Bailey, J;
Cotton, DV;
Howarth, ID;
Lewis, F;
Kedziora-Chudczer, L;
(2020)
The rotation of α Oph investigated using polarimetry.
Monthly Notices of the Royal Astronomical Society
, 494
(2)
pp. 2254-2267.
10.1093/mnras/staa785.
Preview |
Text
Howarth_The rotation of α Oph investigated using polarimetry_VoR.pdf - Published Version Download (3MB) | Preview |
Abstract
Recently we have demonstrated that high-precision polarization observations can detect the polarization resulting from the rotational distortion of a rapidly rotating B-type star. Here, we investigate the extension of this approach to an A-type star. Linear-polarization observations of α Oph (A5IV) have been obtained over wavelengths from 400 to 750 nm. They show the wavelength dependence expected for a rapidly rotating star combined with a contribution from interstellar polarization. We model the observations by fitting rotating-star polarization models and adding additional constraints including a measured v_{e}sin i. However, we cannot fully separate the effects of rotation rate and inclination, leaving a range of possible solutions. We determine a rotation rate (ω = Ω/Ω_{c}) between 0.83 and 0.98 and an axial inclination i > 60°. The rotation-axis position angle is found to be 142 ± 4°, differing by 16° from a value obtained by interferometry. This might be due to precession of the rotation axis due to interaction with the binary companion. Other parameters resulting from the analysis include a polar temperature T_{p} = 8725 ± 175 K, polar gravity log g_{p} = 3.93 ± 0.08 (dex cgs), and polar radius R_{p} = = 2.52 ± 0.06 R_{⊙}. Comparison with rotating-star evolutionary models indicates that α Oph is in the later half of its main-sequence evolution and must have had an initial ω of 0.8 or greater. The interstellar polarization has a maximum value at a wavelength (λ_{max}) of 440 ± 110 nm, consistent with values found for other nearby stars.
| Type: | Article |
|---|---|
| Title: | The rotation of α Oph investigated using polarimetry |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1093/mnras/staa785 |
| Publisher version: | https://doi.org/10.1093/mnras/staa785 |
| Language: | English |
| Additional information: | This version is the version of record. For information on re-use, please refer to the publisher's terms and conditions. |
| Keywords: | polarization, techniques: polarimetric, stars: evolution, stars: rotation |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10095833 |
Archive Staff Only
 |
View Item |
