Radial Pulsations Research Articles

The variability of Betelgeuse explained by surface convection

Betelgeuse is a red supergiant (RSG) that is known to vary semi-regularly on both short and long timescales. The origin of the short period of Betelgeuse has often been associated with radial pulsations, but could also be due to the convection motions present at the surface of RSGs. We investigate the link between surface activity and the variability of the star. Linear polarization in Betelgeuse is a proxy of convection that is unrelated to pulsations. Using ten years of spectropolarimetric data of Betelgeuse, we looked for periodicities in the least-squares deconvolution profiles of Stokes $I$, $Q$, $U$ and the total linear polarization using Lomb-Scargle periodograms. We find periods in linear polarization signals that are similar to those in photometric variability. The 400 d period is too close to a peak of the window function of our data, but the two periods of 330 d and 200 d are present in the periodogram of Stokes $Q$ and $U$, showing that the variability of Betelgeuse can be interpreted as being due to surface convection. Since the linear polarization in the spectrum of Betelgeuse is not known to vary with pulsations, but is linked to surface convection, and since similar periods are found in the time series of photometric measurements and spectropolarimetry, we conclude that the photometric variability is due to the surface convective structures, and not to any pulsation phenomenon.

The progenitor star of SN 2023ixf: a massive red supergiant with enhanced, episodic pre-supernova mass loss

ABSTRACT We identify the progenitor star of SN 2023ixf in Messier 101 using Keck/NIRC2 adaptive optics imaging and pre-explosion Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) images. The supernova, localized with diffraction spikes and high-precision astrometry, unambiguously coincides with a progenitor candidate of $m_\text{F814W}=24.87\pm 0.05$ (AB). Given its reported infrared excess and semiregular variability, we fit a time-dependent spectral energy distribution (SED) model of a dusty red supergiant (RSG) to a combined data set of HST optical, ground-based near-infrared, and Spitzer Infrared Array Camera (IRAC) [3.6], [4.5] photometry. The progenitor resembles an RSG of $T_\text{eff}=3488\pm 39$ K and $\log (L/\mathrm{L}_\odot)=5.15\pm 0.02$, with a $0.13\pm 0.01$ dex ($31.1\pm 1.7$ per cent) luminosity variation at a period of $P=1144.7\pm 4.8$ d, obscured by a dusty envelope of $\tau =2.92\pm 0.02$ at $1\, \mu \text{m}$ in optical depth (or $A_\text{V}=8.43\pm 0.11$ mag). The signatures match a post-main-sequence star of $18.2_{-0.6}^{+1.3}\, \mathrm{M}_\odot$ in zero-age main-sequence mass, among the most massive SN II progenitor, with a pulsation-enhanced mass-loss rate of $\dot{M}=(4.32\pm 0.26)\times 10^{-4} \, \mathrm{M}_\odot \, \text{yr}^{-1}$. The dense and confined circumstellar material is ejected during the last episode of radial pulsation before the explosion. Notably, we find strong evidence for variations of $\tau$ or $T_\text{eff}$ along with luminosity, a necessary assumption to reproduce the wavelength-dependent variability, which implies periodic dust sublimation and condensation. Given the observed SED, partial dust obscuration remains possible, but any unobstructed binary companion over $5.6\, \mathrm{ M}_\odot$ can be ruled out.

Linear adiabatic analysis for general-relativistic instability in primordial accreting supermassive stars

Accreting supermassive stars of $ will eventually collapse directly to a black hole via the general-relativistic (GR) instability. Such direct collapses of supermassive stars are thought to be a possible formation channel for supermassive black holes at $z > 6$. In this work, we investigate the final mass of accreting Population III stars with constant accretion rates between $0.01$ and 1000\ We determined the final mass by solving the differential equation for GR linear adiabatic radial pulsations. We find that models with accretion rates $ experience the GR instability at masses depending on the accretion rates. The critical masses are larger for higher accretion rates, ranging from $8 for $0.05\ to $ for $1000\ The $0.05\ model reaches the GR instability at the end of the core hydrogen burning. The higher-mass models with higher accretion rates reach the GR instability during the hydrogen burning stage.

The VELOCE modulation zoo I. Spectroscopic detection of non-radial modes in the first-overtone Cepheids BG Crucis, QZ Normae, V0391 Normae, and V0411 Lacertae

The photometric observations from the recent decade revolutionized our view on classical pulsators. Low-amplitude signals have been detected photometrically in addition to the dominant high-amplitude radial mode pulsations in many RR Lyrae stars and classical Cepheids. First-overtone pulsators with an additional low-amplitude signal at a period ratio of around 0.61 with the main mode, the so-called 0.61 stars, form the most populous group among these stars. The nature of this signal has been attributed to non-radial pulsations. Another mysterious group are stars in which the additional signal forms a period ratio of around 0.68. These are the 0.68 stars. The origin of the signal remains unknown. Here, we search for similar phenomena in spectroscopic observations of first-overtone classical Cepheids collected as part of the project. We performed a frequency analysis of several parameters derived from cross-correlation functions (CCFs), including radial velocity, the full width at half maximum, the bisector inverse span, and the CCF depth (contrast). Using standard pre-whitening, we searched for additional low-amplitude signals. We identified the location of these stars in various sequences of the Petersen diagram. We detect additional signals in four first-overtone classical Cepheids: BG Cru, QZ Nor, V0391 Nor, and V0411 Lac. We classified BG Cru, QZ Nor, and V0391 Nor as 0.61 stars based on their period ratios. V0411 Lac, however, exhibits a ratio of 0.68 between the two modes, and the additional signal has a longer period. This type of multi-periodicity remains unexplained. CCFs yield the first spectroscopic detections of non-radial pulsation modes in classical Cepheids. This opens an asteroseismic window for pursuing a more detailed understanding of these important stars. While the 0.61 signal of BG Cru, QZ Nor, and V0391 Nor is understood to originate from non-radial modes of moderate degrees, the 0.68 signal of V0411 Lac still lacks a physical explanation.

Compact stars in Rastall gravity: hydrostatic equilibrium and radial pulsations

Compact stars in Rastall gravity: hydrostatic equilibrium and radial pulsations

An Unusual Case of Brachial Artery Thrombosis in a Neonate Following Humerus fracture at Birth

A female infant of a diabetic mother born through LSCS at 39 weeks of gestation with a birth weight of 2908 grams was noted to have a paucity of movement of the left upper limb soon after birth. The extremity was pale, had markedly deranged perfusion, and was cold to touch with absent brachial, radial, and ulnar arterial pulsations. There was a swelling noted over the middle of the left arm, which was tender and associated with crepitus suspicious of a fracture. The right upper limb and lower limbs were normal. An urgent X-ray of the left upper limb showed a displaced fracture of the left humerus fracture and the Doppler study revealed absent flow in the brachial artery distal to the fracture site without thrombus. Urgent close reduction of the fracture following which the doppler showed a thrombus in the brachial artery extending up to its bifurcation. The thrombosis was managed medically with low molecular weight heparin and aspirin. There was a gradual improvement of limb perfusion with normalcy achieved on day 3 of life with no residual complications even on follow-up. The workup of neonatal thrombosis, its immediate management and current evidence for the same have been discussed in detail.

The Hertzsprung progression of classical Cepheids in the Gaia era

ABSTRACT A new fine grid of non-linear convective pulsation models for the so-called ‘bump Cepheids’ is presented to investigate the Hertzprung progression (HP) phenomenon shown by their light and radial pulsation velocity curves. The period corresponding to the centre of the HP is investigated as a function of various model assumptions, such as the efficiency of superadiabatic convection, the mass–luminosity relation, and the metal and helium abundances. The assumed mass–luminosity relation is found to significantly affect the phenomenon but variations in the chemical composition as well as in the stellar mass (at fixed mass–luminosity relation) also play a key role in determining the value of the HP centre period. Finally, the predictive capability of the presented theoretical scenario is tested against observed light curves of bump Cepheids in the ESA Gaia data base, also considering the variation of the pulsation amplitudes and of the Fourier parameters R21 and Φ21 with the pulsation period. A qualitative agreement between theory and observations is found for what concerns the evolution of the light curve morphology as the period moves across the HP centre, as well for the pattern in period–amplitude, period–R21, and period–Φ21 planes. A larger sample of observed Cepheids with accurate light curves and metallicities is required in order to derive more quantitative conclusions.

A theoretical framework for BL Her stars. II. New period-luminosity relations in Gaia passbands

In the era of the Hubble tension, it is crucial to obtain a precise calibration of the period-luminosity ($PL$) relations of classical pulsators. Type II Cepheids (T2Cs; often exhibiting negligible or weak metallicity dependence on $PL$ relations) used in combination with RR Lyraes and the tip of the red giant branch may prove useful as an alternative to classical Cepheids for the determination of extragalactic distances. We present new theoretical $PL$ and period-Wesenheit ($PW$) relations for a fine grid of convective BL Her (the shortest period T2Cs) models computed using mesa-rsp in the $Gaia$ passbands and we compare our results with the empirical relations from $Gaia$ DR3. Our goal is to study the effect of metallicity and convection parameters on the theoretical $PL$ and $PW$ relations. We used the state-of-the-art 1D non-linear radial stellar pulsation tool mesa-rsp to compute models of BL Her stars over a wide range of input parameters:\ metallicity ($-2.0\; dex Fe/H dex $), stellar mass ($0.5M_ odot -0.8M_ odot $), stellar luminosity ($50L_ odot -300L_ odot $), and effective temperature (across the full extent of the instability strip; in steps of 50K). We used the Fourier decomposition technique to analyse the light curves obtained from mesa-rsp and $Gaia$ DR3 and then compared the theoretical and empirical $PL$ and $PW$ relations in the $Gaia$ passbands. The BL Her stars in the All Sky region exhibit statistically different $PL$ slopes compared to the theoretical $PL$ slopes computed using the four sets of convection parameters. We find the empirical $PL$ and $PW$ slopes from BL Her stars in the Magellanic Clouds to be statistically consistent with theoretical relations computed using the different convection parameter sets in the $Gaia$ passbands. There is a negligible effect coming from the metallicity on the $PL$ relations in the individual $Gaia$ passbands. However, there is a small but significant negative coefficient of metallicity in the $PWZ$ relations for the BL Her models using the four sets of convection parameters. This could be attributed to the increased sensitivity of bolometric corrections to metallicities at wavelengths shorter than the $V$ band. Our BL Her models also suggest a dependence of the mass-luminosity relation on metallicity. We found the observed Fourier parameter space to be covered well by our models. Higher mass models ($> 0.6\ odot $) may be needed to reliably model the observed light curves of BL Her stars in the All-Sky region. We also found the theoretical light curve structures (especially the Fourier amplitude parameters) to be affected by the choice of convection parameters.

Active control study in a flow in a model combustion chamber with LES

We conducted the mesh convergence study for an isothermal incompressible air flow in a model combustion chamber with Turbomeca swirler of D = 37 mm using Large-eddy simulations (LES). Simulation were conducted using 4 different meshes ranging from 4 to 24 × 106 cells at the Reynolds number Re = 15 632 with additional air injection of 4.4 % of the main volumetric flow rate from an circular slot. The results revealed that high spanwise slot resolution in the vicinity of the slot is crucial, particularly, for achieving convergence of radial velocity pulsations. Additionally, we analyzed the pressure signal and its spectral characteristics to demonstrate the effectiveness of the circular slot injection in reducing pressure pulsations associated with the precessing vortex core (PVC).

Spectral method for identification of flow regimes in a Couette-Taylor annular flow

The paper presents a study of flow structure in an annular flow of the Couette-Taylor system, employing spectral analysis of moment of resistance and radial dynamic pressure pulsations. Experiments were conducted on a model featuring a single annular gap, with the Reynolds number varied from 582 to 4271. A methodology for the digital recording of flow parameters was devised, comprising the measurement of the moment of resistance to rotation and radial pressure through the application of a strain gauge dynamometer, hydrophone and pressure transducer. The subsequent analysis of the obtained amplitude-frequency spectra enabled the identification of three distinctive ranges of pulsations, which were found to be associated with the relief of the cylinder surface, laminar flow with Taylor vortices and the turbulent regime.

A case of edema cured with miasmatic approach though radial pulsation technique: Detail study

A case of edema cured with miasmatic approach though radial pulsation technique: Detail study

CFD simulation of unstable fluid flows in the rotor of a high-speed precipitation centrifuge

The results of a numerical study of unstable fluid flows in the rotor of a high-speed vertical precipitation centrifuge are presented. It is shown that during the operation of a high-speed precipitation centrifuge, a qualitative change in the hydrodynamic regime is possible from conditionally laminar to conditionally turbulent, characterized by large-scale axial and radial pulsations of the liquid phase, accompanied by a significant decrease in sedimentation efficiency. It has been established that the flow pulsations are not random in nature, but the amplitude of these pulsations first increases with increasing rotation rate of the centrifuge rotor, and after passing a certain “critical” rotation rate it begins to decrease. Thus, the “critical” rotor rotation rate can be considered as a resonant rate, at which the frequency of turbulent flow pulsations (natural oscillation frequency) coincides with the rotor rotation frequency (forced oscillation frequency). The dependences of the pitch, frequency, and amplitude of liquid flow pulsations on the edge of the centrifuge overflow disk on the rotor rotation rate were obtained. It has been established that in the “subcritical” and “supercritical” operating modes, the amplitude and step of liquid pulsations on the overflow disk of the centrifuge are increasing and decreasing respectively.

The optimal puncture time point of prolonged occlusion flow-mediated dilatation in radial artery catheterization: a prospective observational study

Previous studies have demonstrated prolonged occlusion flow-mediated dilatation (PO-FMD) could reduce cannulation failure rates and decrease radial artery pulsation loss during trans-radial coronary angiography. However, the time and degree of radial artery dilatation induced after PO-FMD were unclear. This study aimed to evaluate the degree and duration of the radial artery dilation after PO-FMD, and the time point at which the radial artery diameter is expanded to the maximum. This was a prospective observational study. According to the Chinese guideline on the primary prevention of cardiovascular diseases, 142 patients awaking from general anesthesia were divided into two groups: low-risk (LR) group and high-risk (HR) group. Firstly, the baseline radial artery diameter was measured on the left wrist using ultrasound in both groups. Subsequently, the radial artery diameters were obtained continuously at the same location for 5 min after PO-FMD. The baseline radial artery diameter, the maximum radial artery diameter, and the duration of radial artery dilation in the two groups were recorded. The time point at which the radial artery diameter is expanded to the maximum in the LR group and HR group was 26.49 ± 11.69 s and 46.27 ± 12.03 s, respectively (P < 0.01). The time of radial artery dilation and the percentage changes in arterial diameter in HR group were significantly lower than LR group (duration time: mean [mean ± standard]: 136.65 ± 31.55 s vs. 168.98 ± 33.27 s; percentage changes: median [interquartile range] 10.5 [8.6, 12.9] % vs. 15.2 [12.4, 19.0] %). In this study, the optimal puncture time point of PO-FMD in the LR group was 26 s, and in the HR group was 46 s. It would be helpful to guide the time point in radial artery catheterization after PO-FMD.Chinese Clinical Trial Registry identifier: ChiCTR2200066214.

TESS Observations of Seven Newly Identified High-amplitude δ Scuti Stars

We report seven newly identified high-amplitude δ Scuti (HADS) stars. Among them, two stars (TIC 30977864 and TIC 387379145) exhibit pure radial pulsation without the excitation of non-radial modes. TIC 30977864 is classified as a double-mode HADS star, while the other four stars potentially show triple-mode HADS behavior. TIC 112682462 and TIC 255603395 closely resemble RR Lyrae stars based on their light curves, position in the period–luminosity diagram, and the period ratio diagram. However, without spectral observations, it is challenging to ascertain whether these two stars are HADS or RR Lyrae stars. TIC 281695001 exhibits a fundamental frequency amplitude smaller than that of the first overtone, suggesting the presence of intriguing phenomena that necessitate further analysis. We analyzed the relationship between metallicity and period using data provided by Netzel & Smolec. The metallicities of the 176 stars display a broad distribution ranging from −2.0 dex to 0.5 dex, with periods spanning 0.05 to 0.20 days. This random distribution of metallicities may contribute to the dispersion observed in the P1/P0 ratio. To derive more accurate conclusions, future spectroscopic observations of a larger sample of HADS stars are crucial. These observations will provide precise rotational velocities and more accurate determinations of metallicities.

Effect of Tip Clearance on the Cavitation Performance of High-Speed Pump-Jet Propeller

To investigate the impact of tip clearance variation on the cavitation performance of a high-speed pump-jet propeller, Fluent software was employed for simulation calculations. The study utilized the RNG k-ε turbulence model and ZGB cavitation, conducting three-dimensional numerical simulations under both steady and transient conditions. A pump-jet propeller with a rated speed of 20,000 r/min was used to set three kinds of clearance for simulation, and the simulation proved to be reliable by comparison with the experiment. Initially, the analysis examined the effect of tip clearance on cavitation characteristics and cavitation volume under steady-state conditions, while also studying the distribution patterns of cavitation. Subsequently, the radial force and pressure pulsation of the jet propeller are analyzed by FFT processing, aiming at the influence of tip clearance on the structural strength of the pump-jet propeller. Under the design conditions, the smaller tip clearance shows better performance, while the larger tip clearance shows stronger anti-cavitation ability than the smaller clearance. In addition, the greater the tip clearance, the greater the radial force and pressure pulsation, which will adversely affect the pump-jet structure. The research results provide some references for further research on the effect of high-speed pump-jet propeller structures on performance.

The evolutionary stage of Betelgeuse inferred from its pulsation periods

Abstract Betelgeuse is a well known bright red supergiant that shows semi-regular variations with four approximate periods of 2200, 420, 230, and 185 days. While the longest period was customarily regarded as LSP (long secondary period) of unknown origin, we identify the ∼2200-d period as the radial fundamental mode, and the three shorter periods as the radial first, second, and third overtones. From a linear nonadiabatic pulsation analysis including the pulsation/convection coupling, we have found that these radial pulsation modes are all excited in the envelope of a model in a late stage of the core-carbon burning. Models with similar pulsation property have masses of 11 ∼ 12 M⊙ (19 M⊙ at ZAMS) with luminosities (log L/L⊙ = 5.27 ∼ 5.28) and effective temperatures (log Teff ≈ 3.53) that are consistent with the range of the observational determinations. We also find that a synthetic light curve obtained by adding the fundamental and the first-overtone mode is comparable with the light curve of Betelgeuse up to the Great Dimming. We conclude that Betelgeuse is likely in the late stage of core carbon burning, and a good candidate for the next Galactic Type II supernova.

Temperature-dependent convective parameters for RRc 1D models

ABSTRACT Non-linear pulsation modelling of classical variable stars is among the first topics that were developed at the beginning of the computational era. Various developments were made, and many questions were answered in the past 60 yr, and the models became more complex, describing the genuinely 3D convection in a single dimension. Despite its successes, the recent public availability of the mesa radial stellar pulsations (mesa rsp) module and the emerging results from multidimensional codes made clear that the eight free convective parameters, unique to these models, together with the underlying physical models need calibration. This could be done by comparing them against multidimensional codes, but before that, it is important to scrutinize the free parameters of the 1D codes using observations. This is a follow-up work of our previous calibration on the convective parameters of the budapest-florida and mesa rsp pulsation codes for RRab stars. In this letter, we extend the previous calibration to the RRc stars and the RR Lyrae stars in general. We found that correlations of some of the parameters are present in RRc stars as well but have a different nature, while high-temperature RRc stars’ pulsation properties are very sensitive to the chosen parameter sets.

A Luminous Red Supergiant and Dusty Long-period Variable Progenitor for SN 2023ixf

We analyze pre-explosion near- and mid-infrared (IR) imaging of the site of SN 2023ixf in the nearby spiral galaxy M101 and characterize the candidate progenitor star. The star displays compelling evidence of variability with a possible period of ≈1000 days and an amplitude of Δm ≈ 0.6 mag in extensive monitoring with the Spitzer Space Telescope since 2004, likely indicative of radial pulsations. Variability consistent with this period is also seen in the near-IR J and K s bands between 2010 and 2023, up to just 10 days before the explosion. Beyond the periodic variability, we do not find evidence for any IR-bright pre-supernova outbursts in this time period. The IR brightness ( mag) and color (J − K s = 1.6 mag) of the star suggest a luminous and dusty red supergiant. Modeling of the phase-averaged spectral energy distribution (SED) yields constraints on the stellar temperature ( K) and luminosity (). This places the candidate among the most luminous Type II supernova progenitors with direct imaging constraints, with the caveat that many of these rely only on optical measurements. Comparison with stellar evolution models gives an initial mass of M init = 17 ± 4 M ⊙. We estimate the pre-supernova mass-loss rate of the star between 3 and 19 yr before explosion from the SED modeling at to 3 × 10−4 M ⊙ yr−1 for an assumed wind velocity of v w = 10 km s−1, perhaps pointing to enhanced mass loss in a pulsation-driven wind.

Dual-network ionogel with pyramidal array microarchitecture as a flexible device for body movement sensing and subtle activity monitoring

Flexible piezoresistive devices with high sensitivity serve as important candidates for wearable sensors in common movements and subtle physiological motions. In this work, a soft material based on ionogel was fabricated into a sheet with pyramidal array architecture on one side (PDNIG), which worked as a pressure sensor in a pair combo state with the pyramidal side contacted each other (di-PDNIG). It demonstrates high sensitivity (10.98 kPa−1) and strong durability, which can work well in monitoring primary limb movements and the subtle physiological signals, including radial artery pulsation and heartbeat, associated with cardiovascular function. The tested radial artery pulse through the sensor presents typical artery wave characteristics. Moreover, the artery pulse rate of the subjects is 72 ∼ 90 beats/min, whilst the heartbeat rate is ∼ 80 beats/min. This di-PDNIG suggests a potential material as soft sensor facing toward wellness status monitoring and artificial intelligence system components.

Experimental and numerical investigation on the dynamic response of reactor coolant pump rotor under different inflow conditions

In pressurized water reactors, a reactor coolant pump (RCP) is crucial for circulating coolant through the primary loop. However, in advanced passive (AP) reactors, the steam generator and RCP are not connected by a long pipeline, creating a transition section that leads to a non-uniform inflow at the pump inlet. The non-uniform inflow can affect the operational status of a pump, which in turn affects the motion state of the rotor. In this study, the variation of the axis orbit under non-uniform inflow was analyzed through experiments, and it was found that the shape of the axis orbit had undergone significant changes, and the amplitude of the orbit had also increased significantly, particularly in the y direction, where it increased by 88.6%. Subsequently, a combined approach of pump computational fluid dynamics (CFD) analysis and rotor finite element analysis was used to analyze the cause of the axis orbit change. The study revealed the existence of a vortex with a pulsating frequency of approximately 16.4 Hz at the inlet of the non-uniform inflow. This vortex caused the impeller's attack angle to deviate from the design value, resulting in flow separation inside the impeller, an increase in the impeller's radial force, and radial force pulsation at the same frequency as the vortex. The change in the axis orbit was caused by the superposition of the rotor's unbalance mass and radial force pulsation under non-uniform inflow.