General Relativity and Gravitation

, Volume 43, Issue 4, pp 1047–1060 | Cite as

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

  • Gabriele Ingrosso
  • Sebastiano Calchi Novati
  • Francesco De Paolis
  • Philippe Jetzer
  • Achille Nucita
  • Alexander Zakharov
Research Article


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 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.


Microlensing Exoplanets Spiral galaxies: M31 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Gould, A.: Recent developments in gravitational microlensing. In: Stanek, K. (ed.) The variable universe: a celebration of Bohdan Paczyński, ASP Conference Series, USA, p. 86. Astronomical Society of the Pacific, San Francisco (2009); arXiv:0803.4324v1 [astro-ph]Google Scholar
  2. 2.
    Bennett, D.: Detection of extrasolar planets by gravitational microlensing, arXiv:0902.1761v1 [astro-ph.EP]Google Scholar
  3. 3.
    Mao S., Paczyński B.: Gravitational microlensing by double stars and planetary systems. ApJ 374, L37 (1991)CrossRefADSGoogle Scholar
  4. 4.
    Paczyński, B.: Gravitational microlensing in the local group, ARA&A (1996)Google Scholar
  5. 5.
    Covone G., de Ritis R., Dominik M., Marino A.A.: Detecting planets around stars in nearby galaxies. A&A 357, 816 (2000)ADSGoogle Scholar
  6. 6.
    Baltz E.A., Gondolo P.: Binary events and extragalactic planets in pixel microlensing. ApJ 559, 41 (2001)CrossRefADSGoogle Scholar
  7. 7.
    Crotts A.P.S.: M31: a unique laboratory for gravitational microlensing. ApJ 399, L43 (1992)CrossRefADSGoogle Scholar
  8. 8.
    Baillon P., Bouquet A., Giraud-Heraud Y., Kaplan J.: Detection of Brown Dwarfs by the Microlensing of Unresolved Stars. A&A 277, 1 (1993)ADSGoogle Scholar
  9. 9.
    Gould A.: Theory of Pixel Lensing. ApJ 470, 201 (1996)CrossRefADSGoogle Scholar
  10. 10.
    Ansari R. et al.: AGAPE: a search for dark matter towards M31 by microlensing effects on unresolved stars? A&A 324, 843 (1997)ADSGoogle Scholar
  11. 11.
    Calchi Novati, S.: Pixel-lensing: microlensing towards M31; arXiv:0912.2667 (2009)Google Scholar
  12. 12.
    An J.H. et al.: The anomaly in the candidate microlensing event PA-99-N2. ApJ 601, 845 (2004)CrossRefADSGoogle Scholar
  13. 13.
    Kerins E. et al.: The Angstrom project: a microlensing survey of the structure and composition of the bulge of the Andromeda galaxy. MNRAS 365, 1099 (2006)CrossRefADSGoogle Scholar
  14. 14.
    Riffesser A., Seitz S., Bender R.: The M31 microlensing event WeCAPP-GL1/POINT-AGAPE-S3: evidence for a MACHO component in the dark halo of M31? ApJ 684, 1093 (2008)CrossRefADSGoogle Scholar
  15. 15.
    Calchi Novati S. et al.: Candidate microlensing events from M31 observations with the Loiano telescope. ApJ 695, 442 (2009)CrossRefADSGoogle Scholar
  16. 16.
    Chung S.-J. et al.: The possibility of detecting planets in the Andromeda Galaxy. ApJ 650, 432 (2006)CrossRefADSGoogle Scholar
  17. 17.
    Kim D. et al.: Detection of M31 binaries via high-cadence pixel-lensing surveys. ApJ 666, 236 (2007)CrossRefADSGoogle Scholar
  18. 18.
    Ingrosso G. et al.: Pixel-lensing as a way to detect extrasolar planets in M31. MNRAS 399, 219 (2009)CrossRefADSGoogle Scholar
  19. 19.
    Kerins E. et al.: Theory of pixel lensing towards M31 - I. The density contribution and mass of MACHOs. MNRAS 323, 13 (2001)CrossRefADSGoogle Scholar
  20. 20.
    Ingrosso G. et al.: Monte Carlo analysis of MEGA microlensing events towards M31. A&A 445, 375 (2006)CrossRefADSGoogle Scholar
  21. 21.
    Ingrosso G. et al.: A new analysis of the MEGA M 31 microlensing events. A&A 462, 895 (2007)CrossRefADSGoogle Scholar
  22. 22.
    Tabachnik S., Tremaine S.: Maximum-likelihood method for estimating the mass and period distributions of extrasolar planets.. MNRAS 335, 151 (2002)CrossRefADSGoogle Scholar
  23. 23.
    Jiang, I.-G., et al.: On the fundamental mass-period functions of extrasolar planets, arXiv:0912.2585v1 (2009)Google Scholar
  24. 24.
    Ida S., Lin D.N.C.: Toward a deterministic model of planetary formation II. The formation and retention of gas giant planets around stars with a range of metallicities. ApJ 616, 567 (2004)CrossRefADSGoogle Scholar
  25. 25.
    Witt H.J.: Investigation of high amplification events in light curves of gravitationally lensed quasars. A&A 236, 311 (1990)ADSGoogle Scholar
  26. 26.
    Witt H.J., Mao S.: On the minimum magnification between caustic crossings for microlensing by binary and multiple stars.. ApJ 447, L105 (1995)CrossRefADSGoogle Scholar
  27. 27.
    Griest K., Safizadeh N.: The use of high-magnification microlensing events in discovering extrasolar planets. ApJ 500, 37 (1998)CrossRefADSGoogle Scholar
  28. 28.
    Gould A., Loeb A.: Discovering planetary systems through gravitational microlenses. ApJ 396, 104 (1992)CrossRefADSGoogle Scholar
  29. 29.
    Zakharov A.F., Sazhin M.V.: Gravitational microlensing. Physics–Uspekhi 41, 945 (1998)ADSGoogle Scholar
  30. 30.
    Bozza V.: Perturbative analysis in planetary gravitational lensing. A&A 348, 311 (1999)ADSGoogle Scholar
  31. 31.
    Dong S. et al.: Microlensing event MOA-2007-BLG-400: exhuming the buried signature of a cool, Jovian-mass planet. ApJ 698, 1826 (2009)CrossRefADSGoogle Scholar
  32. 32.
    Paulin-Henriksson S. et al.: The POINT-AGAPE survey: 4 high signal-to-noise microlensing candidates detected towards M 31. A&A 405, 15 (2003)CrossRefADSGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  • Gabriele Ingrosso
    • 1
  • Sebastiano Calchi Novati
    • 2
  • Francesco De Paolis
    • 1
  • Philippe Jetzer
    • 3
  • Achille Nucita
    • 4
  • Alexander Zakharov
    • 5
    • 6
  1. 1.Dipartimento di FisicaUniversità del Salento, INFN Sezione di LecceLecceItaly
  2. 2.Dipartimento di FisicaUniversità di Salerno, INFN Sezione di NapoliBaronissiItaly
  3. 3.Institute for Theoretical PhysicsUniversity of ZürichZurichSwitzerland
  4. 4.XMM-Newton Science Operations Centre, ESAC, ESAMadridSpain
  5. 5.Institute of Theoretical and Experimental PhysicsMoscowRussia
  6. 6.Bogoliubov Laboratory of Theoretical PhysicsJoint Institute for Nuclear ResearchDubnaRussia

Personalised recommendations