J/ApJ/897/180 Multiband photometry of microlensing event Kojima-1 (Zang+, 2020)
Spitzer + VLTI-GRAVITY Measure the Lens Mass of a Nearby Microlensing Event.
Zang W., Dong S., Gould A., Calchi Novati S., Chen P., Yang H., Li S.-S.,
Mao S., Alton K.B., Brimacombe J., Carey S., Christie G.W.,
Delplancke-Strobele F., Feliz D.L., Gaudi B.S., Green J., Hu S.,
Jayasinghe T., Koff R.A., Kurtenkov A., Merand A., Minev M., Mutel R.,
Natusch T., Roth T., Shvartzvald Y., Sun F., Vanmunster T., Zhu W.
<Astrophys. J., 897, 180 (2020)>
=2020ApJ...897..180Z 2020ApJ...897..180Z
ADC_Keywords: Gravitational lensing; Photometry, UBVRIJKLMNH
Keywords: Gravitational microlensing ; Satellite microlensing parallax ;
Stellar masses ; Stellar distance
Abstract:
We report the lens mass and distance measurements of the nearby
microlensing event TCPJ05074264+2447555 (Kojima-1). We measure the
microlens parallax vector πE using Spitzer and ground-based light
curves with constraints on the direction of lens-source relative
proper motion derived from Very Large Telescope Interferometer (VLTI)
GRAVITY observations. Combining this πE determination with the
angular Einstein radius θE measured by VLTI-GRAVITY
observations, we find that the lens is a star with mass
ML=0.495±0.063M☉ at a distance DL=429±21pc. We find
that the blended light basically all comes from the lens. The
lens-source proper motion is µrel,hel=26.55±0.36mas/yr, so
with currently available adaptive-optics instruments, the lens and
source can be resolved in 2021. This is the first microlensing event
whose lens mass is unambiguously measured by
interferometry+satellite-parallax observations, which opens a new
window for mass measurements of isolated objects such as stellar-mass
black holes.
Description:
We use ground-based follow-up data to derive basic single-lens
parameters and constrain microlens parallax. To minimize the impact on
microlens parallax measurements from possible systematic errors, we
choose the ground-based data that were carefully selected and used by
Dong+, 2019ApJ...871...70D 2019ApJ...871...70D, including the data from All-Sky Automatic
Survey for Supernovae (ASAS-SN), 0.6m telescopes at Post Observatory
(RP), 0.5m Iowa Robotic Telescope (Iowa) at the Winer Observatory
(Arizona, USA), 0.4m telescope at Auckland Observatory (AO), and the
1.3m SMARTS telescope at Cerro Tololo Inter-American Observatory
(CTIO).
For Spitzer, observations start on 2017 December 19 (HJD'=8107.2,
HJD'=HJD-2450000). The observations ended on 2018 January 23
(HJD'=8143.7). In total, 21 data points were taken, all using the
3.6µm channel (L-band) of the IRAC camera.
Objects:
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RA (2000) DE Designation(s)
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05 07 42.72 +24 47 56.4 Kojima-1 = TCP J05074264+2447555
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 51 5482 The light curves and data points of Kojima-1
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See also:
I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/366 : ASAS-SN catalog of variable stars (Jayasinghe+, 2018-2020)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJ/814/92 : Spitzer IRAC events observed in crowded fields (Calchi+, 2015)
J/MNRAS/458/3012 : OGLE-III Parallax microlensing events (Wyrzykowski+, 2016)
J/AJ/154/210 : 2015 high-cadence Spitzer microlensing events (Zhu+, 2017)
J/ApJ/891/3 : Follow-up LCs of 2 Spitzer microlensing events (Zang+, 2020)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Obs Observatory identifier (1)
14- 22 A9 --- Band Passband
24- 37 F14.6 d JD [2457832/2458157] Julian Date (2)
39- 45 F7.3 mag mag [9.53/153] Observed magnitude in Band (3)
47- 51 F5.3 mag e_mag [0.002/0.3] Uncertainty in mag
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Note (1): Observatories as follows:
A0 = Auckland Observatory;
AT0 = Antelope Hill Observatory
CBABO = Center for Backyard Astronomy Belgium Observatory
CTIO = Cerro Tololo Inter-American Observatory
CTO-NM-43cm = Coral Towers Observatory; 43cm instrument
CTO-NM-51cm = Coral Towers Observatory; 51cm instrument
CTO-NM-Savannah = Coral Towers Observatory; Savannah instrument
DBO = Desert Bloom Observatory
IW = Iowa Robotic Telescope
PTF = Peking University 40cm Telescope
RP = Post Observatory
Rozhen-2m = Bulgarian National Astronomical Observatory; 2m instrument
Rozhen-50cm = Bulgarian National Astronomical Observatory; 50cm instrument
WH = Weihai Observatory of Shandong University
ASAS-SN = All-Sky Automatic Survey for Supernovae
Spitzer = Spitzer
Note (2): Note that the Spitzer dates are Heliocentric Julian Dates.
Note (3): The Spitzer data is in relative flux density units.
All passbands with "Rel" indicate a relative magnitude.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 30-Sep-2021