Search results for "binaries: close"
showing 10 items of 10 documents
Evolutionary paths of binaries with a neutron star - I. The case of SAX J1808.4 - 3658
2018
The evolutionary status of the low mass X-ray binary SAX J1808.4-3658 is simulated by following the binary evolution of its possible progenitor system through mass transfer, starting at a period of $\sim$6.6 hr. The evolution includes angular momentum losses via magnetic braking and gravitational radiation. It also takes into account the effects of illumination of the donor by both the X-ray emission and the spin down luminosity of the pulsar. The system goes through stages of mass transfer and stages during which it is detached, where only the rotationally powered pulsar irradiates the donor. We show that the pulsar irradiation is a necessary ingredient to reach SAX J1808.4-3658 orbital pe…
INTEGRAL and RXTE observations of accreting millisecond pulsar IGR J00291+5934 in outburst
2005
Simultaneous observations of the accretion-powered millisecond pulsar IGR J00291+5934 by International Gamma-Ray Astrophysics Laboratory and Rossi X-ray Timing Explorer during the 2004 December outburst are analysed. The average spectrum is well described by thermal Comptonization with an electron temperature of 50 keV and Thomson optical depth tau_T ~ 1 in a slab geometry. The spectral shape is almost constant during the outburst. We detect a spin-up of the pulsar with nudot=8.4x10E-13 Hz/s. The ISGRI data reveal the pulsation of X-rays at a period of 1.67 milliseconds up to ~150 keV. The pulsed fraction is shown to increase from 6 per cent at 6 keV to 12--20 per cent at 100 keV. This is n…
Multi-epoch VLTI-PIONIER imaging of the supergiant V766 Cen
2017
Context. The star V766 Cen (=HR 5171A) was originally classified as a yellow hypergiant but lately found to more likely be a 27-36 M red supergiant (RSG). Recent observations indicated a close eclipsing companion in the contact or common-envelope phase. Aims. Here, we aim at imaging observations of V766 Cen to confirm the presence of the close companion. Methods. We used near-infrared H-band aperture synthesis imaging at three epochs in 2014, 2016, and 2017, employing the PIONIER instrument at the Very Large Telescope Interferometer (VLTI). Results. The visibility data indicate a mean Rosseland angular diameter of 4.1 ± 0.8 mas, corresponding to a radius of 1575 ± 400 R. The data show an ex…
Binary evolution of PSR J1713+0747
2007
PSR J1713+0747 is a binary millisecond radio pulsar with a long orbital period (Porb ∼ 68 d) and a very low neutron star mass (M NS = 1.3 ± 0.2 M⊙). We simulate the evolution of this binary system with an accurate numerical code, which keeps into account both the evolution of the primary and of the whole binary system. We show that strong ejection of matter from the system is fundamental to obtain a mass at the end of the evolution that is within 1 - σ from the observed one, but propeller effects are almost negligible in such a system, where the accretion rate is always near to the Eddington limit. We show that there are indeed two mechanisms can account for the amount of mass loss from the…
IGR J17503–2636: a candidate supergiant fast X-ray transient
2019
IGR J17503-2636 is a hard X-ray transient discovered by INTEGRAL on 2018 August 11. This was the first ever reported X-ray emission from this source. Following the discovery, follow-up observations were carried out with Swift, Chandra, NICER, and NuSTAR. We report in this paper the analysis and results obtained from all these X-ray data. Based on the fast variability in the X-ray domain, the spectral energy distribution in the 0.5-80 keV energy range, and the reported association with a highly reddened OB supergiant at ~10 kpc, we conclude that IGR J17503-2636 is most likely a relatively faint new member of the supergiant fast X-ray transients. Spectral analysis of the NuSTAR data revealed …
The near-IR counterpart of IGR J17480-2446 in Terzan 5
2012
Some globular clusters in our Galaxy are noticeably rich in low-mass X-ray binaries. Terzan 5 has the richest population among globular clusters of X- and radio-pulsars and low-mass X-ray binaries. The detection and study of optical/IR counterparts of low-mass X-ray binaries is fundamental to characterizing both the low-mass donor in the binary system and investigating the mechanisms of the formation and evolution of this class of objects. We aim at identifying the near-IR counterpart of the 11 Hz pulsar IGRJ17480-2446 discovered in Terzan 5. Adaptive optics (AO) systems represent the only possibility for studying the very dense environment of GC cores from the ground. We carried out observ…
The different fates of a low-mass X-ray binary - I. Conservative mass transfer
2003
We study the evolution of a low mass x-ray binary coupling a binary stellar evolution code with a general relativistic code that describes the behavior of the neutron star. We assume the neutron star to be low--magnetized (B~10^8 G). In the systems investigated in this paper, our computations show that during the binary evolution the companion transfers as much as 1 solar mass to the neutron star, with an accretion rate of 10^-9 solar masses/yr. This is sufficient to keep the inner rim of the accretion disc in contact with the neutron star surface, thus preventing the onset of a propeller phase capable of ejecting a significant fraction of the matter transferred by the companion. We find th…
GSC 07396-00759 = V4046 Sgr C[D]: A Wide-separation Companion to the Close T Tauri Binary System V4046 Sgr AB
2011
We explore the possibility that GSC 07396-00759 (spectral type M1e) is a widely separated (~2.82', or projected separation ~12,350 AU) companion to the "old" (age ~12 Myr) classical T Tauri binary system V4046 Sgr AB, as suggested by the proximity and similar space motions of the two systems. If the two systems are equidistant and coeval, then GSC 07396--00759, like V4046 Sgr AB, must be a spectroscopic binary with nearly equal-mass components, and V4046 Sgr must be at least ~8 Myr old. Analysis of a serendipitous Chandra X-ray gratings spectrum and light curve as well as XMM-Newton light curves and CCD spectra of GSC 07396-00759 obtained during long exposures targeting V4046 Sgr AB reveals…
Correlated X-ray spectral and timing variability of the Be/X-ray binary V0332+53/BQ Camelopardalis during a type II outburst
2005
We have used INTEGRAL & RXTE data to investigate the timing properties of the source in correlation with its spectral states as defined by different positions in the colour-colour diagram. The source shows two distinct branches in the colour-colour diagram that resemble those of the Z sources. The hard branch (similar to the horizontal branch of Z sources) is characterised by a low-amplitude change of the hard colour compared to the change in the soft colour. In the soft branch (analogue to the normal branch) the amplitude of variability of the hard colour is about three times larger than that of the soft colour. As the count rate decreases the source moves up gradually through the soft…
Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
2017
On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anticoincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB 170817A and GW170817 occurring by chance is $5.0\times 10^{-8}$. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB 170817A provides new insight into fundamental physics and the origin of short gamma-ray bursts. We use the ob…