Preliminary orbital elements of six visual binary stars

International audiencePreliminary new orbital elements were computed for the visual binary stars A 1 - ADS 1345, A 2629 - ADS 3610, BU 560 - ADS 4371, STF 3115 - ADS 4376, STF 1426 AB - ADS 7730 and STF 2437 - ADS 11956. Using Straizys and Kuriliene's data, we derived new formulae for computing dynamical parallaxes for luminosity classes IV and V. The values found for those systems are in agreement with the {Hipparcos} parallaxes and the corresponding systemic masses are consistent with the spectral types

Speckle observations with PISCO in Merate - II. Astrometric measurements of visual binaries in 2004

International audienceWe present relative astrometric measurements of visual binaries taken during the second semester of 2004 with the Pupil Interferometry Speckle camera and Coronagraph (PISCO) at the 1-m Zeiss telescope of the Brera Astronomical Observatory, in Merate, Italy. We performed 207 new observations of 194 objects with angular separations in the range 0.1-4.0 arcsec and an accuracy better than ~0.01 arcsec. Our sample contains orbital couples as well as binaries whose motion is still uncertain. Our purpose is to improve the accuracy of the orbits and constrain the masses of the components. Those measurements show that the orbit of ADS 15115 needs to be revised; we propose a new orbit for this object

Speckle observations with PISCO in Merate - III. Astrometric measurements of visual binaries in 2005 and scale calibration with a grating mask

International audienceWe present relative astrometric measurements of visual binaries made during the first semester of 2005, with the Pupil Interferometry Speckle Camera and Coronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera Astronomical Observatory, in Merate. We performed 214 new observations of 192 objects, with angular separations in the range 0.2-4.3arcsec, and with an average accuracy of 0.01arcsec. Most of the position angles could be determined without the usual 180° ambiguity, and their mean error is . Our sample contains orbital couples as well as binaries whose motion is still uncertain. The purpose of this long-term programme is to improve the accuracy of the orbits and constrain the masses of the components. For the first time with PISCO, the astrometric calibration was made with a grating mask mounted at the entrance of the telescope. The advantage of this procedure is to provide a reliable and fully independent scale determination. We have found two possible new triple systems: ADS 7871 and KUI 15. We propose a preliminary orbit for ADS 4208

Speckle observations of the binary asteroid (22) Kalliope with C2PU/PISCO

We present new speckle measurements of the position of Linus, the satellite of the asteroid (22) Kalliope, obtained at the 1m C2PU-Epsilon telescope on the Plateau de Calern, France. Observations were made in the visible domain with the speckle camera PISCO. We obtained 122 measurements in February-March 2022 and April 2023, with a mean uncertainty close to 10 milli-arcseconds on the angular separation

Speckle observations with PISCO in Merate - V. Astrometric measurements of visual binaries in 2006

International audienceWe present relative astrometric measurements of visual binaries made during the first semester of 2006, with the Pupil Interferometry Speckle camera and COronagraph at the 102-cm Zeiss telescope of the Brera Astronomical Observatory, in Merate. Our sample contains orbital couples as well as binaries whose motion is still uncertain. We obtained 217 new measurements of 194 objects, with angular separations in the range 0.1-4.2arcsec, and an average accuracy of 0.01arcsec. The mean error on the position angles is 0.5°. About half of those angles could be determined without the usual 180° ambiguity by the application of triple-correlation techniques. We also present a revised orbit for ADS 277 for which the previously published orbit resulted in a large residual from our measurements

A neck-line structure in the dust tail of Comet C/2004 F4 (Bradfield)

Three CCD images of Comet C/2004 F4 (Bradfield), taken on three different dates close to the time of the Earth crossing through the plane of the comet orbit (2004 May 2.9280 UT), show a ray-shaped structure (RSS) in the dust tail, accompanied by a short, sunward spike (SWS). This morphology and behaviour strongly recall a Neck-Line Structure (NLS; Kimura & Liu [CITE]; Pansecchi et al. [CITE]). Astrometric measurements of the images show that, on all the three dates, the position on the sky of the observed RSS is consistent with several sky-projected points of a theoretical Neck-Line, computed for the precise date of each observation. Furthermore, the SWS turns out to be a real (not caused by perspective) antitail, which is predicted by NLS models.

Speckle observations with PISCO in Merate. X. Astrometric measurements of visual binaries in 2009

International audienceWe present relative astrometric measurements of visual binaries, made in 2009 with the speckle cameraPISCO at the 102 cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our observing list contains orbital couples as well as binaries whose motion is still uncertain. We obtained 345 new measurementsof 259 objects, with angular separations in the range 0′′.18 — 4′′.6, and an average accuracy of 0′′.011. The mean error on the position angles is 0◦.6. Most of the position angles were determined without theusual 180◦ambiguity with the application of triple-correlation techniques and/or by inspection of the longintegration files. We have found a possible new close component for ADS 2377, which would be a new quadruple star system. We also present new revised orbits for ADS 8035, 9982, 11484 and MLR 198, partly derived from those observations, and infer estimated values for the masses of those systems that are compatible with the spectral types