scholarly journals Proper Motions in the Bulge: Looking Through Plaut's Low Extinction Window

1998 ◽  
Vol 179 ◽  
pp. 223-224
Author(s):  
R.A. Méndez ◽  
R.M. Rich ◽  
W.F. Van Altena ◽  
T.M. Girard ◽  
S. Van Den Bergh ◽  
...  
Keyword(s):  
Proper Motion ◽  
Main Sequence ◽  
Proper Motions ◽  
Galactic Bulge ◽  
Plate Material

We are conducting the deepest and largest photographic proper-motion survey ever undertaken of the Galactic bulge. Our first-epoch plate material (from 1972-3) goes deep enough (Vlim ∼ 22) to reach below the bulge main-sequence turnoff. These plates cover an area of approximately 25′ × 25′ of the bulge in the low-extinction (Av ∼ 0.8 mag) Plaut field at l= 0°, b= −8°, approximately 1 kpc south of the nucleus. This is the point at which the transition between bulge and halo populations likely occurs and is, therefore, an excellent location to study the interface between the dense metal-rich bulge and the metal-poor halo.

scholarly journals Proper Motions Referred to Faint Galaxies

1986 ◽  
Vol 7 ◽  
pp. 89-92
Author(s):  
W. F. van Altena ◽  
T. Girard ◽  
C. E. López ◽  
A. R. Klemola ◽  
B. F. Jones ◽  
...  
Keyword(s):  
Proper Motion ◽  
Reference Frames ◽  
Photographic Plate ◽  
Proper Motions ◽  
Plate Material ◽  
Present Epoch ◽  
Magnitude Range ◽  
Large Numbers ◽  
Material Forming ◽  
Partial Extension

The Lick Northern Proper Motion (NPM) and the Yale-San Juan Southern Proper Motion (SPM) programs have been described on several occasions (Wright 1950; Deutsch and Klemola 1974; Vasilevskis 1973; and Wesselink 1974). The two programs represent an attempt to measure the coordinates and proper motions, with respect to the extragalactic reference frames, for large numbers of stars representing most of the astrophysically-recognized classes. The photographic plate material forming the basis of the NPM program derives from the first (1947-1954) and second (1970-present) epoch phases for 1246 fields with the Lick 51 cm Carnegie double-astrograph for centers at -20° and northward (Shane and Wirtanen 1967). A southern supplement of 144 additional fields takes the program to -30°. The SPM consists of 632 fields with centers at -20° and southward. The first epoch plates were taken between 1965 and 1974 and a partial extension of 72 fields to more northerly declinations is essentially complete. One short and one long exposure permit the measurement of positions and approximate photometry for selected stars and reference galaxies over the blue magnitude range from about 8 to 17-18.

New VIRAC proper motion maps show signature of galactic boxy/peanut bulge

2019 ◽  
Vol 14 (S353) ◽  
pp. 29-30
Author(s):  
Jonathan P. Clarke ◽  
Christopher Wegg ◽  
Ortwin Gerhard ◽  
Leigh C. Smith ◽  
Phil W. Lucas ◽  
...  
Keyword(s):  
Proper Motion ◽  
Dynamical Model ◽  
Line Of Sight ◽  
Selection Function ◽  
Kinematic Structure ◽  
Proper Motions ◽  
Galactic Bulge ◽  
Bulge Region ◽  
Pattern Speed ◽  
Red Clump

AbstractWe have derived absolute proper motions of stars in the Galactic bulge region combining the VVV InfraRed Astrometric Catalogue (VIRAC) and Gaia. We use the proper motions to study the kinematic structure of the bulge both integrated along the line-of-sight and in magnitude intervals using red clump stars as standard candles. In parallel we compare to a made-to-measure barred dynamical model, folding in the VIRAC selection function, to understand and interpret the structures that we observe. The barred dynamical model, which contains a boxy/peanut bulge, and has a pattern speed of 37.5 kms−1 kpc−1, is able to reproduce all structures impressively well.

scholarly journals Variations in External Parallax Errors

1986 ◽  
Vol 109 ◽  
pp. 247-251
Author(s):  
A. R. Upgren
Keyword(s):  
Proper Motion ◽  
Main Sequence ◽  
Space Velocity ◽  
Proper Motions ◽  
Motion Data ◽  
Hyades Cluster ◽  
High Space ◽  
The Individual ◽  
Van Vleck ◽  
High Space Velocity

The present astrometric program of the Van Vleck Observatory began in 1967. Since then it has emphasized parallaxes and proper motions of stars of the lower main sequence which are not identified on the basis of proper motion and are therefore not biased towards high space velocity. Later an analysis was made from parallax and proper motion data from 70 stars in the spectral range dK3-M2 (Upgren 1973) which found the average external mean error in parallax to be 8.0 ± 1.7 mas (milliarcseconds). This external error was found to vary little from one parallax to another and to have no correlation with the formal internal errors for the individual parallax determinations. Hanson and Lutz (1983) confirm this result using the parallaxes of 14 members of the Hyades cluster also determined at Van Vleck. They find a mean external parallax error of 9.4 ± 1.8 mas and suggest that the proximity of the two determinations may be evidence that Van Vleck parallaxes may be characterized by a single external error. Their slightly larger figure may or may not reflect the relatively fewer plates and epochs of observation from which the Hyades parallaxes were determined.

scholarly journals Chemically Dissected Rotation Curves of the Galactic Bulge from Main-sequence Proper Motions

2018 ◽  
Vol 858 (1) ◽  
pp. 46 ◽  
Author(s):  
William I. Clarkson ◽  
Annalisa Calamida ◽  
Kailash C. Sahu ◽  
Thomas M. Brown ◽  
Mario Gennaro ◽  
...  
Keyword(s):  
Main Sequence ◽  
Proper Motions ◽  
Galactic Bulge ◽  
Rotation Curves

scholarly journals New nearby white dwarfs from Gaia DR1 TGAS and UCAC5/URAT

2018 ◽  
Vol 613 ◽  
pp. A26 ◽  
Author(s):  
R.-D. Scholz ◽  
H. Meusinger ◽  
H. Jahreiß
Keyword(s):  
Proper Motion ◽  
Main Sequence ◽  
Orbital Motion ◽  
Angular Separation ◽  
Proper Motions ◽  
Halo Star ◽  
Physical Separation ◽  
Naval Observatory ◽  
Nearby Stars ◽  
Absolute Magnitudes

Aims. Using an accurate Tycho-Gaia Astrometric Solution (TGAS) 25 pc sample that is nearly complete for GK stars and selecting common proper motion (CPM) candidates from the 5th United States Naval Observatory CCD Astrograph Catalog (UCAC5), we search for new white dwarf (WD) companions around nearby stars with relatively small proper motions. Methods. To investigate known CPM systems in TGAS and to select CPM candidates in TGAS+UCAC5, we took into account the expected effect of orbital motion on the proper motion and proper motion catalogue errors. Colour-magnitude diagrams (CMDs) MJ ∕J − Ks and MG ∕G − J were used to verify CPM candidates from UCAC5. Assuming their common distance with a given TGAS star, we searched for candidates that occupied similar regions in the CMDs as the few known nearby WDs (four in TGAS) and WD companions (three in TGAS+UCAC5). The CPM candidates with colours and absolute magnitudes corresponding neither to the main sequence nor to the WD sequence were considered as doubtful or subdwarf candidates. Results. With a minimum proper motion of 60 mas yr−1, we selected three WD companion candidates; two of which are also confirmed by their significant parallaxes measured in URAT data, whereas the third may also be a chance alignment of a distant halo star with a nearby TGAS star that has an angular separation of about 465 arcsec. One additional nearby WD candidate was found from its URAT parallax and GJKs photometry. With HD 166435 B orbiting a well-known G1 star at ≈24.6 pc with a projected physical separation of ≈700 AU, we discovered one of the hottest WDs, classified by us as DA2.0 ± 0.2, in the solar neighbourhood. We also found TYC 3980-1081-1 B, a strong cool WD companion candidate around a recently identified new solar neighbour with a TGAS parallax corresponding to a distance of ≈8.3 pc and our photometric classification as ≈M2 dwarf. This raises the question of whether previous assumptions on the completeness of the WD sample to a distance of 13 pc were correct.

scholarly journals Automated Proper Motion Survey: Data Reduction and Initial System Performance

1970 ◽  
Vol 7 ◽  
pp. 26-47 ◽  
Author(s):  
A. E. La Bonte
Keyword(s):  
Data Reduction ◽  
Proper Motion ◽  
System Performance ◽  
Processing Time ◽  
The Other ◽  
Photographic Emulsion ◽  
Proper Motions ◽  
Plate Material ◽  
Schmidt Telescope ◽  
Plate Center

The Automated Proper Motion Survey (APMS) has three broad goals-accuracy, completeness, and efficiency in the discovery and measurement of stellar proper motions on pairs of red-sensitive photographic star plates taken with the forty-eight inch Schmidt telescope. The specific range of motions sought is from 0.1 to 2.5 seconds-of-arc per year. The lower limit of 0.1 arc sec/year is consistent with the inherent uncertainties in the photographic emulsion and the typical epoch difference between plate exposures. At the opposite end of the scale, extension of the search radius beyond that corresponding to 2.5 arc sec/year would result in a prohibitively large number of spurious matches and a significant increase in processing time while yielding extremely few (though individually interesting) additional stellar motions. The specific range of stellar magnitudes sought is from 12 to 19 red. Significant motions for stars brighter than the limit mred = 12 are already fairly well documented and the corresponding bright Schmidt images begin to show extensive contamination from diffraction spikes, “blazes” radially away from the plate center, and photographic “bloom”. At the other limit, although images of stars fainter than mred = 19 are visually discernible on the plates (the plate limit is typically mred= 20), inspection of the faintest images reveals that they are amorphous and often quite asymmetric clusters of photographic grain. Thus, both the motion limits and the magnitude limits for the survey have been selected to cover the range of reliable and largely unexplored data on the plate material. The implementation of APMS, then, is tailored to these goals and ranges.

scholarly journals Gaia DR2 reveals a very massive runaway star ejected from R136

2018 ◽  
Vol 619 ◽  
pp. A78 ◽  
Author(s):  
D. J. Lennon ◽  
C. J. Evans ◽  
R. P. van der Marel ◽  
J. Anderson ◽  
I. Platais ◽  
...  
Keyword(s):  
Lower Limit ◽  
Proper Motion ◽  
Evolutionary History ◽  
Massive Star ◽  
Position Angle ◽  
Proper Motions ◽  
Central Cluster ◽  
Dynamical Constraints ◽  
Runaway Stars ◽  
Gaia Dr2

A previous spectroscopic study identified the very massive O2 III star VFTS 16 in the Tarantula Nebula as a runaway star based on its peculiar line-of-sight velocity. We use the Gaia DR2 catalog to measure the relative proper motion of VFTS 16 and nearby bright stars to test if this star might have been ejected from the central cluster, R136, via dynamical ejection. We find that the position angle and magnitude of the relative proper motion (0.338±0.046 mas yr−1, or approximately 80±11 km s−1) of VFTS 16 are consistent with ejection from R136 approximately 1.5±0.2 Myr ago, very soon after the cluster was formed. There is some tension with the presumed age of VFTS 16 that, from published stellar parameters, cannot be greater than 0.9+0.3−0.2 Myr. Older ages for this star would appear to be prohibited due to the absence of He I lines in its optical spectrum, since this sets a firm lower limit on its effective temperature. The dynamical constraints may imply an unusual evolutionary history for this object, perhaps indicating it is a merger product. Gaia DR2 also confirms that another very massive star in the Tarantula Nebula, VFTS 72 (alias BI 253; O2 III-V(n)((f*)), is also a runaway on the basis of its proper motion as measured by Gaia. While its tangential proper motion (0.392±0.062 mas yr−1 or 93±15 km s−1) would be consistent with dynamical ejection from R136 approximately 1 Myr ago, its position angle is discrepant with this direction at the 2σ level. From their Gaia DR2 proper motions we conclude that the two ∼100 M⊙ O2 stars, VFTS 16 and VFTS 72, are fast runaway stars, with space velocities of around 100 km s−1 relative to R136 and the local massive star population. The dynamics of VFTS 16 are consistent with it having been ejected from R136, and this star therefore sets a robust lower limit on the age of the central cluster of ∼1.3 Myr.

scholarly journals Proper motions in the Galactic bulge: Plaut's window

2007 ◽  
Vol 3 (S245) ◽  
pp. 351-354
Author(s):  
Katherine Vieira ◽  
Dana Cassetti-Dinescu ◽  
René A. Méndez ◽  
R. Michael Rich ◽  
Terrence M. Girard ◽  
...  
Keyword(s):  
Proper Motion ◽  
Galactic Rotation ◽  
Red Giants ◽  
Proper Motions ◽  
Motion Study ◽  
Solar Motion ◽  
Two Samples ◽  
Red Clump ◽  
Good Agreement ◽  
Peak Value

AbstractA proper motion study of a field of 20′ × 20′ inside Plaut's low extinction window (l,b)=(0o, −8o), has been completed. Relative proper motions and photographicBVphotometry have been derived for ~ 21,000 stars reaching toV~ 20.5 mag, based on the astrometric reduction of 43 photographic plates, spanning over 21 years of epoch difference. Proper motion errors are typically 1 mas yr−1. Cross-referencing with the 2MASS catalog yielded a sample of ~ 8700 stars, from which predominantly disk and bulge subsamples were selected photometrically from theJHcolor-magnitude diagram. The two samples exhibited different proper-motion distributions, with the disk displaying the expected reflex solar motion. Galactic rotation was also detected for stars between ~2 and ~3 kpc from us. The bulge sample, represented by red giants, has an intrinsic proper motion dispersion of (σl, σb) = (3.39, 2.91)±(0.11, 0.09) mas yr−1, which is in good agreement with previous results. A mean distance of$6.37^{+0.87}_{-0.77}$kpc has been estimated for the bulge sample, based on the observedKmagnitude of the horizontal branch red clump. The metallicity [M/H] distribution was also obtained for a subsample of 60 bulge giants stars, based on calibrated photometric indices. The observed [M/H] shows a peak value at [M/H] ~ −0.1 with an extended metal poor tail and around 30% of the stars with supersolar metallicity. No change in proper motion dispersion was observed as a function of [M/H]. We are currently in the process of obtaining CCDUBV RIphotometry for the entire proper-motion sample of ~ 21,000 stars.

scholarly journals Wading Through the Quagmire of Schmidt-Plate Coordinate Systematics

1998 ◽  
Vol 179 ◽  
pp. 384-385 ◽  
Author(s):  
C.-L Lu ◽  
I. Platais ◽  
T.M. Girard ◽  
V. Kozhurina-Platais ◽  
W.F. Van Altena ◽  
...  
Keyword(s):  
Proper Motion ◽  
San Juan ◽  
Proper Motions ◽  
Positional Accuracy

We attempted to quantify the magnitude-dependent systematics in a sample of Schmidt plates by comparison to positions from the Yale/San Juan Southern Proper Motion program which offers star positions and absolute proper motions down to B = 18 with a mean density of about 50 stars per square degree and a positional accuracy of 0.1″ (Platais et al. 1995).

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