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Bowen emission from Aquila X-1: Evidence for multiple components and constraint on the accretion disc vertical structure

Bowen emission from Aquila X-1: Evidence for multiple components and constraint on the accretion disc vertical structure
Bowen emission from Aquila X-1: Evidence for multiple components and constraint on the accretion disc vertical structure

We present a detailed spectroscopic study of the optical counterpart of the neutron star X-ray transient Aquila X-1 during its 2011, 2013 and 2016 outbursts. We use 65 intermediate resolution GTC-10.4 m spectra with the aim of detecting irradiation-induced Bowen blend emission from the donor star.While Gaussian fitting does not yield conclusive results, our full phase coverage allows us to exploit Doppler mapping techniques to independently constrain the donor star radial velocity. By using the component NIII 4640.64/4641.84 Å, we measure Kem = 102 ± 6 km s-1. This highly significant detection (≳13σ) is fully compatible with the true companion star radial velocity obtained from near-infrared spectroscopy during quiescence. Combining these two velocities we determine, for the first time, the accretion disc opening angle and its associated error from direct spectroscopic measurements and detailed modelling, obtaining α = 15.5 -5 +2.5 deg. This value is consistent with theoretical work if significant X-ray irradiation is taken into account and is important in the light of recent observations of GX339-4, where discrepant results were obtained between the donor's intrinsic radial velocity and the Bowen-inferred value.We also discuss the limitations of the Bowen technique when complete phase coverage is not available.

Accretion, Accretion discs, Stars: neutron, X-rays: binaries
0035-8711
4717-4722
Jiménez-Ibarra, F.
36575099-5a2b-4b8b-aa1d-52ac905eb538
Muñoz-Darias, T.
3ce85aef-763c-4783-a13e-586115731bc2
Wang, L.
e4681799-1b24-4ac4-82bc-568102a1147b
Casares, J.
e57ae499-4f86-421a-bcb1-67d17d2bcbfc
Sánchez, D. Mata
cf3bb445-e524-4792-8cea-fa8c0460d2d3
Steeghs, D.
ab1118c0-944a-427a-bfbf-6b82e1320280
Padilla, M. Armas
4ce03893-aeb1-4748-979d-a0c5769e1e0d
Charles, P. A.
0429b380-0754-4dc1-8def-885c7fa6a086
Jiménez-Ibarra, F.
36575099-5a2b-4b8b-aa1d-52ac905eb538
Muñoz-Darias, T.
3ce85aef-763c-4783-a13e-586115731bc2
Wang, L.
e4681799-1b24-4ac4-82bc-568102a1147b
Casares, J.
e57ae499-4f86-421a-bcb1-67d17d2bcbfc
Sánchez, D. Mata
cf3bb445-e524-4792-8cea-fa8c0460d2d3
Steeghs, D.
ab1118c0-944a-427a-bfbf-6b82e1320280
Padilla, M. Armas
4ce03893-aeb1-4748-979d-a0c5769e1e0d
Charles, P. A.
0429b380-0754-4dc1-8def-885c7fa6a086

Jiménez-Ibarra, F., Muñoz-Darias, T., Wang, L., Casares, J., Sánchez, D. Mata, Steeghs, D., Padilla, M. Armas and Charles, P. A. (2018) Bowen emission from Aquila X-1: Evidence for multiple components and constraint on the accretion disc vertical structure. Monthly Notices of the Royal Astronomical Society, 474 (4), 4717-4722. (doi:10.1093/mnras/stx2926).

Record type: Article

Abstract

We present a detailed spectroscopic study of the optical counterpart of the neutron star X-ray transient Aquila X-1 during its 2011, 2013 and 2016 outbursts. We use 65 intermediate resolution GTC-10.4 m spectra with the aim of detecting irradiation-induced Bowen blend emission from the donor star.While Gaussian fitting does not yield conclusive results, our full phase coverage allows us to exploit Doppler mapping techniques to independently constrain the donor star radial velocity. By using the component NIII 4640.64/4641.84 Å, we measure Kem = 102 ± 6 km s-1. This highly significant detection (≳13σ) is fully compatible with the true companion star radial velocity obtained from near-infrared spectroscopy during quiescence. Combining these two velocities we determine, for the first time, the accretion disc opening angle and its associated error from direct spectroscopic measurements and detailed modelling, obtaining α = 15.5 -5 +2.5 deg. This value is consistent with theoretical work if significant X-ray irradiation is taken into account and is important in the light of recent observations of GX339-4, where discrepant results were obtained between the donor's intrinsic radial velocity and the Bowen-inferred value.We also discuss the limitations of the Bowen technique when complete phase coverage is not available.

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More information

Accepted/In Press date: 6 November 2017
e-pub ahead of print date: 14 November 2017
Published date: 1 March 2018
Keywords: Accretion, Accretion discs, Stars: neutron, X-rays: binaries

Identifiers

Local EPrints ID: 420539
URI: http://eprints.soton.ac.uk/id/eprint/420539
ISSN: 0035-8711
PURE UUID: f24e1d05-2af3-4daf-b2b2-2775892aae88

Catalogue record

Date deposited: 10 May 2018 16:30
Last modified: 11 Jul 2019 16:30

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