1,134 research outputs found
Are the Ogle Microlenses in the Galactic Bar?
The analysis of the first two years of OGLE data revealed 9 microlensing
events of the galactic bulge stars, with the characteristic time scales in the
range days, where . The optical depth to
microlensing is larger than , in excess of
current theoretical estimates, indicating a much higher efficiency for
microlensing by either bulge or disk lenses. We argue that the lenses are
likely to be ordinary stars in the galactic bar, which has its long axis
elongated towards us. A relation between and the lens masses remains
unknown until a quantitative model of bar microlensing becomes available. At
this time we have no evidence that the OGLE events are related to dark matter.
The geometry of lens distribution can be determined observationally when the
microlensing rate is measured over a larger range of galactic longitudes, like
, and the relative proper motions of the galactic bulge
(bar) stars are measured with the HST.Comment: 10 pages, 2 figures, revised version accepted for the publication in
ApJL, uses AAS LaTeX aaspp.sty macro, PostScript figures and PostScript
version of the paper available through anonymous ftp from
astro.princeton.edu, directory stanek/tau, or on reques
DIRECT Distances to Nearby Galaxies Using Detached Eclipsing Binaries and Cepheids. III. Variables in the Field M31C
We undertook a long term project, DIRECT, to obtain the direct distances to
two important galaxies in the cosmological distance ladder -- M31 and M33 --
using detached eclipsing binaries (DEBs) and Cepheids. While rare and difficult
to detect, DEBs provide us with the potential to determine these distances with
an accuracy better than 5%. The extensive photometry obtained in order to
detect DEBs provides us with good light curves for the Cepheid variables. These
are essential to the parallel project to derive direct Baade-Wesselink
distances to Cepheids in M31 and M33. For both Cepheids and eclipsing binaries,
the distance estimates will be free of any intermediate steps.
As a first step in the DIRECT project, between September 1996 and October
1997 we obtained 95 full/partial nights on the F. L. Whipple Observatory 1.2 m
telescope and 36 full nights on the Michigan-Dartmouth-MIT 1.3 m telescope to
search for DEBs and new Cepheids in the M31 and M33 galaxies. In this paper,
third in the series, we present the catalog of variable stars, most of them
newly detected, found in the field M31C [(alpha,delta)=(11.10, 41.42) deg,
J2000.0}]. We have found 115 variable stars: 12 eclipsing binaries, 35 Cepheids
and 68 other periodic, possible long period or non-periodic variables. The
catalog of variables, as well as their photometry and finding charts, is
available via anonymous ftp and the World Wide Web. The complete set of the CCD
frames is available upon request.Comment: submitted to the Astronomical Journal, 39 pages, 27 figures; paper
and data available at ftp://cfa-ftp.harvard.edu/pub/kstanek/DIRECT/ and
through WWW at http://cfa-www.harvard.edu/~kstanek/DIRECT
Modelling the Galactic Bar Using Red Clump Giants
The color-magnitude diagrams of stars obtained for 12
fields across the Galactic bulge with the OGLE project reveal a well-defined
population of bulge red clump giants. We find that the distributions of the
apparent magnitudes of the red clump stars are systematically fainter when
moving towards lower galactic fields. The most plausible explanation of
this distinct trend is that the Galactic bulge is a bar, whose nearest end lies
at positive galactic longitude. We model this Galactic bar by fitting for all
fields the observed luminosity functions in the red clump region of the
color-magnitude diagram. We find that almost regardless of the analytical
function used to describe the 3-D stars distribution of the Galactic bar, the
resulting models have the major axis inclined to the line of sight by
, with axis ratios corresponding to . This
puts a strong constraint on the possible range of the Galactic bar models.
Gravitational microlensing can provide us with additional constrains on the
structure of the Galactic bar.Comment: submitted to the New Astronomy, 27 pages, 11 figures; also available
at ftp://www.astro.princeton.edu/stanek/Barmodel and through WWW at
http://www.astro.princeton.edu/~library/prep.htm
Color-Magnitude Diagram Distribution of the Bulge Red Clump Stars - Evidence for the Galactic Bar
The color-magnitude diagrams of stars obtained for 13
fields towards the Galactic bulge with the OGLE project reveal a well-defined
population of bulge red clump stars. We find that the distributions of the
extinction-adjusted apparent magnitudes of the red clump stars in fields lying
at in galactic longitude differ by . Assuming
that the intrinsic luminosity distribution of the red clump stars is the same
on both sides of the Galactic center, this implies that the distances to the
red clump stars in the two fields differ by a factor of . A
plausible explanation of the observed difference in the luminosity distribution
is that the Galactic bulge is a triaxial structure, or bar, which is inclined
to the line of sight by no more than , with the part of the bar at the
positive galactic longitude being closer to us. This agrees rather well with
other studies indicating the presence of the bar in the center of the Galaxy.
Color-magnitude diagram data are accessible over the computer network with
anonymous {\tt ftp}.Comment: 10 pages, 6 figures, uses AAS LaTeX aaspp.sty macro, PostScript
figures available through the anonymous ftp or on request, accepted for the
publication in the ApJ
Germline-focused analysis of tumour-detected variants in 49,264 cancer patients: ESMO Precision Medicine Working Group recommendations
Germline; Tumour-only sequencingLínia germinal; Seqüenciació només de tumorsLínea germinal; Secuenciación solo de tumorsBackground
The European Society for Medical Oncology Precision Medicine Working Group (ESMO PMWG) was reconvened to update its 2018/19 recommendations on follow-up of putative germline variants detected on tumour-only sequencing, which were based on an analysis of 17 152 cancers.
Methods
We analysed an expanded dataset including 49 264 paired tumour-normal samples. We applied filters to tumour-detected variants based on variant allele frequency, predicted pathogenicity and population variant frequency. For 58 cancer-susceptibility genes, we then examined the proportion of filtered tumour-detected variants of true germline origin [germline conversion rate (GCR)]. We conducted subanalyses based on the age of cancer diagnosis, specific tumour types and ‘on-tumour’ status (established tumour-gene association).
Results
Analysis of 45 472 nonhypermutated solid malignancy tumour samples yielded 21 351 filtered tumour-detected variants of which 3515 were of true germline origin. 3.1% of true germline pathogenic variants were absent from the filtered tumour-detected variants. For genes such as BRCA1, BRCA2 and PALB2, the GCR in filtered tumour-detected variants was >80%; conversely for TP53, APC and STK11 this GCR was <2%.
Conclusion
Strategic germline-focused analysis can prioritise a subset of tumour-detected variants for which germline follow-up will produce the highest yield of most actionable true germline variants. We present updated recommendations around germline follow-up of tumour-only sequencing including (i) revision to 5% for the minimum per-gene GCR, (ii) inclusion of actionable intermediate penetrance genes ATM and CHEK2, (iii) definition of a set of seven ‘most actionable’ cancer-susceptibility genes (BRCA1, BRCA2, PALB2, MLH1, MSH2, MSH6 and RET) in which germline follow-up is recommended regardless of tumour type.This work was supported by the European Society for Medical Oncology (no grant number)
Modelling the Galactic Bar Using Red Clump Stars
The color-magnitude diagrams of stars obtained for 19
fields towards the Galactic bulge with the OGLE project reveal a well-defined
population of bulge red clump stars. We found that the distributions of the
extinction-adjusted apparent magnitudes of red clump stars in fields lying at
in galactic longitude differ by . A plausible
explanation of this observed difference in the luminosity distribution is that
the Galactic bulge is a triaxial structure, or a bar, which is inclined to the
line of sight by no more than . The part of the bar at the positive
galactic longitude is closer to us. Work is now under way to model the Galactic
bar by fitting the observed luminosity functions in the red clump region for
various fields. Preliminary results indicate that the angle of the inclination
of the bar to the line of sight can be as small as . Gravitational
microlensing can provide us with additional constrains on the structure of the
Galactic bar.Comment: 4 pages, uuencoded compressed PostScript, talk presented at the IAU
Colloquium 157 "Barred Galaxies"; also available through WWW at
http://www.astro.princeton.edu/~library/prep.htm
The optical gravitational lensing experiment: variable stars in globular clusters; 1, fields 5139A-C in Omega Centauri
Three fields covering the central part of the globular cluster Omega Cen were surveyed in a search for variable stars. We present V-band light curves for 22 periodic variables: 9 SX~Phe stars, 7 contact binaries, 5 detached or semi-detached binaries, and one spotted variable (FK Com or RS CVn type star). Only 2 of these variables were previously known. All SX Phe stars and all contact binaries from our sample belong to blue stragglers. Observed properties of these stars are consistent with their cluster membership. Of particular interest is detection of two well detached binaries with periods P=1.50 day and P=2.47 day. Further study of these two binaries can provide direct information about properties of turnoff stars in Omega Cen. An uncomplete light curve of a Mira variable known as V2 was obtained. We present V vs. V-I color-magnitude diagrams for the monitored part of the cluster
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