J/A+A/617/A135 20 years of photometric microlensing (Mustill+, 2018)
Twenty years of photometric microlensing events predicted by Gaia DR2.
Potential planet-hosting lenses within 100 pc.
Mustill A.-J., Davies M.-B., Lindegren L.
<Astron. Astrophys. 617, A135 (2018)>
=2018A&A...617A.135M 2018A&A...617A.135M (SIMBAD/NED BibCode)
ADC_Keywords: Gravitational lensing ; Positional data ; Stars, nearby ;
Parallaxes, trigonometric ; Photometry, G band ; Proper motions
Keywords: gravitational lensing: micro - astrometry -
planets and satellites: detection
Abstract:
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.
Description:
Data for 30 source-lens pairs. Source and lens Gaia DR2 ids,
astrometric and photometric data are given, together with estimates
for the Einstein radius of the lens and parameters of the lensing
event: probability of alignment within one Einstein radius, minimum
separation, peak magnification, time of peak magnification and
duration of significant magnification, and Solar elongation at peak
magnification.
For many fields, 16th, 50th and 84th percentiles from the Monte-Carlo
simulations of the paper are provided. We also take these percentiles
from the Priam analysis of Gaia DR2 (Andrae et al.,
2018A&A...616A...8A 2018A&A...616A...8A) for stellar Teff. From this we have derived
stellar masses, luminosities and the Einstein radii and habitable zone
radii. Note that Teff does not propagate monotonically into these
latter quantities. Hence, the three values of mass, luminosity and
habitable zone and Einstein radii reported should be regarded as a
qualitative measure of the accuracy of these values, not as quantiles
of a probability density function.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
mlens.dat 497 30 Microlens source-lens pairs
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
Byte-by-byte Description of file: mlens.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- Lens Gaia DR2 id of lens star (DR2id_lens)
21- 25 F5.2 mag Gmagl Gaia DR2 G magnitude of lens (Gmag_lens)
27- 45 F19.15 deg RAldeg Gaia DR2 right ascension of lens
(ICRS, at epoch 2015.5) (RAdeg_lens)
47- 65 F19.15 deg DEldeg Gaia DR2 declination of lens
(ICRS, at epoch 2015.5) (DEdeg_lens)
67- 74 F8.3 mas/yr pmRAl ?=0 Gaia DR2 proper motion in RA of lens
(pmRA_lens)
76- 84 F9.3 mas/yr pmDEl ?=0 Gaia DR2 proper motion in Dec of lens
(pmDE_lens)
86- 92 F7.3 mas plxl ?=0 Gaia DR2 parallax of lens (plx_lens)
94- 97 I4 K b_Teffl ? Priam Teff of lens (16th percentile)
(Tefflenslow)
99-102 I4 K Teffl ? Priam Teff of lens (50th percentile)
(Teff_lens)
104-107 I4 K B_Teffl ? Priam Teff of lens (84th percentile)
(Tefflenshigh)
109-113 F5.3 Msun bMassl Lens mass from Tefflenslow (Mlenslow)
115-119 F5.3 Msun Massl Lens mass from Teff_lens (M_lens)
121-125 F5.3 Msun BMassl Lens mass from Tefflenshigh (Mlenshigh)
127-134 E8.3 Lsun bLuml Lens luminosity from Tefflenslow
(Llenslow)
136-143 E8.3 Lsun Luml Lens luminosity from Teff_lens (L_lens)
145-152 E8.3 Lsun BLuml Lens luminosity from Tefflenshigh
(Llenshigh)
154-161 E8.3 AU bRHZ Habitable zone radius from Tefflenslow
(RHZ_low)
163-170 E8.3 AU RHZ Habitable zone radius from Teff_lens (RHZ)
172-179 E8.3 AU BRHZ Habitable zone radius from Tefflenshigh
(RHZ_high)
181-188 E8.3 arcsec bREas Angular Einstein radius from Tefflenslow
(REaslow)
190-197 E8.3 arcsec REas Angular Einstein radius from Teff_lens
(RE_as)
199-206 E8.3 arcsec BREas Angular Einstein radius from Tefflenshigh
(REashigh)
208-215 E8.3 AU bREau Physical Einstein radius from Tefflenslow
(REaulow)
217-224 E8.3 AU REau Physical Einstein radius from Teff_lens
(RE_au)
226-233 E8.3 AU BREau Physical Einstein radius from Tefflenshigh
(REauhigh)
235-253 I19 --- Source Gaia DR2 id of source star (DR2id_source)
255-259 F5.2 mag Gmag Gaia DR2 G magnitude of source (Gmag_source)
261-278 F18.14 deg RAsdeg Gaia DR2 right ascension of source
(ICRS, at epoch 2015.5) (RAdeg_source)
280-298 F19.15 deg DEsdeg Gaia DR2 declination of source
(ICRS, at epoch 2015.5) (DEdeg_source)
300-305 F6.3 mas/yr pmRAs Gaia DR2 proper motion in RA of source
(pmRA_source)
307-312 F6.3 mas/yr pmDEs Gaia DR2 proper motion in Dec of source
(pmDE_source)
314-319 F6.3 mas plxs Gaia DR2 parallax of source (plx_source)
321-325 F5.2 % prob1RE Probability of alignment within one Einstein
radius (prob_1RE)
327-332 F6.4 arcsec b_Dmin Closest approach (16th percentile) (Dmin_low)
334-339 F6.4 arcsec Dmin Closest approach (50th percentile) (Dmin)
341-346 F6.4 arcsec B_Dmin Closest approach (84th percentile)
(Dmin_high)
348-354 F7.5 --- b_maxmag Maximum magnification ignoring dilution
(16th percentile) (maxmaglow)
356-362 F7.5 --- maxmag Maximum magnification ignoring dilution
(50th percentile) (max_mag)
364-370 F7.5 --- B_maxmag Maximum magnification ignoring dilution
(84th percentile) (maxmaghigh)
372-381 E10.5 --- b_maxmagnet Maximum magnification including dilution
(16th percentile) (maxmagnet_low)
383-392 E10.5 --- maxmagnet Maximum magnification including dilution
(50th percentile) (maxmagnet)
394-403 E10.5 --- B_maxmagnet Maximum magnification including dilution
(84th percentile) (maxmagnet_high)
405-414 A10 "date" b_Tmax Time of maximum magnification
(16th percentile) (Tmax_low)
416-425 A10 "date" Tmax Time of maximum magnification
(50th percentile) (Tmax)
427-436 A10 "date" B_Tmax Time of maximum magnification
(84th percentile) (Tmax_high)
438-442 F5.2 d b_dur Time undiluted magnification exceeds 10-2
(16th percentile) (duration_low)
444-448 F5.2 d dur Time undiluted magnification exceeds 10-2
(50th percentile) (duration)
450-455 F6.2 d B_dur Time undiluted magnification exceeds 10-2
(84th percentile) (duration_high)
457-462 F6.2 d b_durnet Time diluted magnification exceeds 10-4
(16th percentile) (durationnetlow)
464-469 F6.2 d durnet Time diluted magnification exceeds 10-4
(50th percentile) (duration_net)
471-476 F6.2 d B_durnet Time diluted magnification exceeds 10-4
(84th percentile) (durationnethigh)
478-483 F6.2 deg b_Solelong Solar elongation at peak magnification
(16th percentile) (Solelonglow)
485-490 F6.2 deg Solelong Solar elongation at peak magnification
(50th percentile) (Sol_elong)
492-497 F6.2 deg B_Solelong Solar elongation at peak magnification
(84th percentile) (Solelonghigh)
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Acknowledgements:
Alexander Mustill, alex(at)astro.lu.se
(End) Alexander Mustill [Lund, Sweden], Patricia Vannier [CDS] 27-Jul-2018