List Of Stars Research Articles

MEASUREMENTS OF THE ISOTOPIC RATIO6Li/7Li IN STARS WITH PLANETS

High-resolution (R = 143,000), high signal-to-noise (S/N = 700-1100) Gemini-S bHROS spectra have been analyzed in a search for 6Li in 5 stars which host extrasolar planets. The presence of detectable amounts of 6Li in these mature, solar-type stars is a good monitor of accretion of planetary disk material, or solid bodies themselves, into the outer layers of the parent stars. Detailed profile-fitting of the Li I resonance doublet at lambda 6707.8 A reveals no detectable amounts of 6Li in any star in our sample. The list of stars analyzed includes HD 82943 for which 6Li has been previouly detected at the level of 6Li/7Li = 0.05 +/- 0.02. The typical limits in the derived isotopic fraction are 6Li/7Li <= 0.00-0.02. These upper limits constrain the amount of accreted material to less than ~ 0.02 to 0.5 Jovian masses. The presence of detectable amounts of 6Li would manifest itself as a red asymmetry in the Li I line-profile and the derived upper limits on such asymmetries are discussed in light of three-dimensional hydrodynamic model atmospheres, where convective motions also give rise to slight red asymmetries in line profiles.

UBVRIPHOTOMETRIC STANDARD STARS AROUND THE CELESTIAL EQUATOR: UPDATES AND ADDITIONS

New broadband UBVRI photoelectric observations on the Johnson-Kron-Cousins photometric system have been made of 202 stars around the sky, and centered at the celestial equator. These stars constitute both an update of and additions to a previously published list of equatorial photometric standard stars. The list is capable of providing, for both celestial hemispheres, an internally consistent homogeneous broadband standard photometric system around the sky. When these new measurements are included with those previously published by Landolt (1992), the entire list of standard stars in this paper encompasses the magnitude range 8.90 < V < 16.30, and the color index range -0.35 < (B - V) < +2.30.

THE X-RAY ENVIRONMENT DURING THE EPOCH OF TERRESTRIAL PLANET FORMATION:CHANDRAOBSERVATIONS OF h PERSEI

We describe Chandra/ACIS-I observations of the massive ~ 13-14 Myr-old cluster, h Persei, part of the famous Double Cluster (h and ? Persei) in Perseus. Combining the list of Chandra-detected sources with new optical/IR photometry and optical spectroscopy reveals ~ 165 X-ray bright stars with V 23. Roughly 142 have optical magnitudes and colors consistent with cluster membership. The observed distribution of Lx peaks at Lx ~ 1030.3 erg s?1 and likely traces the bright edge of a far larger population of 0.4-2 M ? X-ray active stars. From a short list of X-ray active stars with IRAC 8 ?m excess from warm, terrestrial zone dust, we derive a maximum X-ray flux incident on forming terrestrial planets. Although there is no correlation between X-ray activity and IRAC excess, the fractional X-ray luminosity correlates with optical colors and spectral type. By comparing the distribution of Lx /L versus spectral type and V ? I in h Per with results for other 1-100 Myr-old clusters, we show that stars slightly more massive than the Sun ( 1.5 M ?) fall out of X-ray saturation by 10-15 Myr. Changes in stellar structure for 1.5 M ? stars likely play an important role in this decline of X-ray emission.

Sending and searching for interstellar messages

There is a close interrelation between searching for extraterrestrial intelligence (SETI) and messaging to extraterrestrial intelligence (METI). For example, the answers to the questions “Where to search” and “Where to send” are equivalent, in that both require an identical selection from the same target star lists. Similar considerations lead to a strategy of time synchronization between sending and searching. Both SETI and METI use large reflectors. The concept of “magic frequencies” may be applicable to both SETI and METI. Efforts to understand an alien civilization's interstellar messages (IMs), and efforts to compose our own IMs so they will be easily understood by unfamiliar extraterrestrials, are mutually complementary. Furthermore, the METI-question: “How can we benefit from sending IMs, if a response may come only thousands of years later?” begs an equivalent SETI-question: “How can we benefit from searching, if it is impossible now to perceive the motivations and feelings of those who may have sent messages in the distant past?” A joint consideration of the theoretical and the practical aspects of both sending and searching for IMs, in the framework of a unified, disciplined scientific approach, can be quite fruitful. We seek to resolve the cultural disconnect between those who advocate sending interstellar messages, and others who anathematize those who would transmit.

NEW HIGH PROPER MOTION STARS FROM THE DIGITIZED SKY SURVEY. IV. COMPLETION OF THE SOUTHERN SURVEY AND 170 ADDITIONAL STARS WITH μ &gt; 0.45″ yr–1

Completion of the SUPERBLINK proper motion survey in the southern celestial hemisphere has turned up 170 new stars with proper motion 0.45'' yr–1 1.0'' yr–1. The total list of high proper motion stars recovered by SUPERBLINK in the southern sky now includes 2228 stars with proper motions 0.45'' yr–1 < μ < 2.0'' yr–1.

Brittle-stars (Echinodermata: Ophiuroidea) from the continental shelf and upper slope of the Colombian Caribbean

An annotated brittle star list (Echinodermata: Ophiuroidea) collected by bottom trawling between 20 and 520 m depth during the INVEMAR-MACROFAUNA campaigns (1998-2001) along the continental shelf and upper slope of the Colombian Caribbean is presented. A total of 58 species were identified: 41 genera, 13 families and 2 orders, in which 35 species are new records for the Colombian Caribbean (28 are also new for the continental part of the Caribbean Sea). General and detailed figures are provided. Rev. Biol. Trop. 56 (Suppl. 3): 169-204. Epub 2009 January 05.

X-ray emission from A-type stars

Being fully radiative, stars of spectral type A are not expected to harbor magnetic dynamos and hence such stars are not expected to produce X-ray emission. Indeed, while the X-ray detection rate of such stars in X-ray surveys is low, it is not zero and some of the brighter A-type stars have been detected on different occasions and with different instruments. To study systematically the puzzle of the X-ray emitting A-type stars, we carried out an X-ray study of all A-type stars listed in the Bright Star Catalogue using the ROSAT public data archive. We found a total of 312 bright A-type stars positionally associated with ROSAT X-ray sources; we analyzed the X-ray light curves as well as searched for evidence of RV variations to identify possible late-type companions producing the X-ray emission. In this paper we present a list of X-ray active A-type stars, including the collected data about multiplicity, X-ray luminosity and spectral peculiarities.

Coronal Mass Ejection (CME) Activity of Low Mass M Stars as An Important Factor for The Habitability of Terrestrial Exoplanets. I. CME Impact on Expected Magnetospheres of Earth-Like Exoplanets in Close-In Habitable Zones

Low mass M- and K-type stars are much more numerous in the solar neighborhood than solar-like G-type stars. Therefore, some of them may appear as interesting candidates for the target star lists of terrestrial exoplanet (i.e., planets with mass, radius, and internal parameters identical to Earth) search programs like Darwin (ESA) or the Terrestrial Planet Finder Coronagraph/Inferometer (NASA). The higher level of stellar activity of low mass M stars, as compared to solar-like G stars, as well as the closer orbital distances of their habitable zones (HZs), means that terrestrial-type exoplanets within HZs of these stars are more influenced by stellar activity than one would expect for a planet in an HZ of a solar-like star. Here we examine the influences of stellar coronal mass ejection (CME) activity on planetary environments and the role CMEs may play in the definition of habitability criterion for the terrestrial type exoplanets near M stars. We pay attention to the fact that exoplanets within HZs that are in close proximity to low mass M stars may become tidally locked, which, in turn, can result in relatively weak intrinsic planetary magnetic moments. Taking into account existing observational data and models that involve the Sun and related hypothetical parameters of extrasolar CMEs (density, velocity, size, and occurrence rate), we show that Earth-like exoplanets within close-in HZs should experience a continuous CME exposure over long periods of time. This fact, together with small magnetic moments of tidally locked exoplanets, may result in little or no magnetospheric protection of planetary atmospheres from a dense flow of CME plasma. Magnetospheric standoff distances of weakly magnetized Earth-like exoplanets at orbital distances <or=0.1 AU can be shrunk, under the action of CMEs, to altitudes of about 1,000 km above the planetary surface. Such compressed magnetospheres may have crucial consequences for atmospheric erosion processes.

Astrometric Detection of Terrestrial Planets in the Habitable Zones of Nearby Stars with SIM PlanetQuest

ABSTRACTSIM PlanetQuest (formerly the Space Interferometry Mission) is a space‐borne Michelson interferometer for precision stellar astrometry, with a 9 m baseline, currently slated for launch in 2016. One of the principal science goals is the astrometric detection and orbital characterization of terrestrial planets in the habitable zones of nearby stars. Differential astrometry of the target star against a set of reference stars lying within 1° will allow measurement of the target star’s reflex motion with astrometric accuracy of 1 μas in a single measurement. The purpose of the present paper is to quantitatively assess SIM’s capability for detection (as opposed to characterization by orbital determination) of terrestrial planets in the habitable zones of nearby stars. Note that the orbital periods of these planets are generally shorter than the 5 year SIM mission. We formulate a “joint periodogram” as a tool for planet detection from astrometric data. For adequately sampled orbits (i.e., five or more observations per period over a sampling time span longer than the orbital period), we find that the joint periodogram is more sensitive than the χ2 test for the null hypothesis. In our analysis of the problem, we use Monte Carlo simulations of orbit detection, together with realistic observing scenarios, actual target and reference star lists, realistic estimates of SIM instrument performance, and plausible distributions of planetary system parameters.

Revised and updated catalogue of Byurakan-IRAS stars

Context.Five lists of late-type stars were published in Astrophysics in 1997–2001, found in the First Byurakan Survey low-dispersion spectroscopic plates as optical identifications of unidentified IRAS sources. These identifications were carried out in the region with and with a surface of 1504 deg2. As a result, the catalogue of the Byurakan-IRAS Stars (BIS) was compiled. Its preliminary version has been available at the CDS since 2003.

06/01249 Impact of exothermicity on steady and linearized response of a premixed ducted flame: Mehta, P. G. et al. Combustion and Flame, 2005, 141, (4), 392–405

Records of observations of stars (including the determinatives of the 28 lunar mansions) have been collected and re-edited from five previous editions. After further consulting the star chart of XYXFY∗ and the Suzhou planisphere, we obtain the definitive positions of 360 stars which we can convert into the right ascensions and declinations for 1052 A.D., and hence their identification. Of the traditional 282 asterisms comprising 1464 stars, this list has 282 asterisms comprising 1457 stars, lacking only the star Shaocheng on the left Wall of the Purple Enclosure and the 6 stars of the asterism Ligong. With positions based on actual observations, this list embodies the traditional Chinese star system. It is the second listing after the “Star List of Master Shi” of the Warring Period, and provides an important and reliable reference for historical researches.

Searching for Runaway OB Stars in Supernova Remnants

Searching for runaway stars in Supernova remnants gives us the possibility to estimate the mass ratio in binary systems in which there occur Supernova explosion. Such a method also gives information on portions of spectroscopic and close binaries among the stars on the main sequence with mass > 7–8 M⊙. More importantly, we can learn more about space velocities and spin periods of pulsars by this way. We have searched for runaway OB stars in central parts of 48 Supernova remnants with distances less than about 3 kpc. In 16 of the remnants in our sample, there is no candidate O or B type star and we have shown that pulsars (point sources) might be born not only in spectroscopic and close binaries. We have represented a list of stars which are candidates for runaway B type stars located in Supernova remnants. Spectroscopic investigations on these candidates could provide solutions for the problems mentioned above.

The Metallicity Distribution Function of the Halo of the Milky Way

IAG, University of S˜ao Paolo (Brazil)Abstract.We report on the distribution of metallicities, [Fe/H], for very metal-poor stars in the haloof the Galaxy. Although the primary information on the nature of the Metallicity DistributionFunction (MDF) is obtained from the two major recent surveys for metal-poor stars, the HKsurvey of Beers and collaborators, and the Hamburg/ESO Surveyof Christlieb and collaborators,we also discuss the MDF derived from the publicly available database of stellar spectra andphotometry contained in the third data release of the Sloan Digital Sky Survey (SDSS DR-3).Even though the SDSS was not originally planned as a stellar survey, significant numbers of starshave been observed to date – DR-3 contains spectroscopy for over 70,000 stars, at least half ofwhich are suitable for abundance determinations. There are as many very metal-poor ([Fe/H]< −2.0) stars in DR-3 as have been obtained from all previous survey efforts combined. We alsodiscuss prospects for significant expansion of the list of metal-poor stars to be obtained fromthe recently funded extension of the SDSS, which includes the project SEGUE: Sloan Extensionfor Galactic Understanding and Exploration.Keywords. astronomical data bases: surveys, stars: abundances, stars: Population II, Galaxy:halo

The Progenitor of the Type II-P SN 2004dj in NGC 2403

The Type II-P supernova SN 2004dj in the nearby galaxy NGC 2403 occurred at a position coincident with object 96 in the list of luminous stars and clusters in this galaxy published by Sandage in 1984. The coincidence is established definitively through astrometric registration of our ground-based archival images of NGC 2403 with our recent images showing the SN. The archival images show that Sandage 96 is slightly resolved from the ground. Preoutburst blue spectrograms obtained by Humphreys & Aaronson reveal that Sandage 96 has a composite spectrum, dominated in the blue region by A- and B-type stars, while infrared photometry shows that Sandage 96 also contains red supergiants. These results demonstrate that Sandage 96 is a young compact cluster. We have studied the stellar population of Sandage 96, using published photometric measurements combined with a χ2 fitting code. We derive a cluster age of 13.6 Myr, a reddening of E(4405 - 5495) = 0.172, and a total stellar mass of 24,000 M☉. For this cluster age, the SN progenitor had a main-sequence mass of 15 M☉. Postoutburst photometry of Sandage 96 may establish whether the progenitor was a red or blue supergiant.

Young Stars far from the Galactic Plane: Runaways from Clusters

AbstractQuite recently, a significant number of OB stars far from the galactic plane have been found, situated at z- distances ranging from several hundreds of pc to several kpc. The short lifetimes of these stars pose problems for their interpretation in terms of the standard picture of star formation. Different mechanisms have been put forward to explain the existence of these stars, either within the conventional view, or postulating star formation in the galactic halo itself. These mechanisms range from arguing that they are misidentified evolved or abnormal stars, to postulating powerful ejection mechanisms for young disk stars; in situ formation also admits several variants. We have collected from the literature a list of young stars far from the plane, for which the evidence of youth seems convincing. We discuss two possible formation mechanisms for these stars: ejection from the plane as the result of dynamical evolution of small clusters (Poveda et al. 1967) and in situ formation, via induced shocks created by spiral density waves (Martos et al. 1999). We compute galactic orbits for these stars, and identify the stars that could be explained by one or the other mechanism. We find that about 90 percent of the stars can be accounted for by the cluster ejection mechanism, that is, they can be regarded as runaway stars in the galactic halo.

The stellar content of the ring in NGC 660

We present the results of stellar photometry of the polar-ring galaxy NGC 660 using the Hubble Space Telescope's archival data obtained with the Wide Field Planetary Camera 2. The final list of the resolved stars contains 550 objects, a considerable part of which are blue and red supergiants belonging to the polar ring. The analysis of the Colour-Magnitude Diagram for polar ring stars shows that it is best represented by the isochrones with metallicity Z = 0.008. The process of star formation in the polar ring was continuous and the age of the youngest detected stars is about 7 Myr.

Astrophysical supplements to the ASCC‐2.5. I. Radial velocity data

AbstractWe present a catalogue of radial velocities of Galactic stars with high precision astrometric data CRVAD which is the result of the cross‐identification of star lists from the General Catalog of Average Radial Velocities (GCRV) and from the homogeneous All‐sky Compiled Catalogue of 2.5Million Stars (ASCC‐2.5). The CRVAD includes accurate J2000 equatorial coordinates, proper motions and trigonometric parallaxes in the Hipparcos system, Johnson's BV photometric data, spectral types, multiplicity and variability flags from the ASCC‐2.5, and radial velocities, stellar magnitudes and spectral types from the GCRV for 34553 ASCC‐2.5 stars. The CRVAD was used for the construction of a sample of standard stars with accurate astrometric, photometric and radial velocity data for the RAVE project. A second application of the CRVAD , the radial velocity determination for 292 open clusters (including 97 with previously unknown radial velocities), using their newly defined members from proper motions and photometry in the ASCC‐2.5, is briefly described. (© 2004 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

An electronic version of the second volume of the General Catalogue of Variable Stars with improved coordinates

We present a new electronic version of the second volume of the fourth edition of the General Catalogue of Variable Stars (GCVS), which contains data on 13480 variable stars in the constellations Cygnus-Orion (the order of constellations in the Catalogue follows the Latin alphabet). The new version takes into account the Name Lists of Variable Stars from no. 67 to 76 for the same constellations. The main distinctive feature of the new version is that it contains improved equatorial J2000.0 coordinates for 13446 stars (including those for 5052 stars with an allowance made for proper motions), based on the identifications with positional catalogs using finding charts, as well as on our new measurements. We searched for a number of stars on original plates from the collections of several observatories and using digital sky survey images. The new version also includes a file of remarks to the second and third GCVS volumes. Apart from a complete update of the positional information, we took into account several corrections that were found to be necessary after the publication of the second GCVS volume (1985). We present a list of references to new Internet resources.

Ballistic Jupiter Gravity-Assist, Perihelion-ΔV Trajectories for an Interstellar Explorer

This proposed interstellar precursor mission will penetrate into the nearby interstellar medium by achieving 1000 Astronomical Units from the Sun within the working lifetime (about 50 years) of those who started the mission. A variety of science goals and orbital mechanics constraints contribute to the formulation of a list of candidate stars for targeting the solar system escape trajectory direction. An approach is developed that will minimize both launch energy to Jupiter and a subsequent near-Sun, high-I S P , high-thrust maneuver in order to attain a high-speed escape from the solar system towards a target star. Detailed performance characteristics are given for selected reference trajectories.

High-Precision Near-Infrared Photometry of a Large Sample of Bright Stars Visible from the Northern Hemisphere

We present the results of 8 yr of infrared photometric monitoring of a large sample of stars visible from Teide Observatory (Tenerife, Canary Islands). The final archive is made up of 10,949 photometric measures through a standard InSb single-channel photometer system, principally in JHK, although some stars have measures in L'. The core of this list of stars is the standard-star list developed for the Carlos Sánchez Telescope. A total of 298 stars have been observed on at least two occasions on a system carefully linked to the zero point defined by Vega. We present high-precision photometry for these stars. The median uncertainty in magnitude for stars with a minimum of four observations and thus reliable statistics ranges from 0.0038 mag in J to 0.0033 mag in K. Many of these stars are faint enough to be observable with array detectors (42 are K > 8) and thus to permit a linkage of the bright and faint infrared photometric systems. We also present photometry of an additional 25 stars for which the original measures are no longer available, plus photometry in L' and/or M of 36 stars from the main list. We calculate the mean infrared colors of main-sequence stars from A0 V to K5 V and show that the locus of the H-K color is linearly correlated with J-H. The rms dispersion in the correlation between J-H and H-K is 0.0073 mag. We use the relationship to interpolate colors for all subclasses from A0 V to K5 V. We find that K and M main-sequence and giant stars can be separated on the color-color diagram with high-precision near-infrared photometry and thus that photometry can allow us to identify potential mistakes in luminosity class classification.