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|Interstellar Matter near the Pleiades. VI. Evidence for an Interstellar Three-Body Encounter|
This paper seeks a comprehensive interpretation of new data on Na Iabsorption toward stars in and near the Pleiades, together with existingvisible and infrared data on the distribution of dust and with radiodata on H I and CO in the cluster vicinity. The use of dust and gasmorphology to constrain tangential motions in connection with themeasured radial velocities yields estimates for the space motion of gasnear the Pleiades. Much of the kinematic complexity in the interstellarabsorption toward the Pleiades, including the presence of stronglyblueshifted components that arise in shocked gas, finds explanation inthe interaction between the cluster and foreground gas withVr(LSR)~7 km s-1 associated with the Taurus dustclouds. Taurus gas, however, cannot readily account for an absorptioncomponent having Vr(LSR)~10 km s-1 with a wide,but not continuous distribution and 21 cm emission from gas in thecluster having Vr(LSR)~0 km s-1 associated witheast-west dust filaments. Successive hypotheses for the origin of theseadditional features include Taurus gas at a higher velocity than thepervasive foreground component, additional gas at a radial velocityintermediate between that of the Taurus component and the cluster, and acloud having Vr(LSR)~10 km s-1 approaching thePleiades from the west. A satisfactory account of the full complexity ofthe interstellar medium near the Pleiades requires the last feature andthe Taurus gas, both interacting with the Pleiades and also with eachother.
|Merged catalogue of reflection nebulae|
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (18.104.22.168) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
|Discovery of Reflection Nebulosity around Five Vega-like Stars|
Coronagraphic optical observations of six Vega-like stars revealreflection nebulosities, five of which were previously unknown. Thenebulosities illuminated by HD 4881, HD 23362, HD 23680, HD 26676, andHD 49662 resemble that of the Pleiades, indicating an interstellarorigin for dust grains. The reflection nebulosity around HD 123160 has adouble-arm morphology, but no disklike feature is seen as close as 2.5"from the star in K-band adaptive optics data. We demonstrate that auniform density dust cloud surrounding HD 23362, HD 23680, and HD 123160can account for the observed 12-100 μm spectral energy distributions.For HD 4881, HD 26676, and HD 49662, an additional emission source, suchas from a circumstellar disk or nonequilibrium grain heating, isrequired to fit the 12-25 μm data. These results indicate that insome cases, particularly for Vega-like stars located beyond the LocalBubble (>100 pc), the dust responsible for excess thermal emissionmay originate from the interstellar medium rather than from a planetarydebris system.
|Barnard's Merope Nebula Revisited: New Observational Results|
IC 349 is a small, fan-shaped reflection nebula located only 30" from 23Tau; its nucleus is, by a factor 15, the brightest area of the Pleiadesnebulosity. We propose that IC 349 is a fragment of the Taurus-Aurigamolecular cloud that has been encountered by the Pleiades in thatcluster's southward motion and is being illuminated and shaped by theradiation field of 23 Tau. New Hubble Space Telescope multicolor imageryand the structure, colors, and surface brightness of IC 349 arediscussed in terms of that hypothesis. What is known of the propermotion of the nebula, what can be inferred of the properties of thenebula from its color, and what is expected from radiation pressuretheory appear to be compatible with this cloudlet-encounter hypothesis.
|Examination of the Interstellar Spectrum of AE AUR for Long-Term Changes|
The runaway O9.5 V star AE Aur is moving across the line of sight behindthe curtain provided by the emission/reflection nebula IC 405. Theinterstellar line spectrum of AE Aur was examined on a HIRES spectrogramobtained in 1998 to determine if there had been any change since theoriginal high-resolution observations by Adams in the 1940s. Noequivalent widths were published by Adams, so only a comparison ofradial velocities was possible. No significant changes over theintervening half-century were detected; during that time the crossmotion of AE Aur in the plane of the sky amounted to about 1450 AU.Similarly, no convincing changes were found in the interstellar Ca IIlines of the runaway O star mu Col.
|Barnard's Merope Nebula (IC 349): an Interstellar Interloper|
Barnard's Merope Nebula (IC 349) is the optically brightest portion ofthe diffuse nebulosity that envelops the Pleaides but is notmorphologically similar to those nebulae. Knowledge of its true spacemotion can help clarify whether the object has a kinematic associationand possibly a common origin with the Pleiades. Here we report a meanradial velocity result obtained in 1996 from spectra where v_hel=-44.4km s^-1 and sigma_v=5.42 km s^-1 (N=5). The radial velocity result ispresented along with recent values for the object's proper motion,yielding its space motion vector. Galactic space velocity components (U,V, W)=(50.6+/-5.3, -10.3+/-6.7, 11.3+/-6.4) km s^-1, referred to theLSR, were calculated for the object. In addition, the region wasobserved in the near-infrared to determine if a protostellar object ispresent within the dusty envelope of the nebula; to an equivalentluminosity upper limit of L=0.23+/-0.05 L_solar, none was observed.These results suggest that IC 349 is kinematically unrelated to thePleiades and that it does not harbor a protostellar object in its dustyinterior.
|IC 349: Barnard's Merope Nebula|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1241H&db_key=AST
|IC349 - Barnard's Merope Nebula|
|Studies of bright diffuse galactic nebulae with special regard to their spatial distribution.|
|Measures of Barnard's new Merope nebula.|
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