Validation of the new Hipparcos reduction

Leeuwen, F. van

doi:10.1051/0004-6361:20078357

Cited by 3,103 publications

(1,081 citation statements)

References 21 publications

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“…This is possible because in HIP2 catalogue van Leeuwen (2007bLeeuwen ( , 2011 included full information on the covariance matrix of astrometric parameters. Such a procedure possesses an evident superiority over the individual, independent random drawing of each parameter (which was used for example by Bobylev (2010a,b); Jiménez-Torres et al (2011)) what ignores their obvious mutual dependence.…”

Section: Drawing a Stellar Clonementioning

confidence: 99%

On the accuracy of close stellar approaches determination

Dybczyński

Berski

2015

Monthly Notices of the Royal Astronomical Society

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The aim of this paper is to demonstrate the accuracy of our knowledge of close stellar passage distances in the pre-GAIA era. We used the most precise astrometric and kinematic data available at the moment and prepared a list of 40 stars nominally passing (in the past or future) closer than 2 pc from the Sun. We used a full gravitational potential of the Galaxy to calculate the motion of the Sun and a star from their current positions to the proximity epoch. For this calculations we used a numerical integration in rectangular, Galactocentric coordinates. We showed that in many cases the numerical integration of the star motion gives significantly different results than popular rectilinear approximation. We found several new stellar candidates for close visitors in past or in future.We used a covariance matrices of the astrometric data for each star to estimate the accuracy of the obtained proximity distance and epoch. To this aim we used a Monte Carlo method, replaced each star with 10 000 of its clones and studied the distribution of their individual close passages near the Sun. We showed that for contemporary close neighbours the precision is quite good but for more distant stars it strongly depends on the quality of astrometric and kinematic data. Several examples are discussed in detail, among them the case of HIP 14473. For this star we obtained the nominal proximity distance as small as 0.22 pc 3.78 Myr ago. However there exist strong need for more precise astrometry of this star since the proximity point uncertainty is unacceptably large.

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Section: Drawing a Stellar Clonementioning

confidence: 99%

On the accuracy of close stellar approaches determination

Dybczyński

Berski

2015

Monthly Notices of the Royal Astronomical Society

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“…The original Hipparcos catalogue published a value of π = 0.49 ± 0.68 mas (ESA 1997), which is not significant. However, a revised parallax was published by van Leeuwen et al (2007) as π = 1.44 ± 0.51 mas, corresponding to a 3σ detection, and the final value that appears in the revised Hipparcos parallax catalogue is π = 1.92 ± 0.65 mas (van Leeuwen 2007a; see also van Leeuwen 2007b). Given the limited accuracy of Hipparcos (∼1 mas), we do not have an explanation for this apparent detection of parallax, in disagreement with our determination.…”

Section: Trigonometric Parallaxmentioning

confidence: 99%

The long-period Galactic Cepheid RS Puppis

Kervella¹,

Mérand

Szabados

et al. 2008

A&A

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Context. The bright southern Cepheid RS Pup is surrounded by a circumstellar nebula reflecting the light from the central star. The propagation of the light variations from the Cepheid inside the dusty nebula creates spectacular light echoes that can be observed up to large distances from the star itself. This phenomenon is currently unique in this class of stars. Aims. For this relatively distant star, the trigonometric parallax available from Hipparcos has a low accuracy. A careful observation of the light echoes has the potential to provide a very accurate, geometric distance to RS Pup. Methods. We obtained a series of CCD images of RS Pup with the NTT/EMMI instrument covering the variation period of the star (P = 41.4 d), allowing us to track the progression of the light wavefronts over the nebular features surrounding the star. We measured precisely the phase lag of the photometric variation in several regions of the circumstellar nebula. Results. From our phase lag measurements, we derive a geometric distance of 1992 ± 28 pc to RS Pup. This distance is affected by a total uncertainty of 1.4%, and corresponds to a parallax of π = 0.502 ± 0.007 mas and a distance modulus of µ = 11.50 ± 0.03. Conclusions. The geometric distance we derive is by far the most accurate to a Cepheid, and among the most accurate to any star. RS Pup appears both as somewhat neglected and particularly promising to investigate the mass-loss history of Cepheids. Thanks to its highly accurate distance, it is also bound to become an important luminosity fiducial for the long period part of the period-luminosity diagram.

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“…The O-star δ Ori (HD 36486) is the western star in the belt of Orion, named Mintaka, with a parallax of 4.71(0.58) mas, i.e., at a distance of 212 pc (SIMBAD: Van Leeuwen 2007) 1 . The position in J2000 coordinates is RA = 05 32 00.400 and Dec = −00 17 56.74.…”

Section: Introductionmentioning

confidence: 99%

The X-ray spectrum ofδOrionis observed by LETGS aboardChandra

Raassen

Pollock

2013

A&A

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Aims. We analyze the high-resolution X-ray spectrum of the supergiant O-star δ Orionis (O9.5II) with line ratios of He-like ions and a thermal plasma model, and we examine its variability. Methods. The O-supergiant δ Ori was observed in the wavelength range 5-175 Å by the X-ray detector HRC-S in combination with the grating LETG aboard Chandra. We studied the He-like ions in combination with the UV-radiation field to determine local plasma temperatures and to establish the distance of the X-ray emitting ions to the stellar surface. We measured individual lines by means of Gaussian profiles, folded through the response matrix, to obtain wavelengths, line fluxes, half widths at half maximum (HWHM) and line shifts to characterize the plasma. We consider multitemperature models in collisional ionization equilibrium (CIE) to determine temperatures, emission measures, and abundances.Results. Analysis of the He-like triplets extended to N vi and C v implies ionization stratification with the hottest plasma to be found within a few stellar radii 3 R * (Mg xi) and the coolest farther out, far beyond the acceleration zone, up to 49 R * (N vi) and 75 R * (C v).The observed temperatures cover a range from about 0.1 to 0.7 keV, i.e., 1-8 MK. The X-ray luminosity (L x ) is ∼1.5 × 10 32 erg/s in the range from 0.07 to 3 keV covered by LETGS. Velocity widths of about 1040 km s −1 have been determined.

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Validation of the new Hipparcos reduction

Cited by 3,103 publications

References 21 publications

On the accuracy of close stellar approaches determination

On the accuracy of close stellar approaches determination

The long-period Galactic Cepheid RS Puppis

The X-ray spectrum ofδOrionis observed by LETGS aboardChandra

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