2015A&A...582A..84H


Query : 2015A&A...582A..84H

2015A&A...582A..84H - Astronomy and Astrophysics, volume 582A, 84-84 (2015/10-1)

A radial-velocity survey of Ap stars with HARPS. I. HD 42659: The discovery of the first spectroscopic binary around a rapidly oscillating Ap star.

HARTMANN M. and HATZES A.P.

Abstract (from CDS):

Chemically peculiar Ap stars are main-sequence stars of spectral type B8-F3 which show large overabundances of some chemical elements (e.g., Si, Sr, Cr), especially of rare-earth elements, compared to normal A-type stars. Furthermore, they have strong, global magnetic fields and low rotational velocities. Some Ap stars exhibit high-overtone, low-degree, non-radial p-mode pulsations with periods of 6-24 min and are called rapidly oscillating Ap (roAp) stars. Interestingly, no roAp star is known to be a spectroscopic binary (SB), while many non-oscillating Ap (noAp) stars are found in SB systems. The goal of this survey was to carry out a systematic search for sub-stellar and stellar companions around Ap stars. Between 2004 and 2009, we observed 65 chemically peculiar stars with the HARPS spectrograph at the 3.6-m telescope at the European Southern Observatory (La Silla, Chile). The radial-velocity (RV) measurements were obtained using a new software called HARPS-TERRA which is based on a least-squares matching of each individual spectrum to a high signal-to-noise ratio template for each star. We find significant variability with a period of 93.2-days and a semi-amplitude of 11.85km/s in the RVs of HD 42659, a star of our sample that belongs to the group of roAp stars. This variability is caused by a stellar companion with a minimum mass of 0.47M in a slightly eccentric (e=0.146) orbit at a separation of 0.55AU. This detection makes HD 42659 the first confirmed SB around a roAp star in a relatively close orbit. It shows that tidal interactions in binaries do not necessarily inhibit pulsations in Ap stars.

Abstract Copyright:

Journal keyword(s): techniques: radial velocities - binaries: spectroscopic - stars: chemically peculiar - stars: individual: HD 42659

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
#notes
1 V* UV Lep a2* 06 11 21.7521470568 -15 47 35.016189504   7.01 6.75     ApSrCrEu 59 0
2 * alf Cir a2* 14 42 30.4195804 -64 58 30.493451 3.55 3.43 3.19 2.96 2.86 A7VpSrCrEu 353 0
3 * bet CrB a2* 15 27 49.7315305 +29 06 20.522375 4.08 3.97 3.68 3.50 3.45 F2VpSrCrEuSi 673 0
4 * 10 Aql a2* 18 58 46.9240671288 +13 54 23.941711692 6.23 6.14 5.89     A7VpSrEu_Ksn 278 0
5 HD 177765 * 19 07 09.7793979672 -26 19 54.506413128   9.60 9.15     ApSrEuCr 33 0
6 HD 225914 Ro* 19 48 26.7415463208 +39 51 58.045289040   9.353 9.170     A5VpSrCrEu 23 0
7 * gam Equ a2* 21 10 20.5000721160 +10 07 53.691967776 5.03 4.94 4.68 4.43 4.32 A9VpSrCrEu 533 0

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2022.12.03-06:39:17

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