Predicted microlensing events by nearby very-low-mass objects: Pan-STARRS DR1 vs. Gaia DR2. (arXiv:1811.03421v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Nielsen_M/0/1/0/all/0/1">M. B. Nielsen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bramich_D/0/1/0/all/0/1">D. M. Bramich</a>
Microlensing events can be used to directly measure the masses of single
field stars to a precision of $sim$1-10%. The majority of direct mass
measurements for stellar and sub-stellar objects typically only come from
observations of binary systems. Hence microlensing provides an important
channel for direct mass measurements of single stars. The Gaia satellite has
observed $sim$1.7 billion objects, and analysis of the second data release has
recently yielded numerous event predictions for the next few decades. However,
the Gaia catalog is incomplete for nearby very-low-mass objects such as brown
dwarfs for which mass measurements are most crucial. We employ a catalog of
very-low-mass objects from Pan-STARRS data release 1 (PDR1) as potential lens
stars, and we use the objects from Gaia data release 2 (GDR2) as potential
source stars. We then search for future microlensing events up to the year
2070. The Pan-STARRS1 objects are first cross-matched with GDR2 to remove any
that are present in both catalogs. This leaves a sample of 1,718 possible
lenses. We fit MIST isochrones to the Pan-STARRS1, AllWISE and 2MASS photometry
to estimate their masses. We then compute their paths on the sky, along with
the paths of the GDR2 source objects, until the year 2070, and search for
potential microlensing events. Source-lens pairs that will produce a
microlensing signal with an astrometric amplitude of greater than 0.131 mas, or
a photometric amplitude of greater than 0.4 mmag, are retained.
Microlensing events can be used to directly measure the masses of single
field stars to a precision of $sim$1-10%. The majority of direct mass
measurements for stellar and sub-stellar objects typically only come from
observations of binary systems. Hence microlensing provides an important
channel for direct mass measurements of single stars. The Gaia satellite has
observed $sim$1.7 billion objects, and analysis of the second data release has
recently yielded numerous event predictions for the next few decades. However,
the Gaia catalog is incomplete for nearby very-low-mass objects such as brown
dwarfs for which mass measurements are most crucial. We employ a catalog of
very-low-mass objects from Pan-STARRS data release 1 (PDR1) as potential lens
stars, and we use the objects from Gaia data release 2 (GDR2) as potential
source stars. We then search for future microlensing events up to the year
2070. The Pan-STARRS1 objects are first cross-matched with GDR2 to remove any
that are present in both catalogs. This leaves a sample of 1,718 possible
lenses. We fit MIST isochrones to the Pan-STARRS1, AllWISE and 2MASS photometry
to estimate their masses. We then compute their paths on the sky, along with
the paths of the GDR2 source objects, until the year 2070, and search for
potential microlensing events. Source-lens pairs that will produce a
microlensing signal with an astrometric amplitude of greater than 0.131 mas, or
a photometric amplitude of greater than 0.4 mmag, are retained.
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