scholarly journals Improving sampling and calibration of GRBs as distance indicators

2020 ◽  
Author(s):  
Ariadna Montiel ◽  
J I Cabrera ◽  
Juan Carlos Hidalgo
Keyword(s):  
Error Propagation ◽  
Gamma Ray ◽  
Parametric Curve ◽  
Cosmic Expansion ◽  
Energy Models ◽  
Cosmological Observations ◽  
Independent Technique ◽  
Standard Cosmological Model ◽  
Observational Bias ◽  
Distance Indicators

Abstract We present a sample of 74 Gamma-Ray Bursts (GRBs) from the Fermi-GBM catalogue for which we compute the distance moduli and use them to constrain effective dark energy models. To overcome the circularity problem affecting GRBs as distance indicators, we calibrate the Amati relation of our sample with a cosmology-independent technique. Specifically, we use the latest observational Hubble parameter data, including associated systematics, to approximate the cosmic expansion through a Bezier parametric curve. We subsequently obtain the distance moduli of the GRBs and include the data in a suite of recent cosmological observations of the expansion history (Planck Compressed 2018, 2012 BOSS release of BAO data and Pantheon SNIa), to compute Bayesian posterior constraints for the standard cosmological model ΛCDM, as well as ωCDM, and the CPL parametrization. Throughout the analysis we strive to keep under control the error propagation and limit our GRBs sample to avoid observational bias. As a result, we find no evidence in favour of the alternatives to ΛCDM model. The latter agrees very well with our calibrated sample of GRBs and presently available luminosity distance probes.

scholarly journals Constraints on dark energy models including gamma ray bursts

2008 ◽  
Vol 658 (4) ◽  
pp. 95-100 ◽  
Author(s):  
Hong Li ◽  
Meng Su ◽  
Zuhui Fan ◽  
Zigao Dai ◽  
Xinmin Zhang
Keyword(s):  
Dark Energy ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Energy Models

PALATINI f(R) COSMOLOGY

2008 ◽  
Vol 23 (17n20) ◽  
pp. 1388-1396 ◽  
Author(s):  
SEOKCHEON LEE
Keyword(s):  
Linear Growth ◽  
Matter Density ◽  
Modified Theories Of Gravity ◽  
Cosmic Expansion ◽  
Energy Models ◽  
Modified Gravity Theories ◽  
Theories Of Gravity ◽  
The Stability ◽  
Cosmic Expansion History ◽  
General Gauge

We investigate the modified gravity theories in terms of the effective dark energy models. We compare the cosmic expansion history and the linear growth in different models. We also study the evolution of linear cosmological perturbations in modified theories of gravity assuming the Palatini formalism. We find the stability of the superhorizon metric evolution depends on models. We also study the matter density fluctuation in the general gauge and show the differential equations in super and sub-horizon scales.

DISTANCE INDICATORS OF GAMMA-RAY PULSARS

2013 ◽  
Vol 23 ◽  
pp. 289-294
Author(s):  
WEI WANG
Keyword(s):  
Magnetic Field ◽  
Gamma Ray ◽  
Physical Origin ◽  
Large Area ◽  
Distance Measurements ◽  
Distance Information ◽  
Cascade Processes ◽  
Gamma Ray Emission ◽  
Distance Indicators ◽  
The Magnetic Field

Distance measurements of gamma-ray pulsars are challenging questions in present pulsar studies. The Large Area Telescope (LAT) aboard the Fermi gamma-ray observatory discovered more than 100 gamma-ray pulsars including 24 new gamma-selected pulsars which nearly have no distance information. We study the relation between gamma-ray emission efficiency (η = Lγ/Ė) and pulsar parameters for young radio-selected gamma-ray pulsars with known distance information in the first gamma-ray pulsar catalog reported by Fermi/LAT. We have introduced three generation order parameters to describe gamma-ray emission properties of pulsars, and find the strong correlation of η – ζ3 a generation order parameter which reflects γ-ray photon generations in pair cascade processes induced by magnetic field absorption in pulsar magnetosphere. A good correlation of η – B LC the magnetic field at the light cylinder radius is also found. These correlations would be the distance indicators in gamma-ray pulsars to evaluate distances for gamma-selected pulsars. Distances of 25 gamma-selected pulsars are estimated, which could be tested by other distance measurement methods. Physical origin of the correlations may be also interesting for pulsar studies.

scholarly journals On the theory and applications of modern cosmography

2016 ◽  
Vol 13 (03) ◽  
pp. 1630002 ◽  
Author(s):  
Peter K. S. Dunsby ◽  
Orlando Luongo
Keyword(s):  
A Priori ◽  
Energy Models ◽  
Cosmological Expansion ◽  
History Of ◽  
Independent Technique ◽  
Cosmological Data ◽  
Model Independent ◽  
The Universe ◽  
Important Branch ◽  
Quantities Of Interest

Cosmography represents an important branch of cosmology which aims to describe the universe without the need of postulating a priori any particular cosmological model. All quantities of interest are expanded as a Taylor series around here and now, providing in principle, a way of directly matching with cosmological data. In this way, cosmography can be regarded a model-independent technique, able to fix cosmic bounds, although several issues limit its use in various model reconstructions. The main purpose of this review is to focus on the key features of cosmography, emphasizing both the strategy for obtaining the observable cosmographic series and pointing out any drawbacks which might plague the standard cosmographic treatment. In doing so, we relate cosmography to the most relevant cosmological quantities and to several dark energy models. We also investigate whether cosmography is able to provide information about the form of the cosmological expansion history, discussing how to reproduce the dark fluid from the cosmographic sound speed. Following this, we discuss limits on cosmographic priors and focus on how to experimentally treat cosmographic expansions. Finally, we present some of the latest developments of the cosmographic method, reviewing the use of rational approximations, based on cosmographic Padé polynomials. Future prospects leading to more accurate cosmographic results, able to better reproduce the expansion history of the universe, are also discussed in detail.

scholarly journals Expected Hard X-Ray and Soft Gamma-Ray from Supernovae

2014 ◽  
Vol 1 (1) ◽  
pp. 205-209
Author(s):  
Keiichi Maeda ◽  
Yukikatsu Terada ◽  
Aya Bamba
Keyword(s):  
Direct Evidence ◽  
Gamma Ray ◽  
High Energy ◽  
X Ray ◽  
Sn 1987A ◽  
Energy Emissions ◽  
New Generation ◽  
Distance Indicators ◽  
Opening Up ◽  
Radioactive Species

High energy emissions from supernovae (SNe), originated from newly formed radioactive species, provide direct evidence of nucleosynthesis at SN explosions. However, observational diculties in the MeV range have so far allowed the signal detected only from the extremely nearby core-collapse SN 1987A. No solid detection has been reported for thermonuclear SNe Ia, despite the importance of the direct conrmation of the formation of <sup>56</sup>Ni, which is believed to be a key ingredient in their nature as distance indicators. In this paper, we show that the new generation hard X-ray and soft gamma-ray instruments, on board Astro-H and NuStar, are capable of detecting the signal, at least at a pace of once in a few years, opening up this new window for studying SN explosion and nucleosynthesis.

Toward cosmological-model-independent calibrations for the luminosity relations of Gamma-Ray Bursts

2015 ◽  
Vol 24 (07) ◽  
pp. 1550057 ◽  
Author(s):  
Xuheng Ding ◽  
Zhengxiang Li ◽  
Zong-Hong Zhu
Keyword(s):  
Cosmological Model ◽  
Gamma Ray ◽  
Distance Estimation ◽  
Gamma Ray Bursts ◽  
Type Ia ◽  
Model Independent ◽  
Global Fit ◽  
Ia Supernovae ◽  
Distance Indicators ◽  
The Universe

Gamma-ray bursts (GRBs), have been widely used as distance indicators to measure the cosmic expansion and explore the nature of dark energy. A popular method adopted in previous works is to calibrate the luminosity relations which are responsible for distance estimation of GRBs with more primary (low redshift) cosmic distance ladder objects, type Ia supernovae (SNe Ia). Since distances of SNe Ia in all SN Ia samples used to calibrate GRB luminosity relations were usually derived from the global fit in a specific cosmological model, the distance of GRB at a given redshift calibrated with matching SNe Ia was still cosmological-model-dependent. In this paper, we first directly determine the distances of SNe Ia with the Angular Diameter Distances (ADDs) of galaxy clusters without any assumption for the background of the universe, and then calibrate GRB luminosity relations with our cosmology-independent distances of SNe Ia. The results suggest that, compared to the previous original manner where distances of SNe Ia used as calibrators are determined from the global fit in a particular cosmological model, our treatments proposed here yield almost the same calibrations of GRB luminosity relations and the cosmological implications of them do not suffer any circularity.

THE IMPRINT OF DARK ENERGY

2004 ◽  
Vol 19 (13n16) ◽  
pp. 1063-1070 ◽  
Author(s):  
ROBERT CALDWELL
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Cosmic Microwave Background ◽  
Cosmological Constant ◽  
Negative Pressure ◽  
Inhomogeneous Field ◽  
Time Varying ◽  
Microwave Background ◽  
Cosmic Expansion ◽  
Cosmological Observations

Diverse cosmological observations indicate the existence of dark energy, comprising ~ 70% of the total cosmic energy density and driving the accelerated cosmic expansion. Possible explanations for the dark energy include a cosmological constant and quintessence — a time-varying, inhomogeneous field with negative pressure. In this article we summarize how the dark energy imprints features on the cosmic microwave background. Observation of these features could be useful in discriminating amongst various theories, and could reveal clues as to the nature of the dark energy.

scholarly journals Cosmological Parameter Inference with Bayesian Statistics

Universe ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 213
Author(s):  
Luis E. Padilla ◽  
Luis O. Tellez ◽  
Luis A. Escamilla ◽  
Jose Alberto Vazquez
Keyword(s):  
Bayesian Statistics ◽  
Model Comparison ◽  
General Description ◽  
Inference Procedure ◽  
Parameter Inference ◽  
Mcmc Algorithms ◽  
Cosmological Observations ◽  
Numerical Tools ◽  
Standard Cosmological Model ◽  
The Universe

Bayesian statistics and Markov Chain Monte Carlo (MCMC) algorithms have found their place in the field of Cosmology. They have become important mathematical and numerical tools, especially in parameter estimation and model comparison. In this paper, we review some fundamental concepts to understand Bayesian statistics and then introduce MCMC algorithms and samplers that allow us to perform the parameter inference procedure. We also introduce a general description of the standard cosmological model, known as the ΛCDM model, along with several alternatives, and current datasets coming from astrophysical and cosmological observations. Finally, with the tools acquired, we use an MCMC algorithm implemented in python to test several cosmological models and find out the combination of parameters that best describes the Universe.

DARK ENERGY MODELS AND SUPERNOVA RELIC NEUTRINOS

2007 ◽  
Vol 22 (12) ◽  
pp. 867-882 ◽  
Author(s):  
HIROYUKI ONO ◽  
HIDEYUKI SUZUKI
Keyword(s):  
Dark Energy ◽  
Holographic Dark Energy ◽  
Future Observation ◽  
Energy Models ◽  
Unique Probe ◽  
Cosmological Observations ◽  
Direct Counting ◽  
The Universe ◽  
Energy Element

Recent cosmological observations show that the unknown energy element called dark energy dominates in the universe. In this letter, we investigate to what extent dark energy models influence supernova relic neutrino (SRN) spectra when the supernova rate could be determined by direct counting and discuss the possibility to distinguish dark energy models using future observation of SRN. We found that the total number of SRN events in GCG model will be larger than those in ΛCDM and holographic dark energy models by 20%. As a result, we find a possibility to distinguish GCG model from ΛCDM and holographic dark energy models using observation of SRN. SRN should be a unique probe into dark energy models and will play complementary roles to other observables.

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