Search results for "Orbital motion"
showing 10 items of 14 documents
Astrometric detection of a low-mass companion orbiting the star AB Doradus
1997
International audience; We report submilliarcsecond-precise astrometric measurements for the late-type star AB Doradus via a combination of VLBI (very long baseline interferometry) and HIPPARCOS data. Our astrometric analysis results in the precise determination of the kinematics of this star, which reveals an orbital motion readily explained as caused by gravitational interaction with a low-mass companion. From the portion of the reÑex orbit covered by our data and using a revised mass of the primary star (0.76 M _) derived from our new value of the parallax (66.3 mas \ n \ 67.2 mas), we Ðnd the dynamical mass of the newly discovered companion to be between 0.08 and 0.11 If accurate photom…
Simulations of stellar/pulsar wind interaction along one full orbit
2012
The winds from a non-accreting pulsar and a massive star in a binary system collide forming a bow-shaped shock structure. The Coriolis force induced by orbital motion deflects the shocked flows, strongly affecting their dynamics. We study the evolution of the shocked stellar and pulsar winds on scales in which the orbital motion is important. Potential sites of non-thermal activity are investigated. Relativistic hydrodynamical simulations in two dimensions, performed with the code PLUTO and using the adaptive mesh refinement technique, are used to model interacting stellar and pulsar winds on scales ~80 times the distance between the stars. The hydrodynamical results suggest the suitable lo…
SAX J1808.4-3658, an accreting millisecond pulsar shining in gamma rays?
2016
We report the detection of a possible gamma-ray counterpart of the accreting millisecond pulsar SAX J1808.4-3658. The analysis of ~6 years of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope (Fermi-LAT) within a region of 15deg radius around the position of the pulsar reveals a point gamma-ray source detected at a significance of ~6 sigma (Test Statistic TS = 32), with position compatible with that of SAX J1808.4-3658 within 95% Confidence Level. The energy flux in the energy range between 0.6 GeV and 10 GeV amounts to (2.1 +- 0.5) x 10-12 erg cm-2 s-1 and the spectrum is well-represented by a power-law function with photon index 2.1 +- 0.1. We searched for si…
The discovery of the 401 Hz accreting millisecond pulsar IGR J17498-2921 in a 3.8 h orbit
2011
We report on the detection of a 400.99018734(1) Hz coherent signal in the Rossi X-ray Timing Explorer light curves of the recently discovered X-ray transient, IGR J17498-2921. By analysing the frequency modulation caused by the orbital motion observed between August 13 and September 8, 2011, we derive an orbital solution for the binary system with a period of 3.8432275(3) hr. The measured mass function, f(M_2, M_1, i)=0.00203807(8) Msun, allows to set a lower limit of 0.17 Msun on the mass of the companion star, while an upper limit of 0.48 Msun is set by imposing that the companion star does not overfill its Roche lobe. We observe a marginally significant evolution of the signal frequency …
On the dynamics of the AB Doradus system
2006
We present an astrometric analysis of the binary systems ABDorA /ABDorC and ABDorBa / ABDorBb. These two systems of well-known late-type stars are gravitationally associated and they constitute the quadruple ABDoradus system. From the astrometric data available at different wavelengths, we report: (i) a determination of the orbit of ABDorC, the very low mass companion to ABDorA, which confirms the mass estimate of 0.090Msun reported in previous works; (ii) a measurement of the parallax of ABDorBa, which unambiguously confirms the long-suspected physical association between this star and ABDorA; and (iii) evidence of orbital motion of ABDorBa around ABDorA, which places an upper bound of 0.4…
Radio detection of the young binary HD 160934
2013
Precise determination of dynamical masses of pre-main-sequence (PMS) stars is essential to calibrate stellar evolution models that are widely used to derive theoretical masses of young low-mass objects. Binary stars in young, nearby loose associations are particularly good candidates for this calibration since all members share a common age. Interestingly, some of these young binaries present a persistent and compact radio emission, which makes them excellent targets for astrometric VLBI studies. We aim to monitor the orbital motion of the binary system HD 160934, a member of the AB Doradus moving group. We observed HD 160934 with the Very Large Array and the European VLBI Network at 8.4 an…
Symmetry-induced forces on phase singularities
2010
We show the existence of external forces acting on phase singularities whose origin can be attributed to the presence of short-term discrete-symmetry potentials. These special forces can break highly charged phase singularities into single-charged ones and provide them with non-zero orbital angular momentum even when the potential no longer acts.
Transfer of optical orbital angular momentum to a bound electron
2016
Photons can carry angular momentum, not only due to their spin, but also due to their spatial structure. This extra twist has been used, for example, to drive circular motion of microscopic particles in optical tweezers as well as to create vortices in quantum gases. Here we excite an atomic transition with a vortex laser beam and demonstrate the transfer of optical orbital angular momentum to the valence electron of a single trapped ion. We observe strongly modified selection rules showing that an atom can absorb two quanta of angular momentum from a single photon: one from the spin and another from the spatial structure of the beam. Furthermore, we show that parasitic ac-Stark shifts from…
Chandra study of the eclipsing M dwarf binary, YY Gem
2012
The eclipsing M dwarf binary system, YY Gem, was observed using Chandra covering 140 ks (2Prot) in total, split into two even exposures separated by 0.76 d (0.94 Prot). The system was extremely active: three energetic flares were observed over the course of these observations. The flaring and non-flaring states of the system are analysed in this paper. The activity level increased between the first and second observations even during the quiescent (non-flaring) phases. An analysis of the dynamics of the X-ray-emitting plasma suggests that both components are significantly active. Contemporaneous Hα spectra also suggest that both components show similar levels of activity. The primary star i…
Generation of Schrödinger Cats in Trapped Ions
2004
A quantum system in interaction with a repeatedly measured one is subjected to a non-unitary time evolution provoking the decay of some states in favor of the remaining ones. Under appropriate hypotheses the system may be addressed exactly toward a quantum state or pushed into a pre-selected finite-dimensional subspace. On the basis of such a general strategy, we propose to exploit suitable vibronic couplings in order to ‘extract’ trapped ion center of mass states of motion characterized by well defined absolute value of an angular momentum projection. In particular, since it implies the simultaneous presence of opposite angular momentum projections, we show the realizability of Schrödinger…