Abstract
Aims. We study the effect of the parallax on the search for microlensing events on very long timescales towards the Magellanic Clouds caused by dark massive compact objects within the past MACHO and EROS, the on-going MOA and OGLE, and the future LSST surveys. We quantify what neglecting this effect means in the classical event selection process and also quantify the parallax detectability without the help of follow-up observations. Methods. We defined the distance between true events affected by parallax and the closest events without parallax. This distance was used to estimate the probability of missing the preselection of events because of parallax for any survey characterised by its time sampling and photometric performance. We also defined another distance to quantify the detectability of the parallax effect in order to trigger complementary observations. Results. We find that the preselection of year-long timescale events is marginally affected by parallax for all surveys if the criteria are reasonably tight. We also show that the parallax should be detectable in most of the events found by the LSST survey without follow-up observations.
Highlights
The recently observed gravitational waves (Abbott et al 2016a,b) might be emitted by possible candidates for the Galactic halo dark matter (Bird et al 2016)
Several teams have operated systematic microlensing survey programs to search for hidden massive compact objects after the publication of Paczynski (Paczynski 1986): the Expérience de Recherche d’Objets Sombres (EROS) by Aubourg et al (1993), the survey MAssive Compact Halo Objects (MACHO) by Alcock et al (1993), the Optical Gravitational Lensing Experiment (OGLE) by Udalski et al (1993), and the survey called Microlensing Observations in Astrophysics (MOA) by Sako et al (2007)
In this Letter, we focus on the microlensing detection towards the Large Magellanic Cloud (LMC), and the Small Magellanic Cloud (SMC), where the dark matter signal from compact objects is expected mainly from a distribution model between a spherical halo and a thick disc
Summary
The recently observed gravitational waves (Abbott et al 2016a,b) might be emitted by possible candidates for the Galactic halo dark matter (Bird et al 2016). In this Letter, we examine one specificity of the longtimescale events, which is the distortions expected from the orbital motion of Earth around the Sun (so-called parallax effect in this Letter), which can become significant for events longer than a few months. 3 we describe a procedure for simulating a representative sample of microlensing events that take parallax into account as expected from the distributions of Galactic hidden massive compact objects. We evaluate the parallax detectability from simple representations of surveys based on the time sampling and the photometric resolution in two realistic cases: the MEMO and the LSST projects In this Letter, we focus on the microlensing detection towards the Large Magellanic Cloud (LMC), and the Small Magellanic Cloud (SMC), where the dark matter signal from compact objects is expected mainly from a distribution model between a spherical halo and a thick disc
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