J/ApJS/249/16 Microlensing event in the OGLE-IV GVS survey (Mroz+, 2020)
Microlensing optical depth and event rate in the OGLE-IV Galactic plane fields.
Mroz P., Udalski A., Szymanski M.K., Soszynski I., Pietrukowicz P.,
Kozlowski S., Skowron J., Poleski R., Ulaczyk K., Gromadzki M., Rybicki K.,
Iwanek P., Wrona M.
<Astrophys. J. Suppl. Ser., 249, 16 (2020)>
=2020ApJS..249...16M 2020ApJS..249...16M
ADC_Keywords: Gravitational lensing; Galactic plane; Photometry; Optical
Keywords: Gravitational microlensing ; Microlensing optical depth ;
Microlensing event rate ; Milky Way disk ; Milky Way Galaxy
Abstract:
Searches for gravitational microlensing events are traditionally
concentrated on the central regions of the Galactic bulge but many
microlensing events are expected to occur in the Galactic plane, far
from the Galactic Center. Owing to the difficulty in conducting
high-cadence observations of the Galactic plane over its vast area,
which are necessary for the detection of microlensing events, their
global properties were hitherto unknown. Here, we present results of
the first comprehensive search for microlensing events in the Galactic
plane. We searched an area of almost 3000 square degrees along the
Galactic plane (|b|<7°, 0°<l<50°, 190°<l<360°)
observed by the Optical Gravitational Lensing Experiment (OGLE) during
2013-2019 and detected 630 events. We demonstrate that the mean
Einstein timescales of Galactic plane microlensing events are on
average three times longer than those of Galactic bulge events, with
little dependence on the Galactic longitude. We also measure the
microlensing optical depth and event rate as a function of Galactic
longitude and demonstrate that they exponentially decrease with the
angular distance from the Galactic Center (with the characteristic
angular scale length of 32°). The average optical depth decreases
from 0.5x10-6 at l=10° to 1.5x10-8 in the Galactic anticenter.
We also find that the optical depth in the longitude range
240°<l<330° is asymmetric about the Galactic equator, which we
interpret as a signature of the Galactic warp.
Description:
Here, we present results of the search for microlensing events in the
photometric data collected as part of the Optical Gravitational
Lensing Experiment (OGLE; Udalski+ 2015AcA....65....1U 2015AcA....65....1U) Galaxy
Variability Survey (GVS) during 2013-2019.
The OGLE GVS survey is conducted as part of the OGLE-IV project using
the 1.3m Warsaw telescope located at Las Campanas Observatory, Chile.
All analyzed data were taken in the I band, closely matching that of a
standard Cousins system.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 61 1982 Basic information about analyzed fields
tableb1.dat 272 460 Best-fitting parameters of the analyzed
microlensing events in the OGLE GVS fields
tableb2.dat 107 170 Possible microlensing events
tablec1.dat 69 63424 Surface density of stars in OGLE GVS fields
lcs/* . 630 Individual I-band light curves in ASCII format
of the analyzed and possible microlensing events
eff/* . 2 Detection efficiencies in individual fields
(ASCII format) for sources brighter
than I=21 and I=20
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See also:
II/278 : Transits observed in OGLE 2001-2003 (Udalski+, 2002-2004)
J/AcA/50/1 : OGLE microlensing events in Galactic Bulge (Udalski+, 2000)
J/AcA/50/421 : OGLE-II DIA BUL_SC1 field (Wozniak, 2000)
J/AcA/51/175 : OGLE-II DIA microlensing events (Wozniak+, 2001)
J/A+A/393/887 : SMC Be stars candidates (Mennickent+, 2002)
J/A+A/453/635 : Galactic Interstellar Extinction (Marshall+, 2006)
J/A+A/500/1027 : EROS CMD towards 4 Galactic spiral arms fields (Rahal+, 2009)
J/ApJ/711/L48 : 2008 OGLE Bulge microlensing alerts (Cohen+, 2010)
J/ApJ/778/150 : Microlensing events toward the Bulge from MOA-II (Sumi+, 2013)
J/ApJ/788/48 : X-ray through NIR photometry of NGC 2617 (Shappee+, 2014)
J/ApJS/216/12 : OGLE-III Gal. bulge microlensing events (Wyrzykowski+, 2015)
J/MNRAS/458/3012 : OGLE-III Parallax microlensing events (Wyrzykowski+, 2016)
J/AcA/68/315 : OGLE Galactic Cepheids (Udalski+, 2018)
J/ApJS/244/29 : Microlensing events toward the Galactic bulge (Mroz+, 2019)
J/other/Sci/365.478 : Milky Way classical Cepheids sample (Skowron+, 2019)
J/A+A/633/A98 : Gaia16aye microlensing event photometry (Wyrzykowski+, 2020)
J/A+A/636/A20 : OGLE-III parallax events with Gaia DR2 (Wyrzykowski+, 2020)
http://wis-tns.weizmann.ac.il/ : Transient name server
http://gsaweb.ast.cam.ac.uk/alerts : Gaia alerts
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 A6 --- Field Field name
8- 16 F9.5 deg RAdeg Right ascension in decimal degrees (J2000)
18- 26 F9.5 deg DEdeg Declination in decimal degrees (J2000)
28- 36 F9.5 deg GLON Galactic longitude
38- 46 F9.5 deg GLAT [-15.28/15.74] Galactic latitude
48- 51 F4.2 10+6 Ns [0.07/4.61] Number of stars in the database
53- 56 I4 --- Nep [34/1214] Number of epochs
58- 61 I4 d deltaT [127/3122] Duration of monitoring
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Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
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1- 16 A16 --- OGLE Star name (,
or
in Simbad)
18- 26 A9 --- sField OGLE-IV subfield name
28- 33 I6 --- Star [51/115188] Star ID in the OGLE-IV database
35- 36 I2 h RAh Hour of Right ascension (J2000)
38- 39 I2 min RAm Minute of Right ascension (J2000)
41- 45 F5.2 s RAs Second of Right ascension (J2000)
47 A1 --- DE- Sign of the Declination (J2000)
48- 49 I2 deg DEd Degree of Declination (J2000)
51- 52 I2 arcmin DEm Arcminute of Declination (J2000)
54- 57 F4.1 arcsec DEs Arcsecond of Declination (J2000)
59- 68 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
70- 79 F10.6 deg DEdeg Declination in decimal degrees (J2000)
81- 90 F10.6 deg GLON Galactic longitude
92-101 F10.6 deg GLAT [-11.51/14.91] Galactic latitude
103-113 F11.3 d t0 Best-fit HJD time of closest approach
115-121 F7.3 d tE [3.29/457.6] Best-fit Einstein radius
crossing timescale
123-127 F5.3 --- u0 [0/0.98] Best-fit separation at closest
approach
129-134 F6.3 mag Is [14.1/21] Best-fit source brightness
136-140 F5.3 --- fs [0.014/2.1] Best-fit blending parameter
142-152 F11.3 d t0Med Median HJD time of closest approach
154-160 F7.3 d e_t0 [0.005/23.3] Lower 1σ uncertainty in t0
162-167 F6.3 d E_t0 [0.005/29.7] Upper 1σ uncertainty in t0
169-175 F7.3 d tEMed [3.38/409.5] Median Einstein radius
crossing timescale
177-184 F8.3 d e_tE [0.06/121.1] Lower 1σ uncertainty in tE
186-192 F7.3 d E_tE [0.1/272.5] Upper 1σ uncertainty in tE
194-198 F5.3 --- u0Med [0.002/0.9] Median separation at
closest approach
200-205 F6.3 --- e_u0 [0.001/0.3] Lower 1σ uncertainty in u0
207-211 F5.3 --- E_u0 [0.001/0.41] Upper 1σ uncertainty in u0
213-218 F6.3 mag IsMed [14.4/21.1] Median source brightness
220-225 F6.3 mag e_Is [0.008/1.2] Lower 1σ uncertainty in Is
227-231 F5.3 mag E_Is [0.015/2.8] Upper 1σ uncertainty in Is
233-237 F5.3 --- fsMed [0.017/1.9] Median blending parameter
239-244 F6.3 --- e_fs [0.009/0.7] Lower 1σ uncertainty in fs
246-250 F5.3 --- E_fs [0.007/0.6] Upper 1σ uncertainty in fs
252-259 F8.3 --- weight [7.7/280.2] Inverse of the detection
efficiency
261-272 A12 --- OID Other identifier
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Byte-by-byte Description of file: tableb2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- OGLE Star name
18- 19 I2 h RAh Hour of Right ascension (J2000)
21- 22 I2 min RAm Minute of Right ascension (J2000)
24- 28 F5.2 s RAs Second of Right ascension (J2000)
30 A1 --- DE- Sign of the Declination (J2000)
31- 32 I2 deg DEd Degree of Declination (J2000)
34- 35 I2 arcmin DEm Arcminute of Declination (J2000)
37- 40 F4.1 arcsec DEs Arcsecond of Declination (J2000)
42- 51 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
53- 62 F10.6 deg DEdeg Declination in decimal degrees (J2000)
64- 73 F10.6 deg GLON [2.29/359.4] Galactic longitude
75- 84 F10.6 deg GLAT [-10.05/10.15] Galactic latitude
86-107 A22 --- Remarks Remarks
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Byte-by-byte Description of file: tablec1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- sField Subfield name
11- 17 F7.3 deg RAdeg [85/289.2] Right ascension (J2000)
19- 25 F7.3 deg DEdeg [-70.1/23.6] Declination (J2000)
27- 34 F8.3 deg GLON [-171.5/56.6] Galactic longitude
36- 42 F7.3 deg GLAT [-15.91/16.4] Galactic latitude
44- 48 F5.1 arcmin-2 sigma20 [2.7/798.6] Surface density of sources
brighter than I=20
50- 55 F6.1 arcmin-2 sigma21 [7.8/1549] Surface density of sources
brighter than I=21
57- 62 I6 --- N20 [426/133348] Number of sources brighter
than I=20
64- 69 I6 --- N21 [1245/258646] Number of sources brighter
than I=21
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Byte-by-byte Description of file: lcs/*
--------------------------------------------------------------------------------
Bytes Format Units Label Description
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1- 13 F13.5 d HJD Heliocentric Julian Date
15- 20 F6.3 mag Imag [9.3/22.51] Cousins I-band magnitude (1)
22- 26 F5.3 mag e_Imag [0.004/2.31] Magnitude error (2)
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Note (1): The I-band photometry is calibrated to the standard system.
Note (2): The uncertainties were corrected using the Skowron+ (2016)'s
method.
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Byte-by-byte Description of file: eff/*
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Bytes Format Units Label Description
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1- 5 F5.3 [d] logtE_min Minimal log(t_E)
7- 11 F5.3 [d] logtE_max Maximal log(t_E)
13- 20 F8.6 --- Eff Detection efficiency
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History:
From electronic version of the journal for tables.
Photometry data and efficiencies downloaded from:
http://www.astrouw.edu.pl/ogle/ogle4/galactic_disk_microlensing/
(data.tar.gz, data_c.tar.gz and eff21.tar.gz, eff20.tar.gz files)
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Sep-2020