Long-term variability of the Be/X-ray binary A 0535+26 -- I. Optical and UV spectroscopy

Clark, J. S.; Tarasov, A. E.; Steele, I. A.; Coe, M. J.; Roche, P.; Shrader, C. R.; Buckley, D.; Ларионов, В. М.; Ларионова, Л. В.; Lyuty, V. M.; Зайцева, Г. С.; Grunsfeld, J. M.; Fabregat, J.; Parise, R. A.

doi:10.1046/j.1365-8711.1998.01257.x

Cited by 40 publications

(48 citation statements)

References 9 publications

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“…For ten sources from the target list, we complemented our observations with data taken before 1999. These spectra were obtained in the framework of the Southampton/Valencia collaborative project (Reig et al 1997a), where a number of telescopes were used: the 2.5 m Isaac Newton Telescope (INT) and the 1.0 m Jacobus Kapteyn Telescope (JKT), both located at the Roque de los Muchachos Observatory in La Palma, the 1.5 m at Palomar Mountain (PAL), the 1.9 m telescope of the South Africa Astronomical Observatory (SAAO), and the 2.2 m telescope at Calar Alto in Almería, Spain (CA), and resulted in numerous publications (Clark et al 1998(Clark et al , 1999(Clark et al , 2001Coe et al 1993Coe et al , 1996Gorrod et al 1993;Haigh et al 1999Haigh et al , 2004Negueruela et al 1997Negueruela et al , 1998Negueruela et al , 1999Norton et al 1991;Reig et al 1996Reig et al , 1997cReig et al , 2000Roche et al 1993a,b;Unger et al 1998). For the sake of homogeneity, we re-analysed all the spectra in a consistent way, as explained in the next section.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Long-term optical variability of high-mass X-ray binaries

Reig

Nersesian

Zezas

et al. 2016

A&A

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Context. High-mass X-ray binaries are bright X-ray sources. The high-energy emission is caused by the accretion of matter from the massive companion onto a neutron star. The accreting material comes from either the strong stellar wind in binaries with supergiant companions or the cirscumstellar disk in Be/X-ray binaries. In either case, the Hα line stands out as the main source of information about the state of the accreting material. Aims. We present the results of our monitoring program to study the long-term variability of the Hα line in high-mass X-ray binaries. Our aim is to characterise the optical variability timescales and study the interaction between the neutron star and the accreting material. Methods. We fitted the Hα line with Gaussian profiles and obtained the line parameters and equivalent width. The peak separation in split profiles was used to determine the disk velocity law and estimate the disk radius. The relative intensity of the two peaks (V/R ratio) allowed us to investigate the distribution of gas particles in the disk. The equivalent width was used to characterise the degree of variability of the systems. We also studied the variability of the Hα line in correlation with the X-ray activity. Results. Our results can be summarised as follows: i) we find that Be/X-ray binaries with narrow orbits are more variable than systems with long orbital periods; ii) we show that a Keplerian distribution of gas particles provides a good description of the disks in Be/X-ray binaries, as it does in classical Be stars; iii) a decrease in the Hα equivalent width is generally observed after major X-ray outbursts; iv) we confirm that the Hα equivalent width correlates with disk radius; v) while systems with supergiant companions display multistructured profiles, most of the Be/X-ray binaries show, at some epoch, double-peak asymmetric profiles, which indicates that density inhomogeneities is a common property in the disk of Be/X-ray binaries; vi) the profile variability (V/R ratio) timescales are shorter and the Hα equivalent widths are smaller in Be/X-ray binaries than in isolated Be stars; and vii) we provide new evidence that the disk in Be/X-ray binaries is, on average, denser than in classical Be stars. Conclusions. We carried out the most complete optical spectroscopic study of the global properties of high-mass X-ray binaries with the analysis of more than 1100 spectra from 20 sources. Our results provide further evidence for the truncation of the disk in Be/X-ray binaries. We conclude that the interaction between the compact object and the Be-type star works in two directions: the massive companion provides the source of matter for accretion, affecting the surroundings of the compact object, and the continuous revolution of the neutron star around the optical counterpart also produces the truncation of the Be star's equatorial disk.

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Section: Observations and Data Reductionmentioning

confidence: 99%

Long-term optical variability of high-mass X-ray binaries

Reig

Nersesian

Zezas

et al. 2016

A&A

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“…The long-term variability of optical and IR photometry was discussed by Hao et al (1996), Clark et al (1998Clark et al ( , 1999, Haigh et al (1999Haigh et al ( , 2004, and Lyuty & Zaitseva (2000). The variability of the Hα emission line is related to physical changes in the circumstellar disk around the Be star.…”

Section: Introductionmentioning

confidence: 96%

DISCRETE MASS EJECTIONS FROM THE Be/X-RAY BINARY A0535+26/HD 245770

Yan

2011

ApJ

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We present long-term optical spectroscopic observations on the Be/X-ray binary A0535+26 from 1992 to 2010. Combined with the public V-band photometric data, we find that each giant X-ray outburst occurred in a fading phase of the optical brightness. The anti-correlation between the optical brightness and the Hα intensity during our 2009 observations indicates a mass ejection event had taken place before the 2009 giant X-ray outburst, which might cause the formation of a low-density region in the inner part of the disk. The similar anti-correlation observed around 1996 September indicates the occurrence of the mass ejection, which might trigger the subsequent disk loss event in A0535+26.

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“…First it was assumed that the absence of X-ray outburst at the orbital phase φ = 0.0 is caused by the lower Be star activity and, correspondingly, the decrease of plasma density in the stellar envelope (Giovannelli & Graziati 1992). However, systematic multiwavelength studies of the system reported recently (Clark et al 1998a and references therein) did not confirm this hypothesis: "missing" flare phenomena occured during the period when the optical-IR flux of the star was increasing.…”

Section: Introductionmentioning

confidence: 92%

“…However, systematic optical-IR observations have shown the "missing" flare phenomena to occur also during the periods when the circumstellar disk is in its brightest state (see Clark et al 1998a). This suggests that the low activity of the Be star is not the only reason for the "missing" flare phenomenon and an additional factor, which leads to suppression of X-ray flaring at the periastron, operates in the system.…”

Section: "Missing" Flare Phenomenonmentioning

confidence: 99%

On the accretion flow geometry in A0535+26

Ikhsanov

Larionov

Beskrovnaya

2001

A&A

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Abstract. The geometry of accretion flow in the Be/X-ray transient A0535+26 is explored. It is shown that neither moderate nor giant X-ray flaring events observed in the system can be interpreted within the spherically symmetrical accretion model and hence the formation of an accretion disk around the neutron star magnetosphere during the both types of flares is required. The accretion disk can be formed at the periastron if (i) the expansion velocity of the Be star envelope in the equatorial plane is Vwr < 150 km s −1 and (ii) the parameter accounting for the accretion flow inhomogeneities, ξ, satisfies the following condition: ξ > ∼ 0.16Ṁ −1/7 17, whereṀ17 is the rate of mass capture by the neutron star expressed in units of 10 17 g s −1 . We suggest that the "missing" outburst phenomenon can be associated with the spherically symmetrical accretion onto the interchange-stable magnetosphere of the neutron star. The average spin up rate of the neutron star during moderate flares < ∼ 3.5 10 −12 Hz s −1 is predicted.

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Long-term variability of the Be/X-ray binary A 0535+26 -- I. Optical and UV spectroscopy

Cited by 40 publications

References 9 publications

Long-term optical variability of high-mass X-ray binaries

Long-term optical variability of high-mass X-ray binaries

DISCRETE MASS EJECTIONS FROM THE Be/X-RAY BINARY A0535+26/HD 245770

On the accretion flow geometry in A0535+26

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