scholarly journals Estimating Finite Source Effects in Microlensing Events due to Free-Floating Planets with the Euclid Survey

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Lindita Hamolli ◽  
Mimoza Hafizi ◽  
Francesco De Paolis ◽  
Achille A. Nucita
Keyword(s):  
Spatial Distribution ◽  
Power Law ◽  
Mass Function ◽  
Physical Parameters ◽  
Galactic Bulge ◽  
Source Effect ◽  
Source Effects ◽  
Function Index ◽  
Finite Source ◽  
Einstein Radius

In recent years free-floating planets (FFPs) have drawn a great interest among astrophysicists. Gravitational microlensing is a unique and exclusive method for their investigation which may allow obtaining precious information about their mass and spatial distribution. The planned Euclid space-based observatory will be able to detect a substantial number of microlensing events caused by FFPs towards the Galactic bulge. Making use of a synthetic population algorithm, we investigate the possibility of detecting finite source effects in simulated microlensing events due to FFPs. We find a significant efficiency for finite source effect detection that turns out to be between 20% and 40% for a FFP power law mass function index in the range [0.9, 1.6]. For many of such events it will also be possible to measure the angular Einstein radius and therefore constrain the lens physical parameters. These kinds of observations will also offer a unique possibility to investigate the photosphere and atmosphere of Galactic bulge stars.

scholarly journals The Substellar Members of the Pleiades

2003 ◽  
Vol 211 ◽  
pp. 181-182
Author(s):  
Paul D. Dobbie ◽  
Richard F. Jameson ◽  
Samantha L. Osborne ◽  
Simon T. Hodgkin ◽  
David J. Pinfield
Keyword(s):  
Dark Matter ◽  
Spatial Distribution ◽  
Power Law ◽  
Spatial Model ◽  
Total Mass ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Core Radius ◽  
Brown Dwarf ◽  
Limited Sample

We have compiled the largest magnitude limited sample of candidate substellar Pleiads to date. We fit King profiles to their spatial distribution to determine the Pleiades brown dwarf core radius to be Subsequently we have used our improved spatial model to place stringent limits on the shape of the cluster mass function across and below the stellar/substellar regime. We find this to be a power law with index α = 0.41±0.08 (0.3M⊙ ≥M≥ 0.035M⊙). Extrapolation of this mass function to M= 0.012M⊙ indicates that brown dwarfs contribute only ~ 2% to the total mass of the cluster hence we conclude that brown dwarfs do not contribute significantly to disk dark matter.

scholarly journals 6.12. Microlensing and dynamics of the Galactic bulge

1998 ◽  
Vol 184 ◽  
pp. 285-286
Author(s):  
H.S. Zhao
Keyword(s):  
Spatial Distribution ◽  
Brown Dwarfs ◽  
Mass Function ◽  
Dynamical Model ◽  
Galactic Bulge ◽  
Galactic Disc

Microlensing (μ—lensing) towards the bulge started out as a unique technique of detecting dark objects in the Galactic disc (brown dwarfs) by measuring a rare transient brightening of one star among millions of stars in the Galactic bulge (Paczyński 1991). More than 200 events have been detected towards the Bulge since 1993 by the DUO, MACHO, OGLE etc. survey teams. But where are the lenses? Are they truly dark objects or merely faint stars? I show the results on the mass function, spatial distribution and dynamics of these observed lenses based on a dynamical model of the Galactic bar.

scholarly journals Statistical Investigation of Spectroscopic Binary Stars

1980 ◽  
Vol 88 ◽  
pp. 15-22 ◽  
Author(s):  
A. V. Tutukov ◽  
L. R. Yungelson
Keyword(s):  
Power Law ◽  
Binary Stars ◽  
Mass Function ◽  
Statistical Investigation ◽  
Initial Mass Function ◽  
Initial Mass ◽  
Published Data ◽  
Physical Parameters ◽  
Double Line ◽  
Spectroscopic Binary

A catalog of physical parameters of about 1000 spectroscopic binary stars (SB), based on the Batten catalog, its extensions, and newly published data has been compiled. Masses of stars′ components (M1 and M2), mass ratios of components (q = M1/M2) and orbital angular momenta are computed, wherever possible. It is probable that the initial mass function of the primaries is non-monotonic and is described only approximately by a power-law. The distribution of q of double-line SB has a sharp maximum near q = 1, that of single-line SB, near q = 0.3. SB with 1.5 ≲ M1/M⊙ ≲ 10 and semiaxes of orbits a ≲ 10 R⊙ probably do not form. A number of assumed “initial” distributions of M1, q and a were transformed with the aim of obtaining “observed” distributions taking into account the observational selection due to the luminosities of the components, their radial velocities, inclinations of the orbits, and the effects of matter exchange between the components. The best agreement with the observations is obtained for the combination of a power-law initial mass function ξ(M) ≃ M−2.35, a distribution of q with a maximum near 1 and a distribution of semiaxes with dN/da ≃ 1/a.

scholarly journals A THEORETICAL CALCULATION OF MICROLENSING SIGNATURES CAUSED BY FREE-FLOATING PLANETS TOWARDS THE GALACTIC BULGE

2013 ◽  
Vol 22 (10) ◽  
pp. 1350072 ◽  
Author(s):  
L. HAMOLLI ◽  
M. HAFIZI ◽  
A. A. NUCITA
Keyword(s):  
Distribution Function ◽  
Spatial Distribution ◽  
Theoretical Calculation ◽  
Optical Depth ◽  
Special Interest ◽  
Scientific Community ◽  
Mass Range ◽  
Mass Function ◽  
Galactic Bulge ◽  
Spatial Distribution Function

Free-floating planets (FFPs) are recently drawing a special interest of the scientific community. Gravitational microlensing is up to now the exclusive method for the investigation of FFPs, including their spatial distribution function and mass function. In this paper, we examine the possibility that the future Euclid space-based observatory may allow to discover a substantial number of microlensing events caused by FFPs. Based on latest results about the free-floating planet (FFP) mass function in the mass range [10-5, 10-2]M⊙, we calculate the optical depth towards the Galactic bulge as well as the expected microlensing rate and find that Euclid may be able to detect hundreds to thousands of these events per month. Making use of a synthetic population, we also investigate the possibility of detecting parallax effect in simulated microlensing events due to FFPs and find a significant efficiency for the parallax detection that turns out to be around 30%.

scholarly journals On the emergent system mass function: the contest between accretion and fragmentation

2020 ◽  
Vol 500 (2) ◽  
pp. 1697-1707
Author(s):  
Paul C Clark ◽  
Anthony P Whitworth
Keyword(s):  
Star Formation ◽  
Standard Deviation ◽  
Mass Distribution ◽  
Power Law ◽  
Accretion Rate ◽  
Mass Function ◽  
High Mass ◽  
New Model ◽  
System Formation ◽  
Low Mass

ABSTRACT We propose a new model for the evolution of a star cluster’s system mass function (SMF). The model involves both turbulent fragmentation and competitive accretion. Turbulent fragmentation creates low-mass seed proto-systems (i.e. single and multiple protostars). Some of these low-mass seed proto-systems then grow by competitive accretion to produce the high-mass power-law tail of the SMF. Turbulent fragmentation is relatively inefficient, in the sense that the creation of low-mass seed proto-systems only consumes a fraction, ${\sim }23{{\ \rm per\ cent}}$ (at most ${\sim }50{{\ \rm per\ cent}}$), of the mass available for star formation. The remaining mass is consumed by competitive accretion. Provided the accretion rate on to a proto-system is approximately proportional to its mass (dm/dt ∝ m), the SMF develops a power-law tail at high masses with the Salpeter slope (∼−2.3). If the rate of supply of mass accelerates, the rate of proto-system formation also accelerates, as appears to be observed in many clusters. However, even if the rate of supply of mass decreases, or ceases and then resumes, the SMF evolves homologously, retaining the same overall shape, and the high-mass power-law tail simply extends to ever higher masses until the supply of gas runs out completely. The Chabrier SMF can be reproduced very accurately if the seed proto-systems have an approximately lognormal mass distribution with median mass ${\sim } 0.11 \, {\rm M}_{\odot }$ and logarithmic standard deviation $\sigma _{\log _{10}({M/M}_\odot)}\sim 0.47$).

scholarly journals New Data on the Eclipsing Binary V1848 Ori and Improved Orbital and Light Curve Solutions

2020 ◽  
Vol 29 (1) ◽  
pp. 72-80 ◽  
Author(s):  
Fatemeh Davoudi ◽  
Atila Poro ◽  
Fahri Alicavus ◽  
Afshin Halavati ◽  
Saeed Doostmohammadi ◽  
...  
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Mass Function ◽  
Light Curves ◽  
Complete Analysis ◽  
Physical Parameters ◽  
Mass Ratio ◽  
Third Body ◽  
Eclipsing Binary

AbstractNew observations of the eclipsing binary system V1848 Ori were carried out using the V filter resulting in a determination of new times of minima and new ephemeris were obtained. We presented the first complete analysis of the system’s orbital period behavior and analysis of O-C diagram done by the GA and MCMC approaches in OCFit code. The O-C diagram demonstrates a sinusoidal trend in the data; this trend suggests a cyclic change caused by the LITE effect with a period of 10.57 years and an amplitude of 7.182 minutes. It appears that there is a third body with mass function of f (m3) = 0.0058 M⊙ in this binary system. The light curves were analyzed using the Wilson-Devinney code to determine some geometrical and physical parameters of the system. These results show that V1848 Ori is a contact W UMa binary system with the mass ratio of q = 0.76 and a weak fillout factor of 5.8%. The O’Connell effect was not seen in the light curve and there is no need to add spot.

MASS FUNCTION OF HALOS: A NEW ANALYTICAL APPROACH

2004 ◽  
Vol 13 (07) ◽  
pp. 1345-1349 ◽  
Author(s):  
JOSÉ A. S. LIMA ◽  
LUCIO MARASSI
Keyword(s):  
Power Law ◽  
Free Parameter ◽  
Analytical Approach ◽  
Mass Function ◽  
New Method ◽  
Power Law Distribution ◽  
The Press ◽  
The Universe ◽  
Special Case

A generalization of the Press–Schechter (PS) formalism yielding the mass function of bound structures in the Universe is given. The extended formula is based on a power law distribution which encompasses the Gaussian PS formula as a special case. The new method keeps the original analytical simplicity of the PS approach and also solves naturally its main difficult (the missing factor 2) for a given value of the free parameter.

scholarly journals Halo statistics analysis within medium volume cosmological N-body simulation

2015 ◽  
pp. 11-23 ◽  
Author(s):  
N. Martinovic
Keyword(s):  
Power Law ◽  
Preliminary Analysis ◽  
Growth Function ◽  
Mass Range ◽  
Mass Function ◽  
Number Density ◽  
Statistics Analysis ◽  
Halo Formation ◽  
Major Merger ◽  
Merger Rate

In this paper we present halo statistics analysis of a ?CDM N body cosmological simulation (from first halo formation until z = 0). We study mean major merger rate as a function of time, where for time we consider both per redshift and per Gyr dependence. For latter we find that it scales as the well known power law (1 + z)n for which we obtain n = 2.4. The halo mass function and halo growth function are derived and compared both with analytical and empirical fits. We analyse halo growth through out entire simulation, making it possible to continuously monitor evolution of halo number density within given mass ranges. The halo formation redshift is studied exploring possibility for a new simple preliminary analysis during the simulation run. Visualization of the simulation is portrayed as well. At redshifts z = 0?7 halos from simulation have good statistics for further analysis especially in mass range of 1011 ? 1014 M./h.

scholarly journals New star clusters discovered towards the Galactic bulge direction using Gaia DR2

2021 ◽  
Vol 502 (1) ◽  
pp. L90-L94
Author(s):  
F A Ferreira ◽  
W J B Corradi ◽  
F F S Maia ◽  
M S Angelo ◽  
J F C Santos
Keyword(s):  
Spatial Distribution ◽  
Star Clusters ◽  
Open Clusters ◽  
Systematic Search ◽  
Joint Analysis ◽  
The Sun ◽  
Galactic Bulge ◽  
Gaia Dr2

ABSTRACT We report the discovery of 34 new open clusters and candidates as a result of a systematic search carried out in 200 adjacent fields of 1 × 1 deg2 area projected towards the Galactic bulge, using Gaia DR2 data. The objects were identified and characterized by a joint analysis of their photometric, kinematic, and spatial distribution that has been consistently used and proved to be effective in our previous works. The discoveries were validated by cross-referencing the objects position and astrometric parameters with the available literature. Besides their coordinates and astrometric parameters, we also provide sizes, ages, distances, and reddening for the discovered objects. In particular, 32 clusters are closer than 2 kpc from the Sun, which represents an increment of nearly $39{{\ \rm per\ cent}}$ of objects with astrophysical parameters determined in the nearby inner disc. Although these objects fill an important gap in the open clusters distribution along the Sagittarius arm, this arm, traced by known clusters, appears to be interrupted, which may be an artefact due to the incompleteness of the cluster census.

scholarly journals Weighing the two stellar components of the Galactic bulge

2018 ◽  
Vol 618 ◽  
pp. A147 ◽  
Author(s):  
M. Zoccali ◽  
E. Valenti ◽  
O. A. Gonzalez
Keyword(s):  
Spatial Distribution ◽  
Velocity Dispersion ◽  
Stellar Mass ◽  
Galactic Bulge ◽  
Relative Fraction ◽  
Mass Budget ◽  
Mass Profile ◽  
Main Components ◽  
First Time ◽  
Metallicity Distribution

Context.Recent spectroscopic surveys of the Galactic bulge have unambiguously shown that the bulge contains two main components, which are best separated by their iron content, but also differ in spatial distribution, kinematics, and abundance ratios. The so-called metal poor component peaks at [Fe/H] ∼ −0.4, while the metal rich component peaks at [Fe/H] ∼ +0.3. The total metallicity distribution function is therefore bimodal with a dip at [Fe/H] ∼ 0. The relative fraction of the two components changes significantly across the bulge area. Aims. We provide, for the first time, the fractional contribution of the metal poor and metal rich stars to the stellar mass budget of the Galactic bulge and its variation across the bulge area. Methods. This result follows from the combination of the stellar mass profile obtained empirically, by our group, from VISTA Variables in the Vía Láctea data, with the relative fraction of metal poor and metal rich stars, across the bulge area, derived from the GIRAFFE Inner Bulge spectroscopic Survey. Results. We find that metal poor stars make up 48% of the total stellar mass of the bulge, within the region |l| < 10, |b| < 9.5 and that the remaining 52% are made up of metal rich stars. The latter dominate the mass budget at intermediate latitudes |b| ∼ 4, but become marginal in the outer bulge (|b| > 8). The metal poor component is more axisymmetric than the metal rich component, and it is at least comparable and possibly slightly dominant in the inner few degrees. As a result, the metal poor component, which does not follow the main bar, is not marginal in terms of the total mass budget as previously thought, and this new observational evidence must be included in bulge models. While the trend of the total radial velocity dispersion follows the total stellar mass, when we examine the velocity dispersion of each component individually, we find that metal poor stars have higher velocity dispersion where they make up a smaller fraction of the stellar mass, and vice versa. This is due to the kinematical and spatial distribution of the two metallicity components being significantly different, as already discussed in the literature.

Sign in / Sign up

Export Citation Format

Share Document