OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens

A. Cassan; J. -P. Beaulieu; P. Fouque; S. Brillant; M. Dominik; J. Greenhill; D. Heyrovsky; K. Horne; U. G. Jorgensen; D. Kubas; H. C. Stempels; C. Vinter; M. D. Albrow; D. Bennett; J. A. R. Caldwell; J. J. Calitz; K. Cook; C. Coutures; D. Dominis; J. Donatowicz; K. Hill; M. Hoffman; S. Kane; J. -B. Marquette; R. Martin; P. Meintjes; J. Menzies; V. R. Miller; K. R. Pollard; K. C. Sahu; J. Wambsganss; A. Williams; A. Udalski; M. K. Szymanski; M. Kubiak; G. Pietrzynski; I. Soszynski; K. Zebrun; O. Szewczyk; L. Wyrzykowski

doi:10.1051/0004-6361:20054414

OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens

A. Cassan, J. -P. Beaulieu, P. Fouque, S. Brillant, M. Dominik, J. Greenhill, D. Heyrovsky, K. Horne, U. G. Jorgensen, D. Kubas, H. C. Stempels, C. Vinter, M. D. Albrow, D. Bennett, J. A. R. Caldwell, J. J. Calitz, K. Cook, C. Coutures, D. Dominis, J. DonatowiczK. Hill, M. Hoffman, S. Kane, J. -B. Marquette, R. Martin, P. Meintjes, J. Menzies, V. R. Miller, K. R. Pollard, K. C. Sahu, J. Wambsganss, A. Williams, A. Udalski, M. K. Szymanski, M. Kubiak, G. Pietrzynski, I. Soszynski, K. Zebrun, O. Szewczyk, L. Wyrzykowski

School of Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

Abstract

Aims. We present an analysis of OGLE 2004-BLG-254, a high-magnification (A(o) similar or equal to 60) and relatively short duration (t(E) similar or equal to 13.2 days) microlensing event in which the source star, a Bulge K-giant, has been spatially resolved by a point-like lens. We seek to determine the lens and source distance, and provide a measurement of the linear limb-darkening coefficients of the source star in the I and R bands. We discuss the derived values of the latter and compare them to the classical theoretical laws, and furthermore examine the cases of already published microlensed GK-giants limb-darkening measurements.

Methods. We have obtained dense photometric coverage of the event light curve with OGLE and PLANET telescopes, as well as a high signal-to-noise ratio spectrum taken while the source was still magnified by A similar to 20, using the UVES/VLT spectrograph. We have performed a modelling of the light curve, including finite source and parallax effects, and have combined spectroscopic and photometric analysis to infer the source distance. A Galactic model for the mass and velocity distribution of the stars has been used to estimate the lens distance.

Results. From the spectrum analysis and calibrated color-magnitude of the event target, we found that the source was a K3 III Bulge giant, situated at the far end of the Bulge. From modelling the light curve, we have derived an angular size of the Einstein ring theta(E) similar or equal to 114 mu as, and a relative lens-source proper motion mu = theta(E)/t(E) similar or equal to 3.1 mas/yr. We could also measure the angular size of the source, theta(*) similar or equal to 4.5 mu as, whereas given the short duration of the event, no significant constraint could be obtained from parallax effects. A Galactic model based on the modelling of the light curve then provides us with an estimate of the lens distance, mass and velocity as D-L similar or equal to 9.6 kpc, M similar or equal to 0.11 M-circle dot and v similar or equal to 145 km s(-1) (at the lens distance) respectively. Our dense coverage of this event allows us to measure limb darkening of the source star in the I and R bands. We also compare previous measurements of linear limb-darkening coefficients involving GK-giant stars with predictions from ATLAS atmosphere models. We discuss the case of K-giants and find a disagreement between limb-darkening measurements and model predictions, which may be caused by the inadequacy of the linear limb-darkening law.

Original language	English
Pages (from-to)	277-288
Number of pages	12
Journal	Astronomy & Astrophysics
Volume	460
DOIs	https://doi.org/10.1051/0004-6361:20054414
Publication status	Published - Dec 2006

Keywords

gravitational lensing
techniques : high angular resolution
stars : atmospheres
stars : individual : OGLE 2004-BLG-254
LIMB-DARKENING MEASUREMENT
H-ALPHA LINE
PLANET PHOTOMETRY
MACHO 98-SMC-1
LENS
STAR
ATMOSPHERE
CALIBRATION
SPECTRA
SYSTEMS

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10.1051/0004-6361:20054414

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Cassan, A., Beaulieu, J. .-P., Fouque, P., Brillant, S., Dominik, M., Greenhill, J., Heyrovsky, D., Horne, K., Jorgensen, U. G., Kubas, D., Stempels, H. C., Vinter, C., Albrow, M. D., Bennett, D., Caldwell, J. A. R., Calitz, J. J., Cook, K., Coutures, C., Dominis, D., ... Wyrzykowski, L. (2006). OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens. Astronomy & Astrophysics, 460, 277-288. https://doi.org/10.1051/0004-6361:20054414

@article{38da595d3c0449d4ab773eb4ef039572,

title = "OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens",

abstract = "Aims. We present an analysis of OGLE 2004-BLG-254, a high-magnification (A(o) similar or equal to 60) and relatively short duration (t(E) similar or equal to 13.2 days) microlensing event in which the source star, a Bulge K-giant, has been spatially resolved by a point-like lens. We seek to determine the lens and source distance, and provide a measurement of the linear limb-darkening coefficients of the source star in the I and R bands. We discuss the derived values of the latter and compare them to the classical theoretical laws, and furthermore examine the cases of already published microlensed GK-giants limb-darkening measurements.Methods. We have obtained dense photometric coverage of the event light curve with OGLE and PLANET telescopes, as well as a high signal-to-noise ratio spectrum taken while the source was still magnified by A similar to 20, using the UVES/VLT spectrograph. We have performed a modelling of the light curve, including finite source and parallax effects, and have combined spectroscopic and photometric analysis to infer the source distance. A Galactic model for the mass and velocity distribution of the stars has been used to estimate the lens distance.Results. From the spectrum analysis and calibrated color-magnitude of the event target, we found that the source was a K3 III Bulge giant, situated at the far end of the Bulge. From modelling the light curve, we have derived an angular size of the Einstein ring theta(E) similar or equal to 114 mu as, and a relative lens-source proper motion mu = theta(E)/t(E) similar or equal to 3.1 mas/yr. We could also measure the angular size of the source, theta(*) similar or equal to 4.5 mu as, whereas given the short duration of the event, no significant constraint could be obtained from parallax effects. A Galactic model based on the modelling of the light curve then provides us with an estimate of the lens distance, mass and velocity as D-L similar or equal to 9.6 kpc, M similar or equal to 0.11 M-circle dot and v similar or equal to 145 km s(-1) (at the lens distance) respectively. Our dense coverage of this event allows us to measure limb darkening of the source star in the I and R bands. We also compare previous measurements of linear limb-darkening coefficients involving GK-giant stars with predictions from ATLAS atmosphere models. We discuss the case of K-giants and find a disagreement between limb-darkening measurements and model predictions, which may be caused by the inadequacy of the linear limb-darkening law.",

keywords = "gravitational lensing, techniques : high angular resolution, stars : atmospheres, stars : individual : OGLE 2004-BLG-254, LIMB-DARKENING MEASUREMENT, H-ALPHA LINE, PLANET PHOTOMETRY, MACHO 98-SMC-1, LENS, STAR, ATMOSPHERE, CALIBRATION, SPECTRA, SYSTEMS",

author = "A. Cassan and Beaulieu, {J. -P.} and P. Fouque and S. Brillant and M. Dominik and J. Greenhill and D. Heyrovsky and K. Horne and Jorgensen, {U. G.} and D. Kubas and Stempels, {H. C.} and C. Vinter and Albrow, {M. D.} and D. Bennett and Caldwell, {J. A. R.} and Calitz, {J. J.} and K. Cook and C. Coutures and D. Dominis and J. Donatowicz and K. Hill and M. Hoffman and S. Kane and Marquette, {J. -B.} and R. Martin and P. Meintjes and J. Menzies and Miller, {V. R.} and Pollard, {K. R.} and Sahu, {K. C.} and J. Wambsganss and A. Williams and A. Udalski and Szymanski, {M. K.} and M. Kubiak and G. Pietrzynski and I. Soszynski and K. Zebrun and O. Szewczyk and L. Wyrzykowski",

year = "2006",

month = dec,

doi = "10.1051/0004-6361:20054414",

language = "English",

volume = "460",

pages = "277--288",

journal = "Astronomy & Astrophysics",

issn = "0004-6361",

publisher = "EDP SCIENCES S A",

}

Cassan, A, Beaulieu, J-P, Fouque, P, Brillant, S, Dominik, M, Greenhill, J, Heyrovsky, D, Horne, K, Jorgensen, UG, Kubas, D, Stempels, HC, Vinter, C, Albrow, MD, Bennett, D, Caldwell, JAR, Calitz, JJ, Cook, K, Coutures, C, Dominis, D, Donatowicz, J, Hill, K, Hoffman, M, Kane, S, Marquette, J-B, Martin, R, Meintjes, P, Menzies, J, Miller, VR, Pollard, KR, Sahu, KC, Wambsganss, J, Williams, A, Udalski, A, Szymanski, MK, Kubiak, M, Pietrzynski, G, Soszynski, I, Zebrun, K, Szewczyk, O & Wyrzykowski, L 2006, 'OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens', Astronomy & Astrophysics, vol. 460, pp. 277-288. https://doi.org/10.1051/0004-6361:20054414

TY - JOUR

T1 - OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens

AU - Cassan, A.

AU - Beaulieu, J. -P.

AU - Fouque, P.

AU - Brillant, S.

AU - Dominik, M.

AU - Greenhill, J.

AU - Heyrovsky, D.

AU - Horne, K.

AU - Jorgensen, U. G.

AU - Kubas, D.

AU - Stempels, H. C.

AU - Vinter, C.

AU - Albrow, M. D.

AU - Bennett, D.

AU - Caldwell, J. A. R.

AU - Calitz, J. J.

AU - Cook, K.

AU - Coutures, C.

AU - Dominis, D.

AU - Donatowicz, J.

AU - Hill, K.

AU - Hoffman, M.

AU - Kane, S.

AU - Marquette, J. -B.

AU - Martin, R.

AU - Meintjes, P.

AU - Menzies, J.

AU - Miller, V. R.

AU - Pollard, K. R.

AU - Sahu, K. C.

AU - Wambsganss, J.

AU - Williams, A.

AU - Udalski, A.

AU - Szymanski, M. K.

AU - Kubiak, M.

AU - Pietrzynski, G.

AU - Soszynski, I.

AU - Zebrun, K.

AU - Szewczyk, O.

AU - Wyrzykowski, L.

PY - 2006/12

Y1 - 2006/12

N2 - Aims. We present an analysis of OGLE 2004-BLG-254, a high-magnification (A(o) similar or equal to 60) and relatively short duration (t(E) similar or equal to 13.2 days) microlensing event in which the source star, a Bulge K-giant, has been spatially resolved by a point-like lens. We seek to determine the lens and source distance, and provide a measurement of the linear limb-darkening coefficients of the source star in the I and R bands. We discuss the derived values of the latter and compare them to the classical theoretical laws, and furthermore examine the cases of already published microlensed GK-giants limb-darkening measurements.Methods. We have obtained dense photometric coverage of the event light curve with OGLE and PLANET telescopes, as well as a high signal-to-noise ratio spectrum taken while the source was still magnified by A similar to 20, using the UVES/VLT spectrograph. We have performed a modelling of the light curve, including finite source and parallax effects, and have combined spectroscopic and photometric analysis to infer the source distance. A Galactic model for the mass and velocity distribution of the stars has been used to estimate the lens distance.Results. From the spectrum analysis and calibrated color-magnitude of the event target, we found that the source was a K3 III Bulge giant, situated at the far end of the Bulge. From modelling the light curve, we have derived an angular size of the Einstein ring theta(E) similar or equal to 114 mu as, and a relative lens-source proper motion mu = theta(E)/t(E) similar or equal to 3.1 mas/yr. We could also measure the angular size of the source, theta(*) similar or equal to 4.5 mu as, whereas given the short duration of the event, no significant constraint could be obtained from parallax effects. A Galactic model based on the modelling of the light curve then provides us with an estimate of the lens distance, mass and velocity as D-L similar or equal to 9.6 kpc, M similar or equal to 0.11 M-circle dot and v similar or equal to 145 km s(-1) (at the lens distance) respectively. Our dense coverage of this event allows us to measure limb darkening of the source star in the I and R bands. We also compare previous measurements of linear limb-darkening coefficients involving GK-giant stars with predictions from ATLAS atmosphere models. We discuss the case of K-giants and find a disagreement between limb-darkening measurements and model predictions, which may be caused by the inadequacy of the linear limb-darkening law.

AB - Aims. We present an analysis of OGLE 2004-BLG-254, a high-magnification (A(o) similar or equal to 60) and relatively short duration (t(E) similar or equal to 13.2 days) microlensing event in which the source star, a Bulge K-giant, has been spatially resolved by a point-like lens. We seek to determine the lens and source distance, and provide a measurement of the linear limb-darkening coefficients of the source star in the I and R bands. We discuss the derived values of the latter and compare them to the classical theoretical laws, and furthermore examine the cases of already published microlensed GK-giants limb-darkening measurements.Methods. We have obtained dense photometric coverage of the event light curve with OGLE and PLANET telescopes, as well as a high signal-to-noise ratio spectrum taken while the source was still magnified by A similar to 20, using the UVES/VLT spectrograph. We have performed a modelling of the light curve, including finite source and parallax effects, and have combined spectroscopic and photometric analysis to infer the source distance. A Galactic model for the mass and velocity distribution of the stars has been used to estimate the lens distance.Results. From the spectrum analysis and calibrated color-magnitude of the event target, we found that the source was a K3 III Bulge giant, situated at the far end of the Bulge. From modelling the light curve, we have derived an angular size of the Einstein ring theta(E) similar or equal to 114 mu as, and a relative lens-source proper motion mu = theta(E)/t(E) similar or equal to 3.1 mas/yr. We could also measure the angular size of the source, theta(*) similar or equal to 4.5 mu as, whereas given the short duration of the event, no significant constraint could be obtained from parallax effects. A Galactic model based on the modelling of the light curve then provides us with an estimate of the lens distance, mass and velocity as D-L similar or equal to 9.6 kpc, M similar or equal to 0.11 M-circle dot and v similar or equal to 145 km s(-1) (at the lens distance) respectively. Our dense coverage of this event allows us to measure limb darkening of the source star in the I and R bands. We also compare previous measurements of linear limb-darkening coefficients involving GK-giant stars with predictions from ATLAS atmosphere models. We discuss the case of K-giants and find a disagreement between limb-darkening measurements and model predictions, which may be caused by the inadequacy of the linear limb-darkening law.

KW - gravitational lensing

KW - techniques : high angular resolution

KW - stars : atmospheres

KW - stars : individual : OGLE 2004-BLG-254

KW - LIMB-DARKENING MEASUREMENT

KW - H-ALPHA LINE

KW - PLANET PHOTOMETRY

KW - MACHO 98-SMC-1

KW - LENS

KW - STAR

KW - ATMOSPHERE

KW - CALIBRATION

KW - SPECTRA

KW - SYSTEMS

UR - http://www.scopus.com/inward/record.url?scp=33845332089&partnerID=8YFLogxK

U2 - 10.1051/0004-6361:20054414

DO - 10.1051/0004-6361:20054414

M3 - Article

SN - 0004-6361

VL - 460

SP - 277

EP - 288

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

ER -

OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens

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OGLE 2004-BLG-254: a K3III Galactic bulge giant spatially resolved by a single microlens

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