Astrometric radial velocities. III. Hipparcos measurements of nearby star clusters and associations
(2002) In Astronomy & Astrophysics 381. p.446-463- Abstract
- Radial motions of stars in nearby moving clusters are determined fromaccurate proper motions and trigonometric parallaxes, without any use ofspectroscopy. Assuming that cluster members share the same velocityvector (apart from a random dispersion), we apply a maximum-likelihoodmethod on astrometric data from Hipparcos to compute radial and spacevelocities (and their dispersions) in the Ursa Major, Hyades, ComaBerenices, Pleiades, and Praesepe clusters, and for theScorpius-Centaurus, alpha Persei, and ``HIP 98321'' associations. Theradial motion of the Hyades cluster is determined to within 0.4 kms<SUP>-1</SUP> (standard error), and that of its individual stars towithin 0.6 km s<SUP>-1</SUP>. For other clusters,... (More)
- Radial motions of stars in nearby moving clusters are determined fromaccurate proper motions and trigonometric parallaxes, without any use ofspectroscopy. Assuming that cluster members share the same velocityvector (apart from a random dispersion), we apply a maximum-likelihoodmethod on astrometric data from Hipparcos to compute radial and spacevelocities (and their dispersions) in the Ursa Major, Hyades, ComaBerenices, Pleiades, and Praesepe clusters, and for theScorpius-Centaurus, alpha Persei, and ``HIP 98321'' associations. Theradial motion of the Hyades cluster is determined to within 0.4 kms<SUP>-1</SUP> (standard error), and that of its individual stars towithin 0.6 km s<SUP>-1</SUP>. For other clusters, Hipparcos data yieldastrometric radial velocities with typical accuracies of a few kms<SUP>-1</SUP>. A comparison of these astrometric values withspectroscopic radial velocities in the literature shows a good generalagreement and, in the case of the best-determined Hyades cluster, alsopermits searches for subtle astrophysical differences, such as evidencefor enhanced convective blueshifts of F-dwarf spectra, and decreasedgravitational redshifts in giants. Similar comparisons for the ScorpiusOB2 complex indicate some expansion of its associations, albeit slowerthan expected from their ages. As a by-product from the radial-velocitysolutions, kinematically improved parallaxes for individual stars areobtained, enabling Hertzsprung-Russell diagrams with unprecedentedaccuracy in luminosity. For the Hyades (parallax accuracy 0.3 mas), itsmain sequence resembles a thin line, possibly with wiggles in it.Although this main sequence has underpopulated regions at certaincolours (previously suggested to be ``Böhm-Vitense gaps''), suchare not visible for other clusters, and are probably spurious. Futurespace astrometry missions carry a great potential for absoluteradial-velocity determinations, insensitive to the complexities ofstellar spectra. Based on observations by the ESA Hipparcos satellite.Extended versions of Tables
ef{tab1} and
ef{tab2} are available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.125.8) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/446 (Less)
Please use this url to cite or link to this publication:
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- author
- Madsen, Søren LU ; Dravins, Dainis LU and Lindegren, Lennart LU
- organization
- publishing date
- 2002
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- METHODS: DATA ANALYSIS, TECHNIQUES: RADIAL VELOCITIES, ASTROMETRY, OPEN CLUSTERS AND ASSOCIATIONS: GENERAL, STARS: DISTANCES - STARS: KINEMATICS
- in
- Astronomy & Astrophysics
- volume
- 381
- pages
- 446 - 463
- publisher
- EDP Sciences
- external identifiers
-
- wos:000173343100010
- scopus:0036187649
- ISSN
- 0004-6361
- DOI
- 10.1051/0004-6361:20011458
- language
- English
- LU publication?
- yes
- id
- d3cf488f-8bb3-404d-9525-dfb4bcbe0cbe (old id 130401)
- date added to LUP
- 2016-04-01 16:29:58
- date last changed
- 2024-02-10 00:31:12
@article{d3cf488f-8bb3-404d-9525-dfb4bcbe0cbe, abstract = {{Radial motions of stars in nearby moving clusters are determined fromaccurate proper motions and trigonometric parallaxes, without any use ofspectroscopy. Assuming that cluster members share the same velocityvector (apart from a random dispersion), we apply a maximum-likelihoodmethod on astrometric data from Hipparcos to compute radial and spacevelocities (and their dispersions) in the Ursa Major, Hyades, ComaBerenices, Pleiades, and Praesepe clusters, and for theScorpius-Centaurus, alpha Persei, and ``HIP 98321'' associations. Theradial motion of the Hyades cluster is determined to within 0.4 kms<SUP>-1</SUP> (standard error), and that of its individual stars towithin 0.6 km s<SUP>-1</SUP>. For other clusters, Hipparcos data yieldastrometric radial velocities with typical accuracies of a few kms<SUP>-1</SUP>. A comparison of these astrometric values withspectroscopic radial velocities in the literature shows a good generalagreement and, in the case of the best-determined Hyades cluster, alsopermits searches for subtle astrophysical differences, such as evidencefor enhanced convective blueshifts of F-dwarf spectra, and decreasedgravitational redshifts in giants. Similar comparisons for the ScorpiusOB2 complex indicate some expansion of its associations, albeit slowerthan expected from their ages. As a by-product from the radial-velocitysolutions, kinematically improved parallaxes for individual stars areobtained, enabling Hertzsprung-Russell diagrams with unprecedentedaccuracy in luminosity. For the Hyades (parallax accuracy 0.3 mas), itsmain sequence resembles a thin line, possibly with wiggles in it.Although this main sequence has underpopulated regions at certaincolours (previously suggested to be ``Böhm-Vitense gaps''), suchare not visible for other clusters, and are probably spurious. Futurespace astrometry missions carry a great potential for absoluteradial-velocity determinations, insensitive to the complexities ofstellar spectra. Based on observations by the ESA Hipparcos satellite.Extended versions of Tables <br/><br> ef{tab1} and <br/><br> ef{tab2} are available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.125.8) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/446}}, author = {{Madsen, Søren and Dravins, Dainis and Lindegren, Lennart}}, issn = {{0004-6361}}, keywords = {{METHODS: DATA ANALYSIS; TECHNIQUES: RADIAL VELOCITIES; ASTROMETRY; OPEN CLUSTERS AND ASSOCIATIONS: GENERAL; STARS: DISTANCES - STARS: KINEMATICS}}, language = {{eng}}, pages = {{446--463}}, publisher = {{EDP Sciences}}, series = {{Astronomy & Astrophysics}}, title = {{Astrometric radial velocities. III. Hipparcos measurements of nearby star clusters and associations}}, url = {{https://lup.lub.lu.se/search/files/4691237/624146.pdf}}, doi = {{10.1051/0004-6361:20011458}}, volume = {{381}}, year = {{2002}}, }