J/A+A/640/A83 Mass determination using microlensing by Gaia (Klueter+, 2020)
Expectations on the mass determination using astrometric microlensing by Gaia.
Klueter J., Bastian U., Wambsganss J.
<Astron. Astrophys. 640, A83 (2020)>
=2020A&A...640A..83K 2020A&A...640A..83K (SIMBAD/NED BibCode)
ADC_Keywords: Positional data ; Stars, masses
Keywords: astrometry - gravitational lensing: micro - stars: low-mass -
catalogs - proper motions - white-dwarf
Abstract:
Astrometric gravitational microlensing can be used to determine the
mass of a single star (the lens) with an accuracy of a few percent. To
do so, precise measurements of the angular separations between lens
and background star with an accuracy below 1 milli-arcsecond at
different epochs are needed. Therefore only the most accurate
instruments can be used. However, since the timescale is on the order
of months to years, the astrometric deflection might be detected by
Gaia, even though each star is only observed on a low cadence.
We want to show how accurately Gaia can determine the mass of the
lensing star.
Using conservative assumptions based on the results of the second Gaia
data release (GaiaDR2), we simulated the individual Gaia measurements
for 501 predicted astrometric microlensing events during the Gaia era
(2014.5 - 2026.5). For this purpose we used the astrometric parameters
of Gaia DR2, as well as an approximative mass based on the absolute G
magnitude. By fitting the motion of the lens and source
simultaneously, we then reconstructed the 11 parameters of the lensing
event. For lenses passing by multiple background sources, we also
fitted the motion of all background sources and the lens
simultaneously. Using a Monte-Carlo simulation we determined the
achievable precision of the mass determination.
We find that Gaia can detect the astrometric deflection for 114
events. Furthermore, for 13 events Gaia can determine the mass of the
lens with a precision better than 15% and for 13 + 21 = 34 events with
a precision of 30% or better.
Description:
Estimated uncertainties of mass measurements using astrometric
microlensing with Gaia for single events. The table list the results
for three different cases.
1) Using the data of the extended 10 years mission (deltaM10).
2) Using the data from the nominal 5 years mission (deltaM5).
3) Using the data of the extended mission plus two additional 2D
observations during the epoch of the closest approach (deltaMext).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table.dat 298 114 Determined precision for each event
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: table.dat
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Bytes Format Units Label Explanations
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1- 19 A19 ---- Name Common Name of the Lens
21- 39 I19 ---- LensID Gaia DR2 Source_id of the lens
41- 59 I19 ---- SourceID Gaia DR2 Source_id of the source
61 I1 ---- fivepar [0/1] Does Gaia DR2 provides a
five - parameter solution of the source?
63- 80 F18.13 yr TCA Date of the closest approach
82-100 F19.17 Msun Mass Approximated mass of the Lens
102-121 F20.18 Msun deltaM10 Determined standard error for the mass
determination for the extended 10-years
mission (deltaM_10)
123-143 E21.19 Msun E_deltaM10 upper uncertainty of the standard error for
the extended mission (sigmadeltaM10_+)
145-166 E22.19 Msun e_deltaM10 [] lower uncertainty of the standard error
for the extended mission
(sigmadeltaM10_-)
168-187 F20.18 Msun deltaM5 Determined standard error for the mass
determination for the nominal 5-years
mission (deltaM_5)
189-209 E21.19 Msun E_deltaM5 upper uncertainty of the standard error for
the nominal mission (sigmadeltaM5_+)
211-232 E22.19 Msun e_deltaM5 [] lower uncertainty of the standard error
for the nominal mission (sigmadeltaM5_-)
234-253 F20.18 Msun deltaMext ? Determined standard error for the mass
determination for the extended 10-year
mission including external observations
(deltaM_ext)
255-275 E21.19 Msun E_deltaMext ? upper uncertainty of the standard error
for the nominal mission plus external
observations (sigmadeltaMext_+)
277-298 E22.19 Msun e_deltaMext []? lower uncertainty of the standard error
for the nominal mission plus external
observations (sigmadeltaMext_-)
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Acknowledgements:
Jonas Klueter, klueter(at)ari.uni-heidelberg.de
(End) Jonas Klueter [ARI, Germany], Patricia Vannier [CDS] 29-Jun-2020