Pixel lensing as a way to detect extrasolar planets in M31 |
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| Authors: | G Ingrosso S Calchi Novati F De Paolis Ph Jetzer A A Nucita A F Zakharov |
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| Institution: | Dipartimento di Fisica, Universitàdel Salento and INFN Sezione di Lecce, CP 193, I-73100 Lecce, Italy;Dipartimento di Fisica, Universitàdi Salerno, I-84081 Baronissi (SA) and INFN Sezione di Napoli, Italy;Institute for Theoretical Physics, University of Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland;XMM-Newton Science Operations Centre, ESAC, ESA, PO Box 50727, 28080 Madrid, Spain;Institute of Theoretical and Experimental Physics, B. Cheremushkinskaya 25, 117259 Moscow, Russia;Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna, Russia |
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| Abstract: | We study the possibility to detect extrasolar planets in M31 through pixel-lensing observations. Using a Monte Carlo approach, we select the physical parameters of the binary lens system, a star hosting a planet, and we calculate the pixel-lensing light curve taking into account the finite source effects. Indeed, their inclusion is crucial since the sources in M31 microlensing events are mainly giant stars. Light curves with detectable planetary features are selected by looking for significant deviations from the corresponding Paczyński shapes. We find that the time-scale of planetary deviations in light curves increase (up to 3–4 d) as the source size increases. This means that only few exposures per day, depending also on the required accuracy, may be sufficient to reveal in the light curve a planetary companion. Although the mean planet mass for the selected events is about  , even small mass planets ( M P < 20 M⊕) can cause significant deviations, at least in the observations with large telescopes. However, even in the former case, the probability to find detectable planetary features in pixel-lensing light curves is at most a few per cent of the detectable events, and therefore many events have to be collected in order to detect an extrasolar planet in M31. Our analysis also supports the claim that the anomaly found in the candidate event PA-99-N2 towards M31 can be explained by a companion object orbiting the lens star. |
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| Keywords: | gravitational lensing Galaxy: halo galaxies: individual: M31 |
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