Collisional Dynamics of Stellar Systems in the Northern and Southern Coalsack Regions

Fresneau, A.; Vaughan, A. E.; Argyle, R. W.

doi:10.1086/367778

Cited by 8 publications

(7 citation statements)

References 54 publications

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“…Results were the detection of a density wave linked to the Sagittarius spiral arm (Fresneau et al 2005(Fresneau et al , 2007 and evidence of the deflection of galactic orbits by the Southern Coalsack (Fresneau et al 2003). Our present study suggests evolution of the stability of the stellar system with time, given that the σ w σ v ratio of the velocity ellipse apparently increases from 0.45 up to 0.75 over about 6 Myr.…”

Section: Resultssupporting

confidence: 51%

“…Table 9 of Chiu (1980), we estimated absolute magnitudes -M B = (0.772 ± 0.005) H b − (3.12 ± 0.02) -and dereddened colour -(B − V) 0 = (0.84 ± 0.05)(b − V) + (0.38 ± 0.02) (Fresneau 1994). These relations follow from the assumption that the mean dispersion of the transverse velocity of foreground stars observed along the direction of each 2 • × 2 • field of view is on the order of 45 km s −1 (Fresneau et al 2003). These relations between H b and M b are based on a different stellar sample (Fresneau et al 2005) One then finds a correlation between the statistically derived parallax π in 10 −3 arcsec and the p.m. total component μ in 10 −3 arcsec yr −1 -π = (0.072 ± 0.001)μ + (0.284 ± 0.005) -which is similar to the relation that was found using stars with measured trigonometric parallax π ≥ 10 −3 arcsec and p.m. μ ≥ 10 −2 arcsec yr −1 in the space-based Hipparcos survey of stars brighter than apparent magnitude 11 (Fresneau et al 2005 Table 9 of Chiu 1980), short-term apparent magnitude scatter σ 1 , long-term apparent magnitude scatter σ 2 , error in absolute magnitude determination due to the p.m. component error σ 3 = 2.17 Δμ μ , annual p.m. in arcsec in galactic longitude μ 1 and in galactic latitude μ 2 , derived parallax π in milliarcsec, and a correlation coefficient c, which has values from 0 to 1.0 and will be explained later in our study.…”

Section: Construction Of the Variability Sample Catalog (Vsc)mentioning

confidence: 84%

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A variability sample catalogue selected from the Sydney Observatory Galactic Survey

Fresneau

Osborn²

2009

A&A

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Context. A set of 55 × 10 3 stars brighter than about B-magnitude 14 and having at least three observations are identified in the Sydney Observatory Galactic Survey, carried out over the years 1892-1932 along the galactic equator section l ∈ [275. Short-term (30 min) and long-term (decades) magnitude variations in the data set are analyzed. Aims. Evidence is sought for a correlation between short-term and long-term variabilities which would identify stars in a non-quiescent phase. Methods. We use a reduced proper motion diagram to classify the stars in our sample into probable dwarfs, giants and other types. The validity of the kinematical classification is checked using objective-prism spectroscopic classification for 10 × 10 3 early-type stars. A search is made for statistical correlations between our variability indicators and physical and kinematical stellar properties. Results. We find that suspected photospheric activity for giant and dwarf stellar candidates is correlated with the time to cross the galactic thin disk. We estimate a significant apparent B-magnitude variation of ±0.25 over the 40 years of photographic observations, and candidates for monitoring for possible photospheric activity at the present time are selected employing a statistical colour-diagram which uses the total proper motion component as a distance indicator. Conclusions. Follow up studies of our tentative findings are suggested. Toward this aim the derived data for the set of 55 × 10 3 stars with variability information is archived as the variability Sample Catalogue. The data for a set of 2.4 × 10 5 stars along the section of the galactic equator l ∈ [275 • , 335 • ], |b| ≤ 7 • , and a set of of 1.7 × 10 5 stars along the section of the galactic meridian 330 • ± 5 • , b ∈ [−64 • , −7 • ] is also archived as a quick-look facility for seeking long-term magnitude changes since the century-old photographic observations were obtained.

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Section: Resultssupporting

confidence: 51%

Section: Construction Of the Variability Sample Catalog (Vsc)mentioning

confidence: 84%

A variability sample catalogue selected from the Sydney Observatory Galactic Survey

Fresneau

Osborn²

2009

A&A

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“…In a previous study (Fresneau et al 2003), based on the Tycho-2 catalogue, the following relation was obtained to estimate the mean absolute magnitude of the stellar sample over the celestial sphere:M B = (−3.76 ± 0.01) + (0.711 ± 0.001) H. This relation describes the mixing of stellar ages among the Main Sequence B5 to G2 stars detected around the mean transverse velocity V t ≈ 45 km s −1 in the solar vicinity. We emphasize that the mean relationM B ≈ H − 5 log V t (V t in AU yr −1 ) orM B = H − 4.89 is the exact relation that should be used with V t = 45 km s −1 .…”

Section: Empirical Calibration Of Distances From Total Pmmentioning

confidence: 88%

“…This tilt term is more effective in tracing the deflection of a stellar system in velocity space than the scattering ∆V of the stellar system by a mass M encountered at speed V and impact parameter b and where ∆V ∝ M bV (Fresneau et al 2003). Figure 7 shows the averaged value of the tilt term θ (in degrees) derived from the σ V , σ W and ρ quantities estimated in the (V, W)-plane for the successive samples of 105 stars selected earlier.…”

Section: Selection Effects and Kinematical Biasmentioning

confidence: 99%

Sydney observatory Galactic survey

Fresneau¹,

Vaughan²,

Argyle³

2007

A&A

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Context. First Epoch astrometric and radiometric information of a survey in the optical along the Galactic fourth quadrant is archived for further analysis in the time-domain. Aims. A photographic survey of 1.9 × 10 6 stars down to B-magnitude 14 ± 0.5 along the galactic meridian l = (330 ± 5)• , −64• ≤ b ≤ −7• and along the galactic equator 272• , is provided from century old astrographic plates of Sydney Observatory. Stellar candidates to investigate the Galaxy disk kinematics up to a distance of 1 kpc from the Sun are tentatively selected. Methods. The early data are combined with late epoch observations into a set of 4.8 × 10 5 stars with significant proper motion µ ≥ 0.005 yr −1 and approximate color B − V. The selection effects and the kinematical bias on the stellar system are investigated. F-G stellar candidates with a mean transverse velocity dispersion of 45 km s −1 are suggested. Results. The spin rate of 1 2• pc −1 of the velocity ellipsoid along its long axis is observed over half a thickness of 25 pc of the galactic disk for stars at an estimated distance D ≤ 300 pc from the Sun. Conclusions. A catalogue of 4.8 × 10 5 stars is provided for further investigation of the galactic disk heating by transient spiral wave or by GMC encounter.Key words. surveys -stars: kinematics Retrospective of early astrographic surveysFirst epoch observations used in the proper motion (p.m.) determination of faint stars observed in the Tycho-2 catalogue are based on short exposure plates observed for the Astrographic Catalog (AC) at the beginning of the 20th century over a field of view of 2• × 2 • for each of the 4 × 10 4 AC plates at a scale of 1 mm −1 , proving that photographic observations from the past were indeed durable even at the time of space astrometry (Urban et al. 1998). In order to check the quality of the old plates with a fast measuring machine like APM, used for instance to scan large Schmidt plates (Evans 1992), a set of 104 short exposure plates dating from the late 19th century was selected from the plate vault of Sydney Observatory, archived at Macquarie University.The double exposure technique used in the astrophotographic survey is shown in Fig. 1: stars are identified in the image inventory of a plate scanned with APM by the combination of double images. Along with the x, y plate mean coordinates (in mm) and their errors ∆x, ∆y (in microns), an indication of short term magnitude variability ∆m, is also computed for each star: this information is not available from the AC measurements but is usable to search for flare stars (Fresneau et al. 2001). The (ξ, η) plate coordinates (in arcmin) for the Tycho-2 stars The quality of the best linear unbiased estimation of the set of 12 plate constants (A, B, C, D, E, F and A , B , C , D , E , F ) after the weighted least squares fit is measured by the rms error σ T between the computed and observed equatorial coordinates of the set of Tycho-2 stars (a couple of hundreds per 2 • × 2 • field of view). The same stars are also used to derive a calibrat...

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“…About 700 AC and CdC plated have been measured at APM to about 3 /jm accuracy (ft'3).These include all plates with |b| < 4° over a wide range of longitudes. The most useful science to arise so far has been proper motions to m p g = 14 from CdC plates near the Southern Coalsack (Fresneau et al 2003). in Johannesburg.…”

Section: Discussionmentioning

confidence: 99%

Commission 8: Astrometry (Astrométrie)

Platais¹

2007

Trans. Int. Astron. Union

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Collisional Dynamics of Stellar Systems in the Northern and Southern Coalsack Regions

Cited by 8 publications

References 54 publications

A variability sample catalogue selected from the Sydney Observatory Galactic Survey

A variability sample catalogue selected from the Sydney Observatory Galactic Survey

Sydney observatory Galactic survey

Commission 8: Astrometry (Astrométrie)

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