2002A&A...392..535R


Query : 2002A&A...392..535R

2002A&A...392..535R - Astronomy and Astrophysics, volume 392, 535-540 (2002/9-3)

Control of the convective dynamo in close binaries by tidal locking. Is V471 Tauri the template?

ROTTLER L., BATALHA C., YOUNG A. and VOGT S.

Abstract (from CDS):

We report additional observations of the phase dependent behavior of the chromospheric Hα feature associated with the K-dwarf component of V471 Tau. Previously, all such observations have shown a sharply defined maximum of emission near the middle of the transit phase of the white dwarf across the disk of the K-dwarf. The precision and the reproducibility of that phase lock led many previous observers to conclude that the observed emission was due to chromospheric re-processing of ultraviolet radiation incident upon the K-dwarf from the white dwarf. Comparing these observations with previously published observations, we show that the emission strength has been steadily diminishing between epoch 1985 and epoch 1992 whence it has essentially vanished. The ultraviolet flux from the white dwarf is constant so the resulting re-processed chromospheric emission cannot be time dependent. This leads to the conclusion that most of the emission has been due to magnetically active regions located preferentially at the sub-stellar point of the white dwarf. We propose that tidal coupling in this close binary system preferentially affects the transfer of magnetic energy, coupling the internal dynamo of the K-dwarf to the outer envelope, giving a preferred longitude to magnetic activity. We further suggest that this mechanism may be common in most short period binary systems and in many cases may be the dominant mechanism causing the observed Hα behavior.

Abstract Copyright:

Journal keyword(s): stars: activity - stars: binaries: eclipsing - stars: chromospheres - stars: individual: V471 Tau - stars: magnetic field - stars: white dwarfs

CDS comments: In table 1, EUVE J0720+31.7 is a misprint for J0720-31.7.

Simbad objects: 10

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Number of rows : 10
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 V* FS Cet CV* 02 35 07.5939240480 +03 43 56.816311296 11.027 12.209 12.412 12.325 11.968 DA1+dM 367 0
2 V* V471 Tau SB* 03 50 24.9666549840 +17 14 47.430910716   10.258 9.373   8.393 K2V+DA 668 0
3 HZ 9 WD* 04 32 23.7569977200 +17 45 02.672275356   14.28 13.93 14.21   DA3+dM 150 0
4 V* HR Cam WD* 07 17 09.7856917536 +74 00 40.535184924   14.91 14.97     DA2.6 71 0
5 V* IN CMa CV* 07 20 47.9109655416 -31 47 02.732961552           DAO+dM 91 0
6 HE 1013-0505 WD* 10 16 28.6043334312 -05 20 35.222859276     14.1     DAO+Me 105 0
7 V* EG UMa CV* 12 15 44.0979312096 +52 31 01.289011692   13.0 13.230 13.149   DA+dM 112 1
8 Ton 617 WD* 12 26 30.8730979008 +30 38 52.652529600   16.099 16.05     DA+M3 62 0
9 V* NN Ser RS* 15 52 56.1203524080 +12 54 44.429312196     16.51     DAO1+M4 275 0
10 RX J2013.1+4002 WD* 20 13 09.3685663800 +40 02 24.241439184     14.6     DAO+M2/3e 91 1

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