J/A+A/631/A145 HIP stars DEC proper motions comparison (Damljanovic+, 2019)
Comparison of proper motions in declination for 387 Gaia DR2 and Hipparcos stars
from ILS observations over many decades.
Damljanovic G., Taris F.
<Astron. Astrophys. 631, A145 (2019)>
=2019A&A...631A.145D 2019A&A...631A.145D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, nearby ; Positional data ; Proper motions
Keywords: astrometry - catalogs - proper motions
Abstract:
The second solution of the Gaia catalog, which has been available
since April 2018, plays an important role in the realization of the
future Gaia reference frame. Since 1997, the reference frame has been
materialized by the optical HIPPARCOS positions of about 120000
stars. The HIPPARCOS has been compared with and linked to the
International Celestial Reference Frame (ICRF). The ICRF is
materialized by means of the radio positions of extragalactic sources
using very large baseline interferometry observations. Both, the
HIPPARCOS and Gaia missions belong to the European Space Agency, and
it is important to note that the Gaia catalog is going to replace the
HIPPARCOS catalog.
It has been shown that the International Latitude Service zenith
telescope data pertaining to ground-based surveys that span a time
baseline of about 80yr, and which are also key when measuring proper
motions, could be useful for the accurate determination of µδ
for 387 ILS stars. Therefore, in this study we aim first to reduce
these stars to the HIPPARCOS reference system; second, to made our
original catalog of µδ, which we refer to as the ILS catalog,
for these 387 bright stars; third, to present comparison results of
the four catalogs by pairs (the ILS, HIPPARCOS or HIP, new HIPPARCOS
or NHIP, and Gaia DR2); and fourth, to analyze the differences in
µδ between pairs of catalogs to characterize the µδ
errors for these catalogs with a special focus on the Gaia DR2 and ILS
catalogs.
At seven ILS sites around the world at latitude 39.1°, a set of
seven telescopes was used to monitor the latitude variation via
observations of the same stars for about 80 yr. Here, the inverse task
was applied to improve µδ values of the 387 HIPPARCOS stars
using the previously mentioned observations. Due to the specific
Horrebow-Talcott method of the measured star pair, it is difficult to
determine µδ for each single star. However, we achieved
this by developing the original method and in combination with the
HIPPARCOS data. We used the previously developed least squares method
and formula to determine the coefficients, which describe the
systematic part of differences in µδ between the pairs of
catalogs.
We calculated the coefficients with the aforementioned formula (in
line with the coordinates, stellar magnitude, and color index of every
star) to compare ILS, HIP, NHIP, and Gaia DR2 data of µδ
against each other by using the set of 387 stars. The presented
differences of µδ show that the systematic errors in the
four catalogs are nearly at the same level of 0.1mas/yr. This means
that the DR2 and ILS µδ values are in good agreement with
each other, and with values from the HIPPARCOS and new HIPPARCOS
catalogs. Also, the random errors of differences are small ones; they
are near 1mas/yr for ILS-HIP and ILS-NHIP, and about 2mas/yr for
ILS-DR2, HIP-DR2, and NHIP-DR2. It is important to note that there is
a similar level of proper motion formal errors in HIPPARCOS and new
HIPPARCOS catalogs.
Description:
The files el-tab.dat contains the identification of the sources (HIP
number), the proper motion in declination and the standard deviation
of the proper motion.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 23 387 Proper motions in declination for 387 Gaia DR2
and Hipparcos stars from ILS observations
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See also:
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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2- 7 I6 --- HIP HIP number
11- 17 F7.2 mas/yr pmDE Proper motion in declination (1)
20- 23 F4.2 mas/yr s_pmDE Standard deviation of the proper motion
in declination
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Note (1): Proper motion in accordance with the epoch 1991.25 (HIP epoch).
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Acknowledgements:
Francois Taris, francois.taris(at)obspm.fr
(End) G. Damljanovic [Astronomical Obs., Serbia], P. Vannier [CDS] 02-Oct-2019