2008-02-15T13:10:00Z
100
catalogs
astrometric-microlensing-effect
A catalogue of candidate stars
for observing astrometric microlensing using Gaia.
Candidates for astrometric microlensing
Demleitner, M.; Proft, S.
Optical
2011A&A...536A..50P
To obtain the complete list of microlensing candidates, including
lenses with correct, spurious, and unverified proper motion, click
on the Go button. Otherwise, select your preferred candidates and
their ordering. If you are only interested in the microlensing
candidates with verified proper motion, select "Confirmed?".
More information on the idea behind this catalog and the
description of all properties can be found in the
`service info </amlensing/q/q/info#id7>`_.
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 `_
]]>
//scs#pgs-pos-index
The "input table" containing stars with
relatively high proper motion. Currently, these are generated
PPMX, UCAC3, LSPM-North, and a catalogue of brown dwarfs.
The table of candidate stars. These
are objects from highpm that have a PPMXL object within their
regions of interest.
//scs#pgs-pos-index
The final candidate table with estimates
of minimal distances, epochs, etc.
Position ICRS BARYCENTER Epoch J2000.0 "lensalpha" "lensdelta"
Error "lensalphaErr" "lensdeltaErr"
Velocity "lenspmalpha" "lenspmdelta"
Error "lenspmalphaErr" "lenspmdeltaErr"
Position ICRS "obalpha" "obdelta"
Error "obalphaErr" "obdeltaErr"
Velocity "obpmalpha" "obpmdelta"
Error "obpmalphaErr" "obpmdeltaErr"
if inPars.get(inputKeys[0].name, False):
yield "confirmed"
minDate
am lensing cands
314.7149425
36.1983766667
0.01
def RA(f):
return utils.degToHms(f, ":")
def DEC(f):
return utils.degToDms(f, ":")
def getLensBorder(alpha, delta, pma, pmd, pmaErr, pmdErr,
years, width):
cosD = math.cos(delta/180*math.pi)
# factor for pm for total offset arcsec vector
destA = alpha+(pma*years)/cosD
destD = delta+pmd*years
pmNorm = 1/math.sqrt(pma**2+pmd**2)*(width/2.)/3600.
oal, odl = pmd*pmNorm, pma*pmNorm
return ((RA(alpha+oal/cosD), DEC(delta-odl),
RA(destA+oal/cosD), DEC(destD-odl)),
(RA(alpha-oal/cosD), DEC(delta+odl),
RA(destA-oal/cosD), DEC(destD+odl)))
def getLenseeMark(alpha, delta, pma, pmd, span):
if pma**2+pmd**2<(1/3600./20)**2:
return "draw tag(%s, %s)"%(RA(alpha), DEC(delta))
return "draw line(%s,%s,%s,%s);"%(
RA(alpha), DEC(delta),
RA(alpha+pma*span), DEC(delta+pmd*span))
if data is None:
return ""
span = 25;
lA, lD = data[0], data[1]
oA, oD = data[2], data[3]
lpma, lpmd = data[4], data[5]
opma, opmd = data[6], data[7]
lpmaErr, lpmdErr = data[8], data[9]
upper, lower = getLensBorder(lA, lD, lpma, lpmd, lpmaErr,
lpmdErr, span, 1)
script = ";\\n".join([
"get aladin() %s %s"%(utils.degToHms(lA), utils.degToDms(lD)),
"sync",
"draw mode(radec)",
"draw line(%s,%s,%s,%s)"%upper,
"draw line(%s,%s,%s,%s)"%lower,
getLenseeMark(oA, oD, opma, opmd, span),
])+";"
return T.pre(style="width:8em;height:6em;overflow:scroll")[
script]
/amlensing/q/q/form
self.assertHasStrings(
"Matched: 3",
"LSPM J2135+5428",
"2018.6788",
"sim-coo?Coord=323.78958d%2B54.47421d&Radius=0.100000",
"16735", # dist of 2nd object to search center
"get aladin() 21 30 19.261 +48 42 06.98;\\nsync;\\ndraw mode(radec);"
)
q/scs.xml
rows = self.getVOTableRows()
self.assertEqual(len(rows), 1)
self.assertEqual(rows[0]["confirmed"], False)
self.assertAlmostEqual(rows[0]["minDate"], 2009.2423095703125)
self.assertFalse("aladin" in rows[0])