<i>Beppo</i>SAX observations of XTE J1946+274

Doroshenko, R.; Santangelo, A.; Doroshenko, V. T.; Piraino, S.

doi:10.1051/0004-6361/201630137

Cited by 15 publications

(16 citation statements)

References 29 publications

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“…The NLTE codes SYNSPEC 2 (Hubeny et al 1985) and TLUSTY 3 (Hubeny & Lanz 1995) were used by Fraser et al (2010) to calculate model atmosphere grids. These were then compared with high-resolution (R ∼ 48 000) spectra obtained with the Fiber-fed Extended Range Optical Spectrograph (FEROS) 4 for very many massive stars, including HD 77581, in order to determine the atmospheric parameters (effective temperature, surface gravity, and microturbulent velocity), the surface nitrogen abundances, and the rotational and macroturbulent velocities.…”

Section: Quantitative Spectroscopymentioning

confidence: 99%

“…5.1.2) are listed in Table A. 3. The numbers along the tracks indicate where the system would have been one, two, or three million years ago, based on the assumptions in these publications.…”

Section: Possible Origin In the Vela Ob1 Associationmentioning

confidence: 99%

“…Most commonly, the masses of the two components of the binary have been determined from fits to RV curves (see Sect. 3…”

Section: Masses Radii and Inclinationmentioning

confidence: 99%

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Revisiting the archetypical wind accretor Vela X-1 in depth

Kretschmar

Mellah

Martínez-Núñez

et al. 2021

A&A

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Context. The Vela X-1 system is one of the best-studied X-ray binaries because it was detected early, has persistent X-ray emission, and a rich phenomenology at many wavelengths. The system is frequently quoted as the archetype of wind-accreting high-mass X-ray binaries, and its parameters are referred to as typical examples. Specific values for these parameters have frequently been used in subsequent studies, however, without full consideration of alternatives in the literature, even more so when results from one field of astronomy (e.g., stellar wind parameters) are used in another (e.g., X-ray astronomy). The issues and considerations discussed here for this specific, very well-known example will apply to various other X-ray binaries and to the study of their physics. Aims. We provide a robust compilation and synthesis of the accumulated knowledge about Vela X-1 as a solid baseline for future studies, adding new information where available. Because this overview is targeted at a broader readership, we include more background information on the physics of the system and on methods than is usually done. We also attempt to identify specific avenues of future research that could help to clarify open questions or determine certain parameters better than is currently possible. Methods. We explore the vast literature for Vela X-1 and on modeling efforts based on this system or close analogs. We describe the evolution of our knowledge of the system over the decades and provide overview information on the essential parameters. We also add information derived from public data or catalogs to the data taken from the literature, especially data from the Gaia EDR3 release. Results. We derive an updated distance to Vela X-1 and update the spectral classification for HD 77518. At least around periastron, the supergiant star may be very close to filling its Roche lobe. Constraints on the clumpiness of the stellar wind from the supergiant star have improved, but discrepancies persist. The orbit is in general very well determined, but a slight difference exists between the latest ephemerides. The orbital inclination remains the least certain factor and contributes significantly to the uncertainty in the neutron star mass. Estimates for the stellar wind terminal velocity and acceleration law have evolved strongly toward lower velocities over the years. Recent results with wind velocities at the orbital distance in the range of or lower than the orbital velocity of the neutron star support the idea of transient wind-captured disks around the neutron star magnetosphere, for which observational and theoretical indications have emerged. Hydrodynamic models and observations are consistent with an accretion wake trailing the neutron star. Conclusions. With its extremely rich multiwavelength observational data and wealth of related theoretical studies, Vela X-1 is an excellent laboratory for exploring the physics of accreting X-ray binaries, especially in high-mass systems. Nevertheless, much room remains to improve the accumulated knowledge. On the observational side, well-coordinated multiwavelength observations and observing campaigns addressing the intrinsic variability are required. New opportunities will arise through new instrumentation, from optical and near-infrared interferometry to the upcoming X-ray calorimeters and X-ray polarimeters. Improved models of the stellar wind and flow of matter should account for the non-negligible effect of the orbital eccentricity and the nonspherical shape of HD 77581. There is a need for realistic multidimensional models of radiative transfer in the UV and X-rays in order to better understand the wind acceleration and effect of ionization, but these models remain very challenging. Improved magnetohydrodynamic models covering a wide range of scales are required to improve our understanding of the plasma-magnetosphere coupling, and they are thus a key factor for understanding the variability of the X-ray flux and the torques applied to the neutron star. A full characterization of the X-ray emission from the accretion column remains another so far unsolved challenge.

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Section: Quantitative Spectroscopymentioning

confidence: 99%

Section: Possible Origin In the Vela Ob1 Associationmentioning

confidence: 99%

See 1 more Smart Citation

Revisiting the archetypical wind accretor Vela X-1 in depth

Kretschmar

Mellah

Martínez-Núñez

et al. 2021

A&A

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“…where µ 30 ≡ µ/(10 30 G cm 3 ) andṀ 16 ≡Ṁ/(10 16 g s −1 ), v 8 ≡ v rel /(1000 km s −1 ). The stellar wind velocity in 4U 0114+65 is about v 8 ∼ 0.5−0.7 ( Ferrigno et al 2008;Beri & Paul 2017;Barnstedt et al 2008;Evangelista et al 2010;Hemphill et al 2016;Doroshenko et al 2017;Şahiner et al 2012), and accreting magnetar candidates (green squares; this work; Wang 2013). The values ofṖ/P(s −1 ) are represented in absolute values.…”

Section: Discussionmentioning

confidence: 76%

XMM-Newtonspectroscopy of the accreting magnetar candidate 4U0114+65

Sanjurjo-Ferrrín

Torrejón

Постнов

et al. 2017

A&A

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Aims. 4U0114+65 is one of the slowest known X-ray pulsars. We present an analysis of a pointed observation by the XMM-Newton X-ray telescope in order to study the nature of the X-ray pulsations and the accretion process, and to diagnose the physical properties of the donor's stellar wind. Methods. We analysed the energy-resolved light curve and the time-resolved X-ray spectra provided by the EPIC cameras on board XMM-Newton. We also analysed the first high-resolution spectrum of this source provided by the Reflection Grating Spectrometer. Results. An X-ray pulse of 9350 ± 160 s was measured. Comparison with previous measurements confirms the secular spin up of this source. We successfully fit the pulse-phase-resolved spectra with Comptonisation models. These models imply a very small (r ∼ 3 km) and hot (kT ∼ 2−3 keV) emitting region and therefore point to a hot spot over the neutron star (NS) surface as the most reliable explanation for the X-ray pulse. The long NS spin period, the spin-up rate, and persistent X-ray emission can be explained within the theory of quasi-spherical settling accretion, which may indicate that the magnetic field is in the magnetar range. Thus, 4U 0114+65 could be a wind-accreting magnetar. We also observed two episodes of low luminosity. The first was only observed in the low-energy light curve and can be explained as an absorption by a large over-dense structure in the wind of the B1 supergiant donor. The second episode, which was deeper and affected all energies, may be due to temporal cessation of accretion onto one magnetic pole caused by non-spherical matter capture from the structured stellar wind. The light curve displays two types of dips that are clearly seen during the high-flux intervals. The short dips, with durations of tens of seconds, are produced through absorption by wind clumps. The long dips, in turn, seem to be associated with the rarefied interclump medium. From the analysis of the X-ray spectra, we found evidence of emission lines in the X-ray photoionised wind of the B1Ia donor. The Fe Kα line was found to be highly variable and much weaker than in other X-ray binaries with supergiant donors. The degree of wind clumping, measured through the covering fraction, was found to be much lower than in supergiant donor stars with earlier spectral types. Conclusions. The XMM-Newton spectroscopy provided further support for the magnetar nature of the neutron star in 4U0114+65. The light curve presents dips that can be associated with clumps and the interclump medium in the stellar wind of the mass donor.

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“…In the fast wind limit, the so-called Bondi-Hoyle-Littleton (BHL) formalism (Hoyle & Lyttleton 1939;Bondi & Hoyle 1944;Edgar 2004) provides a robust framework. In this description, the fraction of the wind with an impact parameter lower than the accretion radius R acc will be captured: R acc = 2GM NS /v 2 rel (3) where M NS is the mass of the neutron star and v rel is the relative speed of the wind with respect to the neutron star. In this case, the mass accretion rate is approximately given by:…”

Section: Mass Transfer To the Neutron Starmentioning

confidence: 99%

Revisiting the archetypical wind accretor Vela X-1 in depth -- A case study of a well-known X-ray binary and the limits of our knowledge

Kretschmar,

Mellah,

Martínez-Núñez

et al. 2021

Preprint

View full text Add to dashboard Cite

Context. The Vela X-1 system is one of the best studied X-ray binaries, due to its early detection, persistent X-ray emission and a rich phenomenology at many wavelengths. The system is frequently quoted as an archetype of wind-accreting high-mass X-ray binaries and its parameters referred to as typical examples. Frequently though, specific values for these parameters have been used in subsequent studies, without full consideration of alternatives in the literature -even more so when results from one field of astronomy (e.g., stellar wind parameters) are used in another (e.g., X-ray astronomy). The issues and considerations discussed here for this specific, very well-known example will apply to various other X-ray binaries and the study of their physics. Aims. We aim to provide a robust compilation and synthesis of the accumulated knowledge about Vela X-1 as a solid baseline for future studies, adding new information, where available. Since this overview is targeted at a broader readership, we include more background information on the physics of the system and on methods than usually done. We also attempt to identify specific avenues of future research that could help to clarify open questions or determine certain parameters better than currently possible. Methods. We explore the vast literature for Vela X-1 and on modelling efforts based on this system or close analogues. We describe the evolution of the system knowledge over the decades and provide overview information on the essential parameters. We also add information derived from public data or catalogs to the data taken from the literature, especially data from the Gaia EDR3 release. Results. We derive an updated distance to Vela X-1 and update the spectra classification for HD 77518. At least around periastron, the supergiant star may be very close to filling its Roche lobe. Constraints on the clumpiness of the stellar wind from the supergiant star have improved, but tensions subsist. The orbit is in general very well determined, but a slight tension exists between the latest ephemerides. The orbital inclination remains the least certain factor and contributes significantly to the uncertainty in the neutron star mass. Estimates for the stellar wind terminal velocity and acceleration law have evolved strongly towards lower velocities over the years. Recent results with wind velocities at the orbital distance in the range or of or lower than the orbital velocity of the neutron star support the idea of transient wind-captured disks around the neutron star magnetosphere, for which observational and theoretical hints have emerged. Hydrodynamic models and observations are consistent with an accretion wake trailing the neutron star. Conclusions. With its extremely rich multi-wavelength observational data and wealth of related theoretical studies, Vela X-1 is an excellent laboratory to explore the physics of accreting X-ray binaries, especially in high-mass systems. Nevertheless, a lot of room remains to improve on the accumulated knowledge. On the observational...

show abstract

BeppoSAX observations of XTE J1946+274

Cited by 15 publications

References 29 publications

Revisiting the archetypical wind accretor Vela X-1 in depth

Revisiting the archetypical wind accretor Vela X-1 in depth

XMM-Newtonspectroscopy of the accreting magnetar candidate 4U0114+65

Revisiting the archetypical wind accretor Vela X-1 in depth -- A case study of a well-known X-ray binary and the limits of our knowledge

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