High Proper Motion Research Articles

Catalog of stars with the big proper motion

The catalogue (astrometric and astrophysical parameters) of 555200 stars with high proper motions (more than 0.04″/year) was compiled on the basis of original definitions from the catalogues FONAK1.1, Hipparcos, Tycho-2, UCAC2, CMC (STAR 11), PPM, NPM1, NPM2, XZ80Q, Pul-3, Pul2, NLTT, GCVS, LHS, Lowell Proper Motion Service, and Bruce Proper Motion Service as well as of the information from about 770 other published sources— ftp://ftp.mao.kiev.ua/pub/astro/h-pms2.dat .

GD 552: a cataclysmic variable with a brown dwarf companion?

GD 552 is a high proper motion star with the strong, double-peaked emission lines characteristic of the dwarf nova class of cataclysmic variable (CV) star, and yet no outburst has been detected during the past 12 yr of monitoring. We present spectroscopy taken with the aim of detecting emission from the mass donor in this system. We fail to do so at a level which allows us to rule out the presence of a near-main-sequence star donor. Given GD 552's orbital period of 103 min, this suggests that it is either a system that has evolved through the similar to 80-minute orbital period minimum of CV stars and now has a brown dwarf mass donor, or that has formed with a brown dwarf donor in the first place. This model explains the low observed orbital velocity of the white dwarf and GD 552's low luminosity. It is also consistent with the absence of outbursts from the system.

An extremely wide and very low-mass pair with common proper motion

(abridged) We describe the discovery of an extremely wide pair of low-mass stars with a common large proper motion and discuss their possible membership in a Galactic halo stream crossing the Solar neighbourhood. (...) The late-type (M7) dwarf SSSPM J2003$-$4433 and the ultracool subdwarf SSSPM J1930$-$4311 (sdM7) sharing the same very large proper motion of about 860 mas/yr were found in the same sky region with an angular separation of about 6\degr. From the comparison with other high proper motion catalogues we have estimated the probability of a chance alignment of the two new large proper motions to be less than 0.3%. From the individually estimated spectroscopic distances of about $38^{+10}_{-7}$ pc and $72^{+21}_{-16}$ pc, respectively for the M7 dwarf and the sdM7 subdwarf, and in view of the accurate agreement in their large proper motions we assume a common distance of about 50 pc and a projected physical separation of about 5 pc. The mean heliocentric space velocity of the pair $(U,V,W)=(-232, -170, +74)$ km/s, based on the correctness of the preliminary radial velocity measurement for only one of the components and on the assumption of a common distance and velocity vector, is typical of the Galactic halo population. The large separation and the different metallicities of dwarfs and subdwarfs make a common formation scenario as a wide binary (later disrupted) improbable, although there remains some uncertainty in the spectroscopic classification scheme of ultracool dwarfs/subdwarfs so that a dissolved binary origin cannot be fully ruled out yet. It seems more likely that this wide pair is part of an old halo stream. (...)

NEW HIGH PROPER MOTION STARS FROM THE DIGITIZED SKY SURVEY. IV. COMPLETION OF THE SOUTHERN SURVEY AND 170 ADDITIONAL STARS WITH μ > 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.

Discovery of a Very Bright, Nearby Gravitational Microlensing Event

We report the serendipitous detection of a very bright, very nearby microlensing event. In late 2006 October, an otherwise unremarkable A0 star at a distance of � 1 kpc (GSC 3656� 1328) brightened achromatically by a factor of nearly 40 over the span of several days and then decayed in an apparently symmetrical way. We present a light curve of the event based on optical photometry from the Center for Backyard Astrophysics and the All Sky Automated Survey, as well as near-infrared photometry from the Peters Automated Infrared Imaging Telescope. This light curve is well fit by a generic microlensing model. We also report optical spectra and Swift X-ray and UVobservations that are consistent with the microlensing interpretation. We discuss and reject alternative explanations for this variability. The lens star is probably a low-mass star or brown dwarf, with a relatively high proper motion of k20 mas yr � 1 , and may be visible using precise optical/infrared imaging taken several years from now. A modest, all-sky survey telescope could detect � 10 such events per year, which would enable searches for very low mass planetary companions to relatively nearby stars. Subject headingg gravitational lensing — stars: individual (GSC 3656� 1328) Online material: color figures

Milky Way potentials in cold dark matter and MOdified Newtonian Dynamics. Is the Large Magellanic Cloud on a bound orbit?

We compute the Milky Way potential in different cold dark matter (CDM) based models, and compare these with the MOdified Newtonian Dynamics (MOND) framework. We calculate the axial ratio of the potential in various models, and find that isopotentials are less spherical in MOND than in CDM potentials. As an application of these models, we predict the escape velocity as a function of the position in the Galaxy. This could be useful in comparing with future data from planned or already-underway kinematic surveys (RAVE, SDSS, SEGUE, SIM, Gaia or the hypervelocity stars survey). In addition, the predicted escape velocity is compared with the recently measured high proper motion velocity of the Large Magellanic Cloud (LMC). To bind the LMC to the Galaxy in a MOND model, while still being compatible with the RAVE-measured local escape speed at the Sun's position, we show that an external field modulus of less than 0.03a 0 is needed. © 2008 RAS.

Cross-identifications of stars with high proper motions (Version 2.0)

A cross index list of 493 200 stars with proper motions higher than 0.04″/yr (ftp://ftp.mao.kiev.ua/pub/astro/c-ihpms2) was compiled on the basis of the original determinations for the FONAK1.1 catalog stars, the data from the Hipparcos, Tycho-2, UCAC2, CMC (STAR 11), PPM, NPM1, NPM2, XZ80Q, Pul-3, PUL2, GCVS, NLTT, LHS, Lowell Proper Motion, and Bruce Proper Motion catalogs, as well as the data published in other sources.

OGLE-II high proper motion stars towards the Galactic Centre

The photometry data base of the second phase of the OGLE microlensing experiment, OGLE-II, is a rich source of information about the kinematics and structure of the Galaxy. In this work we use the OGLE-II proper motion catalogue to identify candidate stars which have high proper motions. 521 stars with proper motion mu > 50 mas/yr in the OGLE-II proper motion catalogue (Sumi 2004) were cross-identified with stars in the MACHO high proper motion catalogue, and the DENIS and 2MASS infra-red photometry catalogues. Photometric distances were computed for stars with colours consistent with G/K and M type stars. 6 stars were newly identified as possible nearby (< 50 pc) M dwarfs.

Clouds, Gravity, and Metallicity in Blue L Dwarfs: The Case of 2MASS J11263991−5003550

Optical and near-infrared spectroscopy of the newly discovered peculiar L dwarf 2MASS J11263991–5003550 are presented. Folkes et al. classified this source as a high proper motion L9±1 dwarf based on its strong H2O absorption at 1.4 μ m . We find that the optical spectrum of 2MASS J1126–5003 is in fact consistent with that of a normal L4.5 dwarf with notably enhanced FeH absorption at 9896 A. However, its near-infrared spectrum is unusually blue, with strong H2O and weak CO bands similar in character to several recently identified L Using 2MASS J1126–5003 as a case study, and guided by trends in the condensate cloud models of Burrows et al. and Marley et al., we find that the observed spectral peculiarities of these sources can be adequately explained by the presence of thin and/or large-grained condensate clouds as compared to normal field L dwarfs. Atypical surface gravities or metallicities alone cannot reproduce the observed peculiarities, although they may be partly responsible for the unusual condensate properties. We also rule out unresolved multiplicity as a cause for the spectral peculiarities of 2MASS J1126–5003. Our analysis is supported by examination of Spitzer mid-infrared spectral data from Cushing et al. which show that bluer L dwarfs tend to have weaker 10 μ m absorption, a feature tentatively associated with silicate oxide grains. With their unique spectral properties, blue L dwarfs like 2MASS J1126–5003 should prove useful in studying the formation and properties of condensates and condensate clouds in low-temperature atmospheres.

XO‐2b: Transiting Hot Jupiter in a Metal‐rich Common Proper Motion Binary

We report on a V = 11.2 early K dwarf, XO-2 (GSC 03413-00005), that hosts a Rp = 0.98±0.010.03 RJ, Mp = 0.57 ± 0.06 MJ transiting extrasolar planet, XO-2b, with an orbital period of 2.615857 ± 0.000005 days. XO-2 has high metallicity, [Fe/H ] = 0.45 ± 0.02, high proper motion, μtot = 157 mas yr−1, and a common proper motion stellar companion with 31'' separation. The two stars are nearly identical twins, with very similar spectra and apparent magnitudes. Due to the high metallicity, these early K dwarf stars have a mass and radius close to solar, M⋆ = 0.98 ± 0.02 M☉ and R⋆ = 0.97±0.010.02 R☉. The high proper motion of XO-2 results from an eccentric orbit (Galactic pericenter, Rper < 4 kpc) well confined to the Galactic disk (Zmax ∼ 100 pc). In addition, the phase-space position of XO-2 is near the Hercules dynamical stream, which points to an origin of XO-2 in the metal-rich, inner thin disk and subsequent dynamical scattering into the solar neighborhood. We describe an efficient Markov chain Monte Carlo algorithm for calculating the Bayesian posterior probability of the system parameters from a transit light curve.

The Nearby Young Visual Binary HIP 115147 and Its Common Proper Motion Companion LSPM J2322+7847

We report a late M-type, common proper motion companion to a nearby young visual binary HIP 115147 (V368 Cep), separated by 963'' from the primary K0 dwarf. This optically dim star was identified as a candidate high proper motion, nearby dwarf LSPM J2322+7847 by Lepine in 2005. The wide companion is one of the latest post-T Tauri low-mass stars found within 20 pc. We obtain a trigonometric parallax of 51.6 ± 0.8 mas, in good agreement with the Hipparcos parallax of the primary star (50.7 ± 0.6 mas). Our BVRI photometric data and near-infrared data from 2MASS are consistent with LSPM J2322+7847 being brighter by 1 mag in Ks than field M dwarfs at V - Ks = 6.66, which indicates its pre-main-sequence status. We conclude that the most likely age of the primary HIP 115147 and its 11'' companion HIP 115147B is 20-50 Myr. The primary appears to be older than its close analog PZ Tel (age 12-20 Myr) and members of the TWA association (7 Myr).

Astrometric detection and characterization of brown dwarfs

AbstractAs a result of failed star formation, brown dwarfs (BDs) do not reach the critical mass to ignite the fusion of hydrogen in their cores. Different from their low-mass stellar brothers, the red dwarfs, BDs cool down with their lifetime to very faint magnitudes. Therefore, it was only about 10 to 20 years ago that such ultracool objects began to be detected. Accurate astrometry can be used to detect them indirectly as companions to stars by the signature of the so-called astrometric wobble. Resolved faint BD companions of nearby stars can be identified by their common proper motion (CPM). A direct astrometric detection of the hidden isolated BDs in the Solar neighborhood is possible with deep high proper motion (HPM) surveys. This technique led to the discovery of the first free-floating BD, Kelu 1, and of the nearest BD, ε Indi B. Both were meanwhile found to be binary BDs. The astrometric orbital monitoring of ε Indi Ba+Bb, for which we know an accurate distance from the Hipparcos measurement of its primary, ε Indi A, will allow the determination of individual masses of two low-mass BDs. Hundreds of BDs have been identified for the last decade. Deep optical sky survey (SDSS) and near-infrared sky surveys (DENIS, 2MASS), played a major role in the search mainly based on colours, since BDs emit most of their light at longer wavelengths. However, alternative deep optical HPM surveys based on archival photographic data are not only sensitive enough to detect some of the nearest representatives, they do also uncover many of the rare class of ultracool halo objects crossing the Solar neighborhood at large velocities. SSSPM 1444, with the extremely large proper motion of 3.5 arcsec/yr, is one of the nearest among these subdwarfs with masses at the substellar boundary. We present preliminary parallax results for this and two other ultracool subdwarfs (USDs) from the Calar Alto Omega 2000 parallax program.

A new all-sky catalog of stars with large proper motions

AbstractA new all-sky catalog of stars with proper motions μ &gt; 0.15″ yr−1 is presented. The catalog is largely a product of the SUPERBLINK survey, a data-mining initiative in which the entire Digitized Sky Surveys are searched for moving stellar sources. Findings from earlier proper motions surveys are also incorporated. The new all-sky catalog supersedes the great historic proper motion catalogs assembled by W. J. Luyten (LHS, NLTT), and provides a virtually complete &gt; 98% census of high proper motion stars down to magnitude R = 19.

An Astrometric Companion to the Nearby Metal‐Poor, Low‐Mass Star LHS 1589

We report the discovery of a companion to the high proper motion star LHS 1589, a nearby high-velocity, low-mass subdwarf. The companion (LHS 1589B) is located 0.224'' ± 0.004'' to the southwest of the primary (LHS 1589A), and is 0.5 mag fainter than the primary in the Ks band. The pair was resolved with the IRCAL infrared camera at Lick Observatory, operating with the Laser Guide Star Adaptive Optics system. A low-resolution spectrum of the unresolved pair obtained at the MDM observatory shows the source to be consistent with a cool subdwarf of spectral subtype sdK7.5. A photometric distance estimate places the metal-poor system at a distance d = 81 ± 18 pc from the Sun. We also measure a radial velocity Vrad = 67 ± 8 km s-1, which, together with the proper motion and estimated distance, suggests that the pair is roaming the inner Galactic halo on a highly eccentric orbit. With a projected orbital separation s = 18.1 ± 4.8 AU, and a crude estimate of the system's total mass, we estimate the orbital period of the system to be in the range 75 yr < P < 500 yr. This suggests that the dynamical mass of the system could be derived astrometrically, after monitoring the orbital motion over a decade or so. The LHS 1589AB system could thus provide a much needed constraint to the mass-luminosity relationship of metal-poor, low-mass stars.

Knowing Our Neighbors: Fundamental Properties of Nearby Stars

The stars within 25 pc constitute the sample that we aspire to know thoroughly. A well-understood, volume-limited sample of nearby stars is an essential input for the stellar luminosity function, the mass-luminosity relationship, the stellar velocity distribution, and the stellar multiplicity fraction, including substellar companions. Such samples help define stellar populations and estimate the amount mass contributed by local stars. In addition, the stars in this volume provide insight into stellar evolution and the history of star formation in the disk. These physical relationships and subsamples describe the makeup of our Galaxy and, by extension, more distant galaxies (Kuiper 1942; Reid & Cruz 2002). However, models are being developed from an incomplete catalog with limited parameters. Although trigonometric parallaxes establish both sample membership and the cosmic distance scale, many objects within reach of ground-based telescopes remain unmeasured. To advance the solar neighborhood census, observations of 56 nearby stars are presented, including astrometric companion search results, along with a possible a new infrared parallax program. Among these nearby stars, Barnard’s star is a fascinating M dwarf, not only because of its nearness and high proper motion, but also because of van de Kamp’s (1963) announcement that it had a planet. However, PDS scans and analyses of 900 Leander McCormick Observatory photographic plates failed to detect any planets. This time-series analysis using Lomb-Scargle periodograms (Press et al. 1996) would have detected planets with 2.2 Jupiter masses (MJ) or greater. Prior to the timeseries analysis, the relative parallax, proper motion, and secular acceleration of Barnard’s star were measured to be 546 1 mas, 10.3612 0.0002 yr 1 in 355.905 0.001 , and 1.25 0.04 mas yr , respectively. The available photometry and spectroscopy of the 12 reference stars used indicate a correction to absolute of 6 7 mas would be necessary, resulting in an absolute parallax of 552 7 mas, corresponding to a distance of 1.81 0.02 pc and a transverse velocity of 89 km s . These results are comparable to those obtained with more modern equipment. An additional search for potential nearby planets was undertaken through similar time-series analyses of stars in the University of Virginia Southern Parallax Program (SPP; Ianna 1993). For 12 stars (LHS 34, 271, 337, 532, 1134, 1565, 2310, 2739, 2813, 3064, 3242, and 3418), no indication of any unseen companions was detected. However, LHS 288 shows trends suggestive of a 2.4MJ planet in a 7 yr orbit. These high proper motion stars all lie within the solar neighborhood. With the exception of the white dwarf LHS 34, these stars are M dwarfs. After a minimum of 50 observations spread over at least 3 years, the relative parallax solutions have errors of less than 3 mas. An upper limit to the mass of companions remaining undetected was established for each star individually; for longperiod orbits, these range from 1.7MJ to 18MJ. The lack of any clear signal due to a companion may suggest that gas giants are less common around M dwarfs than solar-type stars. Before astrometric companions are investigated, trigonometric parallaxes are obtained that can establish membership in the solar neighborhood. A subsample of 43 potential nearby stars was included in the Cerro Tololo Inter-American Observatory Parallax Investigation (CTIOPI), based on less accurate photometric and spectroscopic distance estimates. Astrometric, photometric, and spectroscopic observations began in 2003 December. Although at least another year of observations is anticipated to finalize these measurements, preliminary results based on observations through mid-2006 are available. According to preliminary parallaxes from this CTIOPI subsample, 28 of the stars are probable members of the solar neighborhood, including three stars (LP 991-84, LHS 6167, and LP 876-10) that apparently lie within 10 pc. Three more stars lie near the 25 pc boundary, and their final parallaxes may still qualify them as members. In addition, LP 869-26 is an apparent binary with newly resolved components separated by approximately 0.7 0.3 . The nearest stars tend to display large proper motions. As expected, high proper motion stars predominate in this subsample. Preliminary proper motions indicate that nine stars have proper motions greater than 0.5 yr , with 2MASS 02511490 0352459 and 23062928 0502285 moving more than 1.0 yr . For this subsample, the proper motions convert to tangential velocities that range from about 10 to 129 km s . Previously unidentified members of the solar neighborhood are anticipated to be so cool, red, and dim that they were missed in previous studies. Preliminary photometry (VC, RC, and IC) is available for 16 stars in this CTIOPI subsample. These stars range from approximately 10th to 20th magnitude in VC. In

Discovery of a High Proper Motion L Dwarf Binary: 2MASS J15200224−4422419AB

We report the discovery of the wide L1.5+L4.5 binary 2MASS J15200224-4422419AB, identified during spectroscopic follow-up of high proper motion sources selected from the Two Micron All Sky Survey. This source was independently identified by Kendall et al. in the SuperCOSMOS Sky Survey. Resolved JHK photometry and low-resolution near-infrared spectroscopy demonstrate that this system is composed of two well-separated (1.174'' ± 0.016'') L dwarfs. Component classifications are derived using both spectral ratios and comparison to the near-infrared spectra of previously classified field L dwarfs. Physical association for the pair is deduced from the large common proper motion of the components (μ = 0.73'' ± 0.03'' yr-1) and their similar spectrophotometric distances (19 ± 2 pc). The projected separation of the binary, 22 ± 2 AU, is consistent with maximum separation/total system-mass trends for very low mass binaries. The 2MASS J1520-4422 system exhibits both large tangential (66 ± 7 km s-1) and radial velocities (-70 ± 18 km s-1), and its motion in the local standard of rest suggests that it is an old member of the Galactic disk population. This system joins a growing list of well-separated (>0.5''), very low mass binaries, and is an excellent target for resolved optical spectroscopy to constrain its age, as well as trace activity/rotation trends near the hydrogen-burning limit.

Stars of later spectral classes from the FBS survey. Preliminary data for seven special cases

Preliminary data are presented on seven “special” objects found in low-dispersion spectral plates of the FBS survey. The first object, FBS 0250+167, is found to be a class M7 dwarf with a high proper motion (∼5.130 arcsec/year) lying about 3 pc from the sun. Three of the objects, with spectra of classes M8–M9, are suspected of being long-period Mirids with large mass losses and surrounded by dense clouds. The three remaining objects have very short low-dispersion spectra on the FBS survey plates (clearly they are non stellar objects) and are of interest for later detailed study.

New nearby, bright southern ultracool dwarfs

We report the discovery of 21 hitherto unknown bright southern ultracool dwarfs with spectral types in the range M7 to L5.5, together with new observations of a further three late M dwarfs previously confirmed. Three more objects are already identified in the literature as high proper motion stars; we derive their spectral types for the first time. All objects were selected from the Two Micron All-Sky Survey (2MASS) all-sky and SuperCOSMOS point source data bases on the basis of their optical/near-infrared colours, J-band magnitudes and proper motions. Low-resolution (R∼ 1000)JH spectroscopy with the European Southern Observatory (ESO)/New Technology Telescope (NTT) Son of Isaac (SOFI) spectrograph has confirmed the ultracool nature of 24 targets, out of a total of 25 candidates observed. Spectral types are derived by direct comparison with template objects and compared to results from H2O and FeH indices. We also report the discovery of one binary, as revealed by SOFI acquisition imaging; spectra were taken for both components. The spectral types of the two components are L2 and L4 and the distance ∼19 pc. Spectroscopic distances and transverse velocities are derived for the sample. Two ∼L5 objects lie only at ∼0 pc distant. Such nearby objects are excellent targets for further study to derive their parallaxes and to search for fainter, later companions with adaptive optics and/or methane imaging.

The widest ultracool binary

Aims: I test the ejection scenario of formation of brown dwarfs and very low-mass stars through the detection of a very wide ultracool binary. Methods: LEHPM 494 (M6.0 +/- 1.0 V) and DENIS-P J0021.0-4244 (M9.5 +/- 0.5 V) are separated by 1.3 arcmin and are high proper motion co-moving ultracool stars. I have used six astrometric epochs spaced 22 years to confirm their common tangential velocity. Results: The angular separation between both low-mass stars keeps constant with an uncertainty less than 0.1 %. I have also derived their most probable heliocentric distance (23 +/- 2 pc), age interval (2-10 Ga) and masses (0.103 +/- 0.006 and 0.079 +/- 0.004 Msol). The pair, with a projected physical separation of 1800 +/- 170 AU, is by far the widest ultracool binary ever found in the field. Conclusions: This serendipitous and simple detection is inconsistent with ultra low-mass formation ejection scenarios and complements current searches of low-mass tight binaries.

Proper Motions of Faint Ultraviolet‐bright Sources in the Sandage Two‐Color Survey of the Galactic Plane

ABSTRACTProper motions with values ≥10 or ≤−10 mas yr−1 have been extracted from the USNO‐B1.0 and Tycho‐2 catalogs for all Lanning UV‐bright sources identified in the Sandage Two‐Color Survey of the Galactic Plane and presented in Papers I–VI. Of the 572 sources examined, we find at least 213 that exhibit a significantly large proper motion. Based on the location of the sources in a reduced proper motion diagram, we demonstrate that about two‐thirds of the high proper motion sources are likely or very likely to be heretofore unidentified white dwarfs.