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FIRST SPECTROSCOPIC INVESTIGATION OF A MICROLENSING EVENT: NO EVIDENCE FOR THE BINARYI. BOISSE (LAM), A. SANTERNE (IA), J.-P. BEAULIEU (IAP), B. ROYA-AYALA (IA),C. RANC, N.C. SANTOS, V. BATISTA, D. BENNETT, E. SCHLAWIN, J.B. MARQUETTE, S. SOUSA, R. DIAZ, J.-M. ALMENARA, D. JAMES, T. HERTER
Introduction
V
J
E
U
S
N
30 cm/s
3 m/s
1 m/s
RV
Imaging
Transit
!-lensing
from exoplanet.eu and exoplanet.orgJune 2014
OGLE-2011-BLG-0417
Shin et al. 2012Binary system
OGLE-2011-BLG-0417Characteristics
Lens Source
K3 red giant8 kpc
binary M dwarfs0.95 kpcI = 16.3
I = 16.74V = 18.23 V = 19.42
OGLE-2011-BLG-0417Characteristics
Lens Source
K3 red giant8 kpc
binary M dwarfs0.95 kpcI = 16.3
I = 16.74V = 18.23 V = 19.42
OGLE-2011-BLG-0417Gould et al. 2013Predicted RV curve
OGLE-2011-BLG-0417Gould et al. 2013Predicted RV curve
Several km/s
OGLE-2011-BLG-0417Gould et al. 2013Predicted RV curve
Several km/s
P = 1.42 yr
OGLE-2011-BLG-0417Gould et al. 2013Predicted RV curve
Several km/s
P = 1.42 yr
Phase is lost
ObservationsUVES @ VLT, ESO
ObservationsUVES @ VLT, ESO
Crowded field
ObservationsUVES @ VLT, ESO
Crowded field
10 spectra of ~1h
SNR ~ 20 (550nm)
ObservationsUVES @ VLT, ESO
Crowded field
10 spectra of ~1h
SNR ~ 20 (550nm)
1” slit: R~40 000
ObservationsUVES @ VLT, ESO
Crowded field
10 spectra of ~1h
SNR ~ 20 (550nm)
1” slit: R~40 000
Th-Ar calib before and after exposures
Data reductionReduced with Reflex (ESO)
Data reductionCCF with K5 maskReduced with Reflex (ESO)
�80 �60 �40 �20 0 20 40 60 80Radial velocity [km.s�1]
0.75
0.80
0.85
0.90
0.95
1.00
1.05
CC
Fco
ntra
st
source lens
3300 – 4500 A
4800 – 5800 A
5800 – 6800 A
Data reductionCCF with K5 maskReduced with Reflex (ESO)
�80 �60 �40 �20 0 20 40 60 80Radial velocity [km.s�1]
0.75
0.80
0.85
0.90
0.95
1.00
1.05
CC
Fco
ntra
st
source lens
3300 – 4500 A
4800 – 5800 A
5800 – 6800 A
Data reductionCCF with K5 mask
(V-I) = 1.93 ; (V-I) = 2.68sourcelens
Reduced with Reflex (ESO)
�80 �60 �40 �20 0 20 40 60 80Radial velocity [km.s�1]
0.75
0.80
0.85
0.90
0.95
1.00
1.05
CC
Fco
ntra
st
source lens
3300 – 4500 A
4800 – 5800 A
5800 – 6800 A
Data reductionCCF with K5 mask
(V-I) = 1.93 ; (V-I) = 2.68sourcelens
Reduced with Reflex (ESO)
Bluer lens
�80 �60 �40 �20 0 20 40 60 80Radial velocity [km.s�1]
0.75
0.80
0.85
0.90
0.95
1.00
1.05
CC
Fco
ntra
st
source lens
3300 – 4500 A
4800 – 5800 A
5800 – 6800 A
Data reductionCCF with K5 mask
(V-I) = 1.93 ; (V-I) = 2.68sourcelens
Reduced with Reflex (ESO)
Bluer lens
lens source
Data reductionCorrected from BERV
Data reductionCorrected from BERV
Corrected from spectrograph drift (15 to 400 m/s in 1 h)
Data reductionCorrected from BERV
Corrected from spectrograph drift (15 to 400 m/s in 1 h)
But Variation of the illumination of the slit
Data reductionCorrected from BERV
Corrected from spectrograph drift (15 to 400 m/s in 1 h)
But Variation of the illumination of the slit
Corrected from RV telluric reference (O2 lines)
Data reduction
6550 6600 6650 6700 6750 6800 6850 6900 6950Time [BJD - 2 450 000]
�0.6
�0.4
�0.2
0.0
0.2
0.4
0.6
0.8
Rel
ativ
eR
V[k
m.s
�1]
lenssource
Data reduction
6550 6600 6650 6700 6750 6800 6850 6900 6950Time [BJD - 2 450 000]
�0.6
�0.4
�0.2
0.0
0.2
0.4
0.6
0.8
Rel
ativ
eR
V[k
m.s
�1]
lenssource
Stars RV share same systematics !
Data reduction
6550 6600 6650 6700 6750 6800 6850 6900 6950Time [BJD - 2 450 000]
�0.6
�0.4
�0.2
0.0
0.2
0.4
0.6
0.8
Rel
ativ
eR
V[k
m.s
�1]
lenssource
Stars RV share same systematics !
Used RV source as a reference for RV lens
Results
RMS = 94 m/s
6500 6600 6700 6800 6900 7000Time [BJD - 2 450 000]
40
42
44
46
48
50
52
54
Diff
eren
tialR
V(R
Vle
ns
-RV
sourc
e)[k
m.s
�1]
OGLE-2011-BLG-0417
predictedbest modelobserved
6500 6600 6700 6800 6900 7000
42.2
42.4
42.6
42.8
43.0
Results
RMS = 94 m/s
6500 6600 6700 6800 6900 7000Time [BJD - 2 450 000]
40
42
44
46
48
50
52
54
Diff
eren
tialR
V(R
Vle
ns
-RV
sourc
e)[k
m.s
�1]
OGLE-2011-BLG-0417
predictedbest modelobserved
6500 6600 6700 6800 6900 7000
42.2
42.4
42.6
42.8
43.0
Results
RMS = 94 m/s PASTIS validation tool
Diaz et al. 2014
6500 6600 6700 6800 6900 7000Time [BJD - 2 450 000]
40
42
44
46
48
50
52
54
Diff
eren
tialR
V(R
Vle
ns
-RV
sourc
e)[k
m.s
�1]
OGLE-2011-BLG-0417
predictedbest modelobserved
6500 6600 6700 6800 6900 7000
42.2
42.4
42.6
42.8
43.0
Results
RMS = 94 m/s PASTIS validation tool
Diaz et al. 2014Probability < 2 10 -7
Conclusion
Spectroscopic follow-up observations of microlensing event is possible
We don’t confirm the Gould et al. prediction
Boisse et al. 2015
Conclusion
Spectroscopic follow-up observations of microlensing event is possible
We don’t confirm the Gould et al. prediction
Boisse et al. 2015
Yee et al. 2015Recently same method on a different target
Conclusion
Bright component is most probably not the light from the lens
Spectroscopic follow-up observations of microlensing event is possible
We don’t confirm the Gould et al. prediction
Boisse et al. 2015
Yee et al. 2015Recently same method on a different target
Conclusion
Bright component is most probably not the light from the lens
Spectroscopic follow-up observations of microlensing event is possible
The lens is not detectable
We don’t confirm the Gould et al. prediction
Boisse et al. 2015
Yee et al. 2015Recently same method on a different target
Conclusion
Bright component is most probably not the light from the lens
Spectroscopic follow-up observations of microlensing event is possible
The lens is not detectable
We don’t confirm the Gould et al. prediction
High angular resolution observations planned
Boisse et al. 2015
Yee et al. 2015Recently same method on a different target
Keck AO imaging
No blend within 130mas
Probability to have another star within 130mas ~ 50ppm
Santerne et al. (submitted)
Spectral Energy Distribution
0.3 0.4 0.5 0.6 0.7 0.8 1.0 1.3 1.5 1.8 2.0 2.5Wavelength [µm]
10�18
10�17
10�16
10�15
Cal
ibra
ted
flux
[erg
.s�
1.c
m�
2.A
�1]
J H K
Santerne et al. (submitted)
Spectral Energy Distribution
0.3 0.4 0.5 0.6 0.7 0.8 1.0 1.3 1.5 1.8 2.0 2.5Wavelength [µm]
10�18
10�17
10�16
10�15
Cal
ibra
ted
flux
[erg
.s�
1.c
m�
2.A
�1]
Keck AO
J H K
Santerne et al. (submitted)
Spectral Energy Distribution
0.3 0.4 0.5 0.6 0.7 0.8 1.0 1.3 1.5 1.8 2.0 2.5Wavelength [µm]
10�18
10�17
10�16
10�15
Cal
ibra
ted
flux
[erg
.s�
1.c
m�
2.A
�1]
ARCoIRIS @ CTIO
Keck AO
J H K
Santerne et al. (submitted)
Spectral Energy Distribution
0.3 0.4 0.5 0.6 0.7 0.8 1.0 1.3 1.5 1.8 2.0 2.5Wavelength [µm]
10�18
10�17
10�16
10�15
Cal
ibra
ted
flux
[erg
.s�
1.c
m�
2.A
�1]
UVES @ VLT
ARCoIRIS @ CTIO
Keck AO
J H K
Santerne et al. (submitted)
SED analysisA simple model
Foreground star Source
Díaz et al. (2014) Santerne et al. (2015)
Interstellar extinction from Arôme & Lépine (2005)
Assumed K giant in the Bulge
Fitted extinction
Stellar tracks: Dartmouth (Dotter et al. 2008)
Stellar Atmosphere Models: BT-SETTL (Allard et al. 2012) Sa
nter
ne e
t al.
(subm
itted
)
Results
10�18
10�17
10�16
10�15
Cal
ibra
ted
flux
[erg
.s�
1.c
m�
2.A
�1]
Best model Foreground star Source
0.3 0.4 0.5 0.6 0.7 0.8 1.0 1.3 1.5 1.8 2.0 2.5Wavelength [µm]
�0.30.00.3
O-C
[mag
]
Santerne et al. (submitted)
Source giant
Foreground star 0.95 Msun 1.1kpc
The foreground star
0.4 0.5 0.6 0.7 0.8 1.0 2.0 3.0Lens distance [kpc]
0.4
0.6
0.8
1.0
1.2
1.4
Lens
mas
s[M
�]
Value of Gould et al. (2013)SED constraints
Lens total mass assuming ΘE = 2.44mas (Shin et al., 2012)
and Ds = 8.2 kpc
Santerne et al. (submitted)
Sanity checks (I)
10�18
10�17
10�16
10�15
Cal
ibra
ted
flux
[erg
.s�
1.c
m�
2.A
�1]
Best model Foreground star Source
0.3 0.4 0.5 0.6 0.7 0.8 1.0 1.3 1.5 1.8 2.0 2.5Wavelength [µm]
�0.30.00.3
O-C
[mag
]
I-band magnitude observed by OGLE
Santerne et al. (submitted)
Sanity checks (II)
6550 6555 6560 6565 6570 6575
Wavelength [A]
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Nor
mal
ised
flux
OGLE-417GJ825 (M0V)HD147513 (G5V)
5150 5160 5170 5180 5190 5200
Wavelength [A]
0.0
0.5
1.0
1.5N
orm
alis
edflu
x
H alpha
Mg triplet
HR spectrum of OGLE-417 is closer
from a G dwarf than a M dwarf
Lot of contamination from the source star
Source star
Santerne et al. (submitted)
ConclusionsRV observations rule out massive companion to the lens (Boisse, Santerne, Beaulieu et al., 2015)
SED analysis shows the lens primary is a G dwarf and not a M dwarf (Santerne, Beaulieu, Rojas Ayala et al., subm.)
ConclusionsRV observations rule out massive companion to the lens (Boisse, Santerne, Beaulieu et al., 2015)
SED analysis shows the lens primary is a G dwarf and not a M dwarf (Santerne, Beaulieu, Rojas Ayala et al., subm.)
SED characterisation of microlensing event is possible
ConclusionsRV observations rule out massive companion to the lens (Boisse, Santerne, Beaulieu et al., 2015)
SED analysis shows the lens primary is a G dwarf and not a M dwarf (Santerne, Beaulieu, Rojas Ayala et al., subm.)
The Astrophysical Journal, 755:91 (10pp), 2012 August 20 Shin et al.
Figure 2. Light curve of OGLE-2011-BLG-0417. Notations are same as in Figure 1.(A color version of this figure is available in the online journal.)
for thorough investigation of possible degeneracy of solutions.We choose of s⊥, q, and α as the grid parameters because they arerelated to the light curve features in a complex way such that asmall change in the values of the parameters can lead to dramaticchanges in the resulting light curve. On the other hand, the otherparameters are more directly related to the light curve featuresand thus they are searched for by using a downhill approach.For the χ2 minimization in the downhill approach, we use theMarkov Chain Monte Carlo (MCMC) method. Once a solutionof the parameters is found, we estimate the uncertainties of theindividual parameters based on the chain of solutions obtainedfrom MCMC runs.
To compute lensing magnifications affected by the finite-source effect, we use the ray-shooting method (Schneider &Weiss 1986; Kayser et al. 1986; Wambsganss 1997). In thismethod, rays are uniformly shot from the image plane, bentaccording to the lens equation, and land on the source plane.Then, a finite magnification is computed by comparing thenumber densities of rays on the image and source planes.Precise computation of finite magnifications by using thisnumerical technique requires a large number of rays and thusdemands heavy computation. To minimize computation, welimit finite-magnification computation by using the ray-shootingmethod only when the lens is very close to caustics. In theadjacent region, we use an analytic hexadecapole approximation(Pejcha & Heyrovsky 2009; Gould 2008). In the region withlarge enough distances from caustics, we use point-sourcemagnifications.
Table 2Limb-darkening Coefficients
Quantity MOA-2011-BLG-090 OGLE-2011-BLG-0417
ΓV 0.52 0.71ΓR 0.45 0.61ΓI 0.37 0.51Source type FV KIIITeff (K) 6650 4660vturb (km s−1) 2 2log g (cm s−2) 4.5 2.5
In the finite magnification computation, we consider thevariation of the magnification caused by the limb darkeningof the source star’s surface. We model the surface brightnessprofile of a source star as
Sλ = Fλ
πθ⋆2
!1 − Γλ
"1 − 3
2cos ψ
#$, (7)
where Γλ is the linear limb-darkening coefficients, Fλ is thesource star flux, and ψ is the angle between the normal to thesource star’s surface and the line of sight toward the star.The limb-darkening coefficients are set based on the source typethat is determined on the basis of the color and magnitude of thesource. In Table 2, we present the limb-darkening coefficientsused, the corresponding source types, and the measured de-reddened color along with the assumed values of the effective
6
Shin
et al
. (20
12)
An exceptionally long event (> 6months)
Strong degeneracies between Earth orbit, Lens & Source motions (+orbital motion)
Is there a planet after all ?
SED characterisation of microlensing event is possible