A new determination of the orbit and masses of the Be binary system δ Scorpii

Tango, W. J.; Davis, John; Jacob, A. P.; Méndez, Alberto; North, Julian; O'Byrne, J. W.; Seneta, E. B.; Tuthill, P. G.

doi:10.1111/j.1365-2966.2009.14272.x

Cited by 32 publications

(67 citation statements)

References 36 publications

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“…It is interesting to speculate that the periastron passage in 2000 contributed to the observed brightening. The secondary companion has a very eccentric orbit with a period of about 11 yr (for recent calculations see Tango et al 2009;Tycner et al 2011;Meilland et al 2011) and the periastron passage of its companion in 2011 offered an opportunity to study this system. We collected V-and B-band photometry for the 2009, In this work we use our V and B photometry to probe the innermost regions of the disk of δ Sco in order to determine the mass-loss rate and investigate the variability of these outbursts for this system.…”

Section: Introductionmentioning

confidence: 99%

Using Photometry to Probe the Circumstellar Environment of Δ Scorpii

Jones

Wiegert

Tycner

et al. 2013

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We acquired Johnson BV photometry of the binary Be disk system δ Scorpii during its 2009, 2010, 2011, and 2012 observing seasons and used it to probe the innermost regions of the disk. We found that several disk building events have occurred during this time, resulting in an overall brightening in the V band and reddening of the system. In addition to these long-term trends, we found cyclical variability in each observing season on timescales between 60 and 100 days. We were able to reproduce the changes in the magnitude and color of δ Sco using our theoretical models and found that variable mass-loss rates in the range 2.5-7.0 × 10 −9 M yr −1 over ∼35 days can reproduce the observed increase in brightness.

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Section: Introductionmentioning

confidence: 99%

Using Photometry to Probe the Circumstellar Environment of Δ Scorpii

Jones

Wiegert

Tycner

et al. 2013

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“…Observational data supporting the idea of mass-loss events associated with periastron passage exist for the highly eccentric (e ∼ 0.94) binary δ Sco (Bedding 1993;Miroshnichenko et al 2001;Tango et al 2009). And Millour et al (2009) suggested that the dusty circumbinary environment in HD 87643 might be associated with repeated close encounters in the long period and possible highly eccentric binary.…”

Section: Introductionmentioning

confidence: 79%

Eccentric binaries

Moreno

Koenigsberger

Harrington

2011

A&A

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Context. A number of binary systems present evidence of enhanced activity around periastron passage, suggesting a connection between tidal interactions and these periastron effects. Aims. The aim of this investigation is to study the time-dependent response of a star's surface as it is perturbed by a binary companion. Here we focus on the tidal shear energy dissipation. Methods. We derive a mathematical expression for computing the rate of dissipation,Ė, of the kinetic energy by the viscous flows that are driven by tidal interactions on the surface layer of a binary star. The method is tested by comparing the results from a grid of model calculations with the analytical predictions of Hut (1981, A&A, 99, 126) and the synchronization timescales of Zahn (1977, A&A, 57, 383; 2008, EAS Pub. Ser., 29, 67). Results. Our results for the dependence of the average (over orbital cycle) energy dissipation,Ė ave , on orbital separation are consistent with those of Hut (1981) for model binaries with an orbital separation at periastron r per /R 1 > ∼ 8, where R 1 is the stellar radius. The model also reproduces the predicted pseudo-synchronization angular velocity for moderate eccentricities (e ≤ 0.3). In addition, for circular orbits our approach yields the same scaling of synchronization timescales with orbital separation as given by Zahn (1977Zahn ( , 2008 for convective envelopes. The computations give the distribution ofĖ over the stellar surface, and show that it is generally concentrated at the equatorial latitude, with maxima generally located around four clearly defined longitudes, corresponding to the fastest azimuthal velocity perturbations. Maximum amplitudes occur around periastron passage or slightly thereafter for supersynchronously rotating stars. In very eccentric binaries, the distribution ofĖ over the surface changes significantly as a function of orbital phase, with small spatial structures appearing after periastron. An exploratory calculation for a highly eccentric binary system with parameters similar to those of δ Sco (e = 0.94, P = 3944.7 d) indicates thatĖ ave changes by ∼5 orders of magnitude over the 82 days before periastron, suggesting that the sudden and large amplitude variations in surface properties around periastron may, indeed, contribute toward the activity observed around this orbital phase.

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“…The uncertainty of the projected separation obtained is in the sub-milliarcseconds regime (Armstrong et al, 2004;Davis et al, 2005;Tango et al, 2009). …”

Section: Methodsmentioning

confidence: 98%

“…This means this indirect method is not suitable for narrow-angle astrometry for stars that have a wider projected separation. This is the main reason why most of the past experiments (Armstrong et al, 2004;Davis et al, 2005;Tango et al, 2009) using this method is limited to speckle binaries and relatively short baselines.…”

Section: Methodsmentioning

confidence: 99%

Phase-Referenced Interferometry and Narrow-Angle Astrometry With Susi

Kok

Ireland

Tuthill

et al. 2013

J. Astron. Instrum.

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This thesis describes the development of an astrometric facility at the Sydney University Stellar Interferometer (SUSI) with an aim to measure at high precision the relative astrometry of bright close binary stars and ultimately to detect the presence of exoplanets within those binary star systems through observations of the systems' perturbed motion. At the core of the facility is a new beam combiner that is phase-referenced to an existing primary beam combiner in the visible wavelength regime. The latter provides post-processed fringe-tracking information to the former for fringe stabilization and coherent integration of pre-recorded stellar fringes using newly developed data reduction software. Interference fringe packets of a binary star are recorded alternately; first the fringe packet of the primary, then the secondary, finally back to the primary again. The measurement of the fringe packet separation is facilitated by an air-filled differential delay line and a network of interferometer-based metrology systems. Characterizations and initial astronomical observations carried out with the dual beam combiner setup demonstrated for the first time the success of the dual-star phase-referencing technique in visible (ă1µm) wavelengths. The current astrometric precision is larger than 100µas while the long term astrometric accuracy is yet to be characterized. In a parallel development, a complementary observing method using only the primary beam combiner is also demonstrated in this thesis. Relative astrometry of binary stars up to "0.8 2 separation with this technique has been demonstrated to have precision of better than 100µas. A simple detection limit analysis based on a list of target binary stars estimates up to two exoplanet detections can be achieved with SUSI if the new astrometric facility attains precision of 10µas while the primary beam combiner operates at its designed peak performance. Finally, one new stellar companion was resolved and a preliminary astrometry for another suspected companion was estimated from the astronomical observation data collected throughout the course of this thesis.

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A new determination of the orbit and masses of the Be binary system δ Scorpii

Cited by 32 publications

References 36 publications

Using Photometry to Probe the Circumstellar Environment of Δ Scorpii

Using Photometry to Probe the Circumstellar Environment of Δ Scorpii

Eccentric binaries

Phase-Referenced Interferometry and Narrow-Angle Astrometry With Susi

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