Proper motion Pleiades candidate L-type brown dwarfs Authors: G. Bihain, R. Rebolo, V. J. S. Bejar, J. A. Caballero, C. A. L. Bailer-Jones, R. Mundt Comments: 2 pages, 2 figures, ULMSF Workshop, accepted for publication in Astron. Nachrichten (2006) A seismological analysis of Delta Scuti stars in the Pleiades cluster Authors: L.Fox Machado (Instituto de Astrofisica de Canarias, Spain), F. Perez Hernandez (Instituto de Astrofisica de Canarais, Dpto. de Astrofisica Universidad de La Laguna, Spain), J.C. Suarez (Instituto de Astrofisica de Andalucia, CSIC, Spain), E. Michel (Observatoroire de Paris, LESIA, France), Y. Lebreton (Observatoire de Paris, GEPI, France) Comments: 10 pages, 7 figures (2006) A Hubble Space Telescope ACS Search for Brown Dwarf Binaries in the Pleiades Open Cluster Authors: H. Bouy, E. Moraux, J. Bouvier,W. Brandner,E. L. Martin, F. Allard, I. Baraffe, M. Fernandez Comments: 29 pages, 7 figures, 6 tables, accepted for publication in ApJ Journal-ref: Astrophys.J. 637 (2006) Spitzer Observations of G Dwarfs in the Pleiades: Circumstellar Debris Disks at 100 Myr Age Authors: J.R. Stauffer, L. Rebull (Spitzer Science Center),J. Carpenter, L. Hillenbrand (Caltech), D. Backman (NASA-Ames), M.R. Meyer, =J.S. Kim, M.D. Silverstone, E. Young (Steward Observatory, UofA), D.C. Hines (SSI), D.R. Soderblom (STScI), E.E. Mamajek (Harvard-Smithsonian CfA), P. Morris (SSC), J. Bouwman (MPIA-Heidelberg), S.E. Strom (NOAO) Comments: 32 postscript pages including 8 figues and 3 tables. To appear in the Astronomical Journal Constraining the properties of spots on Pleiades very low mass stars Authors: Alexander Scholz (University of Toronto, TLS Tautenburg), Jochen Eisloeffel (TLS Tautenburg), Dirk Froebrich (DIAS Dublin) Comments: 9 pages, 5 figures, Astronomy & Astrophysics, in press Decmber 2004: Confirmation of Errors in Hipparcos Parallaxes from HST/FGS Astrometry of the Pleiades Authors: David R. Soderblom, Ed Nelan (Space Telescope Science Institute), G. Fritz Benedict, Barbara McArthur, Ivan Ramirez, William Spiesman (McDonald Observatory, University of Texas), Burton F. Jones (Lick Observatory, University of California) Comments: 9 pages, 10 tables, 6 figures; AJ in press (March 2005 issue) September 2004: Eclipsing binaries as standard candles: HD 23642 and the distance to the Pleiades Authors: J. Southworth, P. F. L. Maxted, B. Smalley (Keele University, UK) Comments: Accepted for publication in A&A (11 pages, 7 figures). September 2004: The distance to the Pleiades: Main sequence fitting in the near infrared Authors: S.M. Percival (1), M. Salaris (1), M.A.T. Groenewegen (2) ((1) Astrophysics Research Institute, Liverpool John Moores University; (2) Instituut voor Sterrenkunde, Leuven) Comments: 8 pages. A&A accepted. September 2004: A purely geometric distance to the binary star Atlas, a member of the Pleiades Authors: N. Zwahlen (1), P. North (1), Y. Debernardi (1), L. Eyer (2), F. Galland (3), M.A.T. Groenewegen (4), C. Hummel (5) ((1) Laboratoire d'Astrophysique de l'EPFL, (2) Observatoire de Geneve, (3) Observatoire de Grenoble, (4) Leuven, (5) European Southern Observatory) Comments: 5 pages, 3 figures, accepted for publication in A&A Letters. June, 2004: The Pleiades mass function: models versus observations Authors: E. Moraux (1), P. Kroupa (2), J. Bouvier (3) ((1) IoA, Cambridge, UK, (2) Sternwarte Universitat, Bonn, Germany, (3) LAOG, Grenoble, France) Comments: 6 pages, 5 figures, accepted for publication in A&A. June 2004: X-ray emission from a brown dwarf in the Pleiades Authors: K. R. Briggs (1), J. P. Pye (2) ((1) Paul Scherrer Institut, Villigen-PSI, Switzerland; (2) Department of Physics and Astronomy, University of Leicester, Leicester, UK) Comments: 8 pages, 4 figures (6 eps files), accepted for publication in MNRAS, Na I "emission" corrected to "absorption" in description of targets. May 2004: Rotation periods for very low mass stars in the Pleiades. Authors: Alexander Scholz, Jochen Eisloeffel Comments: 13 pages, 11 figures, A&A, in press Journal-ref: Astron.Astrophys. 421 (2004) 259-271. May 3, 2004: Rotation periods for very low mass stars in the Pleiades Alexander Scholz, Jochen Eisloeffel, 13 pages, 11 figures, A&A, in press April 4, 2004: The Solar Neighborhood VIII: Discovery of New High Proper Motion Nearby Stars Using the SuperCOSMOS Sky Survey N.C. Hambly, T.J. Henry, J. Subasavage, M. Brown, W.-C. Jao, 17 pages, 5 figures; accepted for publication in Astronomy Journal March 18, 2004: The distance to the Pleiades from orbital solution of the double-lined eclipsing binary HD 23642 in press in A&A as Letter to the EditorU.Munari, S.Dallaporta, A.Siviero, C.Soubiran, M.Fiorucci, P.Girard Dec 7 2003: Title: Lithium abundance/surface activity connections in solar-type Pleiads Authors: D. Clarke, E.C. MacDonald, S. Owens - (1) Glasgow University, (2) Oxford University) Comments: 8 Pages, 9 Figures. Nov 5, 2003: Proper motion surveys of the young open clusters Alpha Persei and the PleiadesAuthors: N.R. Deacon, N. C. Hambly (Institute for Astronomy, University of Edinburgh)Comments: Comments:13 pages, 20 Figures,Accepted for publication in Astronomy and Astrophysics July 9, 2003: Title: XMM-Newton and the Pleiades -- I: Bright coronal sources and the X-ray emission from intermediate-type stars Authors: K. R. Briggs, J. P. Pye (2) ((1) Paul Scherrer, Institut, Villigen-PSI, Switzerland, (2) Department of Physics and Astronomy, University of Leicester, Leicester, UK) Comments: 14 pages, 7 figs (29 eps files), accepted for publication in MNRAS. Journal-ref: Mon.Not.Roy.Astron.Soc. 345 (2003) 714. We perform X-ray spectral and timing analyses of solar-like (spectral types F5--K8) and intermediate-type (B4--F4) Pleiads observed in a 40-ks XMM-Newton EPIC exposure. All 8 solar-like members have ``quasi-steady'' \lx $\ga 10^{29}$ erg/s and 4 exhibit flares. Using a hydrodynamic modelling technique we derive loop half-lengths ${\cal L} \la 0.5 R_{\star}$ for the two strongest flares, on HII 1032 and HII 1100. HII 1100's lightcurve suggests a total occultation of the flaring loop. Eclipse by a substellar companion in a close orbit is possible but would seem a highly fortuitous event; absorption by a fast-moving cloud of cool material requires \nh at least two orders of magnitude greater than any solar or stellar prominence. An occultation may have been mimicked by the coincidence of two flares, though the first, its decay time shorter than its rise time and suggestive of ${\cal L} \sim 0.02 R_{\star}$, would be unusual. Spectral modelling of the quasi-steady emission shows a rising trend in coronal temperature from F and slowly-rotating G stars through K stars to fast-rotating G stars, and a preference for low coronal metallicity: features consistent with those of nearby solar-like stars, although none of the three stars showing ``saturated'' emission bears the significant component at 2 keV seen in the saturated coronae of AB Dor and 47 Cas. Of 5 intermediate-type stars, 2 are undetected (\lx$ < 4 \times 10^{27}$ erg/s) and 3 show X-ray emission with a spectrum and \lx consistent with origin from an active solar-like companion. June 4, 2003: Title: The Distance to Pleiades. Authors: Bohdan Paczynski. Comments: 3 pages, latex, 1 figure, submitted to Acta Astronomica. The distance to Pleiades remains controversial. There is a simple way to resolve the dispute definitely by measuring the distance to one of its brightest members, Atlas, which is astrometric and spectroscopic binary. June 1, 2003: Title: Why are the K dwarfs in the Pleiades so Blue? John R. Stauffer, Burton F. Jones, Dana Backman, Lee W. Hartmann, David Barrado y Navascues, Marc H. Pinsonneault, Donald M. Terndrup, August A. Muench. Comments: 41 pages, 15 figures, AASTeX5.0. Accepted 05 May 2003; Scheduled for publication in the Astronomical Journal (August 2003)Journal-ref: Astron.J. 126 (2003) 833 Abstract: The K dwarfs in the Pleiades fall nearly one half magnitude below a main sequence isochrone when plotted in a color-magnitude diagram utilizing V magnitude as the luminosity index and B-V as the color index. This peculiarity has been known for forty years but has gone unexplained and mostly ignored. When compared to Praesepe members, the Pleiades K dwarfs again are subluminous (or blue) in a color-magnitude diagram using B-V as the color index. However, using V-I as the color index, stars in the two clusters are coincident to M_V ~ 10; using V-K as the color index, Pleiades late K and M stars fall above the main sequence locus defined by Praesepe members. We believe that the anomalous spectral energy distributions for the Pleiades K dwarfs, as compared to older clusters, are a consequence of rapid stellar rotation and may be primarily due to spottedness. If so, the required areal filling factor for the cool component has to be very large (=> 50%). Weak-lined T Tauri stars have similar color anomalies, and we suspect this is a common feature of all very young K dwarfs (sp. type > K3). The peculiar spectral energy distribution needs to be considered in deriving accurate pre-main sequence isochrone-fitting ages for clusters like the Pleiades since the age derived will depend on the temperature index used. May 3, 2003: An HST/WFPC2 Survey for Brown Dwarf Binaries in the alpha Per and the Pleiades Open Clusters. Authors: Eduardo L. Martin, David Barrado y Navascues, Isabelle Baraffe, Herve Bouy, Scott Dahm Comments: Accepted by ApJ (scheduled publication in volume 594, September 1, 2003) Journal-ref: Astrophys.J. 594 (2003) 525-532 May 1, 2003: Title: An Optical and Near Infrared Search for Brown Dwarfs in the Pleiades Cluster C. Nagashima, P. D. Dobbie, T. Nagayama, Y. Nakajima, T. Nagata, M. Tamura, T. Nakajima, K. Sugitani, H. Nakaya, S. T. Hodgkin, A. J. Pickles, S. Sato 9 pages, 7 figures, accepted for publication in MNRAS Journal-ref: Mon.Not.Roy.Astron.Soc. 343 (2003) 1263. We present the results of a high-resolution imaging survey for brown dwarf (BD) binaries in two open clusters. The observations were carried out with WFPC2 onboard HST. Our sample consists of 8 BD candidates in the alpha Per cluster and 25 BD candidates in the Pleiades. We have resolved 4 binaries in the Pleiades with separations in the range 0".094--0".058, corresponding to projected separations between 11.7~AU and 7.2~AU. No binaries were found among the alpha Per targets. Three of the binaries have proper motions consistent with cluster membership in the Pleiades cluster, and for one of them we report the detection of Halpha in emission and LiI absorption obtained from Keck~II/ESI spectroscopy. One of the binaries does not have a proper motion consistent with Pleiades membership. We estimate that BD binaries wider than 12~AU are less frequent than 9% in the alphaPer and Pleiades clusters. This is consistent with an extension to substellar masses of a trend observed among stellar binaries: the maximum semimajor axis of binary systems decreases with decreasing primary mass. We find a binary frequency of 2 binaries over 13 BDs with confirmed proper motion membership in the Pleiades, corresponding to a binary fraction of 15%(1 sigma error bar +15%/-5%). These binaries are limited to the separation range 7-12~AU and their mass ratios are larger than 0.7. The relatively high binary frequency (>10%), the bias to separations smaller than about 15 AU and the trend to high mass ratios (q>0.7) are fundamental properties of BDs. Current theories of BD formation do not appear to provide a good description of all these properties. July 4, 2003: XMM-Newton and the Pleiades -- I: Bright coronal sources and the X-ray emission from intermediate-type stars K. R. Briggs (1 and 2), J. P. Pye (2) ((1) Paul Scherrer Institut, Villigen-PSI, Switzerland, (2) Department of Physics and Astronomy, University of Leicester, Leicester, UK), 14 pages, 7 figs (29 eps files), accepted for publication in MNRAS (Mon.Not.Roy.Astron.Soc) 345 (2003) 714 March 6, 2003: Brown dwarfs and low-mass stars in the Pleiades and Praesepe:- Membership and binarity D. J. Pinfield (1), P. D. Dobbie (2), R. F. Jameson (2), I. A. Steele (1), H. R. A. Jones (1), A. C. Katsiyannis (3) ((1) Liverpool John Moores University, (2) University of Leicester, (3) Queen's University of Belfast) Comments: (updated version) 22 pages, 11 figures, accepted for publication in MNRAS Journal-ref: Mon.Not.Roy.Astron.Soc. 342 (2003) 1241. We present near infrared J-, H- and K-band photometry and optical spectroscopy of low-mass star and brown dwarf (BD) candidates in the Pleiades and Praesepe open clusters. We find that Pleiades stars with K=10.5--13 are rather redder than the NextGen isochrones. We also identify this effect amongst alphaPer sources from the literature, but find no evidence of it for field stars from the literature. It is possible that the I-K colour of youthful stars is affected by the presence of magnetic activity. In the 2-colour diagram we find no colour change across the "M dwarf gap" (which would be indicative of dust formation). For Teff=2800--3150K, the colours of Praesepe and Pleiades sources differ, which may result from gravity sensitive molecular opacities. Praesepe sources cooler than 2500K agree with the dusty models, but Pleiades sources agree with the NextGen models down to 2000K. It is possible that dust formation does not begin until lower Teffs in sources with lower surface gravities. We also identify unresolved binaries in both clusters, and estimate mass ratios (q) for Pleiades BDs. Most of these have q>0.7, however, 3/18 appear to have lower q values. We determine the binary fraction (BF) for numerous mass ranges in each cluster, and find that it is generally rising towards lower masses. We find a BD BF of 50(+11/-10)%. We also find some evidence suggesting that the BF-q distribution is flat for 0.5-0.35Mo, in contrast to solar type stars. March 19, 1998: A New Pleiades Member at Lithium Substellar Boundary E. L. Martin and G. Basri, ApJ Letters Sky Survey Thesis, Conferences, Papers Mathematician of the Day Numerical Analysis Quotes as a Servicable Substitute for Wit 187 The UnOfficial Chandra Data Archive Search - http://cfa-www.harvard.edu/archive/chandra/search Provides a search tool for the Chandra X-Ray Observatory secondary data products archive. Byte-O-Matic.NET Astronomical Information Archive - http://www.byte-o-matic.net Offers information services, and archiving of various astronomical issues. 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Decmber 2004: Confirmation of Errors in Hipparcos Parallaxes from HST/FGS Astrometry of the Pleiades Authors: David R. Soderblom, Ed Nelan (Space Telescope Science Institute), G. Fritz Benedict, Barbara McArthur, Ivan Ramirez, William Spiesman (McDonald Observatory, University of Texas), Burton F. Jones (Lick Observatory, University of California) Comments: 9 pages, 10 tables, 6 figures; AJ in press (March 2005 issue) September 2004: Eclipsing binaries as standard candles: HD 23642 and the distance to the Pleiades Authors: J. Southworth, P. F. L. Maxted, B. Smalley (Keele University, UK) Comments: Accepted for publication in A&A (11 pages, 7 figures). September 2004: The distance to the Pleiades: Main sequence fitting in the near infrared Authors: S.M. Percival (1), M. Salaris (1), M.A.T. Groenewegen (2) ((1) Astrophysics Research Institute, Liverpool John Moores University; (2) Instituut voor Sterrenkunde, Leuven) Comments: 8 pages. A&A accepted. September 2004: A purely geometric distance to the binary star Atlas, a member of the Pleiades Authors: N. Zwahlen (1), P. North (1), Y. Debernardi (1), L. Eyer (2), F. Galland (3), M.A.T. Groenewegen (4), C. Hummel (5) ((1) Laboratoire d'Astrophysique de l'EPFL, (2) Observatoire de Geneve, (3) Observatoire de Grenoble, (4) Leuven, (5) European Southern Observatory) Comments: 5 pages, 3 figures, accepted for publication in A&A Letters. June, 2004: The Pleiades mass function: models versus observations Authors: E. Moraux (1), P. Kroupa (2), J. Bouvier (3) ((1) IoA, Cambridge, UK, (2) Sternwarte Universitat, Bonn, Germany, (3) LAOG, Grenoble, France) Comments: 6 pages, 5 figures, accepted for publication in A&A. June 2004: X-ray emission from a brown dwarf in the Pleiades Authors: K. R. Briggs (1), J. P. Pye (2) ((1) Paul Scherrer Institut, Villigen-PSI, Switzerland; (2) Department of Physics and Astronomy, University of Leicester, Leicester, UK) Comments: 8 pages, 4 figures (6 eps files), accepted for publication in MNRAS, Na I "emission" corrected to "absorption" in description of targets. May 2004: Rotation periods for very low mass stars in the Pleiades. Authors: Alexander Scholz, Jochen Eisloeffel Comments: 13 pages, 11 figures, A&A, in press Journal-ref: Astron.Astrophys. 421 (2004) 259-271. May 3, 2004: Rotation periods for very low mass stars in the Pleiades Alexander Scholz, Jochen Eisloeffel, 13 pages, 11 figures, A&A, in press April 4, 2004: The Solar Neighborhood VIII: Discovery of New High Proper Motion Nearby Stars Using the SuperCOSMOS Sky Survey N.C. Hambly, T.J. Henry, J. Subasavage, M. Brown, W.-C. Jao, 17 pages, 5 figures; accepted for publication in Astronomy Journal March 18, 2004: The distance to the Pleiades from orbital solution of the double-lined eclipsing binary HD 23642 in press in A&A as Letter to the EditorU.Munari, S.Dallaporta, A.Siviero, C.Soubiran, M.Fiorucci, P.Girard Dec 7 2003: Title: Lithium abundance/surface activity connections in solar-type Pleiads Authors: D. Clarke, E.C. MacDonald, S. Owens - (1) Glasgow University, (2) Oxford University) Comments: 8 Pages, 9 Figures. Nov 5, 2003: Proper motion surveys of the young open clusters Alpha Persei and the PleiadesAuthors: N.R. Deacon, N. C. Hambly (Institute for Astronomy, University of Edinburgh)Comments: Comments:13 pages, 20 Figures,Accepted for publication in Astronomy and Astrophysics
May 3, 2004: Rotation periods for very low mass stars in the Pleiades Alexander Scholz, Jochen Eisloeffel, 13 pages, 11 figures, A&A, in press April 4, 2004: The Solar Neighborhood VIII: Discovery of New High Proper Motion Nearby Stars Using the SuperCOSMOS Sky Survey N.C. Hambly, T.J. Henry, J. Subasavage, M. Brown, W.-C. Jao, 17 pages, 5 figures; accepted for publication in Astronomy Journal March 18, 2004: The distance to the Pleiades from orbital solution of the double-lined eclipsing binary HD 23642 in press in A&A as Letter to the EditorU.Munari, S.Dallaporta, A.Siviero, C.Soubiran, M.Fiorucci, P.Girard Dec 7 2003: Title: Lithium abundance/surface activity connections in solar-type Pleiads Authors: D. Clarke, E.C. MacDonald, S. Owens - (1) Glasgow University, (2) Oxford University) Comments: 8 Pages, 9 Figures. Nov 5, 2003: Proper motion surveys of the young open clusters Alpha Persei and the PleiadesAuthors: N.R. Deacon, N. C. Hambly (Institute for Astronomy, University of Edinburgh)Comments: Comments:13 pages, 20 Figures,Accepted for publication in Astronomy and Astrophysics
Nov 5, 2003: Proper motion surveys of the young open clusters Alpha Persei and the PleiadesAuthors: N.R. Deacon, N. C. Hambly (Institute for Astronomy, University of Edinburgh)Comments: Comments:13 pages, 20 Figures,Accepted for publication in Astronomy and Astrophysics
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