J/AJ/166/107 6111 micro-lensing events with MOA (Koshimoto+, 2023)
Terrestrial- and Neptune-mass Free-Floating Planet Candidates from the MOA-II
9yr Galactic Bulge Survey.
Koshimoto N., Sumi T., Bennett D.P., Bozza V., Mroz P., Udalski A.,
Rattenbury N.J., Abe F., Barry R., Bhattacharya A., Bond I.A., Fujii H.,
Fukui A., Hamada R., Hirao Y., Silva S.I., Itow Y., Kirikawa R., Kondo I.,
Matsubara Y., Miyazaki S., Muraki Y., Olmschenk G., Ranc C., Satoh Y.,
Suzuki D., Tomoyoshi M., Tristram P.J., Vandorou A., Yama H.,
Yamashita K., MOA Collaboration
<Astron. J., 166, 107 (2023)>
=2023AJ....166..107K 2023AJ....166..107K
ADC_Keywords: Gravitational lensing ; Exoplanets ; Photometry, RI
Keywords: Gravitational microlensing exoplanet detection ; Free floating
planets ; Exoplanets
Abstract:
We report the discoveries of low-mass free-floating planet (FFP)
candidates from the analysis of 2006-2014 MOA-II Galactic bulge survey
data. In this data set, we found 6111 microlensing candidates and
identified a statistical sample consisting of 3535 high-quality
single-lens events with Einstein radius crossing times in the range
0.057<tE/days<757, including 13 events that show clear finite-source
effects with angular Einstein radii of 0.90<θE/µas<332.54.
Two of the 12 events with tE<1day have significant finite-source
effects, and one event, MOA-9y-5919, with tE=0.057±0.016days and
θE=0.90±0.14µas, is the second terrestrial-mass FFP
candidate to date. A Bayesian analysis indicates a lens mass of
0.75-0.46+1.23M⊕ for this event. The low detection
efficiency for short-duration events implies a large population of
low-mass FFPs. The microlensing detection efficiency for low-mass
planet events depends on both the Einstein radius crossing times and
the angular Einstein radii, so we have used image-level simulations to
determine the detection efficiency dependence on both tE and θE.
This allows us to use a Galactic model to simulate the tE and θE
distribution of events produced by the known stellar populations and
models of the FFP distribution that are fit to the data. Methods like
this will be needed for the more precise FFP demographics
determinations from Nancy Grace Roman Space Telescope data.
Description:
The data used in this analysis were taken during the 2006-2014 seasons
of the MOA-II high-cadence photometric survey toward the Galactic
bulge. MOA-II uses the 1.8m MOA-II telescope located at the University
of Canterbury's Mount John Observatory in New Zealand. The telescope
is equipped with a wide-field camera, MOA-cam3, which consists of 10
2kx4k pixel CCDs with 15um pixels. With the pixel scale of
0.58"/pixel, this gives a 2.18deg2 field of view (FOV).
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 101 6111 All 6111 visually-identified microlensing events
timescale event candidates of tE<1 day
table6.dat 118 6111 Parameters for 6111 visually-identified
microlensing events
--------------------------------------------------------------------------------
See also:
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/A+A/549/A147 : Abundances microlensed bulge dwarf stars. V. (Bensby+, 2013)
J/ApJ/778/150 : Microlensing events toward the Bulge from MOA-II (Sumi+, 2013)
J/AJ/154/210 : 2015 high-cadence Spitzer microlensing events (Zhu+, 2017)
J/AJ/160/74 : Optical and IR photometry of OGLE-2017-BLG-0406 (Hirao+, 2020)
J/AJ/160/148 : RI-band LC of microlens OGLE-2018-BLG-1269Lb (Jung+, 2020)
J/ApJ/903/L11 : OGLE and KMTNet light curve OGLE-2016-BLG-1928 (Mroz+, 2020)
J/AJ/159/262 : OGLE/KMTnet VI bands photom OGLE-2019-BLG-0551 (Mroz+, 2020)
J/AJ/161/126 : I-band LC of the microlensevent KMT-2017-BLG-2820 (Ryu+, 2021)
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- ID MOA-9y-NNNN sequential identifier (1)
13- 28 A16 --- IID Internal ID, field-chip-subfield-ID
30- 31 I2 h RAh [17/18] Hour of Right Ascension (J2000)
33- 34 I2 min RAm Minute of Right Ascension (J2000)
36- 41 F6.3 s RAs Second of Right Ascension (J2000)
43- 43 A1 --- DE- Sign of the Declination (J2000)
44- 45 I2 deg DEd Degree of Declination (J2000)
47- 48 I2 arcmin DEm Arcminute of Declination (J2000)
50- 54 F5.2 arcsec DEs Arcsecond of Declination (J2000)
56- 67 A12 --- Alert1 Alerted ID
69- 80 A12 --- Alert2 Second Alerted ID
82- 86 F5.2 mag Icmag [13.6/21]? Catalog star's Ic band magnitude
88- 91 F4.2 mag e_Icmag [0.01/3]? Uncertainty in Icmag
93- 97 I5 --- Ndata [317/31548] Ndata (2)
99-101 A3 --- criteria Event Selection Criteria (3)
--------------------------------------------------------------------------------
Note (1): This table includes all of the short sources in Table 3, FSPL
candidates in Table 5, and all remaining events visually identified
according to the criteria in Section 4.1.
Note (2): Note that Ndata is only for MOA-9yr light curve points. The
number of data points listed in Table 5 for MOA-9y-1944 includes
4632 OGLE data points. Those points are not listed here.
Note (3): Event Selection Criteria as defined in Table 2, "CR1" and "CR2".
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- ID MOA-9y-NNNN sequential identifier (1)
13- 22 F10.4 d t0 [-3637/17229] Time of maximum magnification,
Heliocentric Julian Date, HJD-2450000.0
24- 32 F9.4 d e_t0 [0/1029] Uncertainty in t0
34- 45 F12.3 d tE [0.004/64937738] Einstein radius crossing time
47- 58 F12.3 d e_tE [0/71440870] Uncertainty in tE
60- 68 F9.6 --- u0 [0/28.1] minimum impact parameter
70- 78 F9.6 --- e_u0 [0/47.1] Uncertainty in u0
80- 87 F8.5 --- rho [0/10] angular size of the source
89- 96 F8.5 --- e_rho [0/61.2] Uncertainty in rho
98-102 F5.2 mag Ismag [4.63/36.4] Apparent I-band source magnitude
104-110 I7 --- chi2 [79/1363652] χ2
112-118 F7.1 --- dchi2 [-1514/76442] χ2-χ2FS
--------------------------------------------------------------------------------
Note (1): This table includes best-fit parameters for all events
visually identified according to the criteria in Section 4.1.
FSPL fit parameters for short period sources (those listed in
Table 3) have been refined from those given in this table. The
refined values are available in Table 4. Values for the refined
fits by MCMC described in Section 5.2 for objects MOA-9y-770 and
MOA-9y-5919 are given in this table. Values for MOA-9y-1944,
derived from fitting the OGLE and MOA light curves, are given in
this table.
--------------------------------------------------------------------------------
History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 15-Apr-2024