Dominant Period Research Articles

Regional zonation based on seismic vulnerability using local site effect analysis and potential damage to the city of Medan (North Sumatra, Indonesia) due to earthquake

BackgroundMicrozonation becomes important for big cities like Medan (North Sumatra, Indonesia) as population agglomeration increases in urban areas resulting in rapid and unplanned construction. Mitigation efforts must be carried out to minimize losses arising from earthquakes, such as loss of life and environmental damage, and it can be done by analyzing seismic susceptibility and local site effects.PurposeThis study analyzes the potential for environmental damage caused by seismic hazards in the city of Medan, North Sumatra, Indonesia. The purpose of this study is to provide an overview of the definition and methodology of seismic–geotechnical hazard zoning and the methodology used for making seismic hazard maps with the case study of Medan City.MethodsWhile determining the zoning, microzonation measurements and environmental data parameters are involved. To obtain comprehensive results, microzonation measurements were carried out using three methods, namely the Multichannel Seismic Analysis Surface Wave (MASW), Spatial Autocorrelation (SPAC), and Horizontal-To-Vertical Spectral Ratio (HVSR) with 200 measuring points spread throughout the city of Medan. Parameter weighting values such as population, site class, seismic susceptibility, dominant period, land cover, slope, and weather class were obtained using the analytic hierarchy process (AHP) method.ResultsWe presented the result of the survey, including the MASW, SPAC, and HVSR results. In general, medium soil and soft soil dominate almost all areas of Medan city. The estimated depth of engineering bedrock is at a depth of about 291.33 – 735.87 meters from the ground surface. The dominant period values ranged from 0.0907 s to 8.30723 s.ConclusionsWe classified Medan City (North Sumatra) into several zones, based on their seismic vulnerability using local site effect analysis and potential damage due to earthquakes. This study is necessary for future seismic hazard assessment.

259. Comparison of the causes of death in patients with delta variant versus omicron variant infections

Abstract Background Severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) variant strain B.1.1.529 (omicron) has been less virulent than SARS-CoV-2 B.1.617.2 variant (delta), but there are limited data on the comparison of the cause of death between delta variant and omicron variant infections. We thus compared the causes of death in COVID-19 patients with the delta variant and omicron variant. Methods We retrospectively reviewed the medical records of adult patients with COVID-19 who were admitted at Asan Medical Center, Seoul, South Korea, between July 2021 and March 2022. We divided into delta-variant dominant period (from July 2021 to December 2021) and omicron-dominant period (from February 2022 to March 2022) with the exclusion of January 2022 because this period was overlapping of delta and omicron variant. The causes of death were classified into COVID-19-associated pneumonia, other causes, and indeterminate cause. Results A total of 654 patients with COVID-19 were admitted and 42 (6.4%) died during the omicron dominant period (between February and March 2022), while a total of 366 patients with COVID-19 were hospitalized and 42 (11.5%) died during the delta dominant period (between July and December 2021). The primary cause of death was COVID-19-associated pneumonia in 64% (27/42) during the omicron era whereas that was COVID-19-associated pneumonia in 88% (37/42) during the delta era (p value=0.01) (Table 1). Conclusion We found that about two thirds of patients with omicron variant infection died due to COVID-19, while the majority of patients with delta variant infection died due to COVID-19. Disclosures All Authors: No reported disclosures.

Prediction of the Influence of Higher Modes on the Dynamic Response of High-Rise Buildings Subjected to Narrow-Banded Ground Motions

This paper presents the results of a study aimed at assessing the effects of higher modes of vibration on the nonlinear dynamic response of tall framed-buildings subjected to narrow-banded motions. For this purpose, analytical models of a 20-story building were developed under the consideration of two types of hysteretic behavior and subjected to 20 seismic excitations having a dominant period of motion of 1[Formula: see text]s. While the fundamental period of vibration of the building equals 2.7[Formula: see text]s, its second period is close to 1[Formula: see text]s; as a result, the selected seismic excitations over-stimulate the participation of the second mode in the overall dynamic response of the building. The circumstances under which the contribution of higher modes gives place to an excessive response of the upper stories are identified, and quantitative measures are presented. From an engineering point of view, parameters that predict an excessive response of higher-level floors are proposed.

The longitudinal evaluation of COVID-19 in pediatric patients and the impact of delta variant

Pediatric patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) displayed milder symptoms than adults. However, they play an important role in case numbers and virus transmission. Therefore, we aimed to determine the epidemiological features of all pediatric patients infected with SARS-CoV-2 and put forth case numbers longitudinally throughout the delta variant dominant period. A retrospective study was conducted at a university hospital and included patients between 0 and18 years old with a SARS-CoV-2 polymerase chain reaction (PCR) positive result, including inpatients and outpatients. Epidemiological and clinical features were recorded from electronic files, and telephone visits were performed between March 2020 and December 2021. During the study period, 3175 coronavirus disease 2019 (COVID-19) pediatric patients were admitted to our hospital with a mean age of 10.61 ± 4.6 years. Of the 1815 patients who could be interviewed, 85.7% reported at least one symptom. Before the delta variant period, 0-4 years aged children were more commonly infected, while school-aged children and adolescents were more common, and the rate of pediatric cases to all COVID-19 cases increased to 35.8% after the delta variant became dominant. Symptomatic cases were significantly higher before the delta variant (87.8% vs. 84.06%, p = 0.016). The hospitalization rate was higher before the delta variant (p < 0.001), whereas PICU admission showed no statistical difference. The frequency of school-aged children and adolescents raised with the impact of both school openings and the delta variant, and the rate of pediatric cases increased in total COVID-19 patient numbers.

Detection of δ Scuti Pulsators in the Eclipsing Binaries Observed by TESS

Based on 2 minute cadence TESS data from sectors 1–50, we report the results of the systematic extraction of δ Scuti–type pulsations in the 6431 eclipsing binaries with orbital periods shorter than 13 days. A total number of 242 pulsators were found in those systems, including 143 new discoveries. We examined their pulsation properties based on the H-R diagram and the relationships between the dominant pulsation period P dom, orbital period P orb, and effective temperature T eff. As a consequence, 216 targets are likely δ Scuti stars (123 new), 11 likely γ Doradus–δ Scuti hybrid stars (8 new), 5 likely β Cephei stars (4 new), 4 likely δ Scuti–γ Doradus hybrid stars (3 new), 3 likely Maia stars (3 new), 2 likely pulsating red giants (1 new), and a new unclassified star. As for the six new δ Scuti pulsators in eclipsing binaries with P orb < 0.65 days, we found that three of them significantly exceed the upper limits of the P dom/P orb ratio. This may indicate that P dom and P orb are uncorrelated for them. Finally, we statistically analyzed the dominant pulsation periods of the 216 δ Scuti stars in eclipsing binaries. Those stars concentrate around 225 μHz and the proportion of stars in the high-frequency region is significantly higher than that of single stars, which could be ascribed to the mass-transfer process.

Effectiveness of mRNA-1273, BNT162b2, and BBIBP-CorV vaccines against infection and mortality in children in Argentina, during predominance of delta and omicron covid-19 variants: test negative, case-control study

ObjectiveTo estimate the effectiveness of a two dose vaccine schedule (mRNA-1273, BNT162b2, and BBIBP-CorV) against SARS-CoV-2 infection and covid-19 related death and short term waning of immunity in children (3-11...

MICRO-ZONATION STUDY OF POTENTIAL SEISMIC HAZARDS BASED ON PEAK GROUND ACCELERATION (PGA) VALUE IN THE NORTH KONAWE OFFICE AREA

The purpose of this study was to determine the potential for seismic hazard based on the peak ground acceleration value in the North Konawe office area. This study uses the HVSR method to obtain the dominant frequency, amplification factor, dominant period, seismic vulnerability index and Peak Ground Acceleration. The results obtained from the microzonation of the distribution of the dominant frequency value with a high category were found at 5 measurement points, the amplification factor with a low category was found at 1 measurement point, the dominant period with a low category was found at 6 measurement points and the seismic vulnerability index with a low category was found at 5 points. measurement. Overall the research area is included in the level of seismic hazard risk, not high potential but in the low category. While the microzonation of the distribution of PGA values ​​obtained values ​​ranging from 23,2381-23,3231 gal which belong to the low seismic hazard risk level. Where it can be described in this area the earthquake that occurred can be felt by many people but caused damage. The light objects that were hung swayed and the windows shook. So it can be concluded that this research area is included in the category of low seismic hazard level

Spike Spectra for Recurrences.

In recurrence analysis, the τ-recurrence rate encodes the periods of the cycles of the underlying high-dimensional time series. It, thus, plays a similar role to the autocorrelation for scalar time-series in encoding temporal correlations. However, its Fourier decomposition does not have a clean interpretation. Thus, there is no satisfactory analogue to the power spectrum in recurrence analysis. We introduce a novel method to decompose the τ-recurrence rate using an over-complete basis of Dirac combs together with sparsity regularization. We show that this decomposition, the inter-spike spectrum, naturally provides an analogue to the power spectrum for recurrence analysis in the sense that it reveals the dominant periodicities of the underlying time series. We show that the inter-spike spectrum correctly identifies patterns and transitions in the underlying system in a wide variety of examples and is robust to measurement noise.

Network Analysis Measuring the Impact of Volcanic Eruptions

Volcanoes can be extremely damaging to the environment, human society, and also impact climate change. During volcanic eruption, massive amounts of gases and dust particles are thrown into the atmosphere and propagated instantaneously by the stratospheric circulation, resulting in a huge impact on the interactive pattern of the atmosphere. Here, we develop a climate network-based framework to study the temporal evolution of lower stratospheric atmosphere conditions in relation to a volcanic eruption, the Hunga Tonga-Hunga Ha’apai (HTHH) volcano, which erupted on 20 December 2021. Various spatial-temporal topological features of the climate network are introduced to analyze the nature of the HTHH. We show that our framework has the potential to identify the dominant eruption events of the HTHH and reveal the impact of the HTHH eruption. We find that during the eruption periods of the HTHH, the correlation behaviors in the lower stratosphere became much stronger than during normal periods. Both the degree and clustering coefficients increased significantly during the dominant eruption periods, and could be used as indications for the eruption of HTHH. The underlying mechanism for the observed cooperative mode is related to the impact of a volcanic eruption on global mass circulations. The study on the network topology of the atmospheric structure during a volcanic eruption provides a fresh perspective to investigate the impact of volcanic eruptions. It can also reveal how the interactive patterns of the atmosphere respond to volcanic eruptions and improve our understanding regarding the global impacts of volcanic eruptions.

The Mid-Pleistocene Transition: a delayed response to an increasing positive feedback?

Glacial–interglacial cycles constitute large natural variations in Earth’s climate. The Mid-Pleistocene Transition (MPT) marks a shift of the dominant periodicity of these climate cycles from sim 40 to sim 100 kyr. Recently, it has been suggested that this shift resulted from a gradual increase in the internal period (or equivalently, a decrease in the natural frequency) of the system. As a result, the system would then have locked to ever higher multiples of the external forcing period. We find that the internal period is sensitive to the strength of positive feedbacks in the climate system. Using a carbon cycle model in which feedbacks between calcifier populations and ocean alkalinity mediate atmospheric CO_2, we simulate stepwise periodicity changes similar to the MPT through such a mechanism. Due to the internal dynamics of the system, the periodicity shift occurs up to millions of years after the change in the feedback strength is imposed. This suggests that the cause for the MPT may have occurred a significant time before the observed periodicity shift.

Covid-19 vaccination programme effectiveness against SARS-CoV-2 related infections, hospital admissions and deaths in the Apulia region of Italy: a one-year retrospective cohort study

Studies reporting vaccine effectiveness against COVID-19 outcomes concentrate mainly on estimates of one single type of vaccine and variant, seldom considering waning effects. We aimed to estimate the effectiveness of the overall COVID-19 vaccination programme implemented in the Apulia region of Italy at preventing SARS-CoV-2 infections, COVID-19-related hospital admissions and deaths during alpha and delta variant dominant periods. We conducted a retrospective cohort study using electronic health records of persons 16 years and older resident in the Apulia region, assessing the effectiveness of the combined use of BNT162b2, mRNA-1273, ChAdOx1-S and Ad26.COV2.S vaccines against confirmed COVID-19 infections, hospitalisations and deaths, for fully and partially vaccinated persons as well as by time since vaccination and variants. Cox regression models yielding hazard ratios were used to calculate the overall vaccination programme effectiveness. From 1 January to 1 December 2021, we included 3,530,967 eligible persons in the cohort, of whom 2,770,299 were fully vaccinated and 158,313 were COVID-19 positive at the end of the study period. The effectiveness of the programme over the entire study period for fully vaccinated persons against COVID-19 infection, hospitalisation and death were 87.69% (CI95% 87.73–88.18), 94.08% (93.58–94.54) and 95.95% (CI95% 95.26–96.54), respectively. The effectiveness against COVID-19 infection of fully vaccinated subjects during the alpha and delta period was respectively 88.20% (CI95% 87.60–99.78) and 59.31% (CI95% 57.91–60.67), against hospitalisation 93.89% (CI95% 92.67–94.90) and 88.32% (CI95% 86.50–89.90) and against death 93.83% (CI95% 91.65–95.45) and 85.91 (CI95% 79.98–90.09). The waning effects of the programme regarding COVID-19 infection during the delta period were stronger than for alpha, with 75.85% (CI95% 74.38–77.24) effectiveness after 1–2 months and 8.35% (CI95% 3.45–13.01) after 5–6 months after full vaccination. The effectiveness against hospitalisation and death during the delta period waned rapidly and at 7–8-months after the full vaccination respectively decreased to 27.67% (CI95% 7.48–43.45) and 48.47 (CI95% 53.97–34.82). Our study suggests that the COVID-19 vaccination program in Apulia was strongly protective against COVID-19 infection, hospitalisation, and death due to alpha as well as delta variants, although its effectiveness is reduced over time.

Interannual variability of sea surface chlorophyll a in the southern tropical Indian Ocean: Local versus remote forcing

Phytoplankton are crucial to marine ecosystems and the global carbon cycle. This study investigates the characteristics and causes of the interannual variation of the surface chlorophyll a (chl a) in the southern tropical Indian Ocean (STIO). We find that in addition to the Seychelles-Chagos thermocline ridge (SCTR) upwelling zone in the southwestern basin, large interannual variability also shows up in the southeastern tropical Indian Ocean (SETIO; 6°–18°S, 70°–92°E). The chl a in the SCTR shows two dominant periods of four years and two years, whereas it shows a dominant period of six years and a weaker period of three years in the SETIO. Surface wind forcing anomalies within the STIO, but not the Indonesian throughflow, cause the interannual chl a anomaly. In the SETIO region, the thermocline dynamics control the chl a variation via a combination of equal contributions from local Ekman pumping and remote Rossby waves generated by the wind stress curl from the east. In the SCTR region, the thermocline dynamics explain only about 67% of the chl a variation, with a larger contribution from the remotely generated Rossby waves than local Ekman pumping. The circulation in the western basin also contributes to the chl a variation by transporting western equatorial chl a to this region during the boreal summer-fall. Both the Indian Ocean Dipole and the El Niño–Southern Oscillation act to modulate the chl a variation in the STIO. They make comparable contributions in the SETIO, while the Indian Ocean Dipole plays a more important role in the SCTR.

Analysis of photometric and spectroscopic variability of red supergiant Betelgeuse

Betelgeuse is a pulsating red supergiant whose brightness is semi periodically variable and in February 2020 reached a historical minimum, the Great Dimming. The aims of this study are to characterize Betelgeuse’s variability based on available archival data and to study possible causes of light variability. Many spectra, from ultraviolet and optical regions, were evaluated for spectral analysis. The spectra were used primarily to determine radial velocities from different layers of atmosphere and their long-term evolution. Additionally, photometric data were analysed in different filters as well, to construct light curves and to determine periods of the variability. Spectroscopic and photometric variability are compared to each other and given into a context with the Great Dimming.The two most dominant photometric periods are P1=2190±270d and P2=417±17d, while the dominant optical (photospheric) radial velocity periods are P1,vr=2510±440d and P2,vr=415±11d. During the same time, the radial velocity determined from ultraviolet spectra also shows variability and is distinctively different from the variability of photospheric velocity, undergoing longer periods of variability. We attribute these velocities to the velocities at the base of outflowing wind. We also report a maximum of stellar wind velocity during the Great Dimming, accompanied by the previously reported minimum of brightness and the maximum of photospheric radial velocity. After the Dimming, Betelgeuse’s mode of variability has fundamentally changed and is now instead following a shorter period of ∼200d.

Observational and numerical characterization of a recurrent arc-shaped front propagating along a coronal fan

Context. Recurrent, arc-shaped intensity disturbances were detected by extreme-ultraviolet channels in an active region. The fronts were observed to propagate along a coronal loop bundle rooted in a small area within a sunspot umbra. Previous works have linked these intensity disturbances to slow magnetoacoustic waves that propagate from the lower atmosphere to the corona along the magnetic field. Aims. The slow magnetoacoustic waves propagate at the local cusp speed, which is equivalent to the sound speed in a low-β-regime plasma. However, the measured propagation speeds from the intensity images are usually smaller as they are subject to projection effects due to the inclination of the magnetic field with respect to the line of sight. We aim to understand the effect of projection by comparing observed speeds with those from a numerical model. Methods. Using multi-wavelength data, we determined the periods present in the observations at different heights of the solar atmosphere through Fourier analysis. We calculated the plane-of-sky speeds along one of the loops from the cross-correlation time-lags obtained as a function of distance along the loop. We performed a 2D ideal magnetohydrodynamic simulation of an active region embedded in a stratified atmosphere. We drove slow waves from the photosphere with a three-minute periodicity. Synthetic time–distance maps were generated from the forward-modelled intensities in coronal wavelengths and the projected propagation speeds were calculated. Results. The intensity disturbances show a dominant period between 2 and 3 min at different heights of the atmosphere. The apparent propagation speeds calculated for coronal channels exhibit an accelerated pattern with values increasing from 40 to 120 km s−1 as the distance along the loop rises. The propagation speeds obtained from the synthetic time–distance maps also exhibit accelerated profiles within a similar range of speeds. Conclusions. We conclude that the accelerated propagation in our observations is due to the projection effect.

Tsunami free oscillations excited by potential local earthquake sources in Bohai Sea, China

The Bohai Sea is the most seismic active region offshore mainland China. Its coastal region is highly populated. The present work proposed a comprehensive scheme for identifying and examining free oscillations with limited number of tide gauges in an irregular semi-enclosed basin. We combined modal analysis, spectral analysis, and multiple-scenario simulation to investigate tsunami free oscillations in the Bohai Sea Basin and three local bays including Liaodong Bay, Bohai Bay, and Laizhou Bay. The Bohai Sea had broadband periods of free oscillations ranging from 228 to 30 min. There existed both along-shore and cross-shore oscillations in most eigenmodes. The ultra-long dominant periods above 50 min were attributed to the shallow water depth (<20 m). Some free oscillation modes appeared in both the Bohai Sea and local bay domains. In addition, the spatial patterns of dominant eigenmodes were characterized and validated by performing spectral analysis for an Mw 7.8 tsunami scenario. The energy was mainly concentrated in the first three modes (171, 146, and 93 min). This is the first study to characterize the areas prone to tsunami hazards in the Bohai Sea, and the methodology can be further extended to other coastal regions.

Spatiotemporal characteristics of air pollution in Chengdu-Chongqing urban agglomeration (CCUA) in Southwest, China: 2015–2021

Studying the spatiotemporal characteristics of air pollutants in urban agglomerations and their response factors will help to improve the quality of urban living. In combining air quality monitoring data and wavelet analysis from the Chengdu-Chongqing urban agglomeration (CCUA), this study assessed the spatiotemporal distribution characteristics and influential factors of air pollutants on daily, monthly and annual scales. The results showed that the concentration of air pollutants in the CCUA has decreased year by year, and air quality has improved. Except for O3, pollutants in autumn and winter were higher than those in summer. The spatial distribution of air pollutants was obvious distributed in Chengdu, Chongqing, Zigong and Dazhou. Pollution incidents were mainly concentrated in winter. The 6 air pollutants and air quality index (AQI) have dominant periods on multiple time scales. AQI showed positive coherence with PM2.5 and PM10 on multiple time scales, and obvious positive coherence with SO2, CO, NO2 and O3 in the short term scale. AQI was not strongly correlated with the fire point, but exhibited obvious negative coherence in the long term scale. In addition, AQI showed an obvious positive correlation with temperature and sunshine hours in short term, and a clear negative correlation with humidity and rainfall. The research results of this paper will provide a reference for pollution prevention and control in the CCUA.

Multi-centennial Holocene climate variability in proxy records and transient model simulations

Variability on centennial to multi-centennial timescales is mentioned as a feature in reconstructions of the Holocene climate. As more long transient model simulations with complex climate models become available and efforts have been made to compile large proxy databases, there is now a unique opportunity to study multi-centennial variability with greater detail and a large amount of data than earlier. This paper presents a spectral analysis of transient Holocene simulations from 9 models and 120 proxy records to find the common signals related to oscillation periods and geographic dependencies and discuss the implications for the potential driving mechanisms. Multi-centennial variability is significant in most proxy records, with the dominant oscillation periods around 120–130 years and an average of 240 years. Spectra of model-based global mean temperature (GMT) agree well with proxy evidence with significant multi-centennial variability in all simulations with the dominant oscillation periods around 120–150 years. It indicates a comparatively good agreement between model and proxy data. A lack of latitudinal dependencies in terms of oscillation period is found in both the model and proxy data. However, all model simulations have the highest spectral density distributed over the Northern hemisphere high latitudes, which could indicate a particular variability sensitivity or potential driving mechanisms in this region. Five models also have differentiated forcings simulations with various combinations of forcing agents. Significant multi-centennial variability with oscillation periods between 100 and 200 years is found in all forcing scenarios, including those with only orbital forcing. The different forcings induce some variability in the system. Yet, none appear to be the predominant driver based on the spectral analysis. Solar irradiance has long been hypothesized to be a primary driver of multi-centennial variability. However, all the simulations without this forcing have shown significant multi-centennial variability. The results then indicate that internal mechanisms operate on multi-centennial timescales, and the North Atlantic-Arctic is a region of interest for this aspect.

An analysis of core–mantle boundary related seismic waves using full-waveform modelling and adjoint methods

SUMMARYThe core–mantle boundary (CMB) is the most abrupt internal discontinuity in the Earth, marking the solid–fluid boundary between mantle and outer core that strongly affects the dynamics of the Earth’s interior. However, good agreement between models of CMB topographic variations is still lacking. This is probably due to difficulties relating to observations on seismograms and to the lack of good models of lowermost mantle velocity structure. Using spectral-element synthetic seismograms and adjoint methods, we perform traveltime analyses of seismic waves interacting with the CMB. We focus on reflected and refracted P and S waves. We select some of the most important and routinely used seismic phases: ScS, SKS, SKKS, PcP, PKP, PKKP and PcS, given their path through mantle and core and their interaction with the CMB. These seismic waves have been widely deployed by seismologists trying to image CMB topography and lowermost mantle structure. To analyse the reliability of measuring their traveltimes to infer CMB topography, we perform experiments in two ways. First, we compute synthetic seismograms with a dominant period of T ≈ 11s, for computational efficiency, using existing models of CMB topography. We compare traveltime perturbations measured by cross-correlation on the synthetics to those predicted using ray theory. We find deviations from a perfect agreement between ray theoretical predictions of time shifts and those measured on synthetics with and without CMB topography. Second, we calculate Fréchet sensitivity kernels of traveltimes with respect to shear and compressional wave speeds. We also explicitly compute boundary sensitivities with respect to the CMB interface. We observe that the overall sensitivity of the traveltimes is mostly due to volumetric velocity structure and that imprints of CMB on traveltimes are less pronounced. Our study explains the observed difficulties relating to inferring CMB topography using traveltimes and provides a suite of finite frequency sensitivity kernels computed with the adjoint method. The kernels allow us to qualitatively explain the behaviour of measured traveltimes and understand the trade-off between velocity and CMB topography. They can also serve as reference of finite frequency effects on traveltimes of observed seismic phases. From our analyses we conclude that: i) traveltime anomalies measured on Swaves are more in accord with ray theoretical predictions, ii) PcP, PKP, ScS and SKS phases have more pronounced sensitivity to the boundary and iii) separating the greater effects of velocity from those due to the boundary structure is difficult, as they intricately affect the traveltime. We propose that jointly inverting for CMB topography and lowermost mantle velocity structure using full-waveform synthetics and adjoint sensitivity kernels can progress our understanding of deep Earth structure and finite frequency effects on observed waveforms.

Stars on the Verge: From Days to Decades, Studying the Photometric Variations of the Red Supergiant W Persei

W Persei is a massive, luminous and large red supergiant located relatively nearby. W Persei is a probable SN-II progenitor. We analyzed ∼120 yr of photometry from the AAVSO database. The analysis was conducted in the period analysis software Peranso where the CLEANest power spectrum and WWZ-wavelet programs were utilized. Two dominant periods of P = 532 ± 68 days and P = 2922 ± 140 days are found. Intermediate and transitory periods are also uncovered along with period events such as a significant increase in the long-period, period-merging and period-splitting. Using Transiting Exoplanet Survey Satellite observations, stochastic ∼0.3–0.8 mmag light variability on timescales of ∼0.3 day appears present. The physical causes of these variations is discussed.

Evidence for Short Temporal Atmospheric Variations Observed by Infrasonic Signals: 2. The Stratosphere

AbstractThis study uses infrasound detections from a repetitive source to estimate the effect of the atmosphere's temporal variability on infrasound. While a previous paper focused on infrasound propagation through the troposphere to a distance of 54 km, this study uses stratospheric returns detected 256 km from the source. Based on source‐receiver pairs, the empirical Green's function is calculated every 20 s for 52 events; these allow generating a set of synthetic signals where variations are ascribed to variation in the atmosphere. In addition, observations are compared with numerical simulation results based on realistic atmospheric conditions. Results show that variations of stratospheric infrasound signals are observed over timescales ranging from tens of seconds to minutes and have dominant periods ranging from tens to hundreds of seconds. These results motivate using infrasound to probe short temporal changes in the middle atmosphere and study their underlying phenomena.