between different activity indicators. In this study we compare X-ray fluxes measured within the first all-sky survey conducted by the extended ROentgen Survey with an Imaging Telescope Array (eROSITA) instrument on board the Spectrum-Roentgen-Gamma observatory to CaII H&K excess flux measurements RHK+, using observations made with the robotic TIGRE telescope. We created the largest sample of simultaneous X-ray and spectroscopic CaII H&K observations of late-type stars obtained so far, and in addition, previous measurements of CaII H&K for all sample stars were obtained. We find the expected correlation between our log(LX/Lbol) to log(RHK+) measurements, but when the whole stellar ensemble is considered, the correlation between coronal and chromospheric activity indicators does not improve when the simultaneously measured data are used. A more detailed analysis shows that the correlation of log(LX/Lbol) to log(RHK+) measurements of the pseudo-simultaneous data still has a high probability of being better than that of a random set of non-simultaneous measurements with a long time baseline between the observations. Cyclic variations on longer timescales are therefore far more important for the activity flux-flux relations than short-term variations in the form of rotational modulation or flares, regarding the addition of "noise" to the activity flux-flux correlations. Finally, regarding the question of predictability of necessarily space-based log (LX/Lbol) measurements by using ground-based chromospheric indices, we present a relation for estimating log (LX/Lbol) from RHK+ values and show that the expected error in the calculated minus observed (C-O) log (LX/Lbol) values is 0.35 dex.

Abstract Copyright: © ESO 2022

Journal keyword(s): stars: activity - stars: chromospheres - stars: coronae - stars: late-type - X-rays: stars

VizieR on-line data: <Available at CDS (J/A+A/661/A24): table3.dat>

Status at CDS : Tables of objects will be appraised for possible ingestion in SIMBAD.

Simbad objects: 14

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Number of rows : 14
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2022
#notes
1 * alf For ** 03 12 04.5273570 -28 59 15.433684 4.41 4.36 3.85 3.39 3.08 F6V+G7V 258 0
2 * eps Eri BY* 03 32 55.8444911587 -09 27 29.739493865 5.19 4.61 3.73 3.00 2.54 K2V 1808 1
3 * del Eri * 03 43 14.9005379551 -09 45 48.210955899 5.13 4.46 3.54 2.82 2.32 K0+IV 574 0
4 * pi.03 Ori PM* 04 49 50.4109057 +06 57 40.588294 3.620 3.630 3.190 2.77 2.51 F6V 553 0
5 * gam Lep PM* 05 44 27.7906169580 -22 26 54.187756254 4.08 4.07 3.60 3.15 2.89 F6V 412 0
6 * eta Lep PM* 05 56 24.2934904501 -14 10 03.718335613 4.05 4.05 3.72 3.39 3.23 F2V 329 0
7 * ksi Gem PM* 06 45 17.3643205 +12 53 44.131127 3.85 3.79 3.36 2.97 2.74 F5IV-V 211 0
8 * alf CMi SB* 07 39 18.11950 +05 13 29.9552 0.82 0.79 0.37 -0.05 -0.28 F5IV-V+DQZ 1825 0
9 HD 81809 SB* 09 27 46.8088908054 -06 04 17.008787302           G1.5IV-V 288 0
10 HD 97503 PM* 11 13 13.2346348187 +04 28 56.435525801 11 9.79 9.32 8.84 7.335 K5V 87 0
11 * bet Vir PM* 11 50 41.7185158616 +01 45 53.001539131 4.26 4.15 3.60 3.13 2.85 F9V 895 0
12 * tau Boo Ro* 13 47 15.7381720026 +17 27 24.809555600 5.02 4.98 4.49 4.09 3.85 F7IV-V 943 1
13 * mu. Vir PM* 14 43 03.6228218 -05 39 29.532712 4.25 4.26 3.88 3.48 3.26 F2V 220 0
14 * 61 Cyg ** 21 06 53.95 +38 44 57.9           ~ 170 0

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2022.08.09-15:58:39

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