Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in Supergiant Fast X-ray Transient and classical Supergiant X-ray Binaries
| Autor: | S. Martínez-Núñez, Jose M. Torrejon, Lidia M. Oskinova, J. Alonso-Santiago, Andreas Sander, Carlos González-Fernández, Guillermo Bernabeu, A. Giménez-García, Tomer Shenar, A. Gonzalez-Galan, J. J. Rodes-Roca, Wolf-Rainer Hamann |
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| Přispěvatelé: | Leibniz Association, University of Potsdam, Ministerio de Economía y Competitividad (España), Generalitat Valenciana, Universidad de Alicante, European Space Agency, German Research Foundation, National Aeronautics and Space Administration (US), Ministerio de Ciencia e Innovación (España), Universidad de Alicante. Departamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante. Instituto Universitario de Física Aplicada a las Ciencias y las Tecnologías, Astronomía y Astrofísica, Astrofísica Estelar (AE) |
| Rok vydání: | 2016 |
| Předmět: |
Accretion
Astrophysics::High Energy Astrophysical Phenomena Techniques: spectroscopic FOS: Physical sciences Outflows Astrophysics Astrophysics::Cosmology and Extragalactic Astrophysics Vela Stellar classification 01 natural sciences Luminosity spectroscopic [Techniques] X-rays: binaries Methods: observational Física Aplicada 0103 physical sciences Astrophysics::Solar and Stellar Astrophysics observational [Methods] winds outflows [Stars] atmospheres [Stars] winds [Stars] 010303 astronomy & astrophysics Astrophysics::Galaxy Astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Astronomía y Astrofísica Physics High Energy Astrophysical Phenomena (astro-ph.HE) 010308 nuclear & particles physics Institut für Physik und Astronomie Astronomy and Astrophysics Accretion accretion disks Orbital period Accretion (astrophysics) Stars: winds Stars Neutron star Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Accretion disks binaries [X-rays] Astrophysics::Earth and Planetary Astrophysics Stars: atmospheres Supergiant Astrophysics - High Energy Astrophysical Phenomena |
| Zdroj: | RUA. Repositorio Institucional de la Universidad de Alicante Universidad de Alicante (UA) Digital.CSIC. Repositorio Institucional del CSIC instname |
| DOI: | 10.48550/arxiv.1603.00925 |
| Popis: | [Context]: Classical supergiant X-ray binaries (SGXBs) and supergiant fast X-ray transients (SFXTs) are two types of high-mass X-ray binaries (HMXBs) that present similar donors but, at the same time, show very different behavior in the X-rays. The reason for this dichotomy of wind-fed HMXBs is still a matter of debate. Among the several explanations that have been proposed, some of them invoke specific stellar wind properties of the donor stars. Only dedicated empiric analysis of the donors¿ stellar wind can provide the required information to accomplish an adequate test of these theories. However, such analyses are scarce. [Aims]: To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J17544-2619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. [Methods]: We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. [Results]: We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 ± 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e< 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the two stars is their terminal velocities (ν∞ = 1500 km s-1 in IGR J17544-2619 and ν∞ = 700 km s-1 in Vela X-1), which have important consequences on the X-ray luminosity of these sources. [Conclusions]: The donors of IGR J17544-2619 and Vela X-1 have similar spectral types as well as similar parameters that physically characterize them and their spectra. In addition, the orbital parameters of the systems are similar too, with a nearly circular orbit and short orbital period. However, they show moderate differences in their stellar wind velocity and the spin period of their neutron star which has a strong impact on the X-ray luminosity of the sources. This specific combination of wind speed and pulsar spin favors an accretion regime with a persistently high luminosity in Vela X-1, while it favors an inhibiting accretion mechanism in IGR J17544-2619. Our study demonstrates that the relative wind velocity is critical in class determination for the HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters. The work of AG-G was supported by the Spanish MICINN under FPI Fellowship BES-2011-050874 associated to the project AYA2010-15431. T.S. is grateful for financial support from the Leibniz Graduate School for Quantitative Spectroscopy in Astrophysics, a joint project of the Leibniz Institute for Astrophysics Potsdam (AIP) and the Institute of Physics and Astronomy of the University of Potsdam. This work has been partially supported by the Spanish Ministry of Economy and Competitiveness project numbers ESP2013-48637-C2-2P and ESP2014-53672-C3-3-P, the Generalitat Valenciana project number GV2014/088 and the Vicerectorat d’Investigació, Desenvolupament i Innovació de la Universitat d’Alacant under grant GRE12-35. S.M.N. thanks the support of the Spanish unemployment agency, allowing her to continue her scientific collaborations during the critical situation of the Spanish research system. The authors acknowledge the help of the International Space Science Institute at Bern, Switzerland, and the faculty of the European Space Astronomy Centre. A.S. is supported by the Deutsche Forschungsgemeinschaft (DFG) under grant HA 1455/26. Support for MAST for non-HST data is provided by the NASA office of space science via grant NAG5-7584 and by other grants and contracts. |
| Databáze: | OpenAIRE |
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