X-ray Wavebands Research Articles

Parameter study for hot spot trajectories around SgrA*

Context. Intense flaring events in the near-infrared and X-ray wavebands of our Galactic center have been the subject of research for decades. In recent years, the GRAVITY instrument of the Very Large Telescope captured the motion and polarimetric signature of such a flare in close proximity to the supermassive black hole. Aims. This study aims to investigate a broad parameter space for hot spot motion in the vicinity of SgrA* and reproduce the observed flaring behavior. Methods. To this end, we have developed a general relativistic radiative transfer code and conducted a parameter study including both planar and ejected hot spot configurations around supermassive black holes. Results. Super-Keplerian orbital frequencies are favored by circular equatorial, cylindrical and parabolic models, whereas conical hot spot trajectories provide a better fit for orbital frequencies below the Keplerian value. Additionally, a distant observer cannot effectively differentiate between Schwarzschild and Kerr black holes, as well as face-on orbits at different observation angles.

A hybrid approach to event reconstruction for atmospheric Cherenkov Telescopes combining machine learning and likelihood fitting

The imaging atmospheric Cherenkov technique provides potentially the highest angular resolution achievable in astronomy at energies above the X-ray waveband. High-resolution measurements provide the key to progress on many of the major questions in high energy astrophysics, including the sites and mechanisms of particle acceleration to PeV energies. The huge potential of the next-generation CTA observatory in this regard can be realised with the help of improved algorithms for the reconstruction of the air-shower direction and energy.Hybrid methods combining maximum-likelihood-fitting techniques with neural networks represent a particularly promising approach and have recently been successfully applied for the reconstruction of astrophysical neutrinos. Here, we present the FreePACT algorithm, a hybrid reconstruction method for IACTs. In this, making use of the neural ratio estimation technique from the field of likelihood-free inference, the analytical likelihood used in traditional image likelihood fitting is replaced by a neural network that approximates the charge probability density function for each pixel in the camera.The performance of this improved algorithm is demonstrated using simulations of the planned CTA southern array. For this setupFreePACT provides significant performance improvements over analytical likelihood techniques, with improvements in angular and energy resolution of 25% or more over a wide energy range and an angular resolution as low as 40′′ at energies above 50TeV for observations at 20° zenith angle. It also yields more accurate estimations of the uncertainties on the reconstructed parameters and significantly speeds up the reconstruction compared to analytical likelihood techniques while showing the same stability with respect to changes in the observation conditions. Therefore, the FreePACT method is a promising upgrade over the current state-of-the-art likelihood event reconstruction techniques.

X-ray emission from large scale jets of AGNs at high redshifts

The limited angular resolution of the existing telescopes, operating in radio, optical and X-ray wavebands, hinder the study on multi-spectral component (MSC) emissions from the large scale jet of AGNs. This is particularly strenuous for the sources located at high redshifts. Though a few of them were resolved in radio-optical wavebands, their X-ray counterparts have been rarely discovered. This poses a bigger challenge in understanding their emission mechanism. At high redshifts, the X-ray emission from the large scale jets are generally interpreted as inverse-Compton scattering of cosmic microwave background photons (IC/CMB), due to the increase in CMB photon density. However, recent Fermi γ-ray flux upper limit estimates on two high redshift (z>3.5) AGN jets (J1510+5702 and J1421-0643), question the validity of the IC/CMB model. Here, we propose a model by considering the advection of electrons from the sites of particle acceleration (Rahman et al., 2022), to interpret the MSC emission from these sources. We show that observed radio/optical/X-ray emissions can be explained by the synchrotron emission from the advected and accelerated electron distribution. We also show that the IC/CMB spectrum of this composite electron distribution satisfies the constraints drawn from Fermi observations.

Are Quasi-periodic Pulsations Independent of Loop Oscillations in Solar Flare?

We investigated oscillations in an M8.7 solar flare (SOL2014-10-22), including quasi-periodic pulsations (QPPs) in light curves and Doppler shift oscillations in the flare loops. Using Bayesian-based Markov Chain Monte Carlo, Fast Fourier Transform, and wavelet analysis method, QPPs were identified at microwave and hard X-ray wave bands during the impulsive phase, and the dominant period is 40–50 s. They should be associated with a repetitive energy release process, which accelerates nonthermal electrons periodically. On the other hand, we cannot rule out the possibility of the modulation of external waves because of the lower temporal resolution of spectroscopic observation. However, almost immediately after QPPs, a minority of flare loops display their Doppler velocity oscillations with a significant period of ∼4 minutes, which are observed by the Interface Region Imaging Spectrograph at the coronal line Fe xxi 1354.08 Å (T ∼ 107 K), while its intensity and width show no similar oscillation. Our observations suggest that flare loop oscillations are most likely the fast kink mode waves with a phase speed of ∼840 km s−1. The magnetic field strength in flare loops was estimated to be 54–69 G via the coronal seismology. The QPPs and loop oscillation could be independent of each other in this event.

X-ray polarimetry as a tool to measure the black hole spin in microquasars: simulations of IXPE capabilities

ABSTRACT Measurements of the angular momentum (spin) of astrophysical black holes are extremely important, as they provide information on the black hole formation and evolution. We present simulated observations of an X-ray binary system with the Imaging X-ray Polarimetry Explorer (IXPE), with the aim to study the robustness of black hole spin and geometry measurements using X-ray polarimetry. As a representative example, we used the parameters of GRS 1915+105 in its former unobscured, soft state. In order to simulate the polarization properties, we modelled the source emission with a multicolour blackbody accounting for thermal radiation from the accretion disc, including returning radiation. Our analysis shows that the polarimetric observations in the X-ray waveband will be able to estimate both spin and inclination of the system with a good precision [without returning radiation we obtained for the lowest spin Δa ≤ 0.4 (0.4/0.998 ∼ 40 per cent) for spin and Δi ≤ 30° (30°/70$^\circ \, \sim$ 43 per cent) for inclination, while for the higher spin values we obtained Δa ≤ 0.12 (∼12 per cent) for spin and Δi ≤ 20° (∼29 per cent) for inclination, within 1σ errors]. When focusing on the case of returning radiation and treating inclination as a known parameter, we were able to successfully reconstruct spin and disc albedo in Δa ≤ 0.15 (∼15 per cent) interval and Δ albedo ≤0.45 (45 per cent) intervals within 1σ errors. We conclude that X-ray polarimetry will be a useful tool to constrain black hole spins, in addition to timing and spectral-fitting methods.

Theoretical study of soft X-ray emission and dynamics of laser-induced plasma of double stream gas puff

The double stream gas puff-based laser-produced plasma is studied as a source of soft X-ray radiation in nm wavelength spectral range. Dynamics of plasma induced by Nd:YAG laser beam and its emission is simulated with radiation-magnetohydrodynamic code Zstar. The modeling results for krypton gas stream in an annular helium jet as a circumferential gas for various picosecond and nanosecond laser pulses corresponding to the experiments are presented. The spatial–spectral features and temporal behavior of the soft X-ray and EUV emission are investigated. Under ps pulse, the gas is rapidly ionized in the laser beam channel, but it does not have enough time to shift sensibly during the pulse, and the plasma electron density grows against the background of almost constant ion density during the ionization in the laser radiation field. There is ionization instability only capable to be developed in ps range. At ns pulse, the gas ionization and heating leads to gas pushing out of the channel, and the formation of a divergent compression wave transforming into the shock wave. Behind the compression wave front, conditions arise for the development of Rayleigh–Taylor-type instability. The instability leads to the redistribution of plasma temperature and density, and to the formation of increased soft X-ray emission spots. Time evolution of spatial distributions and spectral characteristics of emitted SXR radiation is analyzed for different laser pulses. Transient effects in multicharged ion plasma are discussed, fundamental understanding of those is required for optimization of plasma radiation source. A conversion efficiency of laser energy into soft X-ray wavebands from krypton plasma is scanned by laser parameters and analyzed.

General relativistic MHD simulations of non-thermal flaring in Sagittarius A*

ABSTRACT Sgr A* exhibits regular variability in its multiwavelength emission, including daily X-ray flares and roughly continuous near-infrared (NIR) flickering. The origin of this variability is still ambiguous since both inverse Compton and synchrotron emission are possible radiative mechanisms. The underlying particle distributions are also not well constrained, particularly the non-thermal contribution. In this work, we employ the GPU-accelerated general relativistic magnetohydrodynamics code H-AMR to perform a study of flare flux distributions, including the effect of particle acceleration for the first time in high-resolution 3D simulations of Sgr A*. For the particle acceleration, we use the general relativistic ray-tracing code bhoss to perform the radiative transfer, assuming a hybrid thermal+non-thermal electron energy distribution. We extract ∼60 h light curves in the sub-millimetre, NIR and X-ray wavebands, and compare the power spectra and the cumulative flux distributions of the light curves to statistical descriptions for Sgr A* flares. Our results indicate that non-thermal populations of electrons arising from turbulence-driven reconnection in weakly magnetized accretion flows lead to moderate NIR and X-ray flares and reasonably describe the X-ray flux distribution while fulfilling multiwavelength flux constraints. These models exhibit high rms per cent amplitudes, $\gtrsim 150{{\ \rm per\ cent}}$ both in the NIR and the X-rays, with changes in the accretion rate driving the 230 GHz flux variability, in agreement with Sgr A* observations.

Properties of white dwarf in the binary system AR Scorpii and its observed features

The binary system AR Scorpii hosts an M-type main sequence cool star orbiting around a magnetic white dwarf in the Milky Way Galaxy. The broadband non-thermal emission over radio, optical and X-ray wavebands observed from AR Scorpii indicates strong modulations on the spin frequency of the white dwarf as well as the spin-orbit beat frequency of the system. Therefore, AR Scorpii is also referred to as a white dwarf pulsar wherein a fast spinning white dwarf star plays very crucial role in the broadband non-thermal emission. Several interpretations for the observed features of AR Scorpii appear in the literature without firm conclusions. In this paper, we investigate connection between some of the important physical properties like spin-down power, surface magnetic field, equation of state, temperature and gravity associated with the white dwarf in the binary system AR Scorpii and its observational characteristics. We explore the plausible effects of white dwarf surface magnetic field on the absence of substantial accretion in this binary system and also discuss the gravitational wave emission due to magnetic deformation mechanism.

Modelling the broadband emission from the white dwarf binary system AR Scorpii

AR Scorpii is a compact binary system which consists of a magnetic white dwarf and an M-type main sequence cool star. This binary system was discovered as a source of pulsating radiation in radio, infrared, optical, ultraviolet and X-ray wavebands. In this work, we have analyzed the γ-ray data in the energy range 100 MeV to 500 GeV from the Fermi-Large Area Telescope (LAT) observations for the period August 4, 2008 to March 31, 2019. The γ-ray emission from AR Scorpii over the last decade is not statistically significant and therefore 2σ upper limit on the integral flux above 100 MeV has been estimated. We reproduce the non-thermal broadband spectral energy distribution of AR Scorpii using an emission model having two synchrotron components due to the relativistic electrons in very high magnetic fields. The first component (Synchrotron-1) broadly describes the emissions at radio to high energy X-rays through the synchrotron radiation originating from a spherical region of radius ~ 1.8 × 1010 cm and a magnetic field strength of ~ 103 Gauss. The second component (Synchrotron-2) which reproduces the X-ray emission at lower energies and predicts the γ-ray emission, originates from another spherical region with radius ~ 1.4 × 1010 cm and a magnetic field strength of ~ 106 Gauss. The relativistic electron populations in both the emission regions are described by a smooth broken power law energy distribution. The γ-ray emission predicted by the Synchrotron-2 model is below the broadband sensitivity of the Fermi-LAT and is also consistent with the 95% confidence level upper limit on the integral flux above 100 MeV derived from more than 10 years of observations. According to our model, the binary system AR Scorpii could be a γ-ray source, although its emission level must be below the current detection limit of the Fermi-LAT.

Q wind code release: a non-hydrodynamical approach to modelling line-driven winds in active galactic nuclei

ABSTRACT Ultraviolet (UV) line-driven winds may be an important part of the active galactic nucleus (AGN) feedback process, but understanding their impact is hindered by the complex nature of the radiation hydrodynamics. Instead, we have taken the approach pioneered by Risaliti & Elvis, calculating only ballistic trajectories from radiation forces and gravity but neglecting gas pressure. We have completely rewritten their Qwind code using more robust algorithms and can now quickly model the acceleration phase of these winds for any AGN spectral energy distribution spanning UV and X-ray wavebands. We demonstrate the code using an AGN with black hole mass $10^8\, \text{M}_\odot$ emitting at half the Eddington rate and show that this can effectively eject a wind with velocities ${\simeq}(0.1-0.2)\, c$. The mass loss rates can be up to ≃0.3M⊙ per year, consistent with more computationally expensive hydrodynamical simulations, though we highlight the importance of future improvements in radiation transfer along the multiple different lines of sight illuminating the wind. The code is fully public and can be used to quickly explore the conditions under which AGN feedback can be dominated by accretion disc winds.

X-ray properties of the X-CLASS-redMaPPer galaxy cluster sample: the luminosity–temperature relation

ABSTRACT This article presents the results of a spectroscopic analysis of the X-CLASS-redMaPPer (XC1-RM) galaxy cluster sample. X-CLASS is a serendipitous search for clusters in X-ray wavebands based on the XMM–Newton archive, whereas redMaPPer is an optical cluster catalogue derived from the Sloan Digital Sky Survey (SDSS). The present sample comprises 92 X-ray extended sources identified in optical images within 1 arcmin separation. The area covered by the cluster sample is ∼ 27 deg2. The clusters span a wide redshift range (0.05 < z < 0.6) and 88 clusters benefit from spectrosopically confirmed redshifts using data from SDSS Data Release 14. We present an automated pipeline to derive the X-ray properties of the clusters in three distinct apertures: R500 (at fixed mass overdensity), Rfit (at fixed signal-to-noise ratio) and ${R}_{300\, {\rm kpc}}$ (fixed physical radius). The sample extends over wide temperature and luminosity ranges: from 1–10 keV and from 6 × 1042 to 11 × 1044 erg s−1, respectively. We investigate the luminosity–temperature (L–T) relation of the XC1-RM sample and find a slope equal to 3.03 ± 0.26. It is steeper than predicted by self-similar assumptions, in agreement with independent studies. A simplified approach is developed to estimate the amount and impact of selection biases that might be affecting our recoveredL–Tparameters. The result of this simulation process suggests that the measuredL–Trelation is biased to a steeper slope and higher normalization.

Radio Properties of BL Lac Object S5 2007+777

S5 2007+777 is a typical BL Lac object with a low peak frequency, and a kpc-scale extended X-ray jet. In the literature, the Doppler factor derived at the X-ray waveband by means of model estimation is about 13.0, then the intrinsic jet scale can reach the order of magnitude of 1 Mpc. In this work, we have studied the radio structure of the jet, the brightness temperature, proper motion and other properties of this source with the collected EVN (European VLBI Network) high-resolution archive data, and the American VLBA (Very Long Baseline Array) 15 GHz observed data, etc. It is found that the jet directions measured at the different wavebands of the VLBI (Very Long Baseline Interferometry) are consistent, but slightly different from the direction of the kpc-scale X-ray jet given by the literature and the direction of the VLA (Very Large Array) radio jet, which means that the Doppler brightening effect exists in the jet emission of the source. Both the mean value and median value of the radio Doppler factor of this source estimated from the brightness temperature that measured by the VLBI are 5.0, which is smaller than the Doppler factor at the X-ray waveband given by the literature, but consistent with the Doppler factor at the radio waveband obtained by using the other methods in the literature. Furthermore, by fitting the data observed in multiple epochs, it is found that the various components of the source at the same waveband do not have an evident proper motion in a long epoch, but the proper motion in short epochs exhibits even a super-luminal motion. This may be caused by the transfer of the central position of the component with a low surface brightness. Meanwhile, this also verifies the conclusion that the radio Doppler factor estimated previously is not very large, and smaller than the Doppler factor in the X-ray waveband. By using the obtained radio Doppler factor, it is found that the source has an intrinsic radio jet of rather large scale, which may reach 0.5 Mpc, because the mean value is adopted in this case, thus it indicates that the source also possibly possesses a jet close to the scale of a giant radio galaxy.

Testing Emergent Gravity with Optical, X-Ray, and Weak Lensing Measurements in Massive, Relaxed Galaxy Clusters

Abstract We test the predictions of emergent gravity (EG) using matter densities of relaxed, massive clusters of galaxies observed from optical and X-ray wavebands. We improve upon previous work in this area by including the baryon mass contribution of the brightest cluster galaxy (BCG) in each system, in addition to total mass profiles from gravitational lensing and mass profiles of the X-ray emitting gas from Chandra. We use this data in the context of EG to predict the “apparent” dark matter (DM) distribution from the observed baryon distribution, and vice versa. We find that although the inclusion of the BCG in the analysis improves the agreement with observations in the inner regions of the clusters ( kpc), at larger radii ( kpc) the EG predictions for mass profiles and baryon mass fractions are not in agreement with observations by a factor of up to ∼2−6, though the agreement improves at radii near r 500. At least in its current form, EG does not appear to reproduce the observed characteristics of relaxed galaxy clusters as well as cold DM models.

Design of optical/IR blocking filters for the Lynx X-ray Microcalorimeter

The Lynx mission concept, under development ahead of the 2020 Astrophysics Decadal Review, includes the Lynx X-ray Microcalorimeter (LXM) as one of its primary instruments. The LXM uses a microcalorimeter array at the focus of a high-throughput soft x-ray telescope to enable high-resolution nondispersive spectroscopy in the soft x-ray waveband (0.2 to 15 keV) with exquisite angular resolution. Similar to other x-ray microcalorimeters, the LXM uses a set of blocking filters mounted within the dewar that pass the photons of interest (x-rays) while attenuating the out-of-band long-wavelength radiation. Such filters have been successfully used on previous orbital and suborbital instruments; however, the Lynx science objectives, which emphasize observations in the soft x-ray band (<1keV), pose more challenging requirements on the set of LXM blocking filters. We present an introduction to the design of the LXM optical/IR blocking filters and discuss recent advances in filter capability targeted at LXM. In addition, we briefly describe the external filters and the modulated x-ray sources to be used for onboard detector calibration.

Spectral Energy Distribution for Some Fermi Blazarstwo

The observational data from radio to X-ray wavebands were collected from the SSDC (Italian Space Agency Science Data Center) for 68 Fermi blazars, and their spectral energy distributions (SEDs) were calculated by means of the least square fitting with a log-parabolic function. Based on the SED fitting parameters, the correlations of the synchrotron peak frequency, curvature and effective spectral index were discussed, and an empirical formula was also proposed to estimate the synchrotron peak frequencies by using the effective spectral indexes. The main results are as follows: (1) From the linear correlation between the synchrotron peak frequency (lgνp) and the curvature (k), we find that the result supports the energy-dependent acceleration probability model for all BL Lac objects, while the result for the BL Lac objects of lgνp>15.3 is consistent with the model of fluctuation of fractional acceleration gain. (2) For the sources of nearly same lgνp, a significant correlation between the effective spectral index αro of the radio-optical waveband and the curvature is detected, while the effective spectral index αox of the optical-x-ray waveband is not correlated with the curvature. According to the effective spectral index αro, a relation between the synchrotron peak frequency and the curvature can be defined.

Gamma-Ray Bursts Generated by Hyper-Accreting Kerr Black Hole

The observed properties of Gamma-Ray Bursts such as rapid variability of X-ray light curve and large energies strongly signature the compact binary, disk accreting system. Our work particularly highlights the extremely rotating, disk accreting black holes as physical source of the flares variability and X-ray afterglow plateaus of GRBs. We investigate the compact binary mergers (neutron star - neutron star and neutron star onto black hole) and gravitational core collapse of super massive star, where in both cases hyper-accreting Kerr hole is formed. The core collapse in a powerful gravitational wave explained as a potential source for the radiated flux of hard X-rays spectrum. We described the evolution of rapidly rotating, accreting BH in general relativity and the relativistic accretion flow in resistive MHD for viscous radiation. We compute the structure of accretion disk, the accretion luminosity of the dynamical evolution of inner accretion disk and precisely determine their radiation spectra, and compare to observational data of X-ray satellites. Finally, we obtained the resulting disk radiation basically explained as the X-ray luminosity of the central source, such as LMC X-1 and GRO J1655-40. These results are interestingly consistent with observational data of galactic X-ray source binary systems such as X-ray luminosities of Cygnus X-1 and Seyfert galaxies (NGC 3783, NGC 4151, NGC 4486 (Messier 87)) which are powerful emitters in X-ray and gamma-ray wavebands of the observed X-ray variability with typical luminosity.

Ground calibration of the Astro-H (Hitomi) soft x-ray spectrometer

The Astro-H (Hitomi) Soft X-ray Spectrometer (SXS) was a pioneering imaging x-ray spectrometer with 5 eV energy resolution at 6 keV. The instrument used a microcalorimeter array at the focus of a high-throughput soft x-ray telescope to enable high-resolution nondispersive spectroscopy in the soft x-ray waveband (0.3 to 12 keV). We present the suite of ground calibration measurements acquired from 2012 to 2015, including characterization of the detector system, anti-coincidence detector, optical blocking filters, and filter-wheel filters. The calibration of the 36-pixel silicon thermistor microcalorimeter array includes parameterizations of the energy gain scale and line-spread function for each event grade over a range of instrument operating conditions, as well as quantum efficiency measurements. The x-ray transmission of the set of five Al/polyimide thin-film optical blocking filters mounted inside the SXS dewar has been modeled based on measurements at synchrotron beamlines, including with high spectral resolution at the C, N, O, and Al K-edges. In addition, we present the x-ray transmission of the dewar gate valve and of the filters mounted on the SXS filter wheel (external to the dewar), including beryllium, polyimide, and neutral density filters.

Jet-dominated quiescent state in black hole X-ray binaries: the cases of A0620−00 and XTE J1118+480

The radiative mechanism of black hole X-ray transients (BHXTs) in their quiescent states (defined as the 2–10 keV X-ray luminosity ≲ 1034 erg s−1) remains unclear. In this work, we investigate the quasi-simultaneous quiescent state spectrum (including radio, infrared, optical, ultraviolet and X-ray) of two BHXTs, A0620−00 and XTE J1118+480. We find that these two sources can be well described by a coupled accretion – jet model. More specifically, most of the emission (radio up to infrared, and the X-ray waveband) comes from the collimated relativistic jet. Emission from hot accretion flow is totally insignificant, and it can only be observed in mid-infrared (the synchrotron peak). Emission from the outer cold disk is only evident in the UV band. These results are consistent with our previous investigation on the quiescent state of V404 Cyg and confirm that the quiescent state is jet-dominated.

Constraints on relativistic jets in quiescent black hole X-ray binaries from broad-band spectral modelling

The nature of black hole jets at the lowest detectable luminosities remains an open question, largely due to a dearth of observational constraints. Here, we present a new, nearly-simultaneous broadband spectrum of the black hole X-ray binary (BHXB) XTE J1118+480 at an extremely low Eddington ratio (L_x~1e-8.5 L_Edd). Our new spectral energy distribution (SED) includes the radio, near-infrared, optical, ultraviolet, and X-ray wavebands. XTE J1118 is now the second BHXB at such a low Eddington ratio with a well-sampled SED, providing new constraints on highly sub-Eddington accretion flows and jets, and opening the door for comparison studies. We apply a multi-zone jet model to the new broadband SED, and we compare our results to previous fits to the same source using the same model at 4-5 decades higher luminosity. We find that after a BHXB transitions to the so-called quiescent spectral state, the jet base becomes more compact (by up to an order of magnitude) and slightly cooler (by at least a factor of two). Our preferred model fit indicates that jet particle acceleration is weaker after the transition into quiescence. That is, accelerated non-thermal particles no longer reach high enough Lorentz factors to contribute significant amounts of synchrotron X-ray emission. Instead, the X-ray waveband is dominated by synchrotron self-Compton emission from a population of mildly relativistic electrons with a quasi-thermal velocity distribution associated with the jet base. The corresponding (thermal) synchrotron component emits primarily in the infrared through ultraviolet wavebands. Our results on XTE J1118 are consistent with broadband modeling for A0620-00 and for Sgr A*. The above could therefore represent a canonical baseline geometry for accreting black holes in quiescence. We conclude with suggestions for future studies to further investigate the above scenario.

The physics inside the scaling relations for X-ray galaxy clusters: gas clumpiness, gas mass fraction and slope of the pressure profile

In galaxy clusters, the relations between observables in X-ray and millimetre wave bands and the total mass have normalizations, slopes and redshift evolutions that are simple to estimate in a self-similar scenario. We study these scaling relations and show that they can be efficiently expressed, in a more coherent picture, by fixing the normalizations and slopes to the self-similar predictions, and advocating, as responsible of the observed deviations, only three physical mass-dependent quantities: the gas clumpiness C, the gas mass fraction fg and the logarithmic slope of the thermal pressure profile βP. We use samples of the observed gas masses, temperature, luminosities and Compton parameters in local clusters to constrain normalization and mass dependence of these three physical quantities, and measure C0.5fg = 0.110( ± 0.002 ± 0.002)(EzM/5 × 1014 M⊙)0.198( ± 0.025 ± 0.04) and βP = −dln P/dln r = 3.14( ± 0.04 ± 0.02)(EzM/5 × 1014 M⊙)0.071( ± 0.012 ± 0.004), where both a statistical and systematic error (the latter mainly due to the cross-calibration uncertainties affecting the Chandra and XMM–Newton results used in the present analysis) are quoted. The degeneracy between C and fg is broken by using the estimates of the Compton parameters. Together with the self-similar predictions, these estimates on C, fg and βP define an intercorrelated internally consistent set of scaling relations that reproduces the mass estimates with the lowest residuals.