Measuring the stellar atmosphere parameters using follow-up polarimetry microlensing observations

Abstract

We present an analysis of the potential follow-up polarimetry microlensing observation to study the stellar atmospheres of the distant stars. First, we produce synthetic microlensing events using the Galactic model, stellar population, and interstellar dust toward the Galactic Bulge. We simulate the polarization microlensing light curves and pass them through the instrument specifications of FOcal Reducer and low dispersion Spectrograph (FORS2) polarimeter at Very Large Telescope (VLT), and then analyze them. We find that the accuracy of the VLT telescope lets us constrain the atmosphere of cool RGB stars. Assuming detection of about $3000$ microlensing events per year by the OGLE telescope, we expect to detect almost $20,10,8,$ and $5$ of polarization microlensig events for the four different criteria of being three consecutive polarimetry data points above the baseline with $1\sigma$, $2\sigma$, $3\sigma$, and $4\sigma$, respectively in the polarimetry light curves. We generalize the covariance matrix formulation and present the combination of polarimetry and photometry information that leads us to measure the scattering optical depth of the atmosphere and the inner radius of the stellar envelope of red giant stars. These two parameters could determine the dust opacity of the atmosphere of cool RGB source stars and the radius where dust can be formed.

arXiv comment13 pages, 18 figures, accepted for publication by MNRAS

References in corpus (33)

• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Theoretical isochrones in several photometric systems I. Johnson-Cousins-Glass, HST/WFPC2, HST/NICMOS, Washington, and ESO Imaging Survey filter sets
• A Grid of NLTE Line-Blanketed Model Atmospheres of O-type Stars
• Modelling the Galactic Interstellar Extinction Distribution in Three Dimensions
• A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars
• Reddening and Extinction Toward the Galactic Bulge from OGLE-III: The Inner Milky Way's Rv ~ 2.5 Extinction Curve
• Stellar populations in the Milky Way bulge region : Towards solving the Galactic bulge and bar shapes using 2MASS data
• Systematic Analysis of 22 Microlensing Parallax Candidates
• Korea Microlensing Telescope Network Microlensing Events from 2015: Event-Finding Algorithm, Vetting, and Photometry
• Microlensing with advanced contour integration algorithm: Green's theorem to third order, error control, optimal sampling and limb darkening
• A new method to compute limb-darkening coefficients for stellar atmosphere models with spherical symmetry: the space missions TESS, Kepler, Corot, and MOST
• A synthetic view on structure and evolution of the Milky Way
• Microlensing optical depth and event rate toward the Galactic bulge from 8 yr of OGLE-IV observations
• VBBinaryLensing: a public package for microlensing light curve computation
• OGLE-III Microlensing Events and the Structure of the Galactic Bulge
• Astrometric Microlensing with the GAIA satellite
• ISOCAM observations of Galactic Globular Clusters: mass loss along the Red Giant Branch
• Prediction on detection and characterization of Galactic disk microlensing events by LSST
• Statistical techniques in cosmology
• A Giant Planet beyond the Snow Line in Microlensing Event OGLE-2011-BLG-0251
• Adaptive Contouring -- an efficient way to calculate microlensing light curves of extended sources
• Gravitational Microlensing I: A Unique Astrophysical Tool
• Understanding EROS2 observations toward the spiral arms within a classical Galactic model framework
• Planetary microlensing signals from the orbital motion of the source star around the common barycentre
• Polarization in microlensing towards the Galactic bulge
• Variable polarisation and luminosity for microlensing of extended stellar sources
• Measuring Polarization in microlensing events
• Polarization in binary microlensing events
• The polarisation signature from microlensing of circumstellar envelopes in caustic crossing events
• Finite source effect on the polarization degree induced by a single microlens
• The advantages of using a Lucky Imaging camera for observations of microlensing events
• Stellar rotation effects in polarimetric microlensing
• Polarization and SEDs from Microlensing of Circumstellar Envelopes