University of Hertfordshire

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From the same journal

By the same authors

Ongoing astrometric microlensing events from VVV and Gaia

Research output: Contribution to journalArticle


  • 1905.08270v1

    Accepted author manuscript, 589 KB, PDF document

  • slz073

    Final published version, 513 KB, PDF document

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Original languageEnglish
Number of pages6
Pages (from-to)L7-L12
JournalMonthly Notices of the Royal Astronomical Society
Journal publication dateJul 2019
Early online date22 May 2019
Publication statusPublished - Jul 2019


We extend predictive microlensing event searches using the Vista Variables in the Via Lactea survey and the second Gaia data release. We identify two events with maxima in 2019 that require urgent follow-up. First, we predict that the nearby M2 dwarf L 338-152 will align with a background source with a closest approach of $35^{+35}_{-23}$ mas on 2019 November $16^{+28}_{-27}$ d. This will cause a peak astrometric shift and photometric amplification of the background source of $2.7^{+3.5}_{-1.5}$ mas and $5.6^{+143.2}_{-5.2}$ mmag respectively. This event should be astrometrically detectable by both the Hubble Space Telescope (HST) and the Spectro-Polarimetric High-contrast Exoplanet Research instrument on the Very Large Telescope. Secondly, we predict the likely K dwarf NLTT 45128 will lens a background source with a closest approach of $105.3^{+12.2}_{-11.7}$ mas on 2019 September $26^{+15}_{-15}$ d. This will produce a peak astrometric shift of $0.329^{+0.065}_{-0.059}$ mas. NLTT 45128 is only 3.6 magnitudes brighter than the background source which makes it an excellent candidate for follow-up with HST. Characterisation of these signals will allow direct gravitational masses to be inferred for both L 338-152 and NLTT 45128 with an estimated precision of $\sim9$ and $\sim13$ per cent respectively.


6 pages, 2 figures, accepted MNRAS Letters

ID: 17203126