Ongoing astrometric microlensing events of two nearby stars

• Verfasst von: Klüter, Jonas [VerfasserIn]
• Verfasst von: Bastian, Ulrich [VerfasserIn]
• Verfasst von: Demleitner, Markus [VerfasserIn]
• Verfasst von: Wambsganß, Joachim [VerfasserIn]
• Titel: Ongoing astrometric microlensing events of two nearby stars
• Verf.angabe: J. Klüter, U. Bastian, M. Demleitner, and J. Wambsganss
• E-Jahr: 2018
• Jahr: 20 July 2018
• Umfang: 4 S.
• Fussnoten: Gesehen am 30.07.2018
• Titel Quelle: Enthalten in: Astronomy and astrophysics
• Ort Quelle: Les Ulis : EDP Sciences, 1969
• Jahr Quelle: 2018
• Band/Heft Quelle: 615(2018) Artikel-Nummer L11, 4 Seiten
• ISSN Quelle: 1432-0746
• DOI: doi:10.1051/0004-6361/201833461
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1578040787

Abstract

<i>Context<i/>. Astrometric microlensing is an excellent tool to determine the mass of stellar objects. By measuring the astrometric shift of a background source star in combination with precise predictions of its unlensed position and of the lens position, gravitational lensing allows to one determine the mass of the lensing star with a precision of 1%, independently of any prior knowledge.<i>Aims<i/>. Making use of the recently published <i>Gaia<i/> Data Release 2 (<i>Gaia<i/> DR2) we predict astrometric microlensing events by fore-ground stars of high proper motion passing by a background star in the coming years.<i>Methods<i/>. We compile a list of approximately 148 000 high-proper-motion stars within <i>Gaia<i/> DR2 with <i>µ<i/><sub>tot<sub/> > 150 mas yr<sup>−1<sup/>. We then search for background stars close to their paths and calculate the dates and separations of the closest approaches. Using color and absolute magnitude, we determine approximate masses of the lenses. Finally, we calculate the expected astrometric shifts and magnifications of the predicted events.<i>Results<i/>. We detect two ongoing microlensing events by the high-proper-motion stars Luyten 143-23 and Ross 322 and predict closest separations of (108.5 ± 1.4) mas in July 2018 and (125.3 ± 3.4) mas in August 2018, respectively. The respective expected astrometric shifts are (1.74 ± 0.12) mas and (0.76 ± 0.06) mas. Furthermore, Luyten 143-23 will pass by another star in March 2021 with a closest separation of (280.1 ± 1.1) mas, which results in an expected shift of (0.69 ± 0.05) mas.