J/ApJ/903/L11 OGLE and KMTNet light curve of OGLE-2016-BLG-1928 (Mroz+, 2020)
A Terrestrial-mass Rogue Planet Candidate Detected in the Shortest-timescale
Microlensing Event.
Mroz P., Poleski R., Gould A., Udalski A., Sumi T., Szymanski M.K.,
Soszynski I., Pietrukowicz P., Kozlowski S., Skowron J., Ulaczyk K., Albrow
M.D., Chung S.-J., Han C., Hwang K.-H., Jung Y.K., Kim H.-W., Ryu Y.-H.,
Shin I.-G., Shvartzvald Y., Yee J.C., Zang W., Cha S.-M., Kim D.-J., Kim
S.-L., Lee C.-U., Lee D.-J., Lee Y., Park B.-G., Pogge R.W.
<Astrophys. J., 903, L11 (2020)>
=2020ApJ...903L..11M 2020ApJ...903L..11M
ADC_Keywords: Gravitational lensing; Exoplanets; Optical
Keywords: Gravitational microlensing ; Gravitational microlensing exoplanet
detection ; Finite-source photometric effect ; Free floating
planets
Abstract:
Some low-mass planets are expected to be ejected from their parent
planetary systems during early stages of planetary system formation.
According to planet formation theories, such as the core accretion
theory, typical masses of ejected planets should be between 0.3 and
1.0M⊕. Although in practice such objects do not emit any light,
they may be detected using gravitational microlensing via their
light-bending gravity. Microlensing events due to terrestrial-mass
rogue planets are expected to have extremely small angular Einstein
radii (≲1µas) and extremely short timescales (≲0.1day). Here, we
present the discovery of the shortest-timescale microlensing event,
OGLE-2016-BLG-1928, identified to date (tE∼0.0288day=41.5min. Thanks
to the detection of finite-source effects in the light curve of the
event, we were able to measure the angular Einstein radius of the lens
θE=0.842±0.064µas, making the event the most extreme
short-timescale microlens discovered to date. Depending on its unknown
distance, the lens may be a Mars- to Earth-mass object, with the
former possibility favored by the Gaia proper motion measurement of
the source. The planet may be orbiting a star but we rule out the
presence of stellar companions up to the projected distance of ∼8.0au
from the planet. Our discovery demonstrates that terrestrial-mass
free-floating planets can be detected and characterized using
microlensing.
Description:
The event was found in data from the fourth phase of the Optical
Gravitational Lensing Experiment (OGLE) as part of the search for
wide-separation planetary systems but it has been observed by OGLE
since 1997.
Only OGLE and one of the stations of the Korea Microlensing Telescope
Network (KMTNet), located in Cerro Tololo Interamerican Observatory
(KMT CTIO), captured the magnified part of the light curve. We used
OGLE and KMT CTIO data in single-lens models. For binary-lens
modeling, we included additional data from the KMTNet telescope in the
Southern African Astronomical Observatory (KMT SAAO).
Objects:
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RA (2000) DE Designation(s)
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18 01 31.25 -29 07 46.2 OGLE-2016-BLG-1928 = EWS 2016-BLG-1928
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 33 17444 Light curve of OGLE-2016-BLG-1928
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/AcA/50/421 : OGLE-II DIA BUL_SC1 field (Wozniak, 2000)
J/A+A/533/A134 : Abundances of microlensed stars in the Bulge (Bensby+, 2011)
J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)
J/MNRAS/447/2714 : Flare stars across the H-R diagram (Balona+, 2015)
J/ApJS/232/26 : Catalog of Kepler flare stars (Van Doorsselaere+, 2017)
J/AJ/159/262 : OGLE/KMTnet VI bands photo. OGLE-2019-BLG-0551 (Mroz+, 2020)
Byte-to-byte description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 13 F13.5 d HJD [2455260/2458787] Heliocentric Julian Date
15- 20 F6.3 mag mag [16.8/17.2] Apparent magnitude
22- 26 F5.3 mag e_mag [0.01/0.1] Uncertainty in mag
28- 33 A6 --- Obs Observatory; KMTNet or OGLE
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 25-Feb-2022