Galactic Bulge Pixel‐lensing Events

Gould & DePoy proposed a pixel lensing survey towards the Galactic bulgeusing a small aperture (~65 mm) camera with a large pixel size (10") detectorand deliberately degraded optics achieving 30" PSF. In this paper, we estimatethe event rate of this pixel lensing survey expected under various detectioncriteria, which are characterized by the threshold signal-to-noise ratio,(S/N)_{th}, and event duration, t_{dur,th}, and investigate the characteristicsof the detectable events. From this investigation, we find that the event ratevaries significantly in the range ~6/yr - 120/yr depending strongly on theimposed detection criteria, implying that to maximize event detections it willbe essential to identify events by diligently inspecting light variations andto promptly conduct followup observations for the identified events. Comparedto events detectable from classic lensing surveys, the events detectable fromthe pixel lensing survey will generally involve brighter source stars and havehigher amplifications. For the pixel lensing events detectable under thecriteria of (S/N)_{th}=10 and t_{dur,th}=6 hr, we find that the baselinebrightness of source stars will be in average ~2 mag brighter than those ofclassic lensing events and ~90% will have amplifications A> 20 and ~40% will beextreme EMEs with A>200. Therefore, followup observations of the pixel lensingevents will provide high quality data, which enable one to precisely determinethe lensing parameters and obtain extra-information about the lenses and sourcestars. Especially, high amplifications events with A>20 will be importanttargets for high-efficiency planet detections and one can uniquely determinethe mass, distance, and transverse speed of individual lenses for EMEs.Comment: total 8 pages, including 5 figures and 1 table, ApJ, accepte