J/A+A/657/A16 Chromatic variations in microlensing events (Sajadian+, 2022)
Variation of the stellar color in high-magnification and caustic-crossing
microlensing events.
Sajadian S., Jorgensen U.G.
<Astron. Astrophys. 657, A16 (2022)>
=2022A&A...657A..16S 2022A&A...657A..16S (SIMBAD/NED BibCode)
ADC_Keywords: Gravitational lensing ; Models ; Magnitudes
Keywords: gravitational lensing: micro - instrumentation: photometers -
methods: numerical - planets and satellites: general -
starspots - stars: early-type
Abstract:
To a first approximation, the microlensing phenomenon is achromatic
and great advancements have been achieved with regard to the
interpretation of the achromatic signals, leading to the discovery and
characterization of well above 100 new exoplanets. At a higher order
accuracy in the observations, microlensing has a chromatic component
(a color term) that has thus far been explored to a much lesser
extent.
Here, we analyze the chromatic microlensing effect of four different
physical phenomena, which have the potential to contribute key
knowledge of the stellar properties that is not easily achievable with
other methods of observation. Our simulation is limited to the case of
main-sequence source stars.
Microlensing is particularly sensitive to giant and sub-giant stars
near the Galactic center. While this population can be studied in
short snapshots by the largest telescopes in the world, a general
monitoring and characterization of the population can be achieved by
use of more accessible medium-sized telescopes with specialized
equipment via dual-color monitoring from observatories at sites with
excellent seeing. We limit the results of this study to what will be
achievable from the Danish 1.54m telescope at La Silla observatory
based on the use of the existing dual-color lucky imaging camera. Such
potential monitoring programs of the bulge population from
medium-sized telescopes include the characterization of starspots,
limb-darkening, the frequency of close-in giant planet companions, and
gravity darkening for blended source stars.
We conclude our simulations with quantifying the likelihood of
detecting these different phenomena per object where they are present
to be ∼60 and ∼30% for the above-mentioned phenomena when monitored
during both high-magnification and caustic crossings, respectively.
Description:
In order to determine the error bars in the magnitude in the filters V
and I versus the error in R-band, we fit a linear function between mR
and mV+mI, as mV+mI=a*mR_+b ('a' as slope and 'b' as offset).
The slope and offset and their error bars for stars with different
metallicity ([Fe/H]) and Age are given in tablea1.dat.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 42 1716 The best-fitted parameters of linear relation
between 'mV+mI' versus mR for different
values of the stellar age and metallicity
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 5 F5.2 -- [Fe/H] Metallicity
7- 11 F5.2 Gyr Age Age
13- 19 F7.4 mag b Offset
21- 27 F7.5 mag e_b Error in Offset
29- 34 F6.4 mag a Slope
36- 42 F7.5 mag e_a Error in Slope
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Acknowledgements:
Sedighe Sajadian, sedighe.sajadian(at)gmail.com
(End) S. Sajadian [Isfahan Univ. of Technology], P. Vannier [CDS] 29-Sep-2021