Binary SS Research Articles

Simulations of the Progenitors of Black Hole–Neutron Star Gravitational Wave Sources

Recent discoveries of gravitational wave (GW) events most likely originating from black hole (BH) + neutron star (NS) mergers reveal the existence of BH+NS binaries. The formation of BH+NS binaries and their merger rates through isolated binary evolution have been investigated extensively with population synthesis simulations. A detailed stellar evolution modeling of the formation of this population, however, is missing from the literature. In this work, we create the first complete 1D model of more than 30 BH+NS progenitor systems, which are calculated self-consistently until collapse of the iron core with infall velocity exceeding 1000 km s−1. Focusing on the progenitors of BH–NS GW sources, we apply the MESA code starting from a post-common-envelope binary with short orbital period (<1 day) consisting of a BH and a zero-age main-sequence helium star that experiences stable mass transfer. The (ultra)stripped supernova explosion is subsequently modeled using a semianalytic method to reveal final remnant masses and momentum kicks. Three example systems (A, B, and C) eventually evolve into BH+NS binaries with component masses of (M BH, M NS) = (8.80, 1.53), (8.92, 1.45), and (5.71, 1.34) M ⊙, respectively. These NS masses could be significantly larger depending on the exact mass cut during the supernova explosion. These BH+NS systems are likely to merge and produce GW events within a Hubble time. System C is a potential progenitor of a GW200115-like event, while Systems A and B are possible candidates for a GW200105-like event and may represent the final destiny of the X-ray binary SS 433.

Spatially resolved study of the SS 433/W 50 west region with Chandra: X-ray structure and spectral variation of non-thermal emission

AbstractThe X-ray binary SS 433, embedded in the W 50 nebula (or supernova remnant W 50), shows bipolar jets that are ejected with mildly relativistic velocities and which extend toward the east and west out to scales of tens of parsecs. Previous X-ray observations revealed twin lobes along the jet precession axis that contain compact bright knots dominated by synchrotron radiation, which provide evidence of electron acceleration in this system. Particle acceleration in this system is substantiated by the recently detected gamma rays with energies up to at least 25 TeV. To elucidate the origin of the knots and particle acceleration sites in SS 433/W 50 further, we report here on detailed, spatially resolved X-ray spectroscopy of its western lobe with Chandra. We detect synchrotron emission along the jet precession axis, as well as optically thin thermal emission that is more spatially extended. Between the two previously known knots, w1 and w2, we discover another synchrotron knot, which we call w1.5. We find no significant synchrotron emission between SS 433 and the innermost X-ray knot (w1), suggesting that electrons only begin to be accelerated at w1. The X-ray spectra become gradually steeper from w1 to w2, and then rapidly so immediately outside of w2. Through comparison with a model taking into account electron transport and cooling along the jet, this result indicates that the magnetic field in w2 is substantially enhanced, which also explains its brightness. We discuss possible origins of the enhanced magnetic field of w2 as well as scenarios to explain the other two knots.

The overcontact binary SS arietis

New radial velocity and photometric data for SS Ari have been obtained and analysed using the 2003 versions of the Wilson-Devinney code. Values for fundamental quantities have been obtained: M1 = 0.510 (15) M ʘ, M 2 = 1.521 (26) M ʘ, R1 = 0.87 (2) Rʘ, R2 = 1.42 (2) Rʘ, L1 = 0.88 (8) L ʘ, and L 2 = 2.13 (21) L ʘ. In addition to the values provided by the Wilson-Devinney output, luminosities have been computed directly using photometry from APASS, the Gaia distance, and estimates of the interstellar absorption. Although the two sets of luminosities compare well, the accuracy of the latter set is limited by the uncertainty in the APASS magnitudes. Although the TYC magnitudes for the comparison star are more precise, they produce higher luminosities (but still within error limits). In any case, the good agreement between the luminosities determined by the two methods suggests that they, and all other results in this paper, might be more reliable than previous values in the literature. Inserting the parameters into a Log(L)-Log(Teff) plot for each star using data from Yakut and Eggleton (2005) suggests that the more massive star is somewhat over-luminous and therefore evolved, whereas its companion is under-luminous. Analysis of the period behaviour with the aid of an eclipse timing difference (OC) plot reveals that the double sine relationship Kim et al. (2003) is no longer valid. A new LiTE relationship adding two companion stars has been obtained, but, in view of the fact the putative period of one of them is in the range of ∼600 years, the relationship must be regarded as very tentative indeed.

Does Nature use neutral beams for interstellar plasma heating around compact objects?

ABSTRACT A neutral beam injection technique is employed in all major TOKAMAK facilities for heating of magnetically confined plasma. The question then arises, whether a similar mechanism might work in astrophysical objects? For instance, a hyper-Eddington Galactic binary SS433 possesses baryonic jets, moving at a quarter of the speed of light, and observations revealed signs of gas cooling and recombination on sub-pc scales and equally strong signs of powerful energy deposition on much larger scales ∼100 pc. Here, we consider a model where neutral atoms transport this energy. A sub-relativistic beam of neutral atoms penetrates the interstellar medium; these atoms gradually get ionized and deposit their energy over a region, whose longitudinal dimension is set by the ‘ionization length’. The channel, where the energy is deposited, expands sideways and drives a shock in the lateral direction. Once the density in the channel drops, the heating rate by the beam drops accordingly, and the region of the energy release moves along the direction of the beam. We discuss distinct features associated with this scenario and speculate that such configuration might also boost shock acceleration of the ‘pick-up’ protons that arise due to ionization of neutral atoms both upstream and downstream of the shock.

Light element variations in globular clusters via nucleosynthesis in black hole accretion discs

ABSTRACT Ancient globular clusters contain multiple stellar populations identified by variations in light elements (e.g. C, N, O, Na). Although many scenarios have been suggested to explain this phenomenon, all are faced with challenges when compared with all the observational evidence. In this Letter, we propose a new scenario in which light element variations originate from nucleosynthesis in accretion discs around black holes. Since the black holes form after a few Myrs, the cluster is expected to still be embedded in a gas-rich environment. Through a simplified accretion model, we show that the correct light element anticorrelations can be produced. Assuming a Kroupa stellar initial mass function, each black hole would only have to process ≈300 M⊙ of material in order to explain multiple populations; over a period of 3 Myr this corresponds to ∼10−4 M⊙ yr−1 (similar to the estimated accretion rate for the X-ray binary SS 433).

Multicolour photometry of SS 433

AbstractWe presented long-term optical observations of the high mass X-ray binary system SS 433 (V1343 Aql) with a black hole component. New observations have been obtained by using the 0.6m telescope at the TÜBİTAK National Observatory (TUG) in B, V, R and I filters. We aim to investigate the long-term photometric behavior of the system.

On masses of the components in SS433

A huge optical luminosity of the supercritical accretion disc and powerful stellar wind in the high-mass X-ray binary SS433 make it difficult to reliably estimate the mass ratio of the binary components from spectroscopic observations. We analyse different indirect methods of the mass ratio estimate. We show that with an account of the possible Roche lobe overflow by the optical star, the analysis of X-ray eclipses in the standard and hard X-ray bands suggests the estimate q = Mx/Mv ≳ 0.3. We argue that the double-peak hydrogen Brackett lines in SS433 should form not in the accretion disc but in a circumbinary envelope, suggesting a total mass of |$M_\mathrm{v}+M_\mathrm{x}\gtrsim 40 \, \mathrm{M}_\odot$|⁠. The observed long-term stability of the orbital period in SS433 |$|\dot{P}_b/P_b|\le 1.793\times 10^{-14}$| s−1 over ∼28 yr period is used to place an independent constraint of q ≳ 0.6 in SS433, confirming its being a Galactic microquasar hosting a superaccreting black hole.

LOFAR 150-MHz observations of SS 433 and W 50

We present LOFAR high-band data over the frequency range 115-189 MHz for the X-ray binary SS 433, obtained in an observing campaign from 2013 February - 2014 May. Our results include a deep, wide-field map, allowing a detailed view of the surrounding supernova remnant W 50 at low radio frequencies, as well as a light curve for SS 433 determined from shorter monitoring runs. The complex morphology of W 50 is in excellent agreement with previously published higher-frequency maps; we find additional evidence for a spectral turnover in the eastern wing, potentially due to foreground free-free absorption. Furthermore, SS 433 is tentatively variable at 150 MHz, with both a debiased modulation index of 11 per cent and a $\chi^2$ probability of a flat light curve of $8.2 \times 10^{-3}$. By comparing the LOFAR flux densities with contemporaneous observations carried out at 4800 MHz with the RATAN-600 telescope, we suggest that an observed $\sim$0.5-1 Jy rise in the 150-MHz flux density may correspond to sustained flaring activity over a period of approximately six months at 4800 MHz. However, the increase is too large to be explained with a standard synchrotron bubble model. We also detect a wealth of structure along the nearby Galactic plane, including the most complete detection to date of the radio shell of the candidate supernova remnant G 38.7-1.4. This further demonstrates the potential of supernova remnant studies with the current generation of low-frequency radio telescopes.

The SS433 jet from subparsec to parsec scales

Context. Relativistic jets associated with compact objects, as in the X-ray binary SS433, are known to be multiscale because they spawn over many orders of magnitude in distance. Here we model the precessing SS433 jet and study its dynamics from 𝒪 (0.01) to 𝒪(1) parsec scales.Aims. We aim to solve the discrepancy between the observations on a 0.1 pc scale of SS433, where the jet is clearly precessing with an angle of 20°, and the larger scale observations where the jet of SS433 interacts with the associated supernova remnant W50, requiring a precessing angle of 10°. Methods. We use 3D special relativistic hydrodynamical simulations on a domain of a scale of 1 pc. We use the finite volume code MPI-AMRVAC, solving the relativistic variant of the Euler equations. To cover lengthscale variations from 𝒪(0.001) pc as the jet beam width up to the domain size, we take full advantage of code parallelization and its adaptive mesh refinement scheme.Results. We found that by means of a simple hydrodynamical process, the jet of SS433 can transit from a precessing jet with an angle of 20°, to a continuous hollow non-precessing jet with a smaller opening angle of about 10°. Successive windings of the precessing jet helix undergo gradual deceleration by ISM interaction, to ultimately merge in a hollow straight jet at distances where the ram pressure of individual jet elements match the ISM pressure at about 0.068 pc from the source.Conclusions. We solve the discrepancy with an elegant and simple model that does not require the jet of SS433 to undergo any temporal changes in jet injection dynamics, but does so as a consequence of a hydrodynamically enforced spatial recollimation. Our simulation thus serves to validate simpler model prescriptions for SS433 on large scales, where a continuous jet profile suffices.

Relativistic 3D precessing jet simulations for the X-ray binary SS433

Context. Modern high resolution observations allow to view closer into the objects powering relativistic jets. This is especially the case for SS433, an X-ray binary from which a precessing jet is observed down to the sub-parsec scale. Aims. We want to study full 3D dynamics of relativistic jets associated with AGN or XRB. We study the precessing motion of a jet as a model for the jet associated with the XRB SS433. Our study of the jet dynamics in this system focuses on the sub-parsec scales. We investigate the impact of jet precession and the variation of the Lorentz factor of the injected matter on the general 3D jet dynamics and its energy transfer to the surrounding medium. We realize synthetic radio mapping of the data, to compare our results with observations. Methods. For our study we use the code MPI-AMRVAC with SRHD model of a baryonic jet. We use a AMR scheme and an inner time-dependent boundary prescription to inject the jets. Parameters extracted from observations were used. 3D jet realizations that match the SS433 jet are intercompared. We track the energy content, as deposited in different regions of the domain affected by the jet. Our code also follows a population of particles injected with the jet. This evolving energy spectrum of accelerated electrons, allows to obtain the radio emission from our simulation. Results. we obtain meaningful observations. We find increased energy transfer for a precessing jet compared to a standing jets. We obtain synthetic radio maps for all jets. Conclusions. The synthetic radio map matches best for a model using the canonical kinematic model. Overdense precessing jets experience significant deceleration in their propagation through the ISM, and while the overall jet is of helical shape. This argument show that the kinematic model for SS433 assuming ballistic propagation has to be corrected for this decelretaion.

Baryons in the relativistic jets of the stellar-mass black-hole candidate 4U 1630-47

Accreting black holes are known to power relativistic jets, both in stellar-mass binary systems and at the centres of galaxies. The power carried away by the jets, and, hence, the feedback they provide to their surroundings, depends strongly on their composition. Jets containing a baryonic component should carry significantly more energy than electron-positron jets. Energetic considerations and circular-polarization measurements have provided conflicting circumstantial evidence for the presence or absence of baryons in jets, and the only system in which they have been unequivocally detected is the peculiar X-ray binary SS 433 (refs 4, 5). Here we report the detection of Doppler-shifted X-ray emission lines from a more typical black-hole candidate X-ray binary, 4U 1630-47, coincident with the reappearance of radio emission from the jets of the source. We argue that these lines arise from baryonic matter in a jet travelling at approximately two-thirds the speed of light, thereby establishing the presence of baryons in the jet. Such baryonic jets are more likely to be powered by the accretion disk than by the spin of the black hole, and if the baryons can be accelerated to relativistic speeds, the jets should be strong sources of γ-rays and neutrino emission.

An Accurate Geometric Distance to the Compact Binary SS Cygni Vindicates Accretion Disc Theory

Dwarf novae are white dwarfs accreting matter from a nearby red dwarf companion. Their regular outbursts are explained by a thermal-viscous instability in the accretion disc, described by the disc instability model that has since been successfully extended to other accreting systems. However, the prototypical dwarf nova, SS Cygni, presents a major challenge to our understanding of accretion disc theory. At the distance of 159 ± 12 parsecs measured by the Hubble Space Telescope, it is too luminous to be undergoing the observed regular outbursts. Using very long baseline interferometric radio observations, we report an accurate, model-independent distance to SS Cygni that places the source substantially closer at 114 ± 2 parsecs. This reconciles the source behavior with our understanding of accretion disc theory in accreting compact objects.

ON THE NATURE OF THE COMPACT OBJECT IN SS 433: OBSERVATIONAL EVIDENCE OF X-RAY PHOTON INDEX SATURATION

We present an analysis of the X-ray spectral properties observed from black hole candidate (BHC) binary SS~433. We have analyzed RXTE data from this source, coordinated with Green Bank Interferometer/RATAN-600. We show that SS~433 undergoes a X-ray spectral transition from the low hard state (LHS) to the intermediate state (IS). We show that the X-ray broad-band energy spectra during all spectral states are well fit by a sum of so called ``Bulk Motion Comptonization (BMC) component'' and by two (broad and narrow) Gaussians for the continuum and line emissions respectively. In addition to these spectral model components we also find a strong feature that we identify as a "blackbody-like (BB)" component which color temperature is in the range of 4-5 keV in 24 IS spectra during the radio outburst decay in SS~433. Our observational results on the "high temperature BB" bump leads us to suggest the presence of gravitationally redshifted annihilation line emission in this source. I\ We have also established the photon index saturation at about 2.3 in index vs mass accretion correlation. This index-mass accretion correlation allows us to evaluate the low limit of black hole (BH) mass of compact object in SS~433, M_{bh}> 2 solar masses, using the scaling method using BHC GX 339-4 as a reference source. Our estimate of the BH mass in SS 433 is consistent with recent BH mass measurement using the radial-velocity measurements of the binary system by Hillwig & Gies who find that M_{x}=(4.3+/-0.8 solar masses. This is the smallest BH mass found up to now among all BH sources. Moreover, the index saturation effect versus mass accretion rate revealed in SS~433, like in a number of other BH candidates, is the strong observational evidence for the presence of a BH in SS~433.

STRUCTURE AND MAGNETIC FIELDS IN THE PRECESSING JET SYSTEM SS 433. II. INTRINSIC BRIGHTNESS OF THE JETS

Deep Very Large Array imaging of the binary X-ray source SS 433, sometimes classified as a microquasar, has been used to study the intrinsic brightness distribution and evolution of its radio jets. The intrinsic brightness of the jets as a function of age at emission of the jet material tau is recovered by removal of the Doppler boosting and projection effects. We find that intrinsically the two jets are remarkably similar when compared for equal tau, and that they are best described by Doppler boosting of the form D^{2+alpha}, as expected for continuous jets. The intrinsic brightnesses of the jets as functions of age behave in complex ways. In the age range 60 < tau < 150 days, the jet decays are best represented by exponential functions of tau, but linear or power law functions are not statistically excluded. This is followed by a region out to tau ~ 250 days during which the intrinsic brightness is essentially constant. At later times the jet decay can be fit roughly as exponential or power law functions of tau.

Understanding ULX nebulae in the framework of supercritical accretion

For a long time, the well-known supercritically accreting binary SS433 is being proposed as a prototype for a class of hypothetical bright X-ray sources that may be identified with the so-called Ultraluminous X-ray sources (ULXs) in nearby galaxies or at least with part of them. Like SS433, these objects should be associated with optical nebulae, powered by both radiation of the central source and its wind or jet activity. Indeed, around many ULXs, bright optical nebulae (ULX Nebulae, ULXNe) are found. Here, we use SS433 as a prototype for the power source creating the nebulae around ULXs. Though many factors are important such as the structure of the host star-forming region and the possible supernova remnant formed together with the accreting compact object, we show that most of the properties of ULXNe may be explained by an SS433-like system evolving for up to about one million years in a constant-density environment. The basic stages of evolution of a ULX Nebula include a non-spherical HII-region with a central cavity created by non-radiative shock waves, an elongated or bipolar shock-powered nebula created by jet activity and a large-scale quasi-spherical bubble.

The effect of diffusion of magnetic field on flow structure in close binaries

We use 3D numerical simulations to study MHD flows in close binary system SS Cyg. This star belongs to the class of the semi-detached binaries where the secondary star (donor) fills its Roche lobe and loses mass through the inner Lagrangian point L 1 . The matter accretes to the magnetized primary star – the white dwarf (accretor). To describe the magnetic field we take the value B a = 10 5 G for the magnetic induction on the surface of the compact primary star. We assume that the dipole moment is inclined to the rotation axis at the angle θ = 30 ° and the rotation of the accretor is synchronous with the orbital rotation of the binary system. The developed numerical model takes into account the turbulent diffusion of the magnetic field that is determined by the magnetic reconnections and the electric currents dissipation in turbulent vortexes as well as by the magnetic flux tubes buoyancy. To define the influence of the turbulent dissipation of the magnetic field on the flow structure we used the model of the ideal MHD and that of MHD with non-zero turbulent diffusivity. It was found out that in both models the flow structure has the same qualitative features as in pure HD solution: (i) the magnetized accretion disk forms in the system; (ii) all previously discovered waves still exist in the disk: the shock wave (‘’hot line”) forming due to the interaction between the circumdisk halo and the stream from the inner Lagrangian point L 1 , two arms of the tidal shock, the spiral precessional wave, and the bow shock caused by the motion of the accretor and the disk through the circumbinary envelope. It was also shown that in both models the magnetic field in the disk is mainly toroidal, and the presence of the magnetic field leads to the formation of the magnetosphere and the funnel flow near the magnetic poles of the primary star. Besides, we discovered that taking into consideration the turbulent diffusion of the magnetic field leads to the drastic change of the plasma parameter β (from ∼ 10 - 3 in ideal MHD model to ∼ 10 - 1 for the model with turbulent dissipation) and as a consequence to the significant changes in the obtained MHD flows. As a result, the turbulent diffusion significantly increases the mass of the accretion disk, decreases its outer radius, height and characteristic density. Moreover, we came to the conclusion that the turbulent diffusion decreases the accretion rate (2.5–3 times) of the system that can drastically change the observational properties of the system.

Spectroscopy and doppler mapping of the binary SS Cyg during outburst

We carried out spectroscopy of the binary SSCyg in the Hα, Hβ, and Hγ lines in its active state in August and December 2006. We have estimated the parameters of the main flow elements contributing to the spectra. Profile variations during the orbital period are analyzed, and a Doppler tomogram computed for the Hα line. We consider the evolution of the line profiles with the development of the outburst. A phenomenological model explaining the observed outburst features is suggested. In this model, the main elements of the flow determining the shape of the spectral lines are the accretion disk, a toroidal shell formed in the inner parts of the disk, an expanding spherical shell around the accreting star, a region in front of the bow shock that forms due to the orbital motion of the disk in the circumbinary envelope, and the surface of the donor star near the inner Lagrange point, L1, which is heated by radiation from the accretor.

MODELING THE SS 433 JET BENDS

We fit Chandra HETGS data obtained for the unusual X-ray binary SS 433. While line strengths and continuum levels hardly change, the jet Doppler shifts show aperiodic variations that probably result from shocks in interactions with the local environment. The X-ray and optical emission line regions are found to be related but not coincident as the optical line emission persists for days while the X-ray emission lines fade in less than 5000 s. The X-ray spectrum of the blueshifted jet shows over two dozen emission lines from plasma at a variety of temperatures. The emission measure distribution derived from the spectrum can be used to test jet cooling models.

Unveiling the X-ray point source population of the Young Massive Cluster Westerlund 1

Aims. We investigate the nature of the X-ray point source population within the Young Massive Cluster Westerlund 1. Methods. Chandra observations of 18 ks and 42 ks were used to determine the X-ray properties of emitters within Wd 1, while a comprehensive multiwavelength dataset was employed to constrain their nature. Results. We find X-ray emission from a multitude of different stellar sources within Wd 1, including both evolved high mass and low mass pre-MS stars. We attribute the X-ray emission from the high mass component to both single stars and colliding wind binaries on the basis of their observed flux and spectral properties, with binaries being systematically harder and more luminous than single stars. We are able to infer a high binary fraction for both WN (10/16) and WC stars (7/8), resulting in a combined Wolf Rayet binary fraction of >70%. These represent the most stringent limits currently placed on the binary fraction of very massive (>45 M� ) stars. We place the first observational constraints on X-ray emission from stars transitioning between the Main Sequence and Wolf Rayet phases, finding that both hot (B hypergiants) and cool (yellow hypergiants and red supergiants) spectral types appear to be intrinsically X-ray faint. The B[e] star W9 is found to be X-ray bright and shows similarities to both the X-ray binary SS433 and the Luminous Blue Variable η Carinae. Globally, we find the point source population to be systematically fainter than those found in younger massive star forming regions such as NGC 3603 and R136/30 Doradus, consistent with a loss of the most massive stars to SNe and a reduction in emissivity from the low mass pre-Main Sequence stars. No unambiguous evidence for X-ray emission due to accretion onto relativistic objects of any mass is found, although the current data do not exclude the presence of either a High Mass X-ray Binary or an Intermediate Mass Black Hole accreting at a low rate. Finally, we suggest the progenitor mass for the magnetar CXOU J164710.2-455216 is comparable to that of SGR 1806-20 (∼55 M� ), while that for SGR 1900+14 appears significantly lower (∼15 M� ), implying that magnetars may form from stars with a wide range of initial masses.

XMM-Newton observations of the eastern jet of SS 433

The radio supernova remnant W50 hosts at its center the peculiar galactic X-ray binary SS 433. It shows a central spherical structure with two `ears' which are supposed to be formed by the interaction of the precessing jets of SS 433 with the supernova shell. In two pointings in September/October 2004 for 30 ks each the eastern jet of SS 433 was observed with XMM-Newton to study the outermost parts of the `ear' and the X-ray bright emission region about 35 arcmin from SS 433. The spectra consist of two components: a non-thermal power law with photon index \Gamma ~ 2.17+/-0.02 and a thermal component at a typical temperature of kT ~ 0.3 keV. The X-ray emission seems to fill the whole interior region of the radio remnant W50. The jet terminates in the eastern `ear' in a ring-like terminal shock which indicates a flow with a kind of hollow-cone morphology. The spatial coincidence of X-ray and radio emission suggests physical conditions similar to those found at the outer shocks of ordinary supernova remnants. The bright emission region closer to SS 433 radiates non-thermally in a spatially well confined geometry at higher X-ray energies. At soft X-rays the shape of the region gets blurred, centered on the hard lenticular emission. The shape of this region and the bend in the jet propagation direction might be caused by the interaction of a re-collimated jet with the outer, non homogeneous interstellar matter distribution. The physical conditions leading to the re-collimation of the jet and the peculiar emission morphology are far from being understood and require deeper observations as well as a detailed modeling of the interaction of a jet with its surroundings.