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DATA ON ASTRONOMY PUBLISHED BY A.M. MICKAELIAN AND COLLEAGUES
Science Letter
November 9, 2010
"A new method for combined calculations of proper motions (PMs)
based on accurate measurements of POSS1 and POSS2 epoch plates is
given. The positional accuracy of various surveys and catalogues is
estimated, and statistical weights for each of them are established,"
scientists in Armenia report (see also Astronomy).
"To achieve the best positions, weighted averaging of direct
measurements on DSS1/DSS2, and data from APM, MAPS, USNO-A2.0,
USNO-B1.0 and GSC 2.3.2 catalogues were used. The rms accuracy of
positions achieved for POSS1 is 119 mas in each coordinate and 168
mas total, and for POSS2 it is 69 mas in each coordinate and 98 mas
total. Using these accurate positions and the large separation in
years between POSS1 and POSS2, we calculated the best possible PMs:
3.9 mas yr-1 in each coordinate and 5.5 mas yr-1 total. We developed
methods to control and exclude the accidental errors that appear
in any survey. We compared and combined our PMs with those given in
USNO-B1.0, SDSS DR7 and Tycho-2 catalogues and obtained even better
results: 3.0 mas yr-1 in each coordinate and 4.2 mas yr-1 total PM.
This approach was applied to the First Byurakan Survey blue stellar
objects, containing significant numbers of white dwarfs and subdwarfs.
In total, 640 objects were revealed with PM >= 10 mas yr -1, the
detection limit for this method, and an electronic table of these
objects is given. For more confident PMs, we adopt the limit 20 mas
yr-1 (333 objects). Adopting a 50 km s-1 upper limit for tangential
velocities, we calculated maximum distances and absolute magnitudes
and estimated luminosity types for these objects, obtaining 185
probable white dwarfs (M > 8 mag), 69 possible white dwarfs (6 <
M< 8 mag), and 42 candidate subdwarfs/white dwarfs (3 < M< 6 mag),"
wrote A.M. Mickaelian and colleagues.
The researchers concluded: "Given that we rediscovered 141 genuine
white dwarfs among the classified objects, the success rate for the
discovery of white dwarfs is estimated as 83 per cent, and as 38 per
cent for our probable and possible white dwarfs, respectively."
Mickaelian and colleagues published their study in Monthly Notices of
the Royal Astronomical Society (Proper motions and natures of First
Byurakan Survey blue stellar objects. Monthly Notices of the Royal
Astronomical Society, 2010;407(1):681-690).
For more information, contact A.M. Mickaelian, Byurakan Astrophysics
Observ, Byurakan 0213, Aragatzotn Prov, Armenia.
Publisher contact information for the journal Monthly Notices of
the Royal Astronomical Society is: Wiley-Blackwell Publishing, Inc.,
Commerce Place, 350 Main St., Malden 02148, MA, USA.
From: A. Papazian
Science Letter
November 9, 2010
"A new method for combined calculations of proper motions (PMs)
based on accurate measurements of POSS1 and POSS2 epoch plates is
given. The positional accuracy of various surveys and catalogues is
estimated, and statistical weights for each of them are established,"
scientists in Armenia report (see also Astronomy).
"To achieve the best positions, weighted averaging of direct
measurements on DSS1/DSS2, and data from APM, MAPS, USNO-A2.0,
USNO-B1.0 and GSC 2.3.2 catalogues were used. The rms accuracy of
positions achieved for POSS1 is 119 mas in each coordinate and 168
mas total, and for POSS2 it is 69 mas in each coordinate and 98 mas
total. Using these accurate positions and the large separation in
years between POSS1 and POSS2, we calculated the best possible PMs:
3.9 mas yr-1 in each coordinate and 5.5 mas yr-1 total. We developed
methods to control and exclude the accidental errors that appear
in any survey. We compared and combined our PMs with those given in
USNO-B1.0, SDSS DR7 and Tycho-2 catalogues and obtained even better
results: 3.0 mas yr-1 in each coordinate and 4.2 mas yr-1 total PM.
This approach was applied to the First Byurakan Survey blue stellar
objects, containing significant numbers of white dwarfs and subdwarfs.
In total, 640 objects were revealed with PM >= 10 mas yr -1, the
detection limit for this method, and an electronic table of these
objects is given. For more confident PMs, we adopt the limit 20 mas
yr-1 (333 objects). Adopting a 50 km s-1 upper limit for tangential
velocities, we calculated maximum distances and absolute magnitudes
and estimated luminosity types for these objects, obtaining 185
probable white dwarfs (M > 8 mag), 69 possible white dwarfs (6 <
M< 8 mag), and 42 candidate subdwarfs/white dwarfs (3 < M< 6 mag),"
wrote A.M. Mickaelian and colleagues.
The researchers concluded: "Given that we rediscovered 141 genuine
white dwarfs among the classified objects, the success rate for the
discovery of white dwarfs is estimated as 83 per cent, and as 38 per
cent for our probable and possible white dwarfs, respectively."
Mickaelian and colleagues published their study in Monthly Notices of
the Royal Astronomical Society (Proper motions and natures of First
Byurakan Survey blue stellar objects. Monthly Notices of the Royal
Astronomical Society, 2010;407(1):681-690).
For more information, contact A.M. Mickaelian, Byurakan Astrophysics
Observ, Byurakan 0213, Aragatzotn Prov, Armenia.
Publisher contact information for the journal Monthly Notices of
the Royal Astronomical Society is: Wiley-Blackwell Publishing, Inc.,
Commerce Place, 350 Main St., Malden 02148, MA, USA.
From: A. Papazian