Information on Service 'Candidates for astrometric microlensing'

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A catalogue of candidate stars for observing astrometric microlensing using GAIA.

For a list of all services and tables belonging to this service's resource, see Information on resource 'Candidates for astrometric microlensing'

Service Documentation

The Idea behind this Catalog

We constructed the candidate list to identify stars with large proper motions (>0.15 arcsec/year) that are potential candidates for the astrometric microlensing effect during the Gaia mission [PDW]. With the Gaia mission it will be possible to measure this effect with the required accuracy at best 30 micro-arcsec for a single measurement. The satellite, which is observing since July 2014, surveys the whole sky and has an expected lifetime of five years. It is doing astrometry, photometry and spectroscopy of approximately one billion stars in our galaxy brighter than ~20 mag in visual band [GAIA].

The astrometric microlensing effect allows a precise measurement of the mass of a star that is acting as a lens [PAC]. Ideally, the microlensing event is observed both astrometrically and photometrically. When the unaffected source position is not known or the lens is not visible both measurements are necessary. Photometric microlensing events (with small angular distances of lens and source) are about ten times shorter than the corresponding astrometric event. Hence Gaia will do no or only few photometric measurements. Therefore, an accompanying ground based photometric observations of the events would be advantageous. For this purpose it is very helpful to predict microlensing events.

To predict microlensing events it is essential to have positions and proper motions with a high accuracy (maximal 100 mas in position and 10 mas/year in proper motion). Hence it is important to choose suitable catalogs for the lenses and sources. For the sources, we chose PPMXL [PPMXL], for the lenses the LSPM-NORTH [LSPM] on the northern sky and PPMX [PPMX] and UCAC3 [UCAC3].

Problems

After manual inspection of about one hundred lens proper motions we found out that the majority of the high proper motions in PPMX an UCAC3 are erroneous. While nearly all proper motions from LSPM are correct, only a small fraction of high proper motions (<1%) from PPMX and UCAC3 are physical. This means that a high number of the predicted events from our candidate list is wrong.

Confirmed Microlensing Candidates (2012-2019)

In our previous work the assembled microlensing catalog comprised 910 candidates for the years 2012 to 2017. Their proper motion analysis yielded that 96% of the (high) proper motions of the lensing stars were erroneous. We were thus left with only 43 confirmed microlensing candidates. Due to an improvement of the search width around potential lensing stars, we can predict 50 additional astrometric microlensing events with correct proper motion now between 2014 and 2019. All confirmed astrometric microlensing candidates are marked with true in the "Confirmed?"-column.

References

[PDW]Proft, S., Demleitner, M. and Wambsganss, J. (2011). Prediction of astrometric microlensing events during the Gaia mission. 2011A%26A...536A..50P
[GAIA]Science Performance of the Gaia Satellite. www.cosmos.esa.int/web/gaia/science-performance
[LSPM]Lepine, S. and Shara, M. M. (2005). A Catalog of Northern Stars With Annual Proper Motions Larger Than 0.15 Seconds of Arc (LSPM catalog - North). 2005AJ....129.1483L
[PAC]Paczynski, B. (1995). The Masses of Nearby Dwarfs can be Determined with Gravitational Microlensing. 1995AcA....45..345P
[PPMXL]Roeser, S., Demleitner, M. and Schilbach, E. (2010). The PPMXL catalog of positions and proper motions on the ICRS. Combining USNOB1.0 and 2MASS. 2010AJ....139.2440R
[PPMX]Roeser, S. et al. (2008). PPM Extended (PPMX) - a catalogue of positions and proper motions. 2008A&A...488..401R
[UCAC3]Zacharias, N. et al. (2010). The Third US Naval Observatory CCD Astrograph Catalog (UCAC3). 2010AJ....139.2184Z

Overview

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Input Fields

The following fields are available to provide input to the service (with some renderers, some of these fields may be unavailable):

NameTable Head DescriptionUnitUCD
confirmed Confirmed? Only show candidates for which the encounter is confirmed (i.e., proper motions are right) N/A N/A
DEC Delta (ICRS) Declination (ICRS decimal) deg pos.eq.dec
hscs_pos Position/Name Coordinates (as h m s, d m s or decimal degrees), or SIMBAD-resolvable object N/A N/A
hscs_sr Search radius Search radius in arcminutes N/A N/A
lensmag Lens mag PPMX catalogue magnitude of lens mag N/A
minDate T(min) Estimated time of closest approach (julian year) yr N/A
minDist D(min) Estimated minimal distance deg N/A
obB Object B mag USNO-B B mag magnitude of lensed N/A N/A
RA Alpha (ICRS) Right Ascension (ICRS decimal) deg pos.eq.ra
source Lens src. Source of the data of the lens N/A meta.code
SR Search Radius Search radius deg N/A

Default Output Fields

The following fields are contained in the output by default. More fields may be available for selection; these would be given below in the VOTable output fields.

NameTable Head DescriptionUnitUCD
_r Dist. Distance to cone center deg pos.distance
aladin Aladin View in Aladin N/A N/A
confirmed Confirmed? 1 if lensing event confirmed N/A N/A
dist2010 Dist 2010 N/A deg N/A
dist2013 Dist 2013 N/A deg N/A
dist2016 Dist 2016 N/A deg N/A
dist2019 Dist 2019 N/A deg N/A
lensalpha Lensing alpha J2000 PPMX alpha of lens deg pos.eq.ra;meta.main
lensdelta Lensing delta J2000 PPMX delta of lens deg pos.eq.dec;meta.main
lensmag Lens mag PPMX catalogue magnitude of lens mag N/A
minDate T(min) Estimated time of closest approach (julian year) yr N/A
minDist D(min) Estimated minimal distance deg N/A
obalpha Object alpha J2000 USNO alpha of lensed object deg N/A
obB Object B mag USNO-B B mag magnitude of lensed N/A N/A
obdelta Object delta J2000 USNO delta of lensed object deg N/A
simbad In Simbad Cone search around given position in Simbad N/A N/A
source Lens src. Source of the data of the lens N/A meta.code
srcId Lensing ob. Id of lensing object N/A meta.id;meta.main

VOTable Output Fields

The following fields are available in VOTable output. The verbosity level is a number intended to represent the relative importance of the field on a scale of 1 to 30. The services take a VERB argument. A field is included in the output if their verbosity level is less or equal VERB*10.

NameTable Head DescriptionUnitUCD Verb. Level
lensalpha Lensing alpha J2000 PPMX alpha of lens deg pos.eq.ra;meta.main 1
lensdelta Lensing delta J2000 PPMX delta of lens deg pos.eq.dec;meta.main 1
srcId Lensing ob. Id of lensing object N/A meta.id;meta.main 5
_r Dist. Distance to cone center deg pos.distance 10
source Lens src. Source of the data of the lens N/A meta.code 10
lensalphaErr Err(L.alpha) Error of lens alpha deg stat.error;pos.eq.ra;meta.main 15
lensdeltaErr Err(L.delta) Error of lens delta deg stat.error;pos.eq.dec;meta.main 15
confirmed Confirmed? 1 if lensing event confirmed N/A N/A 20
lensmag Lens mag PPMX catalogue magnitude of lens mag N/A 20
obalpha Object alpha J2000 USNO alpha of lensed object deg N/A 20
obdelta Object delta J2000 USNO delta of lensed object deg N/A 20
obB Object B mag USNO-B B mag magnitude of lensed N/A N/A 20
minDate T(min) Estimated time of closest approach (julian year) yr N/A 20
minDist D(min) Estimated minimal distance deg N/A 20
dist2010 Dist 2010 N/A deg N/A 20
dist2013 Dist 2013 N/A deg N/A 20
dist2016 Dist 2016 N/A deg N/A 20
dist2019 Dist 2019 N/A deg N/A 20
lenspmalpha L. PM alpha Lens PM in alpha, cos(delta) applied deg/yr N/A 20
lenspmdelta L. PM delta Lens PM in delta deg/yr N/A 20
lenspmalphaErr Err(L. PM alpha) Error of Lens PM in alpha deg/yr N/A 20
lenspmdeltaErr Err(L. PM delta) Error of Lens PM in delta deg/yr N/A 20
lensRmag Lens R PPMX Ru mag of lens mag N/A 20
lensBmag Lens B mag Lens B mag as in PPMX mag N/A 20
lensVmag Lens V mag Lens V mag as in PPMX mag N/A 20
lensJmag Lens J mag Lens J mag as in PPMX mag N/A 20
lensHmag Lens H mag Lens H mag as in PPMX mag N/A 20
lensKmag Lens K mag Lens K mag as in PPMX mag N/A 20
obalphaErr Err(O. alpha) Positional error of lensed object in alpha deg N/A 20
obdeltaErr Err(O. delta) Positional error of lensed object in delta deg N/A 20
obpmalpha O. PM alpha Object PM in alpha deg/yr N/A 20
obpmdelta O. PM delta Object PM in delta deg/yr N/A 20
obpmalphaErr Err(O. PM alpha) Error of Object PM in alpha deg/yr N/A 20
obpmdeltaErr Err(O. PM delta) Error of Object PM in delta deg/yr N/A 20
obR Object R mag USNO-B R mag magnitude of lensed N/A N/A 20
obI Object I mag USNO-B I mag magnitude of lensed N/A N/A 20
obJ Object J mag 2MASS J mag magnitude of lensed N/A N/A 20
obH Object H mag 2MASS H mag magnitude of lensed N/A N/A 20
obK Object K mag 2MASS K mag magnitude of lensed N/A N/A 20
minDateErr Err. T(min) Error in estimation of time of closest approach yr N/A 20
minDistErr Err. D(min) Error in estimation of minimal distance deg N/A 20

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