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601. 20 years of photometric microlensing
ID:
ivo://CDS.VizieR/J/A+A/617/A135
Title:
20 years of photometric microlensing
Short Name:
J/A+A/617/A135
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gaia DR2 offers unparalleled precision on stars' parallaxes and proper motions. This allows the prediction of microlensing events for which the lens stars (and any planets they possess) are nearby and may be well studied and characterised. We identify a number of potential microlensing events that will occur before the year 2035.5, 20 years from the Gaia DR2 reference epoch. We query Gaia DR2 for potential lenses within 100pc, extract parallaxes and proper motions of the lenses and background sources, and identify potential lensing events. We estimate the lens masses from Priam effective temperatures, and use these to calculate peak magnifications and the size of the Einstein radii relative to the lens stars' habitable zones. We identify 7 future events with a probability >10% of an alignment within one Einstein radius. Of particular interest is DR2 5918299904067162240 (WISE J175839.20-583931.6), magnitude G=14.9, which will lens a G=13.9 background star in early 2030, with a median 23% net magnification. Other pairs are typically fainter, hampering characterisation of the lens (if the lens is faint) or the ability to accurately measure the magnification (if the source is much fainter than the lens). Of timely interest is DR2 4116504399886241792 (2MASS J17392440-2327071), which will lens a background star in July 2020, albeit with weak net magnification (0.03%). Median magnifications for the other 5 high-probability events range from 0.3% to 5.3%. The Einstein radii for these lenses are 1-10 times the radius of the habitable zone, allowing these lensing events to pick out cold planets around the ice line, and filling a gap between transit and current microlensing detections of planets around very low-mass stars. We provide a catalogue of the predicted events to aid future characterisation efforts. Current limitations include a lack of many high-proper motion objects in Gaia DR2 and often large uncertainties on the proper motions of the background sources (or only 2-parameter solutions). Both of these deficiencies will be rectified with Gaia DR3 in 2020. Further characterisation of the lenses is also warranted to better constrain their masses and predict the photometric magnifications.
602. 12 years positional measurements of 8 binaries
ID:
ivo://CDS.VizieR/J/AJ/159/266
Title:
12 years positional measurements of 8 binaries
Short Name:
J/AJ/159/266
Date:
21 Oct 2021
Publisher:
CDS
Description:
The orbits of eight systems with low-mass components (HIP14524, HIP16025, HIP28671, HIP46199, HIP47791, HIP60444, HIP61100, and HIP73085) are presented. Speckle interferometric data were obtained at the 6m Big Telescope Alt-azimuth Special Astrophysical Observatory of the Russian Academy of Sciences (BTA SAO RAS) from 2007 to 2019. New data, together with measures already in the literature, made it possible to improve upon previous orbital solutions in six cases and to construct orbits for the first time in the two remaining cases (HIP14524 and HIP60444). Mass sums are obtained using both Hipparcos and Gaia parallaxes, and a comparison with previously published values is made. Using the Worley & Heintz criteria, the classification of the orbits constructed is carried out.
603. YSOs in the Gould Belt regions with Gaia-DR2 data
ID:
ivo://CDS.VizieR/J/ApJ/867/151
Title:
YSOs in the Gould Belt regions with Gaia-DR2 data
Short Name:
J/ApJ/867/151
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the astrometric results from the Gaia second data release (DR2) for young stellar objects (YSOs) in star-forming regions related to the Gould Belt (GB). These regions are Barnard 59, Lupus 1 to 4, Chamaeleon I and II, {epsilon} Chamaeleontis, the Cepheus flare, IC 5146, and Corona Australis. The mean distance to the YSOs in each region is consistent with earlier estimations, though a significant improvement in the final errors was obtained. The mean distances to the star-forming regions were used to fit an ellipsoid of size (358+/-7)x(316+/-13)x(70+/-4)pc^3^, centered at (X0,Y0,Z0)=(-82+/-15,39+/-7,-25+/-4)pc, consistent with recently determined parameters of the GB. The mean proper motions were combined with radial velocities from the literature to obtain the three- dimensional motions of the star-forming regions, which are consistent with a general expansion of the GB. We estimate that this expansion is occurring at a velocity of 2.5+/-0.1km/s. This is the first time that motions of YSOs have been used to investigate the kinematics of the GB. As an interesting side result, we also identified stars with large peculiar velocities.
604. Yunnan Observatory photoelectric astrolabe catalogue
ID:
ivo://CDS.VizieR/J/A+AS/118/239
Title:
Yunnan Observatory photoelectric astrolabe catalogue
Short Name:
J/A+AS/118/239
Date:
21 Oct 2021
Publisher:
CDS
Description:
The positions of 53 FK5, 70 FK5 Extension and 486 GC stars are given for equator and the equinox J2000.0 and for the mean observation epoch of each star which are determined with the photoelectric astrolabe of Yunnan Observatory. The internal mean errors in right ascension and declination are 0.046" and 0.059", respectively. The mean observation epoch is 1989.51.

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