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Determination of short-term proper motions of fast stars with Pulkovo Normal Astrograph.
A.A. Berezhnoj, E.V. Khrutskaya, M.Yu. Khovritchev

Laboratory of Astrometry and Stellar Astronomy of the Pulkovo Observatory, RAS, Saint-Petersburg


Observations

Normal Astrograph (D/F=33 cm/3.5m), CCD camera: S2C, FOV = 18x16 arcmin, Pixel size 900x900 mas


Determination of the new proper motions of 413 LSPM stars 1 epoch: CCD-surveys and catalogs -- M2000, CMC14, 2MASS, SDSS DR7 2 epoch: CCD-observations with the Pulkovo Normal astrograph

A linear model of stellar motion was applied ..and model with quadratic terms

x (t )=x (t
0.

0

)+ x (t - t 0 )

x( - t t

)

2

Left: Histogram of epoch differences.

Right: Histogram of numbers of positions per star.


Determination of pixel coordinates of stars and analysis of systematic errors

Lorentz profile was used to approximate stellar images. Data within 40-pixels aperture centered at the photocenter of the image was used to calculate PSF parameters. Astrometric calibrations were performed with "good" UCAC3 stars. Analysis of systematic residuals of pixels coordinates allowed us to calculate corrections depended on x,y and mag.

Example of residuals of the pixels coordinates as function of y.


Analysis of obtained proper motions.
Example of histogram of standard errors of the proper motions

PUL-LSPM systematic differences of the proper motions as functions of magnitudes and colors


Searching of -binaries candidates

F=

2


2

2 RA
RA

+


2

2 Dec
De c





Criterion to reveal -binaries. It was constructed as similar value in the paper of
R. Wielen et al. Astron. Astrophys. 346, 675 (1999)

F > 2.49
Difference between average and quasi instant motion of photocenter of binary star. Figure was taken from the paper of R.
Wielen et al. Astron. Astrophys. 346, 675 (1999)

Stars with this value of F may be considered as -binaries candidates. The level of significance is 0.95.


Testing of the technique of searching of -binaries
Motion of star J0758+5705 Vmag=15.8 F=2.91 WDS_flag=0

48 stars from WDS catalog were contained in our material. About half of them were qualified as -binaries candidates. It is significantly more than expected in the case of random work of criterion.

70 non-WDS stars among 413 program stars
were detected as -binaries candidates.

Motion of star J0955+2229 Vmag=13.0 F=4.50 WDS_flag=0


Image-to-image reduction

2. Pulkovo-image (epoch is 2010) 1. SDSS-image (epoch is about 2004) or POSSI-image (epoch is about 1955)

x 2 = a x x 1+ b x y + c x + px + qx 1 y

2 1

1 2 1

y 2= a y x1+ b y y 1+ c y + px 1 y 1+ q y

The model with inclination terms was applied to calculate pixel positions of investigated star in the coordinates of reference CCD frame. It is caused by relatively large differences between optical centers (Pulkovo -- SDSS). Unit weight errors are within 10 to 30 mas. Examples of short-term proper motions (Pulkovo -- SDSS) and comparisons of F-factors
Star Pm RA [mas/] Pm Dec [mas/]

Error PM RA [mas]

Error PM Dec [mas]

Epoch difference [yr]

Star

F
Image to image

F Catalog based 10.67 9.16

J1309+5918 J1309+5918 J1516+6054 -499.7 56.7 68.3 -432.0 11.1 3.6 3.1 12.3 7.36 10.14 J1516+6054

17.3 2.19


Conclusions
The proper motions of LSPM 413 stars were determined with the Pulkovo Normal astrograph and CCD-surveys data (SDSS, 2MASS, CMC14, M2000). Accuracy of these new proper motions in HCRF is about 1 to 4 mas/yr. It confirmed by comparisons with Kiev catalog and LSPM data. The results of work allows us to say that the Wielen approach to detect binary nature of stars of FK6 calalog can be used for stars with large proper motions. 70 stars were detected as -binaries candidates using comparison between quasi instant proper motions determined in this work with average proper motions taken from Kiev catalog and LSPM catalog. Determination of the proper motions from image-to-image reductions (Pulkovo ­ SDSS, Pulkovo ­ POSSI) is performed. Standard error of transformation of pixels coordinates of stars from SDSS CCD-image to Pulkovo CCD-image is 10 to 30 mas. The majority of previous -binaries detections are confirmed by analysis of the results of image-to-image reductions . All data presented in this work available in appropriate publications and via web (www.puldb.ru).

Acknowledgments
Authors express their thanks to Russian Foundation of Basic Research (project # 09-02-00419-). In addition, the authors express their gratitude to A. Kulikova for her participation in developing of image-to-image reductions.