1,622 research outputs found
Around Gaia Alerts in 20 questions
Gaia is a European Space Agency (ESA) astrometry space mission, and a
successor to the ESA Hipparcos mission. Gaia's main goal is to collect
high-precision astrometric data (i.e. positions, parallaxes, and proper
motions) for the brightest 1 billion objects in the sky. These data,
complemented with multi-band, multi-epoch photometric and spectroscopic data
collected from the same observing platform, will allow astronomers to
reconstruct the formation history, structure, and evolution of the Galaxy.
Gaia will observe the whole sky for 5 years, providing a unique opportunity
for the discovery of large numbers of transient and anomalous events, e.g.
supernovae, novae and microlensing events, GRB afterglows, fallback supernovae,
and other theoretical or unexpected phenomena. The Photometric Science Alerts
team has been tasked with the early detection, classification and prompt
release of anomalous sources in the Gaia data stream. In this paper, we discuss
the challenges we face in preparing to use Gaia to search for transient
phenomena at optical wavelengths.Comment: Text of the poster presented at the IAU Symposium #285 "New Horizons
in Time Domain Astronomy", Oxford, UK, 19-23 September 2011, included in the
proceedings Eds. R.E.M. Griffin, R.J. Hanisch & R. Seaman. Original poster is
available under this link:
http://www.ast.cam.ac.uk/ioa/wikis/gsawgwiki/images/3/33/AroundGaiaPoster2011.pd
The sightseeing attractions of Wrocław and their potential exploitation
The article presents the more important results of research concerning the sightseeing attractions of Wrocław which can then be used to inform the organisation of the tourism offer of the city
Constraining the masses of microlensing black holes and the mass gap with Gaia DR2
Context: Gravitational microlensing is sensitive to compact-object lenses in
the Milky Way, including white dwarfs, neutron stars or black holes, and could
potentially probe a wide range of stellar remnant masses. However, the mass of
the lens can be determined only in very limited cases, due to missing
information on both source and lens distances and their proper motions.
Aims: We aim at improving the mass estimates in the annual parallax
microlensing events found in the 8 years of OGLE-III observations towards the
Galactic Bulge (Wyrzykowski et al. 2016) with the use of Gaia Data Release 2
(DR2).
Methods: We use Gaia DR2 data on distances and proper motions of non-blended
sources and recompute the masses of lenses in parallax events. We also identify
new events in that sample which are likely to have dark lens; the total number
of such events is now 18.
Results: The derived distribution of masses of dark lenses is consistent with
a continuous distribution of stellar remnant masses. A mass gap between
neutron-star and black-hole masses in the range between 2 and 5 solar masses is
not favoured by our data, unless black holes receive natal-kicks above 20-80
km/s. We present 8 candidates for objects with masses within the putative mass
gap, including a spectacular multi-peak parallax event with mass of
located just at 600 pc. The absence of an
observational mass gap between neutron stars and black holes, or, conversely,
the evidence for black hole natal kicks if a mass gap is assumed, can inform
future supernova modelling efforts.Comment: 12 pages, published as Wyrzykowski&Mandel, 2020, A&A, 636, A2
Explicit positive representation for weights on
It is an old idea to replace averages of observables with respect to a
complex weight by expectation values with respect to a genuine probability
measure on complexified space. This is precisely what one would like to get
from complex Langevin simulations. Unfortunately, these fail in many cases of
physical interest. We will describe method of deriving positive representations
by matching of moments and show simple examples of successful constructions. It
will be seen that the problem is greatly underdetermined.Comment: 8 pages, 3 figures. Material presented in Lattice 2017 conference in
Granad
Techniques for Observing Binaries in Other Galaxies
I present an overview of the techniques used for detecting and following up
binaries in nearby galaxies and present the current census of extragalactic
binaries, with a focus on eclipsing systems. The motivation for looking in
other galaxies is the use of eclipsing binaries as distance indicators and as
probes of the most massive stars.Comment: 5 pages, 1 table, to appear in the proceedings of the IAUS 282 on
"From Interacting Binaries to Exoplanets: Essential Modelling Tools"
(Tatranska Lomnica, Slovakia, July 2011), Cambridge University Pres
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