Cent Confidence Research Articles

Evidence for mass-dependent peculiar velocities in compact object binaries: towards better constraints on natal kicks

ABSTRACT We compile a catalogue of low-mass and high-mass X-ray binaries, some recently reported binaries that likely host a neutron star (NS) or a black hole (BH), and binary pulsars (a pulsar and a non-degenerated companion) that have measured systemic radial velocities (γ). Using Gaia and radio proper motions together with γ, we integrate their Galactic orbits and infer their post-supernova (post-SN) 3D peculiar velocities ($v_\mathrm{pec }^{z=0}$ at Galactic plane crossing); these velocities bear imprints of the natal kicks that compact objects received at birth. With the sample totalling 85 objects, we model the overall distribution of $v_\mathrm{pec }^{z=0}$ and find a two-component Maxwellian distribution with a low- ($\sigma _v \approx 21\, \mathrm{km s^{-1}}$) and a high-velocity ($\sigma _v \approx 107\, \mathrm{km s^{-1}}$) component. A further comparison between distributions of binary subgroups suggests that binaries hosting high-mass donors/luminous companions mostly have $v_\mathrm{pec }^{z=0}\lesssim 100\, \mathrm{km s^{-1}}$, while binaries with low-mass companions exhibit a broader distribution that extends up to $\sim 400\, \mathrm{km s^{-1}}$. We also find significant anticorrelations of $v_\mathrm{pec }^{z=0}$ with binary total mass (Mtot) and orbital period (Porb), at over 99 per cent confidence. Specifically, our fit suggests $v_\mathrm{pec }^{z=0}\propto M_\mathrm{tot}^{-0.5}$ and $v_\mathrm{pec }^{z=0}\propto P_\mathrm{orb}^{-0.2}$. Discussions are presented on possible interpretation of the correlations in the context of kinematics and possible biases. The sample should enable a range of follow-up studies on compact object binary kinematics and evolution.

The 95 per cent confidence interval for the mean sea-level change rate derived from tide gauge data

SUMMARYTide gauge (TG) data are crucial for assessing global sea-level and climate changes, coastal subsidence and inundation. Mean sea-level (MSL) time-series derived from TG data are autocorrelated. The conventional ordinary least-squares regression method provides reasonable estimates of relative sea-level (RSL) change rates (linear trends) but underestimates their uncertainties. In order to cope with the autocorrelation issue, we propose an approach that uses an ‘effective sample size’ (${N}_{\mathrm{ eff}}$) to estimate the uncertainties (±95 per cent confidence interval, or 95 per cent CI for short). The method involves decomposing the monthly MSL time-series into three components: a linear trend, a periodic component and a noise time-series. The ${N}_{\mathrm{ eff}}$ is calculated according to the autocorrelation function (ACF) of the noise time-series. We present an empirical model that fits an inverse power-law relationship between 95 per cent CI and time span (T) based on 1160 TG data sets globally distributed, where $95\ \mathrm{ per}\ \mathrm{ cent}\,\mathrm{ CI} = 179.8{T}^{ - 1.29}$. This model provides a valuable tool for projecting the optimal observational time span needed for the desired uncertainty in sea-level rise rate or coastal subsidence rate from TG data. It suggests that a 20-yr TG time-series may result in a 3–5 mm yr−1 uncertainty (95 per cent CI) for the RSL change rate, while a 30-yr data set may achieve about 2 mm yr−1 uncertainty. To achieve a submillimetre per year (< 1 mm yr−1) uncertainty, approximately 60 yr of TG observations are needed. We also present a Python module (TG_Rate_95CI.py) for implementing the methodology. The Python module and the empirical model have broad applications in global sea-level rise and climate change studies, and coastal environmental and infrastructure planning, as well as Earth science education.

Type Ia supernova constraints on compact object dark matter

ABSTRACT The nature of dark matter (DM) is a central question in cosmology today. While elementary particles could explain DM, compact astrophysical objects such as black holes formed in the early Universe offer a theoretically appealing alternate route. Here, we constrain the fraction of DM that can be made up of primordial black holes (PBHs) with masses $M \gtrsim 0.01\, {\rm M}_\odot$, with Type Ia supernovae. Utilizing the Dyer–Roeder distance relation, we find a maximum fractional amount of DM in compact objects (fp) of 0.50 at 95 per cent confidence level (C.L.), in the flat Lambda cold dark matter model and 0.49 when marginalizing over a constant dark energy equation of state or spatial curvature, demonstrating robustness to the cosmological model. With a prior on the homogeneity parameter, η, including values >1, we derive η = 1.08 ± 0.17, hence, fp < 0.32 at 95 per cent C.L., showing that the prior assumption of η ≤ 1 gives a conservative upper limit on fp. The Hubble constant we infer is consistent with the homogeneous case, showing that inhomogeneities like compact DM cannot account for the observed Hubble tension. In conclusion, we can exclude stellar masses PBHs as comprising all of the observed DM.

Consistent constraints on the equivalence principle from localized fast radio bursts

ABSTRACT Fast radio bursts (FRBs) are short astrophysical transients of extragalactic origin. Their burst signal is dispersed by the free electrons in the large-scale-structure (LSS), leading to delayed arrival times at different frequencies. Another potential source of time delay is the well known Shapiro delay, which measures the space–space and time–time metric perturbations along the line-of-sight. If photons of different frequencies follow different trajectories, i.e. if the universality of free fall guaranteed by the weak equivalence principle (WEP) is violated, they would experience an additional relative delay. This quantity, however, is not observable at the background level as it is not gauge independent, which has led to confusion in previous papers. Instead, an imprint can be seen in the correlation between the time delays of different pulses. In this paper, we derive robust and consistent constraints from twelve localized FRBs on the violation of the WEP in the energy range between 4.6 and 6 meV. In contrast to a number of previous studies, we consider our signal to be not in the model, but in the covariance matrix of the likelihood. To do so, we calculate the covariance of the time delays induced by the free electrons in the LSS, the WEP breaking terms, the Milky Way and host galaxy. By marginalizing both host galaxy contribution and the contribution from the free electrons, we find that the parametrized post-Newtonian parameter γ characterizing the WEP violation must be constant in this energy range to 1 in 1013 at 68 per cent confidence. These are the tightest constraints to-date on Δγ in this low-energy range.

JWST observations of dust reservoirs in type IIP supernovae 2004et and 2017eaw

ABSTRACT Supernova (SN) explosions have been sought for decades as a possible source of dust in the Universe, providing the seeds of galaxies, stars, and planetary systems. SN 1987A offers one of the most promising examples of significant SN dust formation, but until the James Webb Space Telescope (JWST), instruments have traditionally lacked the sensitivity at both late times (>1 yr post-explosion) and longer wavelengths (i.e. >10 μm) to detect analogous dust reservoirs. Here we present JWST/MIRI observations of two historic Type IIP SNe, 2004et and SN 2017eaw, at nearly 18 and 5 yr post-explosion, respectively. We fit the spectral energy distributions as functions of dust mass and temperature, from which we are able to constrain the dust geometry, origin, and heating mechanism. We place a 90 per cent confidence lower limit on the dust masses for SNe 2004et and 2017eaw of >0.014 and >4 × 10−4 M⊙, respectively. More dust may exist at even colder temperatures or may be obscured by high optical depths. We conclude dust formation in the ejecta to be the most plausible and consistent scenario. The observed dust is radiatively heated to ∼100–150 K by ongoing shock interaction with the circumstellar medium. Regardless of the best fit or heating mechanism adopted, the inferred dust mass for SN 2004et is the second highest (next to SN 1987A) mid-infrared inferred dust mass in extragalactic SNe thus far, promoting the prospect of SNe as potential significant sources of dust in the Universe.

Uncovering the geometry of the hot X-ray corona in the Seyfert galaxy NGC 4151 with IXPE

ABSTRACT We present an X-ray spectropolarimetric analysis of the bright Seyfert galaxy NGC 4151. The source has been observed with the Imaging X-ray Polarimetry Explorer (IXPE) for 700 ks, complemented with simultaneous XMM–Newton (50 ks) and NuSTAR (100 ks) pointings. A polarization degree Π = 4.9 ± 1.1 per cent and angle Ψ = 86° ± 7° east of north (68 per cent confidence level) are measured in the 2–8 keV energy range. The spectropolarimetric analysis shows that the polarization could be entirely due to reflection. Given the low reflection flux in the IXPE band, this requires, however, a reflection with a very large (>38 per cent) polarization degree. Assuming more reasonable values, a polarization degree of the hot corona ranging from ∼4 to ∼8 per cent is found. The observed polarization degree excludes a ‘spherical’ lamppost geometry for the corona, suggesting instead a slab-like geometry, possibly a wedge, as determined via Monte Carlo simulations. This is further confirmed by the X-ray polarization angle, which coincides with the direction of the extended radio emission in this source, supposed to match the disc axis. NGC 4151 is the first active galactic nucleus with an X-ray polarization measure for the corona, illustrating the capabilities of X-ray polarimetry and IXPE in unveiling its geometry.

Investigating the OH-H2 relation in diffuse Galactic clouds

Abstract We investigate the correlation between OH and H2 column densities in diffuse Galactic clouds, in order to identify potential molecular tracers of interstellar H2. For this, we analyse near-UV spectra extracted from the ESO/VLT archives towards seventeen sightlines (five of them new) with known N(H2), along with nine sightlines with no H2 information. N(OH) shows only marginal correlation with N(H2) (1020 to 2 × 1021 cm−2), at the 95 per cent confidence level. We use orthogonal distance regression analysis to obtain N(OH) /N(H2) = (1.32±0.15) × 10−7, which is ∼ 33 per cent higher than the previous estimates based on near-UV data. We also obtain N(CH) /N(H2) = (3.83±0.23) × 10−8 and a significant correlation between N(OH) and N(CH), with N(OH) = (2.61±0.19) × N(CH), both of which are consistent with previous results. Comparison with predictions of numerical models indicate that OH absorption arises from diffuse gas (nH ∼ 50 cm−3) illuminated by radiation fields ∼ 0.5–5 G0, while CH is associated with higher density of 500 cm−3. We posit that the apparent dichotomy in the properties of the diffuse clouds giving rise to OH and CH absorption could be due to either (a) the presence of multiple spectroscopically unresolved clouds along the line-of-sight, or, (b) density gradients along the line-of-sight within a single cloud.

A systematic review and meta-analysis of Stereotactic radiosurgery as primary treatment in fast-growing vestibular schwannomas.

Stereotactic radiosurgery has been shown to be an effective method of managing vestibular schwannomas. The primary aim here is to establish the impact of pre-treatment fast-growing vestibular schwannomas on the efficacy of stereotactic radiosurgery. PubMed, Medline and Embase databases were used. The ROBINS-I ('Risk Of Bias In Non-randomised Studies - of Interventions') tool was utilised to assess for risk of bias. Proportionate meta-analysis and sub-analysis for fast-growing tumours were performed to explore the success rate of stereotactic radiosurgery in stabilising or decreasing the tumour burden in vestibular schwannomas. Four moderate risk studies were included in the analysis. Overall, 91 per cent (95 per cent confidence interval = 0.83-0.97, p < 0.01, I2 = 80 per cent) of the tumours demonstrated successful size reduction or stabilisation following stereotactic radiosurgery. Nevertheless, the efficacy of stereotactic radiosurgery in reducing or stabilising fast-growing vestibular schwannomas decreased by 79 per cent (95 per cent confidence interval = 0.64-0.91, p = 0.11, I2 = 62 per cent). Stereotactic radiosurgery has a statistically significant success rate in stabilising or decreasing the vestibular schwannoma size. This success rate is diminished in fast-growing vestibular schwannomas.

A new small glitch in Vela discovered with a hidden Markov model

ABSTRACT A striking feature of the Vela pulsar (PSR J0835−4510) is that it undergoes sudden increases in its spin frequency, known as glitches, with a fractional amplitude of the order of 10−6 approximately every 900 d. Glitches of smaller magnitudes are also known to occur in Vela. Their distribution in both time and amplitude is less well constrained but equally important for understanding the physical process underpinning these events. In order to better understand these small glitches in Vela, an analysis of high-cadence observations from the Mount Pleasant Observatory is presented. A hidden Markov model (HMM) is used to search for small, previously undetected glitches across 24 yr of observations covering MJD 44929 to MJD 53647. One previously unknown glitch is detected around MJD 48636 (1992 January 15), with fractional frequency jump Δf/f = (8.19 ± 0.04) × 10−10 and frequency derivative jump $\Delta \dot{f}/\dot{f} = (2.98 \pm 0.01) \times 10^{-4}$ . Two previously reported small glitches are also confidently redetected, and independent estimates of their parameters are reported. Excluding these events, 90 per cent confidence frequentist upper limits on the sizes of missed glitches are also set, with a median upper limit of $\Delta f^{90~{{\% }}}/f = 1.35 \times 10^{-9}$. Upper limits of this kind are enabled by the semi-automated and computationally efficient nature of the HMM, and are crucial to informing studies that are sensitive to the lower end of the glitch size distribution.

A von Mises–Fisher distribution for the orbital poles of the plutinos

ABSTRACT Small Solar system bodies have widely dispersed orbital poles, posing challenges to dynamical models of Solar system origin and evolution. To characterize the orbit pole distribution of dynamical groups of small bodies it helps to have a functional form for a model of the distribution function. Previous studies have used the small-inclination approximation and adopted variations of the normal distribution to model orbital inclination dispersions. Because the orbital pole is a directional variable, its distribution can be more appropriately modelled with directional statistics. We describe the von Mises–Fisher (vMF) distribution on the surface of the unit sphere for application to small bodies’ orbital poles. We apply it to the orbit pole distribution of the observed Plutinos. We find a mean pole located at inclination i0 = 3.57° and longitude of ascending node Ω0 = 124.38° (in the J2000 reference frame), with a 99.7 per cent confidence cone of half-angle 1.68°. We also estimate a debiased mean pole located 4.6° away, at i0 = 2.26°, Ω0 = 292.69°, of similar-size confidence cone. The vMF concentration parameter of Plutino inclinations (relative to either mean pole estimate) is κ = 31.6. This resembles a Rayleigh distribution function, with width parameter σ = 10.2°. Unlike previous models, the vMF model naturally accommodates all physical inclinations (and no others), whereas Rayleigh or Gaussian models must be truncated to the physical inclination range 0–180°. Further work is needed to produce a theory for the mean pole of the Plutinos against which to compare the observational results.

Radio multifrequency observations of the galaxy cluster pair Abell 399 − 401 with WSRT

ABSTRACT Galaxy clusters are assembled via merging of smaller structures, in a process that generates shocks and turbulence in the intra cluster medium and produces radio diffuse emission in the form of halos and relics. The cluster pair A 399–A 401 represents a special case: both clusters host a radio halo. Recent Low Frequency Array (LOFAR) observations at 140 MHz revealed the presence of a radio bridge connecting the two clusters along with two relic candidates. These relics include one South of A 399 and the other in between the two clusters, in proximity of a shock front detected in X-ray observations. In this paper we present observations of the A 399–A 401 cluster pair at 1.7, 1.4, 1.2 GHz, and 346 MHz from the Westerbork Synthesis Radio Telescope (WSRT). We detect the radio halo in the A 399 cluster at 346 MHz, extending up to ∼650 kpc and with a 125 ± 6 mJy flux density. Its spectral index between 140 MHz and 346 MHz is α = 1.75 ± 0.14. The two candidate relics are also seen at 346 MHz and we determine their spectral indices to be α = 1.10 ± 0.14 and α = 1.46 ± 0.14. The low surface brightness bridge connecting the two clusters is below the noise level at 346 MHz therefore we constrain the bridge average spectral index to be steep, i.e. α &amp;gt; 1.5 at 95 per cent confidence level. This result favours the scenario where dynamically-induced turbulence is a viable mechanism to reaccelerate a population of mildly relativistic particles and amplify magnetic fields on scales of a few Mpcs.

Prevalence and causes of violent deaths in Nairobi Kenya: An autopsy study

This study aimed to investigate fatalities resulting from violent deaths to inform public health policy on the need for their prevention. This is a descriptive prospective study of violent deaths in Nairobi. The study included all cases of deaths from violent deaths for twelve consecutive months. Data was entered on a proforma datasheet. Data were analysed using SPSS. Out of 2566 autopsy cases in one year, between June 1, 2009, and May 31 2010, 47.3 per cent of deaths were due to homicide, 43.6 per cent deaths were due to accidents, and 9.1 per cent deaths were due to suicide. Among homicides, 41.5 per cent were due to gunshots, 39.3 per cent were due to blunt injuries, 4.5 per cent were due to stabbing, and 0.4 per cent were due to strangulation. Police shootings comprised 95 per cent of the gunshots, and mob justice comprised 57.3 per cent of the blunt injuries. Among accidents, road traffic accidents contributed 87.3 per cent, with pedestrians as the majority at 46.9 per cent. Amongst the other accidents, burns contributed 35.6 per cent. Among suicide, hanging contributed to 79 per cent. A p-value of 0.03 (95 per cent confidence interval) was found when the data were analysed using an F-test. There was a statistically significant difference (p=0.03) between violent death and alcohol intoxication. Violent deaths require to be studied in the background of the social setting of the death.

Palaeosecular variation in Northern Patagonia recorded by 0–5 Ma Caviahue–Copahue lava flows

SUMMARY Palaeosecular variation (PSV) determinations and studies of the geometry of the Earth’s main magnetic field provide important information about the field evolution, and to constrain numerical geodynamo models. Palaeomagnetic directional data from lava flows over the last few million years is of particular interest because the regional and global tectonic effects are minimal. However, the distribution of this type of palaeomagnetic data is uneven where the Southern Hemisphere is the destitute side. Therefore, the better knowledge of the geomagnetic field behaviour depends on the increased availability of high-quality data, especially in the Southern Hemisphere. A PSV and the time-averaged field (TAF) study was then performed in 0–5 Ma lava flows from the Caviahue–Copahue Volcanic Complex located in Northern Patagonia, Argentina (37°0′S, 71°10′W). The magnetic mineralogy of lava flows was investigated through thermomagnetic susceptibility curves, isothermal remanent magnetization (IRM) acquisition curves, hysteresis loops and first-order reversal curves (FORCs). Samples are essentially comprised of titanomagnetite with different Ti contents and magnetic domain structures typical of vortex state particles. A total of 50 volcanic sites were sampled, which provided 42 reliable palaeomagnetic site-mean directions after alternating field and thermal demagnetization. From these 42 sites, 36 are of normal and 6 are of reversed polarity. The mean direction from normal (reversed) sites is D = 356.2°, I = −50.1°, α95 = 4.0° and N = 36 (D = 176.5°, I = 59.5°, α95 = 14.1° and N = 6). Using only site-level data with the precision parameter k ≥ 100, we obtain 26 palaeomagnetic sites for PSV and TAF investigations in the study region. The filtered data set has a mean direction (D = 354.4°, I = −53.2° and α95 = 5.1°) close to the expected direction for a geocentric axial dipole (GAD) field (IGAD = −57.3°). The palaeopole (Plat = 84.4°, Plon = 229.1° and A95 = 5.7°) coincides with the Earth’s spin axis within the 95 per cent confidence interval. Virtual geomagnetic pole scatter ($S_{B} = {15.8^{18.9}_{11.8}}^{\circ }$) and the inclination anomaly ($\Delta I = 4.1_{-1.0}^{{9.2}^{\circ }}$) are both consistent at the 95 per cent confidence level with recent PSV and TAF models, respectively. Our results support the presence of small non-dipole field contributions (&amp;lt;3 per cent) superimposed on the GAD term, as reported by South American studies at mid southern latitudes.

Beyond – ΛCDM constraints from the full shape clustering measurements from BOSS and eBOSS

ABSTRACT We analyse the full shape of anisotropic clustering measurements from the extended Baryon Oscillation Spectroscopic Survey quasar sample together with the combined galaxy sample from the Baryon Oscillation Spectroscopic Survey. We obtain constraints on the cosmological parameters independent of the Hubble parameter h for the extensions of the Lambda cold dark matter (ΛCDM) models, focusing on cosmologies with free dark energy equation of state parameter w. We combine the clustering constraints with those from the latest cosmic microwave background data from Planck to obtain joint constraints for these cosmologies for w and the additional extension parameters – its time evolution wa, the physical curvature density ωK and the neutrino mass sum ∑mν. Our joint constraints are consistent with a flat ΛCDM cosmological model within 68 per cent confidence limits. We demonstrate that the Planck data are able to place tight constraints on the clustering amplitude today, σ12, in cosmologies with varying w and present the first constraints for the clustering amplitude for such cosmologies, which is found to be slightly higher than the ΛCDM value. Additionally, we show that when we vary w and allow for non-flat cosmologies and the physical curvature density is used, Planck prefers a curved universe at 4σ significance, which is ∼2σ higher than when using the relative curvature density ΩK. Finally, when w is varied freely, clustering provides only a modest improvement (of 0.021 eV) on the upper limit of ∑mν.

A preliminary investigation of the empirical relationship between small-amplitude Forbush Decreases and solar wind disturbances

ABSTRACTHigh-magnitude (amplitude $\le -3{{\ \rm per\ cent}}$) Forbush decreases (FDs) are generally employed by researchers investigating the solar-terrestrial connection mechanisms. Although it has been observed that small-amplitude FDs are relatively important as they may be the outcome of the response of cosmic ray time-intensity variations to solar ejections that generate interplanetary and solar wind plasma disturbances, empirical relations between weak FDs and solar-terrestrial parameters are rarely tested. In an attempt to analyse the suggested strong connections between weak FDs and solar-terrestrial phenomena, we employed some comparatively more efficient, accurate, and highly sensitive versions of the recently developed computer FD event selection software. Large catalogues of low-amplitude (FD(per cent) ≥−3) Forbush events were selected from Apatity, Moscow, Newark, and Oulu NMs. These catalogues allow us to test, for the first time, the empirical relations between small-amplitude FDs and solar wind data. We find significant negative correlations between solar wind speed (SWS) and the small FDs at OULU, NWRK, and MOSC stations. While the relation at OULU is strong and statistically significant at 95 per cent confidence level, the weak correlation at NWRK and MOSC is only significant at a 90 per cent level. The negative correlation between the small events at OULU and the interplanetary magnetic field (IMF) is also significant at the a 95 per cent level. The relation between SWS and IMF and high-amplitude FDs were also tested, and the correlation coefficients were negative, strong, and statistically significant at a 99.9 per cent level of significance.

Is the Harrison-Zel’dovich spectrum coming back? ACT preference forns∼ 1 and its discordance with Planck

ABSTRACTThe Data Release 4 of the Atacama Cosmology Telescope (ACT) shows an agreement with an Harrison-Zel’dovich primordial spectrum (ns = 1.009 ± 0.015), introducing a tension with a significance of 99.3 per cent Confidence Level (CL) with the results from the Planck satellite. The discrepancy on the value of the scalar spectral index is neither alleviated with the addition of large scale structure information nor with the low multipole polarization data. We discuss possible avenues to alleviate the tension relying on either neglecting polarization measurements from ACT or in extending different sectors of the theory.

Searching for bounce signature in the early universe from current and future large-scale structure surveys

ABSTRACT The bounce scenario has been an interesting research topic in cosmology, due to its ability to resolve both the singularity problem and the trans-Planckian issue, which are left from the standard inflationary theory. In previous works, we considered an inflationary cosmology with a preceding non-singular bounce and found that this model could suppress the primordial power spectrum at large scales and leave the signature on the angular power spectra of cosmic microwave background (CMB). In this work, we extend this analysis to the large-scale structure (LSS) measurements. Firstly, we consider the angular power spectrum of current LSS data sets, such as the 2MPZ, SDSS-DR12, and DES Y3 galaxy surveys at low redshifts and the NVSS radio survey at high redshifts, and do not obtain good constraint on the model parameters, due to the precision limitation at large scales. When we include the Planck CMB measurements, the constraints become a little bit better: the amplitude Ar = 0.8 ± 0.2 and the slope ${\rm log_{10}}(k_B)=-2.6^{+0.3}_{-1.0}$ at 68 per cent confidence level. In order to evaluate the constraining ability of future LSS surveys, we forecast the clustering measurements, such as the galaxy angular power spectrum and the galaxy lensing shear power spectrum, based on the China Space Station Telescope photometric survey. We find that the standard deviations of model parameters will be significantly shrunk, ΔAr = 0.1 and Δlog10(kB) = 0.1, due to the high precision measurements. Finally, we consider the bounce feature and the primordial non-Gaussianity from inflation theory simultaneously and find that in the bounce inflationary model the limit on fNL will be weaker than that obtained in the standard inflationary model, due to the strong degeneracy among parameters.

Distribution of Fast Radio Burst Dispersion Measures in CHIME/FRB Catalog 1: Implications on the Origin of FRBs

Recently, CHIME/FRB project published its first fast radio burst (FRB) catalog (hereafter, Catalog 1), which contains in total 536 unique bursts. With the help of the latest set of FRBs in this large-size catalog, we aim to investigate the dispersion measure (DM) or redshift ( $$z$$ ) distribution of the FRB population, and solution of this problem could be used to clarify the question of FRB origin. In this study, we adopted the M&E 2018 model to fit the observed $$z$$ distribution of FRBs in Catalog 1. In the M&E 2018 model, we are mostly interested in the $$\Phi (z)$$ function, i.e., number of bursts per proper time per comoving volume, which is represented by the star formation rate (SFR) with a power-law index $$n$$ . Our estimated value of $$n$$ is $$0.0_{{ - 0.0}}^{{ + 0.6}}$$ ( $$0.0_{{ - 0.0}}^{{ + 2.1}}$$ ) at the 68 (95) per cent confidence level, implying that the FRB population evolves with redshift consistent with, or faster than, the SFR. Specially, the consistency of the $$n$$ values estimated by this study and the SFR provides a potential support for the hypothesis of FRBs originating from young magnetars.

Search for the Epoch of Reionization with HERA: upper limits on the closure phase delay power spectrum

ABSTRACT Radio interferometers aiming to measure the power spectrum of the redshifted 21 cm line during the Epoch of Reionization (EoR) need to achieve an unprecedented dynamic range to separate the weak signal from overwhelming foreground emissions. Calibration inaccuracies can compromise the sensitivity of these measurements to the effect that a detection of the EoR is precluded. An alternative to standard analysis techniques makes use of the closure phase, which allows one to bypass antenna-based direction-independent calibration. Similarly to standard approaches, we use a delay spectrum technique to search for the EoR signal. Using 94 nights of data observed with Phase I of the Hydrogen Epoch of Reionization Array (HERA), we place approximate constraints on the 21 cm power spectrum at z = 7.7. We find at 95 per cent confidence that the 21 cm EoR brightness temperature is ≤(372)2 ‘pseudo’ mK2 at 1.14 ‘pseudo’ h Mpc−1, where the ‘pseudo’ emphasizes that these limits are to be interpreted as approximations to the actual distance scales and brightness temperatures. Using a fiducial EoR model, we demonstrate the feasibility of detecting the EoR with the full array. Compared to standard methods, the closure phase processing is relatively simple, thereby providing an important independent check on results derived using visibility intensities, or related.

Using X-ray continuum-fitting to estimate the spin of MAXI J1305–704

ABSTRACT MAXI J1305–704 is a transient X-ray binary with a black hole primary. It was discovered on 2012 April 9, during its only known outburst. MAXI J1305–704 is also a high inclination low-mass X-ray binary with prominent dip features in its light curves, so we check the full catalogue of 92 Swift/XRT continuous observations of MAXI J1305–704, focusing only on the stable spectra. We select 13 ‘gold’ spectra for which the rms &amp;lt;0.075 and the coronal scattered fraction $f_{\mathrm{sc}} \lesssim 25$ per cent. These ‘gold’ data are optimal thermal-state observations for continuum-fitting modelling, in which the disc extends to the innermost stable circular orbit and is geometrically thin. The black hole spin was unknown for this object before. By utilizing the X-ray continuum fitting method with the relativistic thin disc model kerrbb2 and supplying the known dynamical binary system parameters, we find MAXI J1305–704 has a moderate spin ($a_{*}=0.87_{-0.13}^{+0.07}$) at a 68.3 per cent confidence level. This is the first determination of MAXI J1305–704’s spin.