scholarly journals Updated parameter estimates for GW190425 using astrophysical arguments and implications for the electromagnetic counterpart

2020 ◽  
Vol 494 (1) ◽  
pp. 190-198 ◽  
Author(s):  
Ryan J Foley ◽  
David A Coulter ◽  
Charles D Kilpatrick ◽  
Anthony L Piro ◽  
Enrico Ramirez-Ruiz ◽  
...  
Keyword(s):  
Total Mass ◽  
Milky Way ◽  
Confidence Region ◽  
High Mass ◽  
Parameter Estimates ◽  
Compact Binary ◽  
Best Fitting ◽  
Almost All ◽  
Hubble Time ◽  
Fitting Parameters

ABSTRACT The progenitor system of the compact binary merger GW190425 had a total mass of $3.4^{+0.3}_{-0.1}$ M⊙ (90th-percentile confidence region) as measured from its gravitational wave signal. This mass is significantly different from the Milky Way (MW) population of binary neutron stars (BNSs) that are expected to merge in a Hubble time and from that of the first BNS merger, GW170817. Here, we explore the expected electromagnetic (EM) signatures of such a system. We make several astrophysically motivated assumptions to further constrain the parameters of GW190425. By simply assuming that both components were NSs, we reduce the possible component masses significantly, finding $m_{1}=1.85^{+0.27}_{-0.19}$ M⊙ and $m_{2}=1.47^{+0.16}_{-0.18}$ M⊙. However, if the GW190425 progenitor system was an NS–black hole (BH) merger, we find best-fitting parameters $m_{1}=2.19^{+0.21}_{-0.17}$ M⊙ and $m_{2}=1.26^{+0.10}_{-0.08}$ M⊙. For a well-motivated BNS system where the lighter NS has a mass similar to the mass of non-recycled NSs in MW BNS systems, we find $m_{1}=2.03^{+0.15}_{-0.14}$ M⊙ and m2 = 1.35 ± 0.09 M⊙, corresponding to only 7 per cent mass uncertainties. For all scenarios, we expect a prompt collapse of the resulting remnant to a BH. Examining detailed models with component masses similar to our best-fitting results, we find the EM counterpart to GW190425 is expected to be significantly redder and fainter than that of GW170817. We find that almost all reported search observations were too shallow to detect the expected counterpart to GW190425. If the LIGO–Virgo Collaboration promptly provides the chirp mass, the astronomical community can adapt their observations to improve the likelihood of detecting a counterpart for similarly ‘high-mass’ BNS systems.

scholarly journals The milky way total mass profile as inferred from Gaia DR2

2020 ◽  
Vol 494 (3) ◽  
pp. 4291-4313 ◽  
Author(s):  
Marius Cautun ◽  
Alejandro Benítez-Llambay ◽  
Alis J Deason ◽  
Carlos S Frenk ◽  
Azadeh Fattahi ◽  
...  
Keyword(s):  
Total Mass ◽  
Rotation Curve ◽  
Milky Way ◽  
Galactic Rotation ◽  
Best Fitting ◽  
Galactic Rotation Curve ◽  
Systematic Biases ◽  
Mass Profile ◽  
Hydrodynamical Simulations ◽  
Gaia Dr2

ABSTRACT We determine the Milky Way (MW) mass profile inferred from fitting physically motivated models to the Gaia DR2 Galactic rotation curve and other data. Using various hydrodynamical simulations of MW-mass haloes, we show that the presence of baryons induces a contraction of the dark matter (DM) distribution in the inner regions, r ≲ 20 kpc. We provide an analytic expression that relates the baryonic distribution to the change in the DM halo profile. For our galaxy, the contraction increases the enclosed DM halo mass by factors of roughly 1.3, 2, and 4 at radial distances of 20, 8, and 1 kpc, respectively compared to an uncontracted halo. Ignoring this contraction results in systematic biases in the inferred halo mass and concentration. We provide a best-fitting contracted NFW halo model to the MW rotation curve that matches the data very well.1 The best-fit has a DM halo mass, $M_{200}^{\rm DM}=0.97_{-0.19}^{+0.24}\times 10^{12}\,\mathrm{M}_\odot$, and concentration before baryon contraction of $9.4_{-2.6}^{+1.9}$, which lie close to the median halo mass–concentration relation predicted in ΛCDM. The inferred total mass, $M_{200}^{\rm total}=1.08_{-0.14}^{+0.20} \times 10^{12}\,\mathrm{M}_\odot$, is in good agreement with recent measurements. The model gives an MW stellar mass of $5.04_{-0.52}^{+0.43}\times 10^{10}\,\mathrm{M}_\odot$ and infers that the DM density at the Solar position is $\rho _{\odot }^{\rm DM}=8.8_{-0.5}^{+0.5}\times 10^{-3}\,\mathrm{M}_\odot \,\mathrm{pc}^{-3}\equiv 0.33_{-0.02}^{+0.02}\,\rm {GeV}\,\rm {cm}^{-3}$. The rotation curve data can also be fitted with an uncontracted NFW halo model, but with very different DM and stellar parameters. The observations prefer the physically motivated contracted NFW halo, but the measurement uncertainties are too large to rule out the uncontracted NFW halo.

Preliminary Evaluation of a Weibull Function for Fitting Slow-Component Eye Velocity over the Time Course of Caloric-Induced Nystagmus

1989 ◽  
Vol 32 (3) ◽  
pp. 681-687 ◽  
Author(s):  
C. Formby ◽  
B. Albritton ◽  
I. M. Rivera
Keyword(s):  
Time Course ◽  
Slow Component ◽  
Weibull Function ◽  
Preliminary Evaluation ◽  
Mathematical Function ◽  
Before And After ◽  
Best Fitting ◽  
Eye Velocity ◽  
Fitting Parameters ◽  
Weibull Equation

We describe preliminary attempts to fit a mathematical function to the slow-component eye velocity (SCV) over the time course of caloric-induced nystagmus. Initially, we consider a Weibull equation with three parameters. These parameters are estimated by a least-squares procedure to fit digitized SCV data. We present examples of SCV data and fitted curves to show how adjustments in the parameters of the model affect the fitted curve. The best fitting parameters are presented for curves fit to 120 warm caloric responses. The fitting parameters and the efficacy of the fitted curves are compared before and after the SCV data were smoothed to reduce response variability. We also consider a more flexible four-parameter Weibull equation that, for 98% of the smoothed caloric responses, yields fits that describe the data more precisely than a line through the mean. Finally, we consider advantages and problems in fitting the Weibull function to caloric data.

scholarly journals The globular cluster system of the Auriga simulations

2020 ◽  
Vol 496 (1) ◽  
pp. 638-648 ◽  
Author(s):  
Timo L R Halbesma ◽  
Robert J J Grand ◽  
Facundo A Gómez ◽  
Federico Marinacci ◽  
Rüdiger Pakmor ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Milky Way ◽  
Cluster Formation ◽  
Solar Radius ◽  
High Mass ◽  
Formation Model ◽  
The Galaxy ◽  
High Mass Loss ◽  
Globular Cluster System ◽  
Varying Mass

ABSTRACT We investigate whether the galaxy and star formation model used for the Auriga simulations can produce a realistic globular cluster (GC) population. We compare statistics of GC candidate star particles in the Auriga haloes with catalogues of the Milky Way (MW) and Andromeda (M31) GC populations. We find that the Auriga simulations do produce sufficient stellar mass for GC candidates at radii and metallicities that are typical for the MW GC system (GCS). We also find varying mass ratios of the simulated GC candidates relative to the observed mass in the MW and M31 GCSs for different bins of galactocentric radius metallicity (rgal–[Fe/H]). Overall, the Auriga simulations produce GC candidates with higher metallicities than the MW and M31 GCS and they are found at larger radii than observed. The Auriga simulations would require bound cluster formation efficiencies higher than 10 per cent for the metal-poor GC candidates, and those within the Solar radius should experience negligible destruction rates to be consistent with observations. GC candidates in the outer halo, on the other hand, should either have low formation efficiencies, or experience high mass-loss for the Auriga simulations to produce a GCS that is consistent with that of the MW or M31. Finally, the scatter in the metallicity as well as in the radial distribution between different Auriga runs is considerably smaller than the differences between that of the MW and M31 GCSs. The Auriga model is unlikely to give rise to a GCS that can be consistent with both galaxies.

scholarly journals Probing non-spherical dark halos in the Galactic dwarf satellites

2013 ◽  
Vol 9 (S298) ◽  
pp. 411-411
Author(s):  
Kohei Hayashi ◽  
Masashi Chiba
Keyword(s):  
Dark Matter ◽  
Cold Dark Matter ◽  
Milky Way ◽  
Velocity Dispersion ◽  
Line Of Sight ◽  
Spherical Structure ◽  
Spherical Models ◽  
Galactic Satellites ◽  
Best Fitting

AbstractWe construct axisymmetric mass models for dwarf spheroidal (dSph) galaxies in the Milky Way to obtain realistic limits on the non-spherical structure of their dark halos. This is motivated by the fact that the observed luminous parts of the dSphs are actually non-spherical and cold dark matter models predict non-spherical virialized dark halos on sub-galactic scales. Applying these models to line-of-sight velocity dispersion profiles along three position angles in six Galactic satellites, we find that the best fitting cases for most of the dSphs yield not spherical but oblate and flattened dark halos. We also find that the mass of the dSphs enclosed within inner 300 pc varies depending on their total luminosities, contrary to the conclusion of previous spherical models. This suggests the importance of considering non-spherical shapes of dark halos in dSph mass models.

scholarly journals Intermittent maser flare around the high-mass young stellar object G353.273+0.641

2012 ◽  
Vol 8 (S287) ◽  
pp. 98-102
Author(s):  
Kazuhito Motogi ◽  
Kazuo Sorai ◽  
Kenta Fujisawa ◽  
Koichiro Sugiyama ◽  
Mareki Honma
Keyword(s):  
Light Curve ◽  
Small Area ◽  
Linear Acceleration ◽  
High Mass ◽  
Velocity Range ◽  
Time Resolved ◽  
Almost All ◽  
Maser Sources ◽  
Water Maser

AbstractThe water maser site associated with G353.273+0.641 is classified as a dominant blueshifted H2O maser, which shows an extremely wide velocity range (± 100 km s−1) with almost all flux concentrated in the highly blueshifted emission. The previous study has proposed that this peculiar H2O maser site is excited by a pole-on jet from high mass protostellar object. We report on the monitoring of 22-GHz H2O maser emission from G353.273+0.641 with the VLBI Exploration of Radio Astrometry (VERA) and the Tomakamai 11-m radio telescope. Our VLBI imaging has shown that all maser features are distributed within a very small area of 200 × 200 au2, in spite of the wide velocity range (> 100 km s−1). The light curve obtained by weekly single-dish monitoring shows notably intermittent variation. We have detected three maser flares during three years. Frequent VLBI monitoring has revealed that these flare activities have been accompanied by a significant change of the maser alignments. We have also detected synchronized linear acceleration (−5 km s−1yr−1) of two isolated velocity components, suggesting a lower-limit momentum rate of 10−3 M⊙ km s−1yr−1 for the maser acceleration. All our results support the previously proposed pole-on jet scenario, and finally, a radio jet itself has been detected in our follow-up ATCA observation. If highly intermittent maser flares directly reflect episodic jet-launchings, G353.273+0.641 and similar dominant blueshifted water maser sources can be suitable targets for a time-resolved study of high mass protostellar jet.

scholarly journals Reanalysis of nearby open clusters using Gaia DR1/TGAS and HSOY

2018 ◽  
Vol 615 ◽  
pp. A12 ◽  
Author(s):  
Steffi X. Yen ◽  
Sabine Reffert ◽  
Elena Schilbach ◽  
Siegfried Röser ◽  
Nina V. Kharchenko ◽  
...  
Keyword(s):  
Milky Way ◽  
Open Cluster ◽  
Star Clusters ◽  
Open Clusters ◽  
Parameter Estimates ◽  
Cluster Membership ◽  
Fitting Procedure ◽  
Cluster Data ◽  
The Galaxy ◽  
Automatic Tool

Context. Open clusters have long been used to gain insights into the structure, composition, and evolution of the Galaxy. With the large amount of stellar data available for many clusters in the Gaia era, new techniques must be developed for analyzing open clusters, as visual inspection of cluster color-magnitude diagrams is no longer feasible. An automatic tool will be required to analyze large samples of open clusters. Aims. We seek to develop an automatic isochrone-fitting procedure to consistently determine cluster membership and the fundamental cluster parameters. Methods. Our cluster characterization pipeline first determined cluster membership with precise astrometry, primarily from TGAS and HSOY. With initial cluster members established, isochrones were fitted, using a χ2 minimization, to the cluster photometry in order to determine cluster mean distances, ages, and reddening. Cluster membership was also refined based on the stellar photometry. We used multiband photometry, which includes ASCC-2.5 BV, 2MASS JHKs, and Gaia G band. Results. We present parameter estimates for all 24 clusters closer than 333 pc as determined by the Catalogue of Open Cluster Data and the Milky Way Star Clusters catalog. We find that our parameters are consistent to those in the Milky Way Star Clusters catalog. Conclusions. We demonstrate that it is feasible to develop an automated pipeline that determines cluster parameters and membership reliably. After additional modifications, our pipeline will be able to use Gaia DR2 as input, leading to better cluster memberships and more accurate cluster parameters for a much larger number of clusters.

scholarly journals Gaia DR2 proper motions of dwarf galaxies within 420 kpc

2018 ◽  
Vol 619 ◽  
pp. A103 ◽  
Author(s):  
T. K. Fritz ◽  
G. Battaglia ◽  
M. S. Pawlowski ◽  
N. Kallivayalil ◽  
R. van der Marel ◽  
...  
Keyword(s):  
Milky Way ◽  
Dwarf Galaxies ◽  
High Mass ◽  
Proper Motions ◽  
Proper Understanding ◽  
Satellite Problem ◽  
Cosmological Context ◽  
Good Consistency ◽  
Gaia Dr2 ◽  
Limited Accuracy

A proper understanding of the Milky Way (MW) dwarf galaxies in a cosmological context requires knowledge of their 3D velocities and orbits. However, proper motion (PM) measurements have generally been of limited accuracy and are available only for more massive dwarfs. We therefore present a new study of the kinematics of the MW dwarf galaxies. We use the Gaia DR2 for those dwarfs that have been spectroscopically observed in the literature. We derive systemic PMs for 39 galaxies and galaxy candidates out to 420 kpc, and generally find good consistency for the subset with measurements available from other studies. We derive the implied Galactocentric velocities, and calculate orbits in canonical MW halo potentials of low (0.8 × 1012 M⊙) and high mass (1.6 × 1012 M⊙). Comparison of the distributions of orbital apocenters and 3D velocities to the halo virial radius and escape velocity, respectively, suggests that the satellite kinematics are best explained in the high-mass halo. Tuc III, Crater II, and additional candidates have orbital pericenters small enough to imply significant tidal influences. Relevant to the missing satellite problem, the fact that fewer galaxies are observed to be near apocenter than near pericenter implies that there must be a population of distant dwarf galaxies yet to be discovered. Of the 39 dwarfs: 12 have orbital poles that do not align with the MW plane of satellites (given reasonable assumptions about its intrinsic thickness); 10 have insufficient PM accuracy to establish whether they align; and 17 satellites align, of which 11 are co-orbiting and (somewhat surprisingly, in view of prior knowledge) 6 are counter-orbiting. Group infall might have contributed to this, but no definitive association is found for the members of the Crater-Leo group.

scholarly journals On the delay times of merging double neutron stars

2020 ◽  
Vol 500 (2) ◽  
pp. 1755-1771
Author(s):  
Laura Greggio ◽  
Paolo Simonetti ◽  
Francesca Matteucci
Keyword(s):  
Neutron Stars ◽  
Binary Systems ◽  
Milky Way ◽  
Gamma Ray ◽  
Chemical Properties ◽  
Redshift Distribution ◽  
Strong Constraint ◽  
Delay Times ◽  
Best Fitting ◽  
Short Grbs

ABSTRACT The merging rate of double neutron stars (DNS) has a great impact on many astrophysical issues, including the interpretation of gravitational waves signals, of the short gamma-ray bursts (GRBs), and of the chemical properties of stars in galaxies. Such rate depends on the distribution of the delay times (DDT) of the merging events. In this paper, we derive a theoretical DDT of merging DNS following from the characteristics of the clock controlling their evolution. We show that the shape of the DDT is governed by a few key parameters, primarily the lower limit and the slope of the distribution of the separation of the DNS systems at birth. With a parametric approach, we investigate on the observational constraints on the DDT from the cosmic rate of short GRBs and the europium-to-iron ratio in Milky Way stars, taken as tracer of the products of the explosion. We find that the local rate of DNS merging requires that $\sim \! 1 {{\ \rm per\ cent}}$ of neutron stars progenitors live in binary systems which end their evolution as merging DNS within a Hubble time. The redshift distribution of short GRBs does not yet provide a strong constraint on the shape of the DDT, although the best-fitting models have a shallow DDT. The chemical pattern in Milky Way stars requires an additional source of europium besides the products from merging DNS, which weakens the related requirement on the DDT. At present both constraints can be matched with the same DDT for merging DNS.

scholarly journals Minimally-modeled search of higher multipole gravitational-wave radiation in compact binary coalescences.

2021 ◽  
Author(s):  
G. Vedovato ◽  
Edoardo Milotti ◽  
Giovanni Andrea Prodi ◽  
Sophie Bini ◽  
Marco Drago ◽  
...  
Keyword(s):  
Wave Radiation ◽  
Full Detail ◽  
Parameter Estimates ◽  
Spectral Features ◽  
Operating Characteristics ◽  
Fast Analysis ◽  
Time Frequency ◽  
Compact Binary ◽  
Frequency Representation ◽  
Novel Method

Abstract As the Advanced LIGO and Advanced Virgo interferometers, soon to be joined by the KAGRA interferometer, increase their sensitivity, they detect an ever-larger number of gravitational waves with a significant presence of higher multipoles in addition to the dominant (2, 2) multipole. These higher multipoles can be detected with different approaches, such as the minimally-modeled burst search methods, and here we discuss one such approach based on the coherent WaveBurst pipeline (cWB). During the inspiral phase the higher multipoles produce chirps whose instantaneous frequency is a multiple of the dominant (2, 2) multipole, and here we describe how cWB can be used to detect these spectral features. The search is performed within suitable regions of the time-frequency representation; their shape is determined by optimizing the Receiver Operating Characteristics. This novel method has already been used in the GW190814 discovery paper (Astrophys. J. Lett. 896 L44) and is very fast and flexible. Here we describe in full detail the procedure used to detect the (3, 3) multipole in GW190814 as well as searches for other higher multipoles during the inspiral phase, and apply it to another event that displays higher multipoles, GW190412, replicating the results obtained with different methods. The procedure described here can be used for the fast analysis of higher multipoles and to support the findings obtained with the model-based Bayesian parameter estimates.

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