arXiv subjects

Maria Giovanna Dainotti

Publications and source records attributed to Maria Giovanna Dainotti.

At least 55 records · Page 3Linked to original sources

arXiv2023

Quasars: standard candles up to z=7.5 with the precision of Supernovae Ia

Currently, the $Λ$ Cold Dark Matter model, which relies on the existence of cold dark matter and a cosmological constant $Λ$, best describes the Universe. However, we lack information in the high-redshift ($z$) region between Type Ia Supernovae (SNe Ia) (up to $z=2.26$) and the Cosmic Microwave Background ($z=1100$), an interval crucial to test cosmological models and their possible evolution. We have defined a sample of 983 Quasars up to $z=7.54$ with reduced intrinsic dispersion $δ=0.007$ which determines the matter density parameter $Ω_M$ with the same precision of SNe Ia. Although previous analysis have been used Quasars as cosmological tools (e.g. Risaliti and Lusso 2019), this is the first time that high-redshift sources, in this case Quasars, as standalone cosmological probes yield such tight constraints on $Ω_M$. Our results show the importance of correcting cosmological relationships for selection biases and redshift evolution and how the choice of a golden sample reduces considerably the intrinsic scatter. This proves the reliability of Quasars as standard cosmological candles.

astro-ph.CO↗

arXiv2023

Progenitors of Low Redshift Gamma-ray Bursts

Bimodal distribution of the observed duration of gamma-ray bursts (GRBs) has led to two distinct progenitors; compact star mergers, either two neutron stars (NSs) or a NS and a black hole (BH), for short GRBs (SGRBs), and so-called collapsars for long GRBs (LGRBs). It is therefore expected that formation rate (FR) of LGRBs should be similar to the cosmic star formation rate (SFR), while that of SGRBs to be delayed relative to the SFR. The localization of some LGRBs in and around the star forming regions of host galaxies and some SGRBs away form such regions support this expectation. Another distinct feature of SGRBs is their association with gravitational wave (GW) sources and kilonovae. However, several independent investigations of the FRs of long and short bursts, using the Efron-Petrosian non-parametric method have shown a LGRB FR that is significantly larger than SFR at low redhift, and similar to the FR of SGRBs. In addition, recent discovery of association of a low redshift long GRB211211A with a kilonova raises doubt about its collapsar origin. In this letter we review these results and show that low redshift LGRBs could also have compact star mergers as progenitor increasing the expected rate of the GW sources and kilonovae significantly.

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arXiv2023

Reducing the uncertainty on the Hubble constant up to 35\% with an improved statistical analysis: different best-fit likelihoods for Supernovae Ia, Baryon Acoustic Oscillations, Quasars, and Gamma-Ray Bursts

Cosmological models and their parameters are widely debated, especially about whether the current discrepancy between the values of the Hubble constant, $H_{0}$, obtained by type Ia supernovae (SNe Ia), and the Planck data from the Cosmic Microwave Background Radiation could be alleviated when alternative cosmological models are considered. Thus, combining high-redshift probes, such as Gamma-Ray Bursts (GRBs) and Quasars (QSOs), together with Baryon Acoustic Oscillations (BAO) and SNe Ia is important to assess the viability of these alternative models and if they can cast further light on the Hubble tension. In this work, for GRBs, we use a 3-dimensional relation between the peak prompt luminosity, the rest-frame time at the end of the X-ray plateau, and its corresponding luminosity in X-rays: the 3D Dainotti fundamental plane relation. Regarding QSOs, we use the Risaliti-Lusso relation among the UV and X-ray luminosities for a sample of 2421 sources. We correct both the QSO and GRB relations by accounting for selection and evolutionary effects with a reliable statistical method. We here use both the traditional Gaussian likelihoods ($\cal L_G$) and the new best-fit likelihoods ($\cal L_N$) to infer cosmological parameters of a non-flat $Λ$CDM and flat $w$CDM models. We obtain for all the parameters reduced uncertainties, up to $35\%$ for $H_{0}$, when applying the new $\cal L_N$ likelihoods in place of the Gaussian ones. Our results remain consistent with a flat $Λ$CDM model, although with a shift of the dark energy parameter $w$ toward $w<-1$ and a curvature density parameter toward $Ω_k<0$.

astro-ph.CO↗

arXiv2023

A bias-free cosmological analysis with quasars alleviating $H_0$ tension

Cosmological models and their parameters are widely debated because of theoretical and observational mismatches of the standard cosmological model, especially the current discrepancy between the value of the Hubble constant, $H_{0}$, obtained by Type Ia supernovae (SNe Ia), and the Cosmic Microwave Background Radiation (CMB). Thus, considering high-redshift probes like quasars (QSOs), having intermediate redshifts between SNe Ia and CMB, is a necessary step. In this work, we use SNe Ia and the most updated QSO sample, reaching redshifts up to $z\sim7.5$, applying the Risaliti-Lusso QSO relation based on a non-linear relation between ultraviolet and X-ray luminosities. We consider this relation both in its original form and corrected for selection biases and evolution in redshift through a reliable statistical method also accounting for the circularity problem. We also explore two approaches: with and without calibration on SNe Ia. We then investigate flat and non-flat standard cosmological models and a flat $w$CDM model, with a constant dark energy equation of state parameter $w$. Remarkably, when correcting for the evolution as a function of cosmology, we obtain closed constraints on $Ω_M$ using only non-calibrated QSOs. We find that considering non-calibrated QSOs combined with SNe Ia and accounting for the same correction, our results are compatible with a flat $Λ$CDM model with $Ω_M = 0.3$ and $H_0 = 70 \, \mathrm{km\,s^{-1}\,Mpc^{-1}}$. Intriguingly, the $H_0$ values obtained place halfway between the one from SNe Ia and CMB, paving the way for new insights into the $H_0$ tension.

astro-ph.CO↗

arXiv2022

Revealing Intrinsic Flat $Λ$CDM Biases with Standardizable Candles

Emerging high redshift cosmological probes, in particular quasars (QSOs), show a preference for larger matter densities, $Ω_{m} \approx 1$, within the flat $Λ$CDM framework. Here, using the Risaliti-Lusso relation for standardizable QSOs, we demonstrate that the QSOs recover the \textit{same} Planck-$Λ$CDM Universe as Type Ia supernovae (SN), $Ω_m \approx 0.3$ at lower redshifts $ 0 < z \lesssim 0.7$, before transitioning to an Einstein-de Sitter Universe ($Ω_m =1$) at higher redshifts $z \gtrsim 1$. We illustrate the same trend, namely increasing $Ω_{m}$ and decreasing $H_0$ with redshift, in SN but poor statistics prevent a definitive statement. We explain physically why the trend is expected in the flat $Λ$CDM cosmology, illustrate the intrinsic bias and non-Gaussian tails with mock Pantheon data, and identify a similar trend in BAO below $z=1$. Our results highlight an intrinsic bias in the flat $Λ$CDM Universe, whereby $Ω_m$ increases, $H_0$ decreases and $S_8$ increases with effective redshift, thus providing a new perspective on $Λ$CDM tensions; even in a Planck-$Λ$CDM Universe the current tensions might have been expected.

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arXiv2022

The Optical Two and Three-Dimensional Fundamental Plane Correlations for Nearly 180 Gamma-Ray Burst Afterglows with Swift/UVOT, RATIR, and the SUBARU Telescope

Gamma-ray bursts (GRBs) are fascinating events due to their panchromatic nature. We study optical plateaus in GRB afterglows via an extended search into archival data. We comprehensively analyze all published GRBs with known redshifts and optical plateaus observed by many ground-based telescopes (e.g., Subaru Telescope, RATIR) around the world and several space-based observatories such as the Neil Gehrels Swift Observatory. We fit 500 optical light curves (LCs), showing the existence of the plateau in 179 cases. This sample is 75% larger than the previous one (arXiv:2105.10717), and it is the largest compilation so far of optical plateaus. We discover the 3D fundamental plane relation at optical wavelengths using this sample. This correlation is between the rest-frame time at the end of the plateau emission, $T^{*}_{\rm opt}$, its optical luminosity, $L_{\rm opt}$, and the peak in the optical prompt emission, $L_{\rm peak, opt}$, thus resembling the three-dimensional (3D) X-ray fundamental plane relation (arXiv:1604.06840). We correct our sample for redshift evolution and selection effects, discovering that this correlation is indeed intrinsic to GRB physics. We investigate the rest-frame end time distributions in X-rays and optical ($T^{*}_{\rm opt}$, $T^{*}_{\rm X}$), and conclude that the plateau is achromatic only when selection biases are not considered. We also investigate if the 3D optical correlation may be a new discriminant between optical GRB classes and find that there is no significant separation between the classes compared to the Gold sample plane after correcting for evolution.

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arXiv2022

Gamma-Ray Bursts, Supernovae Ia and Baryon Acoustic Oscillations: a binned cosmological analysis

Cosmological probes at any redshift are necessary to reconstruct consistently the cosmic history. Studying properly the tension on the Hubble constant, $H_0$, obtained by Supernovae Type Ia (SNe Ia) and the Planck measurements of the Cosmic Microwave Background Radiation would require complete samples of distance indicators at any epoch. Gamma-Ray Bursts (GRBs) are necessary for the aforementioned task because of their huge luminosity that allows us to extend the cosmic ladder at very high redshifts. However, using GRBs alone as standard candles is challenging because their luminosity varies widely. To this end, we choose a reliable correlation for GRBs with a very small intrinsic scatter: the so-called fundamental plane correlation for GRB afterglows corrected for selection biases and redshift evolution. We choose a well-defined sample: the platinum sample, composed of 50 Long GRBs. To further constrain cosmological parameters, we use Baryon Acoustic Oscillations (BAOs) given their reliability as standard rulers. Thus, we have applied GRBs, SNe Ia, and BAOs in a binned analysis in redshifts so that GRBs' contribution is fully included in the last redshift bin, which reaches $z=5$. We use the fundamental plane correlation together with SNe Ia and BAOs, to constrain $H_0$ and the density matter today, $Ω_{M}$. This methodology allows us to assess the role of GRBs combined with SNe Ia and BAOs. We have obtained results for $H_0$ and $Ω_{M}$ using GRBs+ SNe Ia+BAOs with better precision than the SNe Ia alone for every bin, thus confirming the beneficial role of BAOs and GRBs added together. In addition, consistent results between GRBs+ SNe Ia +BAOs are obtained when compared with the SNe Ia +BAOs, showing the importance of GRBs since the distance ladder is extended up to $z=5$ with a similar precision obtained with other probes without including the GRBs.

astro-ph.CO↗

arXiv2022

Optical and X-ray GRB Fundamental Planes as Cosmological Distance Indicators

Gamma-Ray Bursts (GRBs), can be employed as standardized candles, extending the distance ladder beyond Supernovae Type Ia (SNe Ia, $z=2.26$). We standardize GRBs using the 3D fundamental plane relation (the Dainotti relation) among the rest-frame end time of the X-ray plateau emission, its corresponding luminosity, and the peak prompt luminosity. Combining SNe Ia and GRBs, we constrain $Ω_{\text{M}}= 0.299 \pm 0.009$ assuming a flat $Λ$CDM cosmology with and without correcting GRBs for selection biases and redshift evolution. Using a 3D optical Dainotti correlation, we find this sample is as efficacious in the determination of $Ω_{\text{M}}$ as the X-ray sample. We trimmed our GRB samples to achieve tighter planes to simulate additional GRBs. We determined how many GRBs are needed as standalone probes to achieve a comparable precision on $Ω_{\text{M}}$ to the one obtained by SNe Ia only. We reach the same error measurements derived using SNe Ia in 2011 and 2014 with 142 and 284 simulated optical GRBs, respectively, considering the errorbars on the variables halved. These error limits will be reached in 2038 and in 2047, respectively. Using a doubled sample (obtained by future machine learning approaches allowing a lightcurve reconstruction and the estimates of GRB redhifts when z is unknown) compared to the current sample, with errorbars halved we will reach the same precision as SNe Ia in 2011 and 2014, now and in 2026, respectively. If we consider the current SNe precision, this will be reached with 390 optical GRBs by 2054.

astro-ph.CO↗

arXiv2022

Running Hubble constant from the SNe Ia Pantheon sample?

The mismatch between different independent measurements of the expansion rate of the Universe is known as the Hubble constant ($H_0$) tension, and it is a serious and pressing problem in cosmology. We investigate this tension considering the dataset from the Pantheon sample, a collection of 1048 Type Ia Supernovae (SNe Ia) with a redshift range $0<z<2.26$. We perform a binned analysis in redshift to study if the $H_0$ tension also occurs in SNe Ia data. Hence, we build equally populated subsamples in three and four bins, and we estimate $H_{0}$ in each bin considering the $Λ$CDM and $w_{0}w_{a}$CDM cosmological models. We perform a statistical analysis via a Markov Chain Monte Carlo (MCMC) method for each bin. We observe that $H_0$ evolves with the redshift, using a fit function $H_{0}(z)=\tilde{H}_{0} (1+z)^{-α}$ with two fitting parameters $α$ and $\tilde{H}_{0}$. Our results show a decreasing behavior of $H_0$ with $α\sim 10^{-2}$ and a consistency with no evolution between 1.2 $σ$ and 2.0 $σ$. Considering the $H_0$ tension, we extrapolate $H_{0}(z)$ until the redshift of the last scattering surface, $z=1100$, obtaining values of $H_0$ consistent in 1 $σ$ with the cosmic microwave background (CMB) measurements by Planck. Finally, we discuss possible $f(R)$ modified gravity models to explain a running Hubble constant with the redshift, and we infer the form of the scalar field potential in the dynamically equivalent Jordan frame.

astro-ph.CO↗

arXiv2022

Quasar standardization: Overcoming Selection Biases and Redshift Evolution

Quasars (QSOs) are extremely luminous active galatic nuclei currently observed up to redshift $z=7.642$. As such, they have the potential to be the next rung of the cosmic distance ladder beyond SNe Ia, if they can reliably be used as cosmological probes. The main issue in adopting QSOs as standard candles (similarly to Gamma-Ray Bursts) is the large intrinsic scatter in the relations between their observed properties. This could be overcome by finding correlations among their observables that are intrinsic to the physics of QSOs and not artifacts of selection biases and/or redshift evolution. The reliability of these correlations should be verified through well-established statistical tests. The correlation between the ultraviolet (UV) and X-ray fluxes developed by Risaliti \& Lusso is one of the most promising relations. We apply a statistical method to correct this relation for redshift evolution and selection biases. \textbf{Remarkably, we recover the the same parameters of the slope and the normalization as Risaliti \& Lusso. Our results establish the reliability of this relation, which is intrinsic to the QSO properties and not merely an effect of selection biases or redshift evolution. Hence,} the possibility to standardize QSOs as cosmological candles, thereby extending the Hubble diagram up to $z=7.54$.

astro-ph.HE↗

arXiv2022

Using Multivariate Imputation by Chained Equations to Predict Redshifts of Active Galactic Nuclei

Redshift measurement of active galactic nuclei (AGNs) remains a time-consuming and challenging task, as it requires follow up spectroscopic observations and detailed analysis. Hence, there exists an urgent requirement for alternative redshift estimation techniques. The use of machine learning (ML) for this purpose has been growing over the last few years, primarily due to the availability of large-scale galactic surveys. However, due to observational errors, a significant fraction of these data sets often have missing entries, rendering that fraction unusable for ML regression applications. In this study, we demonstrate the performance of an imputation technique called Multivariate Imputation by Chained Equations (MICE), which rectifies the issue of missing data entries by imputing them using the available information in the catalog. We use the Fermi-LAT Fourth Data Release Catalog (4LAC) and impute 24% of the catalog. Subsequently, we follow the methodology described in Dainotti et al. (2021) and create an ML model for estimating the redshift of 4LAC AGNs. We present results which highlight positive impact of MICE imputation technique on the machine learning models performance and obtained redshift estimation accuracy.

astro-ph.IM↗

arXiv2022

On the evolution of the Hubble constant with the SNe Ia Pantheon Sample and Baryon Acoustic Oscillations: a feasibility study for GRB-cosmology in 2030

The difference from 4 to 6 $σ$ in the Hubble constant ($H_0$) between the values observed with the local (Cepheids and Supernovae Ia, SNe Ia) and the high-z probes (CMB obtained by the Planck data) still challenges the astrophysics and cosmology community. Previous analysis has shown that there is an evolution in the Hubble constant that scales as $f(z)=\mathcal{H}_{0}/(1+z)^η$, where $\mathcal{H}_0$ is $H_{0}(z=0)$ and $η$ is the evolutionary parameter. Here, we investigate if this evolution still holds by using the SNe Ia gathered in the Pantheon sample and the BAOs. We assume $H_{0}=70 \textrm{km s}^{-1}\textrm{Mpc}^{-1}$ as the local value and divide the Pantheon into 3 bins ordered in increasing values of redshift. Similar to our previous analysis but varying two cosmological parameters contemporaneously ($H_0$, $Ω_{0m}$ in the $Λ$CDM model and $H_0$, $w_a$ in the $w_{0}w_{a}$CDM model), for each bin we implement a MCMC analysis obtaining the value of $H_0$ $[...]$. Subsequently, the values of $H_0$ are fitted with the model $f(z)$. Our results show that a decreasing trend with $η\sim10^{-2}$ is still visible in this sample. The $η$ coefficient reaches zero in 2.0 $σ$ for the $Λ$CDM model up to 5.8 $σ$ for $w_{0}w_{a}$CDM model. This trend, if not due to statistical fluctuations, could be explained through a hidden astrophysical bias, such as the effect of stretch evolution, or it requires new theoretical models, a possible proposition is the modified gravity theories, $f(R)$ $[...]$. This work is also a preparatory to understand how the combined probes still show an evolution of the $H_0$ by redshift and what is the current status of simulations on GRB cosmology to obtain the uncertainties on the $Ω_{0m}$ comparable with the ones achieved through SNe Ia.

astro-ph.CO↗

arXiv2022

Predicting the redshift of gamma-ray loud AGNs using Supervised Machine Learning: Part 2

Measuring the redshift of active galactic nuclei (AGNs) requires the use of time-consuming and expensive spectroscopic analysis. However, obtaining redshift measurements of AGNs is crucial as it can enable AGN population studies, provide insight into the star formation rate, the luminosity function, and the density rate evolution. Hence, there is a requirement for alternative redshift measurement techniques. In this project, we aim to use the Fermi gamma-ray space telescope's 4LAC Data Release (DR2) catalog to train a machine learning model capable of predicting the redshift reliably. In addition, this project aims at improving and extending with the new 4LAC Catalog the predictive capabilities of the machine learning (ML) methodology published in Dainotti et al. (2021). Furthermore, we implement feature engineering to expand the parameter space and a bias correction technique to our final results. This study uses additional machine learning techniques inside the ensemble method, the SuperLearner, previously used in Dainotti et al.(2021). Additionally, we also test a novel ML model called Sorted L-One Penalized Estimation (SLOPE). Using these methods we provide a catalog of estimated redshift values for those AGNs that do not have a spectroscopic redshift measurement. These estimates can serve as a redshift reference for the community to verify as updated Fermi catalogs are released with more redshift measurements.

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arXiv2021

A new perspective on cosmology through Supernovae Ia and Gamma Ray Bursts

The actual knowledge of the structure and future evolution of our universe is based on the use of cosmological models, which can be tested through the so-called 'probes', namely astrophysical phenomena, objects or structures with peculiar properties that can help to discriminate among different cosmological models. Among all the existing probes, of particular importance are the Supernovae Ia (SNe Ia) and the Gamma Ray Bursts (GRBs): the former are considered among the best standard candles so far discovered but suffer from the fact that can be observed until redshift $z=2.26$, while the latter are promising standardizable candles which have been observed up to $z=9.4$, surpassing even the farthest quasar known to date, which is at $z=7.64$. The standard candles can be used to test the cosmological models and to give the expected values of cosmological parameters, in particular the Hubble constant value. The Hubble constant is affected by the so-called \say{Hubble constant tension}, a discrepancy in more than 4 $σ$ between its value measured with local probes and its value measured through the cosmological probes. The increase in the number of observed SNe Ia, as well as the future standardization of GRBs through their correlations, will surely be of help in alleviating the Hubble constant tension and in explaining the structure of the universe at higher redshifts. A promising class of GRBs for future standardization is represented by the GRBs associated with Supernovae Ib/c, since these present features similar to the SNe Ia class and obey a tight correlation between their luminosity at the end of the plateau emission in X-rays and the time at the end of the plateau in the rest-frame.

astro-ph.CO↗

arXiv2021

Predicting the redshift of gamma-ray loud AGNs using supervised machine learning

AGNs are very powerful galaxies characterized by extremely bright emissions coming out from their central massive black holes. Knowing the redshifts of AGNs provides us with an opportunity to determine their distance to investigate important astrophysical problems such as the evolution of the early stars, their formation along with the structure of early galaxies. The redshift determination is challenging because it requires detailed follow-up of multi-wavelength observations, often involving various astronomical facilities. Here, we employ machine learning algorithms to estimate redshifts from the observed gamma-ray properties and photometric data of gamma-ray loud AGN from the Fourth Fermi-LAT Catalog. The prediction is obtained with the Superlearner algorithm, using LASSO selected set of predictors. We obtain a tight correlation, with a Pearson Correlation Coefficient of 71.3% between the inferred and the observed redshifts, an average Δz_norm = 11.6 x 10^-4. We stress that notwithstanding the small sample of gamma-ray loud AGNs, we obtain a reliable predictive model using Superlearner, which is an ensemble of several machine learning models.

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arXiv2021

On the Hubble constant tension in the SNe Ia Pantheon sample

The Hubble constant ($H_0$) tension between Type Ia Supernovae (SNe Ia) and Planck measurements ranges from 4 to 6 $σ$. To investigate this tension, we estimate $H_{0}$ in the $Λ$CDM and $w_{0}w_{a}$CDM models by dividing the Pantheon sample, the largest compilation of SNe Ia, into 3, 4, 20 and 40 bins. We fit the extracted $H_{0}$ values with a function mimicking the redshift evolution: $g(z)={H_0}(z)=\tilde{H}_0/(1+z)^α$, where $α$ indicates an evolutionary parameter and $\tilde{H}_0=H_0$ at $z=0$. We set the absolute magnitude of SNe Ia so that $H_0=73.5\,\, \textrm{km s}^{-1}\,\textrm{Mpc}^{-1}$, and we fix fiducial values for $Ω_{0m}^{ΛCDM}=0.298$ and $Ω_{0m}^{w_{0}w_{a}CDM}=0.308$. We find that $H_0$ evolves with redshift, showing a slowly decreasing trend, with $α$ coefficients consistent with zero only from 1.2 to 2.0 $σ$. Although the $α$ coefficients are compatible with 0 in 3 $σ$, this however may affect cosmological results. We measure locally a variation of $H_0(z=0)-H_0(z=1)=0.4\, \textrm{km s}^{-1}\,\textrm{Mpc}^{-1}$ in 3 and 4 bins. Extrapolating ${H_0}(z)$ to $z=1100$, the redshift of the last scattering surface, we obtain values of $H_0$ compatible in 1 $σ$ with Planck measurements independently of cosmological models and number of bins we investigated. Thus, we have reduced the $H_0$ tension from $54\%$ to $72\%$ for the $Λ$CDM and $w_{0}w_{a}$CDM models, respectively. If the decreasing trend of $H_0(z)$ is real, it could be due to astrophysical selection effects or to modified gravity.

astro-ph.CO↗

arXiv2021

On the Existence of the Plateau Emission in High-Energy Gamma-Ray Burst LightCurves observed byFermi-LAT

The Large Area Telescope (LAT) on board the \Fermi Gamma-ray Space Telescope (\Fermi) shows long-lasting high-energy emission in many gamma-ray bursts (GRBs), similar to X-ray afterglows observed by the Neil Gehrels Swift Observatory \citep[\textit{Swift};][]{gehrels2004}. Some LAT light curves (LCs) show a late-time flattening reminiscent of X-ray plateaus. We explore the presence of plateaus in LAT temporally extended emission analyzing GRBs from the second \lat GRB Catalog \citep[2FLGC;][]{Ajello2019apj} from 2008 to May 2016 with known redshifts, and check whether they follow closure relations corresponding to 4 distinct astrophysical environments predicted by the external forward shock (ES) model. We find that three LCs can be fit by the same phenomenological model used to fit X-ray plateaus \citep{Willingale2007} and show tentative evidence for the existence of plateaus in their high-energy extended emission. The most favorable scenario is a slow cooling regime, whereas the preferred density profile for each GRBs varies from a constant density ISM to a $r^{-2}$ wind environment. We also compare the end time of the plateaus in $γ$-rays and X-rays using a statistical comparison with 222 \textit{Swift} GRBs with plateaus and known redshifts from January 2005 to August 2019. Within this comparison, the case of GRB 090510 shows an indication of chromaticity at the end time of the plateau. Finally, we update the 3-D fundamental plane relation among the rest frame end time of the plateau, its correspondent luminosity, and the peak prompt luminosity for 222 GRBs observed by \textit{Swift}. We find that these three LAT GRBs follow this relation.

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arXiv2021

Cosmological Evolution of the Formation Rate of Short Gamma-ray Bursts With and Without Extended Emission

Originating from neutron star-neutron star (NS-NS) or neutron star-black hole (NS-BH) mergers, short gamma-ray bursts (SGRBs) are the first electromagnetic emitters associated with gravitational waves. This association makes the determination of SGRB formation rate (FR) a critical issue. We determine the true SGRB FR and its relation to the cosmic star formation rate (SFR). This can help in determining the expected Gravitation Wave (GW) rate involving small mass mergers. We present non-parametric methods for the determination of the evolutions of the luminosity function (LF) and the FR using SGRBs observed by {\it Swift}, without any assumptions. These are powerful tools for small samples, such as our sample of 68 SGRBs. We combine SGRBs with and without extended emission (SEE), assuming that both descend from the same progenitor. To overcome the incompleteness introduced by redshift measurements we use the Kolmogorov-Smirnov (KS) test to find flux thresholds yielding a sample of sources with a redshift drawn from the parent sample including all sources. Using two subsamples of SGRBs with flux limits of $4.57 \times 10^{-7}$ and $2.15 \times 10^{-7}$ erg cm$^{-2}$ s$^{-1}$ with respective KS {\it p=(1, 0.9)}, we find a 3 $σ$ evidence for luminosity evolution (LE), a broken power-law LF with significant steepening at $L\sim 10^{50}$ erg s$^{-1}$, and a FR evolution that decreases monotonically with redshift (independent of LE and the thresholds). Thus, SGRBs may have been more luminous in the past with a FR delayed relative to the SFR as expected in the merger scenario.

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