2008A&A...479..557F


C.D.S. - SIMBAD4 rel 1.7 - 2021.02.26CET20:45:53

2008A&A...479..557F - Astronomy and Astrophysics, volume 479, 557-565 (2008/2-4)

Spots, plages, and flares on λ Andromedae and II Pegasi.

FRASCA A., BIAZZO K., TAS G., EVREN S. and LANZAFAME A.C.

Abstract (from CDS):

We present the results of a contemporaneous photometric and spectroscopic monitoring of two RS CVn binaries, namely {lambda} And and II Peg. The aim of this work is to investigate the behavior of surface inhomogeneities in the atmospheres of the active components of these systems that have nearly the same temperatures but different gravities. The light curves and the modulation of the surface temperature, as recovered from line-depth ratios (LDRs), were used to map the photospheric spots, while the Hα emission was used as an indicator of chromospheric inhomogeneities. The spot temperatures and sizes were derived from a spot model applied to the contemporaneous light and temperature curves. We find larger and cooler spots on II Peg (Tsp≃3600K) than on λ And (Tsp≃3900K); this could be the result of both the difference in gravity and the higher activity level of the former. Moreover, we find a clear anti-correlation between the Hα emission and the photospheric diagnostics (temperature and light curves). We have detected a modulation in the intensity of the HeI D3 line with the star rotation, suggesting surface features also in the upper chromosphere of these stars. A rough reconstruction of the 3D structure of their atmospheres was also performed by applying a spot/plage model to the light and temperature curves and to the Hα flux modulation. In addition, a strong flare affecting the Hα, the HeI D3, and the cores of NaI D1,2 lines has been observed on II Peg. The spot/plage configuration has been reconstructed in the visible component of λ And and II Peg, which have nearly the same temperature but very different gravities and rotation periods. A close spatial association of photospheric and chromospheric active regions, at the time of our observations, was found in both stars. Larger and cooler spots were found on II Peg, the system with the active component of higher gravity and a higher activity level. The area ratio of plages to spots seems to decrease when the spots get bigger. Moreover, with both this and literature data, a correlation between the temperature difference ΔT=Tph-Tsp and the surface gravity is also suggested.

Abstract Copyright:

Journal keyword(s): stars: activity - stars: starspots - stars: chromospheres - stars: individual: λ And - stars: individual: II Peg

Simbad objects: 19

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Number of rows : 19

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 V* VY Ari RS* 02 48 43.7283572894 +31 06 54.592580835   7.72   6.4   G9 211 0
2 V* UX Ari RS* 03 26 35.3764089427 +28 42 54.211100955 7.76 7.28 6.37     K0IV 668 0
3 HD 22468 RS* 03 36 47.2911034958 +00 35 15.938962144 7.09 6.63   5.4   K2:Vnk 1132 0
4 * del Eri RS* 03 43 14.9008787 -09 45 48.208444 5.13 4.46 3.54 2.82 2.32 K0+IV 551 0
5 HD 283750 BY* 04 36 48.2413370074 +27 07 55.898311812   9.354   7.4   K2.5Ve 258 2
6 V* LQ Hya BY* 09 32 25.5684079124 -11 11 04.687410738 9.316 8.761 7.891 7.288 6.815 K1Vp 408 0
7 HD 118100 Er* 13 34 43.2063348511 -08 20 31.335294003 11.578 10.552 9.372 8.602 7.930 K5Ve 327 0
8 * sig CrB RS* 16 14 40.85557 +33 51 30.9497           F6V+G0V 479 0
9 * alf Aql dS* 19 50 46.99855 +08 52 05.9563 1.07 0.98 0.76 0.62 0.49 A7Vn 828 0
10 V* VW Cep EB* 20 37 21.6248469581 +75 36 01.889162699   8.13   7.0   G8V+K0V 528 0
11 V* HK Lac RS* 22 04 56.6089126762 +47 14 04.482220545   8.01 6.96     K0III 232 0
12 * mu. Peg PM* 22 50 00.1931506 +24 36 05.698380 5.10 4.42 3.48 2.80 2.33 G8+III 279 0
13 V* IM Peg RS* 22 53 02.2658951462 +16 50 28.291474642   7.024 5.890     K2III 322 1
14 * lam And RS* 23 37 33.8426114 +46 27 29.337984 5.54 4.84 3.82 3.04 2.47 G8IVk 646 0
15 * kap And PM* 23 40 24.5076320 +44 20 02.156595 3.80 4.06 4.14 4.15 4.22 B9IVn 181 0
16 * psi And ** 23 46 02.0469653187 +46 25 12.972436405   6.064 4.966     G3Ib-II 176 0
17 HD 224083 * 23 54 56.3882963210 +29 28 32.210277527   6.73 6.77     B9 18 0
18 HD 224085 RS* 23 55 04.0516465022 +28 38 01.248194500 8.88 8.20   6.9   K2+IVeFe-1 690 0
19 BD+27 4648 * 23 56 25.1339472433 +28 42 16.871259939   10.41 9.37     G5 12 0

    Equat.    Gal    SGal    Ecl

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