J/ApJ/891/3 Follow-up LCs of 2 Spitzer microlensing events (Zang+, 2020)
Spitzer microlensing parallax reveals two isolated stars in the Galactic bulge.
Zang W., Shvartzvald Y., Wang T., Udalski A., Lee C.-U., Sumi T.,
Skottfelt J., Li S.-S., Mao S., Zhu W., Yee J.C., Calchi Novati S.,
Beichman C.A., Bryden G., Carey S., Gaudi B.S., Henderson C.B., Mroz P.,
Skowron J., Poleski R., Szymanski M.K., Soszynski I., Pietrukowicz P.,
Kozlowski S., Ulaczyk K., Rybicki K.A., Iwanek P., Bachelet E.,
Christie G., Green J., Hennerley S., Maoz D., Natusch T., Pogge R.W.,
Street R.A., Tsapras Y., Albrow M.D., Chung S.-J., Gould A., Han C.,
Hwang K.-H., Jung Y.K., Ryu Y.-H., Shin I.-G., Cha S.-M., Kim D.-J.,
Kim H.-W., Kim S.-L., Lee D.-J., Lee Y., Park B.-G., Bond I.A., Abe F.,
Barry R., Bennett D.P., Bhattacharya A., Donachie M., Fukui A., Hirao Y.,
Itow Y., Kondo I., Koshimoto N., Alex Li M.C., Matsubara Y., Muraki Y.,
Miyazaki S., Nagakane M., Ranc C., Rattenbury N.J., Suematsu H.,
Sullivan D.J., Suzuki D., Tristram P.J., Yonehara A., Dominik M.,
Hundertmark M., Jorgensen U.G., Rahvar S., Sajadian S., Snodgrass C.,
Bozza V., Burgdorf M.J., Evans D.F., Jaimes R.F., Fujii Y.I., Mancini L.,
Longa-Pena P., Helling C., Peixinho N., Rabus M., Southworth J.,
Unda-Sanzana E., von Essen C.
<Astrophys. J., 891, 3 (2020)>
=2020ApJ...891....3Z 2020ApJ...891....3Z
ADC_Keywords: Gravitational lensing; Photometry, infrared; Photometry, RI
Keywords: Gravitational microlensing ; Satellite microlensing parallax ;
Stellar masses ; Stellar distance
Abstract:
We report the mass and distance measurements of two single-lens events
from the 2017 Spitzer microlensing campaign. The ground-based
observations yield the detection of finite-source effects, and the
microlens parallaxes are derived from the joint analysis of
ground-based observations and Spitzer observations. We find that the
lens of OGLE-2017-BLG-1254 is a 0.60±0.03M☉ star with
DLS=0.53±0.11kpc, where DLS is the distance between the lens and the
source. The second event, OGLE-2017-BLG-1161, is subject to the known
satellite parallax degeneracy, and thus is either a
0.51-0.10+0.12M☉ star with DLS=0.40±0.12kpc or a
0.38-0.12+0.13M_☉ star with DLS=0.53±0.19kpc. Both of the
lenses are therefore isolated stars in the Galactic bulge. By
comparing the mass and distance distributions of the eight published
Spitzer finite- source events with the expectations from a Galactic
model, we find that the Spitzer sample is in agreement with the
probability of finite-source effects occurring in single-lens events.
Description:
Figures 1 and 2 show the ground-based and Spitzer data together with
the best-fit models for OGLE-2017-BLG-1161 and OGLE-2017-BLG-1254,
respectively. The observations of OGLE-2017-BLG-1161 and
OGLE-2017-BLG-1254 both consist of Spitzer, ground-based survey, and
ground-based follow-up observations.
OGLE-2017-BLG-1161 was discovered by the OGLE collaboration on 2017
June 20. The I/H-band observations from the 1.3m SMARTS telescope at
CTIO (CT13) intensively covered the falling side of the peak.
OGLE-2017-BLG-1161 was also densely observed by the Las Cumbres
Observatory (LCO) network, the 0.4m telescope at Auckland Observatory
(AO), and the 0.36m telescope at Kumeu Observatory (Kumeu). The
Spitzer observations began on 2017 June 30 and ended on 2017 July 13
with 16 data points in total. See Section 2.1.
OGLE-2017-BLG-1254 was first alerted by the OGLE collaboration on 2017
July 2. The KMTNet group observed this event in its two slightly
offset fields BLG02 and BLG42, with combined cadence of Γ=4hr-1.
The LCO, µFUN, and MiNDSTEp follow-up teams also observed this event.
The H-band observations taken by CT13 were important for
characterizing the source star. The Spitzer observations began on 2017
July 7 and ended on 2017 August 3 with a cadence of ∼1 observation per
day. See Section 2.2.
Objects:
--------------------------------------------------------------------
RA (ICRS) DE Designation(s)
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17 41 12.65 -26 44 28.1 OGLE-2017-BLG-1161 = EWS 2017-BLG-1161
17 57 23.56 -27 13 13.3 OGLE-2017-BLG-1254 = EWS 2017-BLG-1254
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 35 1170 The light curves of event OGLE-2017-BLG-1161
fig2.dat 50 19870 The light curves of event OGLE-2017-BLG-1254
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See also:
II/337 : VISTA Variables in the Via Lactea Survey DR1 (Saito+, 2012)
J/AJ/119/1448 : Improved properties for cool stars (Houdashelt+, 2000)
J/AcA/50/421 : OGLE-II DIA BUL_SC1 field (Wozniak, 2000)
J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)
J/ApJ/814/92 : Spitzer IRAC events 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)
Byte-by-byte Description of file: fig1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1 I1 --- Obs [1/9] Observation code (1)
3- 13 F11.6 d HJD [5288.86/8248.71] Heliocentric Julian Date;
HJD-2450000
15- 22 F8.4 --- Flux [12.65/179.24] Observed flux
24- 31 F8.6 --- e_Flux [0.0027/0.32] Uncertainty in Flux
33- 35 A3 --- x_Flux Flux units (2)
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Note (1): Observation code as follows:
1 = OGLE I band (635 occurrences)
2 = The 0.4m telescope at Auckland Observatory (AO) number 12
Wratten filter (to R band); 90 occurrences
3 = The 0.36m telescope at Kumeu Observatory in Auckland (58 occurrences)
4 = CT13 I band (50 occurrences)
5 = CT13 H band (292 occurrences)
6 = LCO_SSO SDSS-i' band (9 occurrences)
7 = LCO_CTIO SDSS-i' band (6 occurrences)
8 = LCO_SAAO SDSS-i' band (14 occurrences)
9 = Spitzer/IRAC 3.6um band (16 occurrences)
Note (2): All flux units are in magnitudes except for the Spitzer data which
is the relative flux.
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Byte-by-byte Description of file: fig2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- Obs [1/14] Observation code (1)
4- 17 F14.9 d HJD [5288.85/8058.89] Heliocentric Julian Date;
HJD-2450000 (2)
19- 32 F14.6 --- Flux [-110767/179941.4] Observed flux
34- 46 F13.9 --- e_Flux [0.0013/999.4] Uncertainty in Flux
48- 50 A3 --- x_Flux Flux units (3)
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Note (1): Observation code as follows:
1 = OGLE I band (567 occurrences);
2 = MOA-Red filter (similar to the sum of the standard
Cousins R- and I-band filters); 7695 occurrences
3 = KMTA02 I band (1722 occurrences)
4 = KMTA42 I band (1810 occurrences)
5 = KMTC02 I band (1585 occurrences)
6 = KMTC42 I band (1580 occurrences)
7 = KMTS02 I band (2222 occurrences)
8 = KMTS42 I band (2245 occurrences)
9 = Danish 1.54m telescope sited at ESO's La Silla observatory in Chile,
non-standard filter (77 occurrences)
10 = CT13 I band (27 occurrences)
11 = CT13 H band (159 occurrences)
12 = LCO_SSO SDSS-i' band (93 occurrences)
13 = LCO_SAAO SDSS-i' band (64 occurrences)
14 = Spitzer/IRAC 3.6um band (24 occurrences)
Note (2): Note that the MOA dates are JD and not HJD.
Note (3): All flux units are in magnitudes except for the MOA, LCO and
Spitzer data which are relative fluxes.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 04-Aug-2021