J/ApJ/810/L20 VISTA KS photometry of EWS 2012-BLG-548 (Minniti+, 2015)
VVV survey observations of a microlensing stellar mass black hole candidate
in the field of the globular cluster NGC 6553.
Minniti D., Contreras Ramos R., Alonso-Garcia J., Anguita T., Catelan M.,
Gran F., Motta V., Muro G., Rojas K., Saito R.K.
<Astrophys. J., 810, L20 (2015)>
=2015ApJ...810L..20M 2015ApJ...810L..20M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Gravitational lensing ; Photometry, infrared
Keywords: globular clusters: individual: NGC 6553;
gravitational lensing: micro; infrared: stars; surveys
Abstract:
We report the discovery of a large timescale candidate microlensing
event of a bulge stellar source based on near-infrared observations
with the VISTA Variables in the Via Lactea Survey (VVV). The new
microlensing event is projected only 3.5 arcmin away from the center
of the globular cluster NGC 6553. The source appears to be a bulge
giant star with magnitude Ks=13.52, based on the position in the
color-magnitude diagram. The foreground lens may be located in the
globular cluster, which has well-known parameters such as distance and
proper motions. If the lens is a cluster member, we can directly
estimate its mass simply following Paczynski which is a modified
version of the more general case due to Refsdal. In that case, the
lens would be a massive stellar remnant, with M=1.5-3.5M☉. If
the blending fraction of the microlensing event appears to be small,
and this lens would represent a good isolated black hole (BH)
candidate, that would be the oldest BH known. Alternative explanations
(with a larger blending fraction) also point to a massive stellar
remnant if the lens is located in the Galactic disk and does not
belong to the globular cluster.
Description:
VISTA Variables in the Via Lactea (VVV) is a public ESO near-infrared
(IR) variability survey aimed at scanning the inner Milky Way (Minniti
et al. 2010NewA...15..433M 2010NewA...15..433M). The observations are acquired with the
VISTA 4m telescope at ESO Paranal Observatory. The Ks-band
observations continue, and the variability light curves so far span
from 2010 to 2015.
Objects:
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RA (ICRS) DE Designation(s)
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18 09 13.86 -25 57 52.7 EWS 2012-BLG-548 = EWS 2012-BLG-548
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 26 208 VISTA Variables in the Via Lactea (VVV) Survey
near-IR photometry of the candidate
microlensing event
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See also:
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/AJ/149/99 : VVV globulars. I. 2MASS-GC 02, Terzan 10 (Alonso-Garcia+, 2015)
J/AJ/143/70 : Differential reddening in MW globulars (Alonso-Garcia+, 2012)
J/ApJ/625/796 : X-ray sources in the globular cluster 47 Tuc (Heinke+, 2005)
http://ogle.astrouw.edu.pl/ogle4/ews/2012/ews.html : OGLE-IV EWS 2012
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 12 F12.6 d Epoch [55298.3/56955.1] Ks-band observation epoch (MJD)
14- 20 F7.4 mag Ksmag [12.82/13.68] Ks-band observations
22- 26 F5.3 mag e_Ksmag [0.007/0.08] uncertainty in Ksmag
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 18-Dec-2015