Search for exoplanets in M31 with pixel-lensing and the PA-99-N2 event revisited

TL;DR

This paper explores the potential for detecting exoplanets in M31 via pixel-lensing, demonstrating that even small planets can cause observable deviations, especially in long-duration events, with high-cadence observations.

Contribution

It introduces a method to detect exoplanets in M31 using pixel-lensing and reanalyzes a specific microlensing event to assess planetary detection efficiency.

Findings

Detectable planetary systems have a mean mass of about 2 Jupiter masses.

Small exoplanets under 20 Earth masses can cause observable deviations.

Long-duration, bright events have higher efficiency for planetary detection.

Abstract

Several exoplanets have been detected towards the Galactic bulge with the microlensing technique. We show that exoplanets in M31 may also be detected with the pixel-lensing method, if telescopes making high cadence observations of an ongoing microlensing event are used. Using a Monte Carlo approach we find that the mean mass for detectable planetary systems is about $2 M_{\rm {J}}$. However, even small mass exoplanets ($M_{\rm P} < 20 M_{\oplus}$) can cause significant deviations, which are observable with large telescopes. We reanalysed the POINT-AGAPE microlensing event PA-99-N2. First, we test the robustness of the binary lens conclusion for this light curve. Second, we show that for such long duration and bright microlensing events, the efficiency for finding planetary-like deviations is strongly enhanced with respect to that evaluated for all planetary detectable events.