scholarly journals Inclination Estimates from Off-Axis GRB Afterglow Modelling

Universe ◽  
2021 ◽  
Vol 7 (9) ◽  
pp. 329
Author(s):  
Gavin P. Lamb ◽  
Joseph J. Fernández ◽  
Fergus Hayes ◽  
Albert K. H. Kong ◽  
En-Tzu Lin ◽  
...  
Keyword(s):  
Neutron Star ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Lateral Spreading ◽  
Line Of Sight ◽  
Temporal Behaviour ◽  
Model Free ◽  
Relativistic Jet ◽  
Free Parameters ◽  
Jet Structure

For gravitational wave (GW) detected neutron star mergers, one of the leading candidates for electromagnetic (EM) counterparts is the afterglow from an ultra-relativistic jet. Where this afterglow is observed, it will likely be viewed off-axis, such as the afterglow following GW170817/GRB 170817A. The temporal behaviour of an off-axis observed GRB afterglow can be used to reveal the lateral jet structure, and statistical model fits can put constraints on the various model free-parameters. Amongst these parameters is the inclination of the system to the line of sight. Along with the GW detection, the afterglow modelling provides the best constraint on the inclination to the line-of-sight and can improve the estimates of cosmological parameters, for example, the Hubble constant, from GW-EM events. However, modelling of the afterglow depends on the assumed jet structure and—often overlooked—the effects of lateral spreading. Here we show how the inclusion of lateral spreading in the afterglow models can affect the estimated inclination of GW-EM events.

scholarly journals Inclination Estimates from Off-Axis GRB Afterglow Modelling

2021 ◽  
Author(s):  
Gavin P. Lamb ◽  
Joseph J. Fernandez ◽  
Fergus Hayes ◽  
Albert K. H. Kong ◽  
En-Tzu Lin ◽  
...  
Keyword(s):  
Neutron Star ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Lateral Spreading ◽  
Line Of Sight ◽  
Temporal Behaviour ◽  
Model Free ◽  
Relativistic Jet ◽  
Free Parameters ◽  
Jet Structure

For gravitational wave (GW) detected neutron star mergers, one of the leading candidates for electromagnetic (EM) counterparts is the afterglow from an ultra-relativistic jet. Where this afterglow is observed, it will likely be viewed off-axis, such as the afterglow following GW170817/GRB 170817A. The temporal behaviour of an off-axis observed GRB afterglow can be used to reveal the lateral jet structure, and statistical model fits can put constraints on the various model free-parameters. Amongst these parameters is the inclination of the system to the line of sight. Along with the GW detection, the afterglow modelling provides the best constraint on the inclination to the line-of-sight and can improve the estimates of cosmological parameters e.g. the Hubble constant, from GW-EM events. However, modelling of the afterglow depends on the assumed jet structure and, often overlooked, the effects of lateral spreading. Here we show how the inclusion of lateral spreading in the afterglow models can affect the estimated inclination of GW-EM events.

scholarly journals TDCOSMO

2020 ◽  
Vol 642 ◽  
pp. A194 ◽  
Author(s):  
D. Gilman ◽  
S. Birrer ◽  
T. Treu
Keyword(s):  
Dark Matter ◽  
Time Delay ◽  
Time Delays ◽  
Arrival Time ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Line Of Sight ◽  
Gravitational Lenses ◽  
Additional Source ◽  
Precision Limit

Time delay cosmography uses the arrival time delays between images in strong gravitational lenses to measure cosmological parameters, in particular the Hubble constant H0. The lens models used in time delay cosmography omit dark matter subhalos and line-of-sight halos because their effects are assumed to be negligible. We explicitly quantify this assumption by analyzing mock lens systems that include full populations of dark matter subhalos and line-of-sight halos, applying the same modeling assumptions used in the literature to infer H0. We base the mock lenses on six quadruply imaged quasars that have delivered measurements of the Hubble constant, and quantify the additional uncertainties and/or bias on a lens-by-lens basis. We show that omitting dark substructure does not bias inferences of H0. However, perturbations from substructure contribute an additional source of random uncertainty in the inferred value of H0 that scales as the square root of the lensing volume divided by the longest time delay. This additional source of uncertainty, for which we provide a fitting function, ranges from 0.7 − 2.4%. It may need to be incorporated in the error budget as the precision of cosmographic inferences from single lenses improves, and it sets a precision limit on inferences from single lenses.

scholarly journals The confrontation of the shock-powered synchrotron maser model with the Galactic FRB 200428

2020 ◽  
Vol 500 (2) ◽  
pp. 2704-2710 ◽  
Author(s):  
Yun-Wei Yu ◽  
Yuan-Chuan Zou ◽  
Zi-Gao Dai ◽  
Wen-Fei Yu
Keyword(s):  
Line Of Sight ◽  
Model Parameters ◽  
Observational Constraints ◽  
Synchrotron Emission ◽  
Physical Processes ◽  
X Ray ◽  
Emission Efficiency ◽  
Free Parameters ◽  
Fast Radio Burst ◽  
Parameter Constraints

ABSTRACT The association of FRB 200428 with an X-ray burst (XRB) from the Galactic magnetar SGR 1935+2154 offers important implications for the physical processes responsible for the fast radio burst (FRB) phenomena. By assuming that the XRB emission is produced in the magnetosphere, we investigate the possibility that the FRB emission is produced by shock-powered synchrotron maser (SM), which is phenomenologically described with a number of free parameters. The observational constraints on the model parameters indicate that the model can in principle be consistent with the FRB 200428 observations, if the ejecta lunched by magnetar activities can have appropriate ingredients and structures and the shock processes occur on the line of sight. To be specific, a complete burst ejecta should consist of an ultra-relativistic and extremely highly collimated e± component and a sub-relativistic and wide-spreading baryonic component. The internal shocks producing the FRB emission arise from a collision between the e± ejecta and the remnant of a previous baryonic ejecta at the same direction. The parameter constraints depend on the uncertain spectrum and efficiency of the SM emission. While the spectrum is tentatively described by a spectral index of −2, we estimate the emission efficiency to be around 10−4 by requiring that the synchrotron emission of the shocked material cannot be much brighter than the magnetosphere XRB emission.

scholarly journals The obstructed jet in Mrk 231

2021 ◽  
Author(s):  
Ailing Wang ◽  
Tao An ◽  
Sumit Jaiswal ◽  
Prashanth Mohan ◽  
Yuchan Wang ◽  
...  
Keyword(s):  
Large Scale ◽  
Position Angle ◽  
Opening Angle ◽  
Luminous Infrared Galaxies ◽  
Multi Scale ◽  
Long Baseline ◽  
Relativistic Jet ◽  
Multi Phase ◽  
Jet Structure ◽  
Projected Distance

Abstract Mrk 231 is the closest radio-quiet quasar known and one of the most luminous infrared galaxies in the local Universe. It is characterised by the co-existence of a radio jet and powerful multi-phase multi-scale outflows, making it an ideal laboratory to study active galactic nucleus (AGN) feedback. We analyse the multi-epoch very long baseline interferometry data of Mrk 231 and estimate the jet head advance speed to be ≲ 0.013 c, suggesting a sub-relativistic jet flow. The jet position angle changes from −113○ in the inner parsec to −172○ at a projected distance of 25 parsec. The jet structure change might result from either a jet bending following the rotation of the circum-nuclear disc or the projection of a helical jet on the plane of the sky. In the large opening angle (∼60○) cone, the curved jet interacts with the interstellar medium and creates wide-aperture-angle shocks which subsequently dissipate a large portion of the jet power through radiation and contribute to powering the large-scale outflows. The low power and bent structure of the Mrk 231 jet, as well as extensive radiation dissipation, are consistent with the obstruction of the short-length jet by the host galaxy’s environment.

LIGO/Virgo Listens to Neutron Stars

2020 ◽  
pp. 137-145
Author(s):  
John W. Moffat
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Waves ◽  
Gamma Ray ◽  
Accurate Determination ◽  
Hubble Constant ◽  
Gravitational Theory ◽  
Optical Signal ◽  
Gravity Models ◽  
Expansion Of The Universe

On August 8, 2017, LIGO/Virgo detected the merging of two neutron stars 130 million light years away. Just 1.7 seconds later, the Fermi Gamma Ray Space Telescope received an optical signal—a short gamma ray burst (GRB). Thus began a new era of “multimessenger astronomy.” The GRBs are very energetic explosions observed in galaxies. The neutron star merger offers the first evidence that heavy metals such as gold, platinum, and uranium were created by the collision of neutron stars in a “kilonova.” The resulting gravitational waves offer a new way of measuring the Hubble constant, which determines the rate of expansion of the universe. An important result from the neutron star merger is an extremely accurate determination of the speed of gravitational waves; they move at the speed of light. This has significant ramifications for gravitational theory. It falsifies many proposed modified gravity models.

scholarly journals Using quasar X-ray and UV flux measurements to constrain cosmological model parameters

2020 ◽  
Vol 497 (1) ◽  
pp. 263-278 ◽  
Author(s):  
Narayan Khadka ◽  
Bharat Ratra
Keyword(s):  
Cosmological Parameters ◽  
Hubble Constant ◽  
Acoustic Oscillation ◽  
Joint Analysis ◽  
Model Parameters ◽  
Density Parameter ◽  
Current Standard ◽  
X Ray ◽  
Flux Measurements ◽  
Parameter Constraints

ABSTRACT Risaliti and Lusso have compiled X-ray and UV flux measurements of 1598 quasars (QSOs) in the redshift range 0.036 ≤ z ≤ 5.1003, part of which, z ∼ 2.4 − 5.1, is largely cosmologically unprobed. In this paper we use these QSO measurements, alone and in conjunction with baryon acoustic oscillation (BAO) and Hubble parameter [H(z)] measurements, to constrain cosmological parameters in six different cosmological models, each with two different Hubble constant priors. In most of these models, given the larger uncertainties, the QSO cosmological parameter constraints are mostly consistent with those from the BAO + H(z) data. A somewhat significant exception is the non-relativistic matter density parameter Ωm0 where QSO data favour Ωm0 ∼ 0.5 − 0.6 in most models. As a result, in joint analyses of QSO data with H(z) + BAO data the 1D Ωm0 distributions shift slightly towards larger values. A joint analysis of the QSO + BAO + H(z) data is consistent with the current standard model, spatially-flat ΛCDM, but mildly favours closed spatial hypersurfaces and dynamical dark energy. Since the higher Ωm0 values favoured by QSO data appear to be associated with the z ∼ 2 − 5 part of these data, and conflict somewhat with strong indications for Ωm0 ∼ 0.3 from most z < 2.5 data as well as from the cosmic microwave background anisotropy data at z ∼ 1100, in most models, the larger QSO data Ωm0 is possibly more indicative of an issue with the z ∼ 2 − 5 QSO data than of an inadequacy of the standard flat ΛCDM model.

scholarly journals Cosmological constraints from H ii starburst galaxy apparent magnitude and other cosmological measurements

2020 ◽  
Vol 497 (3) ◽  
pp. 3191-3203 ◽  
Author(s):  
Shulei Cao ◽  
Joseph Ryan ◽  
Bharat Ratra
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Angular Size ◽  
Hubble Constant ◽  
Joint Analysis ◽  
Apparent Magnitude ◽  
Starburst Galaxy ◽  
Density Parameter ◽  
Acoustic Oscillations ◽  
Combined Data

ABSTRACT We use H ii starburst galaxy apparent magnitude measurements to constrain cosmological parameters in six cosmological models. A joint analysis of H ii galaxy, quasar angular size, baryon acoustic oscillations peak length scale, and Hubble parameter measurements result in relatively model-independent and restrictive estimates of the current values of the non-relativistic matter density parameter $\Omega _{\rm m_0}$ and the Hubble constant H0. These estimates favour a 2.0–3.4σ (depending on cosmological model) lower H0 than what is measured from the local expansion rate. The combined data are consistent with dark energy being a cosmological constant and with flat spatial hypersurfaces, but do not strongly rule out mild dark energy dynamics or slightly non-flat spatial geometries.

scholarly journals A Bayesian approach to matching thermonuclear X-ray burst observations with models

2019 ◽  
Vol 490 (2) ◽  
pp. 2228-2240 ◽  
Author(s):  
A J Goodwin ◽  
D K Galloway ◽  
A Heger ◽  
A Cumming ◽  
Z Johnston
Keyword(s):  
Neutron Star ◽  
Rotation Axis ◽  
Line Of Sight ◽  
Type I ◽  
X Ray ◽  
Star Mass ◽  
Disc Model ◽  
Neutron Star Mass ◽  
Hydrogen Mass ◽  
Neutron Star Radius

ABSTRACT We present a new method of matching observations of Type-I (thermonuclear) X-ray bursts with models, comparing the predictions of a semi-analytic ignition model with X-ray observations of the accretion-powered millisecond pulsar SAX J1808.4–3658 in outburst. We used a Bayesian analysis approach to marginalize over the parameters of interest and determine parameters such as fuel composition, distance/anisotropy factors, neutron star mass, and neutron star radius. Our study includes a treatment of the system inclination effects, inferring that the rotation axis of the system is inclined $\left(69^{+4}_{-2}\right)^\circ$ from the observers line of sight, assuming a flat disc model. This method can be applied to any accreting source that exhibits Type-I X-ray bursts. We find a hydrogen mass fraction of $0.57^{+0.13}_{-0.14}$ and CNO metallicity of $0.013^{+0.006}_{-0.004}$ for the accreted fuel is required by the model to match the observed burst energies, for a distance to the source of $3.3^{+0.3}_{-0.2}\, \mathrm{kpc}$. We infer a neutron star mass of $1.5^{+0.6}_{-0.3}\, \mathrm{M}_{\odot }$ and radius of $11.8^{+1.3}_{-0.9}\, \mathrm{km}$ for a surface gravity of $1.9^{+0.7}_{-0.4}\times 10^{14}\, \mathrm{cm}\, \mathrm{s}^{-2}$ for SAX J1808.4–3658.

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