scholarly journals Nature of Circinus X-1

1979 ◽  
Vol 32 (2) ◽  
pp. 43 ◽  
Author(s):  
RF Haynes ◽  
David L Jauncey ◽  
I Lerche ◽  
PG Murdin

X-ray, radio and optical observations have been used to derive a binary star model for CircinusX-1. Mass transfer between the primary star (Mp ~ 20Mo) and the compact companion star (Me ~ Mo) triggers one or more expanding shock fronts in the vicinity of the compact star. These shocks produce the observed radio emission. Variable optical emission arises both from the changing Roche lobe surface in the highly eccentric system (e ~ 0�8) and from degradation of shock-produced X-ray photons to the optical band by material overlying the expanding shock. The X-ray radiation results from matter in the accretion disc dribbling down on to the surface of the compact star. Mass replenishment at a rate of 5 x 10-8 to 5 X 10-10 Mo per orbit (16�6 day period) occurs near periastron passage. The variation of the X-ray emission arises from absorption in the stellar wind of the primary star. The model predicts an apsidal rotation period for the elliptical orbit of 7-400 yr, an orbital circularization time of ~ 500 yr and a period change of about 0�5 day per 10 yr.

1987 ◽  
Vol 125 ◽  
pp. 249-249
Author(s):  
Tong Yi ◽  
Fang Geng ◽  
Mao Xinjie

Usually we think a X-ray source may be a compact(neutron) binary star on which the X-ray radiation might be generated by gravitational acceleration for the particles coming from the primary and going along magnetic field lines of the compact star to the poles. But, in the past, people don't consider well the problem of particle acceleration. It seems to be simplified for the situation only to consider the gravitation effect, because some electric-magnetic effect in a strong magnetic field could not be neglected. However, it is unreasonable to neglect the plasma turbulent waves in an electric-magnetic field, because strong enough turbulent waves such as Alfven waves, whistlers generated nearby the surface of neutron stars probably contribute energy to accelerate particles, which may be more important than gravitation sometimes. For a binary system with a neutron star if ion number density N > 1017 /cm3 in its surface atmosphere, the turbulent wavess will be stimulated that will accelerate the particles reaching a speed over 108cm/s. they strike the atmosphere of the compact star in the system, so that a shock wave is formed which turns part of kinetic energy to heat to form hot spots of about 108K to emit X-ray.


Author(s):  
J A Toalá ◽  
G Rubio ◽  
E Santamaría ◽  
M A Guerrero ◽  
S Estrada-Dorado ◽  
...  

Abstract We present the analysis of XMM-Newton European Photon Imaging Camera (EPIC) observations of the nova shell IPHASX J210204.7+471015. We detect X-ray emission from the progenitor binary star with properties that resemble those of underluminous intermediate polars such as DQ Her: an X-ray-emitting plasma with temperature of TX = (6.4 ± 3.1) × 106 K, a non-thermal X-ray component, and an estimated X-ray luminosity of LX = 1030 erg s−1. Time series analyses unveil the presence of two periods, the dominant with a period of 2.9 ± 0.2 hr, which might be attributed to the spin of the white dwarf, and a secondary of 4.5 ± 0.6 hr that is in line with the orbital period of the binary system derived from optical observations. We do not detect extended X-ray emission as in other nova shells probably due to its relatively old age (130–170 yr) or to its asymmetric disrupted morphology which is suggestive of explosion scenarios different to the symmetric ones assumed in available numerical simulations of nova explosions.


1974 ◽  
Vol 2 (5) ◽  
pp. 278-280 ◽  
Author(s):  
B. A. Peterson

Important observations of X-ray sources and searches for the optical counterparts of X-ray and radio pulsars require a capability of detecting and analysing light variations with a time scale of milliseconds. X-ray sources in binary star systems are expected to be collapsed objects – neutron stars or black holes (Peterson 1973) – and are expected to produce light variations. In the case of a neutron star, pulses with the same period as the rotation period of the neutron star would be produced, and such have been observed from Cen X-3 (schreier et al. 1972) in the X-ray, and from Her X-1 (Middleditch and Nelson 1973) and the Crab Nebula pulsar (Cocke et al. 1969) in the X-ray optical.


2020 ◽  
Vol 493 (1) ◽  
pp. 940-951
Author(s):  
E López-Navas ◽  
N Degenaar ◽  
A S Parikh ◽  
J V Hernández Santisteban ◽  
J van den Eijnden

ABSTRACT Accreting neutron stars and black holes in low-mass X-ray binaries (LMXBs) radiate across the electromagnetic spectrum. Linking the emission produced at different wavelengths can provide valuable information about the accretion process and any associated outflows. In this work, we study simultaneous X-ray and ultraviolet (UV)/optical observations of the neutron star LMXB Aql X-1, obtained with the Neil Gehrels Swift Observatory during its 2013, 2014, and 2016 accretion outbursts. We find that the UV/optical and X-ray emission are strongly correlated during all three outbursts. For the 2013 and 2014 episodes, which had the best Swift sampling, we find that the correlation between the UV/optical and X-ray fluxes is significantly steeper during the decay (soft state) of the outburst than during the rise (hard-to-soft state). We observe a UV/optical hysteresis behaviour that is likely linked to the commonly known X-ray spectral hysteresis pattern. For the decays of the three outbursts, we obtain a correlation index that cannot be directly explained by any single model. We suspect that this is a result of multiple emission processes contributing to the UV/optical emission, but we discuss alternative explanations. Based on these correlations, we discuss which mechanisms are likely dominating the UV/optical emission of Aql X-1.


1980 ◽  
Vol 5 ◽  
pp. 231-245
Author(s):  
Herbert Gursky ◽  
Robert Davis

In 1972, when the request for observing programs for the International Ultraviolet Explorer (IUE) was first made by NASA, ESA and the United Kingdom, a number of scientists recognized that observations in the ultraviolet of the strong galactic X-ray sources could be a fruitful activity. The underlying nature of those objects was understood. Their binary nature had been discovered through the X-ray observations which, combined with extensive optical observations and the insight gained through the tie to traditional ideas of stellar evolution, led to a picture whose general features are still accepted. The strong X-ray sources were taken to be close binary systems in which one object was a compact star, either a neutron star or a black hole, and the other object a common star in a stage of its life when it was undergoing great mass loss, either as a stellar wind or through Roche-lobe overflow.


1976 ◽  
Vol 56 (6) ◽  
pp. 1772-1780
Author(s):  
R. Hoshi
Keyword(s):  

1998 ◽  
Vol 188 ◽  
pp. 358-359 ◽  
Author(s):  
T. Kotani ◽  
N. Kawai ◽  
M. Matsuoka ◽  
W. Brinkmann

Here we present a very short review of the ASCA observation campaign of the enigmatic galactic jet system SS433. The campaign started in 1994 just after the launch, and ended in 1996. Various phases of the 162.5-day precession and 13-day orbital motion were sampled. With ASCA, the Doppler-shifted pairs from various ion species from Si to Ni were resolved for the first time (Kotani et al. 1994). The Doppler-shift parameters were determined with an accuracy comparable to optical spectroscopy (Kawai 1995). No velocity gradient was found between the X-ray emission region of the jet and the optical. The distance between them was constrained to be less than 1015 cm. Line intensity ratios of Fe XXVI/Fe XXV give the base temperature of the jet to be 20 keV (Kotani et al. 1996). The variation of the apparent base temperature of the jet can be explained in terms of the partial occultation of the jet by a precessing accretion disk (Kotani et al. 1997a). From the variation, the disk radius and the disk height in unit of the X-ray jet length were estimated to be 0.23 ± 0.10 and 0.0232 ± 0.0049, respectively. (These are an improved version of the values in Kotani et al. (1997a).) SS433 is also known as an eclipsing binary. Because the emission from each jet with ASCA, it is possible to know how much of which jet is occulted by the companion star during an eclipse. Relative size of the companion star gives Roche lobe size and thus mass ratio MX/MC = 0.22+0.09-0.16 (Kotani 1997b). With the help of Doppler modulation, compact star mass is constrained. However, the values of Doppler modulation reported from optical observations largely scatters. D'Odorico et al. (1991) reported 112 km s−1 and this gives MX = 0.68+0.43-0.53 M⊙, i.e., a white dwarf, while Fabrika and Bychkova (1990) reported 175 km s−1, which gives 2.6+1.6-2.0 M⊙. (This error includes systematic errors of the X-ray data, and will be reduced in future analysis.) On the other hand, the absolute size of the system were determined with a satisfactory precision. For example, the X-ray jet length was determined to be 2×1013 cm, ten times larger than previous estimations (Kotani et al. 1997c). Other physical parameters of the jet can be derived from the X-ray jet length. Mass outflow rate and the kinetic luminosity of both jet were determined to be 8 × 10−6 M⊙ yr−1 and 1.6 × 1040 erg s−1 (Kotani et al. 1997d), implicating a highly super critical accretion. Most of these values are first precise measurements and/or “radical” revisions of previous estimations. The new picture of SS433 drawn here is far stormy and highly energetic.


2019 ◽  
Vol 485 (4) ◽  
pp. 5235-5243
Author(s):  
M Armas Padilla ◽  
T Muñoz-Darias ◽  
J Sánchez-Sierras ◽  
B De Marco ◽  
F Jiménez-Ibarra ◽  
...  

Abstract MAXI J1813-095 is an X-ray transient discovered during an outburst in 2018. We report on X-ray and optical observations obtained during this event, which indicate that the source is a new low-mass X-ray binary. The outburst lasted ∼70 d and peaked at LX(0.5–10 keV) ∼ 7.6 × 1036 erg s−1, assuming a distance of 8 kpc. Swift/XRT follow-up covering the whole activity period shows that the X-ray emission was always dominated by a hard power-law component with a photon index in the range of 1.4–1.7. These values are consistent with MAXI J1813-095 being in the hard state, in agreement with the ∼30 per cent fractional root-mean-square amplitude of the fast variability (0.1–50 Hz) inferred from the only XMM–Newton observation available. The X-ray spectra are well described by a Comptonization emission component plus a soft, thermal component (kT ∼ 0.2 keV), which barely contributes to the total flux (≲8 per cent). The Comptonization y-parameter (∼1.5), together with the low temperature and small contribution of the soft component supports a black hole accretor. We also performed optical spectroscopy using the Very Large Telescope and Gran Telescopio Canarias telescopes during outburst and quiescence, respectively. In both cases, the spectrum lacks emission lines typical of X-ray binaries in outburst. Instead, we detect the Ca ii triplet and H α in absorption. The absence of velocity shifts between the two epochs, as well as the evolution of the H α equivalent width, strongly suggest that the optical emission is dominated by an interloper, likely a G–K star. This favours a distance ≳3 kpc for the X-ray transient.


2018 ◽  
Vol 621 ◽  
pp. A15 ◽  
Author(s):  
G. Rauw ◽  
A. Pigulski ◽  
Y. Nazé ◽  
A. David-Uraz ◽  
G. Handler ◽  
...  

Context. HD 149 404 is an evolved non-eclipsing O-star binary that has previously undergone a Roche lobe overflow interaction. Aims. Understanding some key properties of the system requires a determination of the orbital inclination and of the dimensions of the components. Methods. The BRITE-Heweliusz satellite was used to collect photometric data of HD 149 404. Additional photometry was retrieved from the SMEI archive. These data were analysed using a suite of period search tools. The orbital part of the lightcurve was modelled with the nightfall binary star code. The Gaia-DR2 parallax of HD 149 404 was used to provide additional constraints. Results. The periodograms reveal a clear orbital modulation of the lightcurve with a peak-to-peak amplitude near 0.04 mag. The remaining non-orbital part of the variability is consistent with red noise. The lightcurve folded with the orbital period reveals ellipsoidal variations, but no eclipses. The minimum when the secondary star is in inferior conjunction is deeper than the other minimum due to mutual reflection effects between the stars. Combined with the Gaia-DR2 parallaxes, the photometric data indicate an orbital inclination in the range of 23°–31° and a Roche lobe filling factor of the secondary larger than or equal to 0.96. Conclusions. The luminosity of the primary star is consistent with its present-day mass, whereas the more evolved secondary appears overluminous for its mass. We confirm that the primary’s rotation period is about half the orbital period. Both features most probably stem from the past Roche lobe overflow episode.


1998 ◽  
Vol 188 ◽  
pp. 388-389
Author(s):  
A. Kubota ◽  
K. Makishima ◽  
T. Dotani ◽  
H. Inoue ◽  
K. Mitsuda ◽  
...  

About 10 X-ray binaries in our Galaxy and LMC/SMC are considered to contain black hole candidates (BHCs). Among these objects, Cyg X-1 was identified as the first BHC, and it has led BHCs for more than 25 years(Oda 1977, Liang and Nolan 1984). It is a binary system composed of normal blue supergiant star and the X-ray emitting compact object. The orbital kinematics derived from optical observations indicates that the compact object is heavier than ~ 4.8 M⊙ (Herrero 1995), which well exceeds the upper limit mass for a neutron star(Kalogora 1996), where we assume the system consists of only two bodies. This has been the basis for BHC of Cyg X-1.


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