First microlensing candidate towards M 31 from the Nainital microlensing survey

Abstract

We report our first microlensing candidate NMS-E1 towards M 31 from the data accumulated during the four years of Nainital Microlensing Survey. Cousin R and I band observations of ∼13´ × 13´ field in the direction of M 31 have been carried out since 1998 and data is analysed using the pixel technique proposed by the AGAPE collaboration. NMS-E1 lies in the disk of M 31 at α = 0ʰ 43ᵐ 33ᶳ.3 and δ = +41° 06´ 44´´ , about 15.5 arcmin to the South-East direction of the center of M 31. .The photometric analysis of the candidate shows that it reached R ∼ 20.1 mag at the time of maximum brightness and the colour of the source star was estimated to be (R − I)₀ ∼ 1.1 mag. The microlensing candidate is blended by red variable stars; consequently the light curves do not strictly follow the characteristic Paczyński shape and achromatic nature. However its long period monitoring and similar behaviour in R and I bands supports its microlensing nature.