2016A&A...586A..85M


C.D.S. - SIMBAD4 rel 1.7 - 2020.07.08CEST16:48:33

2016A&A...586A..85M - Astronomy and Astrophysics, volume 586A, 85-85 (2016/2-1)

HD 18078: A very slowly rotating Ap star with an unusual magnetic field structure.

MATHYS G., ROMANYUK I.I., KUDRYAVTSEV D.O., LANDSTREET J.D., PYPER D.M. and ADELMAN S.J.

Abstract (from CDS):

The existence of a significant population of Ap stars with very long rotation periods (up to several hundred years) has progressively emerged over the past two decades. However, only lower limits of the periods are known for most of them because their variations have not yet been observed over a sufficient timebase. We determine the rotation period of the slowly rotating Ap star HD 18078 and we derive constraints on the geometrical structure of its magnetic field. We combine measurements of the mean magnetic field modulus obtained from 1990 to 1997 with determinations of the mean longitudinal magnetic field spanning the 1999-2007 time interval to derive an unambiguous value of the rotation period. We show that this value is consistent with photometric variations recorded in the Stroemgren uvby photometric system between 1995 and 2004. We fit the variations of the two above-mentioned field moments with a simple model to constrain the magnetic structure. The rotation period of HD 18078 is (1358±12)d. The geometrical structure of its magnetic field is consistent to first order with a colinear multipole model whose axis is offset from the centre of the star. HD 18078 is only the fifth Ap star with a rotation period longer than 1000 d for which the exact value of that period (as opposed to a lower limit) could be determined. The strong anharmonicity of the variations of its mean longitudinal magnetic field and the shift between their extrema and those of the mean magnetic field modulus are exceptional and indicative of a very unusual magnetic structure.

Abstract Copyright:

Journal keyword(s): stars: individual: HD 18078 - stars: chemically peculiar - stars: rotation - stars: magnetic field

VizieR on-line data: <Available at CDS (J/A+A/586/A85): table3.dat>

Simbad objects: 9

goto Full paper

goto View the reference in ADS

Number of rows : 9

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 V* GY And a2* 01 38 31.8241484792 +45 23 58.950612500   6.343 6.380     A2:VpSiSrCrEu 239 0
2 HD 17429 * 02 50 00.3284754571 +55 29 47.357694550   8.26 8.11     A0 5 0
3 HD 18078 a2* 02 56 32.0100802361 +56 10 41.427097237   8.50 8.27     ~ 78 0
4 HD 18460 * 03 00 24.4231149907 +56 18 48.681325152   8.82 8.43     kA3hA8mF2 20 0
5 V* V827 Mon a2* 07 29 35.4522068599 -09 15 33.315319853   8.40 7.94     A6IIIpSr 57 0
6 V* KQ Vel a2* 10 55 01.0018015910 -42 15 04.062281118 5.78 6.03 6.11     Ap(SiCr) 117 0
7 V* AX CVn a2* 12 39 16.8607725899 +35 57 07.052954412   6.466 6.385     A0pSrCrEuKsn 157 0
8 V* V3961 Sgr a2* 19 51 50.6105485243 -39 52 27.724256879 5.05 5.27 5.33     ApCr(Si) 167 0
9 * gam Equ a2* 21 10 20.5001160337 +10 07 53.682085548 5.03 4.94 4.68 4.43 4.32 A9VpSrCrEu 513 0

    Equat.    Gal    SGal    Ecl

To bookmark this query, right click on this link: simbad:objects in 2016A&A...586A..85M and select 'bookmark this link' or equivalent in the popup menu


2020.07.08-16:48:33

© Université de Strasbourg/CNRS

    • Contact