scholarly journals On two possible groups of flare stars in Pleiades

1990 ◽  
Vol 137 ◽  
pp. 77-80
Author(s):  
A.L. Mirzoyan ◽  
M.A. Mnatsakanian
Keyword(s):  
Proper Motion ◽  
Star Cluster ◽  
Proper Motions ◽  
Mean Frequency ◽  
Cluster Region ◽  
Flare Stars ◽  
The Mean

The correlation between the magnitude of the proper motion and the mean frequency of flares for flare stars in the Pleiades cluster region is discussed. The magority of them are physical members of this star cluster. It is shown that there exist probably two groups of flare stars which differ each other by their parameters, in particular by the magnitude of proper motions. A possible explanation of this phenomenon is suggested.

scholarly journals Globular clusters in the era of precision astrometry

2019 ◽  
Vol 14 (S351) ◽  
pp. 412-415
Author(s):  
Paolo Bianchini
Keyword(s):  
Formation Mechanism ◽  
Proper Motion ◽  
Measurement Errors ◽  
Globular Clusters ◽  
Tangential Component ◽  
Proper Motions ◽  
The Mean ◽  
Motion Measurements ◽  
Precision Astrometry

Abstracthe study of the kinematics of globular clusters (GCs) offers the possibility of unveiling their long term evolution and uncovering their yet unknown formation mechanism. Gaia DR2 has strongly revitalized this field and enabled the exploration of the 6D phase-space properties of Milky Way GCs, thanks to precision astrometry. However, to fully leverage on the power of precision astrometry, a thorough investigations of the data is required. In this contribution, we show that the study of the mean radial proper motion profiles of GCs offers an ideal benchmark to assess the presence of systematics in crowded fields. Our work demonstrates that systematics in Gaia DR2 for the closest 14 GCs are below the random measurement errors, reaching a precision of ∼0.015 mas yr−1 for mean proper motion measurements. Finally, through the analysis of the tangential component of proper motions, we report the detection of internal rotation in a sample of ∼50 GCs, and outline the implications of the presence of angular momentum for the formation mechanism of proto-GC. This result gives the first taste of the unparalleled power of Gaia DR2 for GCs science, in preparation for the subsequent data releases.

scholarly journals Densifying the Optical Reference Frame: The Tycho-2 Catalog of 2.5 Million Stars

2000 ◽  
Vol 180 ◽  
pp. 75-79
Author(s):  
S.E. Urban ◽  
G.L. Wycoff
Keyword(s):  
Reference Frame ◽  
Proper Motion ◽  
Proper Motions ◽  
Naval Observatory ◽  
Optical Reference ◽  
The Mean ◽  
The U.S

AbstractSince the establishment of the Hipparcos Catalog as the defining source of the optical reference frame, densification beyond its ≈ 120,000 stars has been made possible by the utilization of the Tycho-1 Catalog. The ACT, combining the old Astrographic Catalog (AC) data with the Tycho-1 positions, is the best known example of this. The Tycho-2 consortium, led by E. Høg, has performed new reductions on the Tycho data. This not only has increased the astrometric and photometric accuracies of the original 1 million Tycho-1 stars, but also has added an additional 1.5 million stars. The U.S. Naval Observatory led the effort to compute the proper motions of these 2.5 million stars. They are based not only on the AC data but also include over 140 other ground-based catalogs, all directly reduced to the Hipparcos system. The result of these efforts is the Tycho-2 Catalog, available since February 2000. Positions, proper motions, and BT and VT magnitudes are given for 2.5 million stars. The catalog is 99% complete to V=11.0, and 90% complete to V=11.5. Positional accuracies at the mean epochs vary from < 10 mas for stars V < 9 to just under 100 mas for V > 12. Proper motion accuracies are estimated to be 1.3 mas/year to 3.0 mas/year for the same magnitude ranges. Photometric accuracies range from 0.02 magnitudes for the brightest stars to 0.25 magnitudes for the faintest.

scholarly journals Absolute Proper Motions of the Dwarf Spheroidal Galaxies in Draco and Ursa Minor

1994 ◽  
Vol 161 ◽  
pp. 535-539 ◽  
Author(s):  
R.-D. Scholz ◽  
M.J. Irwin
Keyword(s):  
Proper Motion ◽  
Globular Clusters ◽  
Reduction Process ◽  
Systematic Errors ◽  
Base Line ◽  
Proper Motions ◽  
Dwarf Spheroidal Galaxies ◽  
Accuracy Level ◽  
Ursa Minor ◽  
The Mean

Palomar and Tautenburg Schmidt plates with a base line of about 35 years have been measured with the Automated Photographic Measuring (APM) system in Cambridge (UK) in order to obtain the proper motions of the Galactic dwarf spheroidal satellites (dSph) in Draco and Ursa Minor with respect to a well defined extragalactic reference frame. The investigations were encouraged by the accuracy level achieved for the mean absolute proper motions of galactic globular clusters (0.05 arcsec/century from 25 years base line Tautenburg plate pairs) which is comparable to the expected proper motion of the Draco and Ursa Minor dSph assuming tangential motions of about 100 km/s. Different methods for the removal of systematic errors in the absolute proper motion introduced by the measuring and reduction process are discussed. The more accurate relative proper motions of individual stars in both dSphs obtained by Stetson (1980) and by Cudworth, Olszewski &amp; Schommer (1986) provide an external comparison and are also used to obtain the mean absolute proper motion of the dSphs.

scholarly journals The New Catalogue of Positions and Proper Motions of 5115 Bright Stars Compiled as the Result of the International “Bright Stars” Program

1995 ◽  
Vol 166 ◽  
pp. 353-353
Author(s):  
O.A. Molotaj ◽  
V.V. Tel'Nyuk-Adamchuk ◽  
N.A. Chernega ◽  
N.D. Kanivec'
Keyword(s):  
Proper Motion ◽  
The Other ◽  
Standard Errors ◽  
Star System ◽  
Proper Motions ◽  
International Program ◽  
Motion System ◽  
Stellar Astronomy ◽  
The Mean ◽  
The One

At Kyiv University Observatory, in accordance with IAU resolution, the Combined Catalogue of Positions and Proper Motions of 5115 Bright Stars in the FK5 system for Epoch and Equinox J2000.0 (BSC, see reference) has been compiled using 20 source catalogues obtained within the framework of ‘Bright Stars’ International Program. The source catalogs are Bordeaux-66, Bucharest-65, Bucharest-68, Belgrade-79, Cape-68, Kharkiv-70n, Kharkiv-70s, Kyiv-66, Kyiv-73, El Leoncito-70, Moscow-76, Mykolaiv-65, Perth-70, Perth-75, Santiago-65, Santiago-67, Strasbourg-65, Tashkent-64, Tokyo-68, Washington-66. The BSC accumulates around 30,000 source catalogue positions observed within 1960-1980. The standard errors of BSC do not exceed 0.1 arcsec and 0.25 arcsec/cy for positions and proper motions, respectively. The systematic differences between BSC and FK5 in positions for the mean BSC epoch 1970 as a rule do not exceed several hundredths of arcsec. A comparison of the BSC with the PPM catalogue indicates that in the latter the accuracy of positions and proper motions of the ordinary bright stars is slightly worse than that of average values given by the authors of the PPM. It is important to note that the comparison of the BSC with PPM for various star subsets shows deviations of both the HPS bright star system and the rest of the PPM bright stars, on the one hand, from the stars of the FK5 Extension contained in the PPM on the other hand. To examine the BSC proper motion system the stellar astronomy constants and correction to precession have been determined using the BSC proper motions. The parameters obtained agree with the standard ones. But the Oort constants are slightly smaller than those of standard.The BSC catalogue as a whole is acceptable for astrometry usage with respect to both accidental and systematic accuracy.

scholarly journals The Tautenburg Part Of The Programme Studying The Main Meridional Section Of The Galaxy

1988 ◽  
Vol 133 ◽  
pp. 451-454
Author(s):  
E. Schilbach
Keyword(s):  
Proper Motion ◽  
Proper Motions ◽  
Schmidt Telescope ◽  
Meridional Section ◽  
Mean Error ◽  
The Galaxy ◽  
The Mean

The programme for the determination of proper motions with reference to galaxies for 6000 stars on 17 fields near the main meridional section of the Galaxy is presented. For each field there are 2 or 3 first-epoch plates taken with the Tautenburg Schmidt-telescope before 1970. In preliminary investigations the mean error of an individual proper motion was found to be per century both for bright (8m–12m) and for faint (16m–18m) stars.

scholarly journals The Milky Way bar/bulge in proper motions: a 3D view from VIRAC and Gaia

2019 ◽  
Vol 489 (3) ◽  
pp. 3519-3538 ◽  
Author(s):  
Jonathan P Clarke ◽  
Christopher Wegg ◽  
Ortwin Gerhard ◽  
Leigh C Smith ◽  
Phil W Lucas ◽  
...  
Keyword(s):  
Proper Motion ◽  
Milky Way ◽  
Selection Function ◽  
Full Potential ◽  
Proper Motions ◽  
Bulge Region ◽  
Similar Distance ◽  
Pattern Speed ◽  
The Mean ◽  
Red Clump

Abstract We have derived absolute proper motions of the entire Galactic bulge region from VVV Infrared Astrometric Catalogue (VIRAC) and Gaia. We present these both as integrated on-sky maps and, after isolating standard candle red clump (RC) stars, as a function of distance using RC magnitude as a proxy. These data provide a new global, 3D view of the Milky Way barred bulge kinematics. We find a gradient in the mean longitudinal proper motion, $\langle \mu _ l^\star \rangle $, between the different sides of the bar, which is sensitive to the bar pattern speed. The split RC has distinct proper motions and is colder than other stars at similar distance. The proper motion correlation map has a quadrupole pattern in all magnitude slices showing no evidence for a separate, more axisymmetric inner bulge component. The line-of-sight integrated kinematic maps show a high central velocity dispersion surrounded by a more asymmetric dispersion profile. $\sigma _{\mu _l} / \sigma _{\mu _b}$ is smallest, ≈1.1, near the minor axis and reaches ≈1.4 near the disc plane. The integrated $\langle \mu_b\rangle$ pattern signals a superposition of bar rotation and internal streaming motion, with the near part shrinking in latitude and the far part expanding. To understand and interpret these remarkable data, we compare to a made-to-measure barred dynamical model, folding in the VIRAC selection function to construct mock maps. We find that our model of the barred bulge, with a pattern speed of 37.5 $\mathrm{ \mathrm{ km \, s^{-1}} \, kpc^{-1} }$, is able to reproduce all observed features impressively well. Dynamical models like this will be key to unlocking the full potential of these data.

scholarly journals With and without spectroscopy: Gaia DR2 proper motions of seven ultra-faint dwarf galaxies

2018 ◽  
Vol 620 ◽  
pp. A155 ◽  
Author(s):  
D. Massari ◽  
A. Helmi
Keyword(s):  
Radial Velocity ◽  
Proper Motion ◽  
Dwarf Galaxies ◽  
Stellar System ◽  
Initial Guess ◽  
Proper Motions ◽  
Spectroscopic Information ◽  
The Mean ◽  
Astrometric Data ◽  
Full Covariance Matrix

Aims. We present mean absolute proper motion measurements for seven ultra-faint dwarf galaxies orbiting the Milky Way, namely Boötes III, Carina II, Grus II, Reticulum II, Sagittarius II, Segue 2, and Tucana IV. For four of these dwarfs our proper motion estimate is the first ever provided. Methods. The adopted astrometric data come from the second data release of the Gaia mission. We determine the mean proper motion for each galaxy starting from an initial guess of likely members, based either on radial velocity measurements or using stars on the horizontal branch identified in the Gaia (GBP – GRP, G) colour-magnitude diagram in the field of view towards the UFD. We then refine their membership iteratively using both astrometry and photometry. We take into account the full covariance matrix among the astrometric parameters when deriving the mean proper motions for these systems. Results. Our procedure provides mean proper motions with typical uncertainties of ∼0.1 mas yr−1, even for galaxies without prior spectroscopic information. In the case of Segue 2 we find that using radial velocity members only leads to biased results, presumably because of the small number of stars with measured radial velocities. Conclusions. Our procedure allows the number of member stars per galaxy to be maximized regardless of the existence of prior spectroscopic information, and can therefore be applied to any faint or distant stellar system within reach of Gaia.

scholarly journals Preliminary proper motion analysis of the Carina dwarf spheroidal

2007 ◽  
Vol 3 (S248) ◽  
pp. 492-493
Author(s):  
J. L. Carlin ◽  
S. R. Majewski ◽  
D.I. Casetti-Dinescu ◽  
T. M. Girard
Keyword(s):  
Motion Analysis ◽  
Proper Motion ◽  
Precise Measurement ◽  
Proper Motions ◽  
Preliminary Results ◽  
Motion Study ◽  
The Mean ◽  
Absolute Frame

AbstractWe present preliminary results from a proper motion study of the Carina dwarf spheroidal galaxy. Our proper motions show a scatter of ~1.1 mas yr−1 per Carina member star, and we determinate the mean ensemble motion to an accuracy of ~7 mas century−1. While this is a precise measurement of the relative proper motions of Carina members, our correction to an absolute frame is limited by the small number of measured QSOs in the field.

Status of “AGK4” Project

1978 ◽  
Vol 48 ◽  
pp. 527-533
Author(s):  
Chr. de Vegt
Keyword(s):  
Northern Hemisphere ◽  
Proper Motion ◽  
The Mean ◽  
Spectral Bandpass

The present accuracy limit for the majority of fainter stars on the northern hemisphere is set by the AGK2/3-catalogue, recently completely finished, but it should be noted that its epoch is much earlier (1960). Furtheron the AGK3-catalogue is a direct repetition of the AGK2, the plates have been taken with the same astrograph in a broad blue spectral bandpass and measured visually with the same equipment, therefore virtually an instrumental standard of 1930 is realized again. Figure 1 shows the mean errors of the AGK2/3 catalogue positions as a function of magnitude. The best accuracy for the AGK2/3 data is obtained for the stars of about ninth magnitude: 017 (AGK2) and 020 (AGK3) but decreases for the faint stars with mpg11 to 019 (AGK2) and Pg 027 (AGK3). Here the AGK3 data are even less accurate. With increasing distance to the catalogue epochs, the accuracy of positions decreases due to the proper motion errors. In the upper part of figure 2 the dependence of the AGK2/3 catalogue accuracy on time is shown for the faint stars separately and an averaged value.

35Cl NQR Spectroscopy on Salts and Molecular Compounds of Trichloroacetic Acid

1986 ◽  
Vol 41 (1-2) ◽  
pp. 215-224 ◽  
Author(s):  
Winfried Fichtner ◽  
Axel Markworth ◽  
Norbert Weiden ◽  
Alarich Weiss
Keyword(s):  
Frequency Shift ◽  
Temperature Dependence ◽  
Linear Relation ◽  
Trichloroacetic Acid ◽  
Mean Frequency ◽  
35Cl Nqr ◽  
The Mean ◽  
Molecular Compounds

The temperature dependence of salts M(1)H(Cl3CCOO)2 and molecular compounds of trichloroacetic acid with amines and benzaldehydes, TCA · X, was studied,The data fit rather well to the known dependence of the mean frequency shift Δ <v(35Cl)> on the pkadifference of X with respect to TCA. A linear relation is observed between the bleaching out temperature Tb of the 35Cl NQR lines and Δ <v(35Cl)> for M(1)H(Cl3CCOO)2 and for TCA · X, X = benzaldehydes.

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