Cross-correlation Function Analysis Research Articles

A Formally Motivated Retrieval Framework Applied to the High-resolution Transmission Spectrum of HD 189733 b

Ground-based high-resolution spectra provide a powerful tool for characterizing exoplanet atmospheres. However, they are greatly hampered by the dominating telluric and stellar lines, which need to be removed prior to any analysis. Such removal techniques (“preparing pipelines”) deform the spectrum; hence, a key point is to account for this process in the forward models used in retrievals. We develop a formal derivation on how to prepare froward models for retrievals, in the case where the telluric and instrumental deformations can be represented as a matrix multiplied element-wise with the data. We also introduce the notion of a “bias pipeline metric,” which can be used to compare the bias potential of preparing pipelines. We use the resulting framework to retrieve simulated observations of 1D and 3D exoplanet atmospheres and to reanalyze high-resolution ( R≈80,400 ) near-infrared (0.96–1.71 μm) CARMENES transit data of HD 189733 b. We compare these results with those obtained from a cross-correlation function analysis. With our fiducial retrieval, we find a blueshift of the absorption features of −5.51−0.53+0.66 km s−1. In addition, we retrieve a H2O log10(VMR) of −2.39−0.16+0.12 and a temperature of 660−11+6 K. We are also able to put upper limits for the abundances of CH4, CO, H2S, HCN, and NH3, consistent with a subsolar-metallicity atmosphere enriched in H2O. We retrieve a broadened line shape, consistent with rotation- and wind-induced line broadening. Finally, we find a lower limit for the pressure of an opaque cloud consistent with a clear atmosphere, and we find no evidence for hazes.

Unveiling Economic Synchrony: Analyzing Lag Dynamics between GDP Growth and Construction Activity in Poland and Other EU Countries

This study examines the dynamic relationship between the business cycle and the construction sector activity in 27 EU countries, focusing on Poland. Using the cross-correlation function (CCF) and a set of economic- and construction-related variables, including GDP growth, construction production, building permits, and construction operating time by backlog, quarterly data from 2000Q1 to 2023Q2 (94 quarters in total) are analyzed. Beyond the CCF analysis, causality is also examined using Toda–Yamamoto tests to explore the nuanced temporal relationships between GDP growth and construction activity proxies. The research uncovers synchronized positive lag max results for construction production, suggesting a harmonized response to broader economic changes, especially within 9 to 11 quarters. In contrast, building permits and construction time by backlog show divergent positive lag max values, suggesting the need for tailored, localized strategies. Negative lag max values emphasize the anticipatory role of the construction sector as an early indicator of economic change. Overcoming methodological challenges, this study provides insights critical for policymakers and researchers, promoting a nuanced understanding of economic synchrony and guiding informed strategies for sustainable development. Future recommendations include refining localized strategies based on lag patterns for optimal economic management.

Forecasting and Cross-Correlation of Series on the Waste Generation, Population, GDP and Household Consumption Expenditures in Jordan

The household waste is the biggest contributor to the total municipal solid waste generation. The main objective of the research is to discover the Jordanian economy in four dimensions: the household waste generation, the number of population, the gross domestic product (GDP) at purchasers’ prices, and the household final consumption expenditures. In the focus of interest are (1) finding adequate time series models for forecasting of the number of population, the GDP at purchasers’ prices, the household final consumption expenditures, and the household waste generation; (2) the cross-correlation between the household waste generation variable and other variables – population, GDP and household final consumption expenditures. The analysis of cross-correlation functions has revealed that pairs of series (waste/gdp, waste/consumption, waste/population) move in one direction with no shift in time of one series to the other. The relationship in every pair of series is significant. It is expected that in the short-run, ceteris paribus, with the growth of the population numbers, GDP and/or household consumption expenditures, the level of household waste generation in the country will also grow in a close relationship. Appropriate ARIMA models have been proposed to use for the short-run forecastsing of time series. The research outcomes are useful for policy makers to realize the scale of the household waste problem and to optimize capital expenditures into the waste management system of Jordan.

Применение зондирующих ФКМ-сигналов с нулевой зоной автокорреляции для улучшения качества измерений в РСА

For SARs, a polyphase (p-phase, where p is a prime number) probing signal with a zero autocorrelation zone has been synthesized, which is a train of p phase-code shift keyed (PCSK) pulses coded by complementary sequences of a p-ary D-code with additional phase-code shift-keying of the sub-pulses (discretes) of pulses by an M-sequences. To assess the quality of radar images of point targets and extended surfaces, the levels of the maximum side lobe and one-way integrated correlation noise of the autocorrelation function (ACF) are used, respectively. For this purpose, the work carried out a comparative analysis of the total ACFs of the synthesized ensemble of signals with ensembles of orthogonal chirp and PCSK-signals used in adjacent SAR sounding cycles. The work also considers the problem of superimposition of SAR echo signals from different ranges at a relatively high repetition rate of probing pulses. To assess the level of suppression of recurrent interference from point targets and from extended surfaces, the levels of the maximum side lobe and one-sided integral correlation noise of the cross-correlation function (CCF) are used, respectively. For this purpose, the work carried out a comparative analysis of the total CCFs of the synthesized ensemble of signals with ensembles of orthogonal chirp and PCSK- signals used in the SAR aperture synthesis modes. The use of orthogonal chirp and PCSK-signals makes it possible to successfully suppress false signals from bright point targets from adjacent repetition periods. However, the high level of integral correlation noise of the CCF of orthogonal signals distorts radar images of weakly reflecting surfaces located next to bright extended objects. The indicators of the total correlation characteristics of the synthesized ensemble of signals exceed the corresponding indicators of the total correlation characteristics of the ensemble of orthogonal PCSK-and chirp signals, both without mismatch and with Doppler frequency mismatch. This makes it possible to successfully use an PCSK-signal with a zero autocorrelation zone to improve the quality of radar images and suppress recurrent range interference in SAR.

Using cross-correlation analysis of multi-channel near infrared spectroscopy to assess the hemodynamic response to cupping therapy.

Cupping therapy is a common intervention for the management of musculoskeletal impairment. Previous studies have demonstrated that cupping therapy can improve muscle hemodynamic responses using single-channel near-infrared spectroscopy (NIRS). However, the effects of cupping therapy on spatial hemodynamic responses as well as the correlation between oxyhemoglobin and deoxy-hemoglobin are largely unknown. The cross-correlation function (CCF) algorithm was used to determine the correlation between time-series NIRS signals from inside and outside the cup as well as time-series oxyhemoglobin and deoxy-hemoglobin under 4 cupping intensities, including -225 and -300 mmHg for 5 and 10 min. The main finding was that the maximum CCF values of oxyhemoglobin was significantly higher than those in deoxy-hemoglobin (p < 0.05). Furthermore, it was found that there was a correlation between deoxy-hemoglobin with a longer duration and a larger magnitude of negative pressure. This is the first study investigating time-series hemodynamic responses after cupping therapy using cross-correlation function analysis of multi-channel NIRS signals.

Inflation surge of 2021-2023 and monetary policy in Eastern European countries

This article provides an in-depth analysis of the current global economic landscape, with a particular focus on Moldova, Ukraine, Romania, and Poland. The scope of this article is to examine central banks’ responses to the challenges posed by 2021-2023 inflation. The research employs a combination of scientific methods, including empirical analysis and quantitative research. It utilizes data from reputable sources like the World Bank, National Banks, and National Bureaus of Statistics to examine various economic indicators. Statistical software R is used for data analysis, including Cross-Correlation Function (CCF) analysis. In response to rising inflation, Moldova and Ukraine raised interest rates significantly. Moldova later eased rates gradually, while Ukraine maintained a high rate to safeguard its currency. Romania and Poland, with stronger economies, saw milder rate hikes and less inflation increase compared to other Eastern European nations, adopting a cautious and delayed approach and still not reducing their base rates. A critical aspect of the research is the implementation of cross-correlation function (CCF) analysis, which is used to explore the time-lagged correlations between different economic variables, such as the Base policy rate, Commodity price index and IPC. The analyses conducted have revealed two significant patterns: a deficiency in the proactive adjustment of base rates by central banks in response to inflation and the lead-lag relationship between ascending commodity prices and inflation. These findings underscore the cautious approach taken by central banks and their delayed response to the impact of external factors on inflation dynamics.

Detection of Single Charge Trapping Defects in Semiconductor Particles by Evaluating Photon Antibunching in Delayed Photoluminescence.

Time-resolved analysis of photon cross-correlation function g(2)(τ) is applied to photoluminescence (PL) of individual submicrometer size MAPbI3 perovskite crystals. Surprisingly, an antibunching effect in the long-living tail of PL is observed, while the prompt PL obeys the photon statistics typical for a classical emitter. We propose that antibunched photons from the PL decay tail originate from radiative recombination of detrapped charge carriers which were initially captured by a very limited number (down to one) of shallow defect states. The concentration of these trapping sites is estimated to be in the range 1013-1016 cm-3. In principle, photon correlations can be also caused by highly nonlinear Auger recombination processes; however, in our case it requires unrealistically large Auger recombination coefficients. The potential of the time-resolved g(2)(0) for unambiguous identification of charge rerecombination processes in semiconductors considering the actual number of charge carries and defects states per particle is demonstrated.

Detection of clock errors in seismic records and estimation of time shifts for a seismic network

In the records of autonomous seismological observations occurrence of quartz watch clock drift often leads to incorrect time records. This paper presents a method for detecting such errors in a seismic station network based on the analysis of ambient seismic noise cross-correlation functions using Monte-Carlo Markov chain (MCMC) approach without using a reference signal. The proposed method was tested on the seismic data of a temporary seismic network installed on Paramushir Island in 2021-2022 for which time shifts were successfully estimated and corrections to the cross-correlation functions were made.

1074. Surveillance of SARS-CoV-2 variants of concern (VOC) in hospital wastewater (WW) and its correlation with hospitalized cases of COVID-19 and the occurrence of outbreaks

Abstract Background WW surveillance enables real time monitoring of SARS-CoV-2 burden in defined sewer catchment areas. Here, we assessed the occurrence of total, Delta and Omicron SARS-CoV-2 RNA in sewage from three tertiary-care hospitals in Calgary, Canada. Methods Nucleic acid was extracted from hospital (H) WW using the 4S-silica column method. H-1 and H-2 were assessed via a single autosampler whereas H-3 required three separate monitoring devices (a-c). SARS-CoV-2 RNA was quantified using two RT-qPCR approaches targeting the nucleocapsid gene; N1 and N200 assays, and the R203K/G204R and R203M mutations. Assays were positive if Cq&amp;lt; 40. Cross-correlation function analyses (CCF) was performed to determine the time-lagged relationships between WW signal and clinical cases. SARS-CoV-2 RNA abundance was compared to total hospitalized cases, nosocomial-acquired cases, and outbreaks. Statistical analyses were conducted using R. Results Ninety-six percent (188/196) of WW samples collected between Aug/21-Jan/22 were positive for SARS-CoV-2. Omicron rapidly supplanted Delta by mid-December and this correlated with lack of Delta-associated H-transmissions during a period of frequent outbreaks. The CCF analysis showed a positive autocorrelation between the RNA concentration and total cases, where the most dominant cross correlations occurred between -3 and 0 lags (weeks) (Cross-correlation values: 0.75, 0.579, 0.608, 0.528 and 0.746 for H-1, H-2, H-3a, H-3b and H-3c; respectively). VOC-specific assessments showed this positive association only to hold true for Omicron across all hospitals (cross-correlation occurred at lags -2 and 0, CFF value range between 0.648 -0.984). We observed a significant difference in median copies/ml SARS-CoV-2 N-1 between outbreak-free periods vs outbreaks for H-1 (46 [IQR: 11-150] vs 742 [IQR: 162-1176], P&amp;lt; 0.0001), H-2 (24 [IQR: 6-167] vs 214 [IQR: 57-560], P=0.009) and H-3c (2.32 [IQR: 0-19] vs 129 [IQR: 14-274], P=0.001). Conclusion WW surveillance is a powerful tool for early detection and monitoring of circulating SARS-CoV-2 VOCs. Total SARS-CoV-2 and VOC-specific WW signal correlated with hospitalized prevalent cases of COVID-19 and outbreak occurrence. Disclosures All Authors: No reported disclosures.

Double-lined spectroscopic binaries in M11

ABSTRACT We have developed a new method for spectral analysis of binaries. Our method successfully identifies double-lined spectroscopic binary (SB2) candidates from high-resolution Gaia-ESO spectra. Compared to the commonly used cross-correlation function analysis, it works for binaries with rapidly rotating components. We test our method on synthetic and observational spectra of BAFG stars with vsin i from 1 to $330~\, {\rm km}\, {\rm s}^{-1}$ in the open cluster M11. We confirm five previously detected SB2 candidates and find 19 new ones. For three SB2 candidates, we find circular orbits and obtain dynamical mass ratios.

Linking human activities and global climatic oscillation to phytoplankton dynamics in a subtropical lake

Human activities and climate change are two major stressors affecting lake ecosystems as well as phytoplankton communities worldwide. However, how the temporal dynamics of phytoplankton are directly or indirectly linked to anthropogenic activities and climatic oscillation remains unclear. We assessed the annual trends (1988–2018) in phytoplankton abundance (PA) in Lake Dongting, China and related it to five groups of variables characterizing human activities, global climate oscillation, water nutrients, hydrology, and meteorology. We found a significant increase in PA, urbanization (Upop), total nitrogen (TN), fertilizer application (FA), number of summer days (SU), and the warm speed duration index (WSDI) and a significant decrease in the water discharge of three inlets (TIWD) and the sediment discharge of three inlets (TISD) and four tributaries (FTSD) and the net sediment deposition (NSD). However, no significant annual trends were observed for the number of rainstorm days (R50mm), the simple precipitation intensity index (SDII) and yearly anomalies of El Niño-Southern oscillation events (ENSOi). Cross-correlation Function analyses demonstrated that the operation of the Three George Dam (TGD) strengthened the effects of hydrology, rainfall patterns and ENSOi on phytoplankton, but strongly weakened the association between water nutrients, human activities and phytoplankton abundance. Path analysis revealed that TP, TN, FA, R50 mm as well as WSDI had a direct positive effect on PA, while a direct negative effect was found for ENSOi, NSD and TISD. Human activities (Upop and FA), warming (WSDI and SU), and rainfall patterns (SDII and R50 mm) exerted indirect controls on phytoplankton through changes in water nutrients and hydrology. Climate change (ENSOi) had a direct effect on PA, but also showed twelve indirect pathways via changes in hydrology and meteorology (both positive and negative effects were found). Overall, meteorology contributed most markedly to the variations of PA (29.3%), followed by hydrology (25.3%), human activities (24%), water nutrients (10.5%), and ENSOi (1.9%). Our results highlight a strongly causal connection between human activities as well as global climate change and phytoplankton and the benefits of considering multiple environmental drivers in determining the temporal dynamics of lake biotic communities.

Changing look AGN Mrk 590: broad-line region and black hole mass from photometric reverberation mapping

ABSTRACT We present the results of photometric reverberation mapping observations on the changing look active galactic nucleus Mrk 590 at z = 0.026. The observations were carried out from 2018 July to December using broad-bandB-,R-, and narrow-band H α and S ii filters. The B band traces the continuum emission from the accretion disc, the R band encompasses both the continuum emission from the accretion disc and the redshifted H α line from the broad-line region (BLR), the S ii band contains the redshifted H α emission and the H α band traces the continuum emission underneath the S ii band. All the light curves showed strong variation with a fractional root-mean-square variation of 0.132 ± 0.001 in the B band and 0.321 ± 0.001 in H α line. From cross-correlation function analysis, we obtained a delayed response of H α line emission to the opticalB-band continuum emission of $21.44^{+1.49}_{-2.11}$ d in the rest frame of the source, corresponding to a linear size of the BLR of 0.018 pc. This is consistent with previous estimates using H β. By combining the BLR size with the H α line full width at half-maximum of 6478 ± 240 km s−1 measured from a single-epoch spectrum obtained with the Subaru telescope, we derived a black hole mass of $1.96^{+0.15}_{-0.21}\times 10^8 {\rm M}_{\odot }$.

Incipient Surge Analysis in Time and Frequency Domain for Centrifugal Compressors

Abstract The use of centrifugal compressors has been increasing tremendously in the last decade as they are a key component in the present energy scenario both in the modern internal combustion engine design and in advanced cycles and innovative plant layouts as fuel cell systems. Instability phenomena limit the operating range of the whole compressor system, especially during fast transients. The target is therefore to extend the minimum flow limit in order to improve the operability of each unit while avoiding compressor surge operation and guaranteeing safe operation. For this reason, it is necessary to develop a monitoring system capable of preventing surge and extending the operating range of these machines, their performance, and reliability to allow the integration with the other plant components. The experimental investigation carried out at the University of Genoa turbocharger test facility and presented in this work, consists of steady-state and transient measurements used to characterize and identify compressor behavior in correspondence of surge inception conditions to determine different techniques which could represent surge precursors. The data analysis concentrates on pressure and vibro-acoustic signals by applying different signal processing techniques in the time and frequency domain to classify compressor operation as stable or unstable. The cross correlation function and wavelet analysis have been identified as techniques to define a precursor able to detect incipient surge conditions. Through cross correlation function analysis, it has been possible to identify the presence of propagation phenomena in the system and to evaluate how these events become more significant near an unstable low-mass flow rate condition. At low mass flow rate condition, spikes of significant amplitude are well detectable in the cross correlation function indicating the rise of significant random content in the system responses associated with the rise of incipient surge condition. Additionally, the continuous wavelet transform has been applied to operational signals to show how their time-dependent spectral structure responses can highlight the rise of unstable phenomena, not easily identifiable with traditional signal processing techniques. Exploiting its features in terms of good frequency and time resolution allowed us to identify different contents in system responses regarding phenomena that take place close to surge line and were able to detect their nature in conditions very close to deep surge ones (e.g., rotating stall with its intermitting characteristic nature). Moreover, system response was studied in high frequency range and through a demodulation technique, it was found how blade passes frequency energy content change interacting with rotating stall inception, moving close to surge line. The obtained results provide an interesting diagnostic and predictive solution to detect compressor instabilities at low mass flow rate operating conditions and to prevent compressor fails.

Association of bilateral lower limb coordination while standing with body sway control and aging

Purpose Coordinated movements of both lower limbs may be a clinically important indicator of motor control during quiet standing. From a neurological point of view, it is known that extensive coupling of muscles must be coordinated an upright posture. However, movement coordination between the lower limbs is the final motor output, is unknown. In this study, we focussed on the ground reaction force (GRF) vector and clarified the time and frequency characteristics of the force vectors of both lower limbs. Materials and methods A total of 16 healthy young adults and 18 healthy older adults participated and placed each bare foot on one of two force plates to measure the GRF vectors (i.e., anteroposterior, mediolateral, and vertical) of each lower limb and determine the centre of mass (COM) acceleration in the anteroposterior direction (COMacc). Characteristics of the coordination of both lower limbs during movements were analysed using coherence analysis and cross-correlation function analysis (CCF). Results The coherence levels of the force vectors of both lower limbs were higher in all three directions and significantly increased in the older adults. CCF analysis showed that the force vectors of both lower limbs were negatively correlated at the zero-time lag. Moreover, a weak correlation was observed between COMacc and coherence values. Conclusions The assessment of bilateral lower limb connectivity using force vectors can be used as an evaluation method to reflect changes in the ability to control bipedal standing during ageing.

Interannual variability of chlorophyll-a and impact of extreme climatic events in the South Eastern Arabian Sea

South Eastern Arabian Sea (SEAS) is an upwelling dominated region, where the distribution of chlorophyll-a (Chl-a) is mainly controlled by basin-scale to mesoscale processes associated with seasonal reversal of winds and currents. The analysis of long-term satellite-derived Chl-a data revealed interannual variability in association with extreme climatic events. Chl-a data were obtained from Ocean Colour Climate Change Initiative (OC-CCI) which provides high resolution cloud free data for the Arabian Sea during summer monsoon season (June to September). Satellite measurements of Sea Level Anomaly (SLA), Sea Surface Temperature (SST) and sea surface wind data were also compiled from various sources. The monthly data for the above environmental variables during 1998 to 2016 were analysed as representatives of the possible causative physical processes influencing the variability in Chl-a. The time series and Hovmöller analyses shows that the maximum variability occurred during summer monsoon. This study shows that the interannual variability in Chl-a was prominently influenced by the underlying processes involved in coastal upwelling. The relative variability in Chl-a and associated environmental variables with these events was remarkable during strong El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) events. Cross Correlation Function (CCF) analysis points out that Chl-a content is negatively correlated with IOD to an extent of one month lag or less whereas, ENSO does not indicate such direct relations. Further, the variability associated with IOD was more conspicuous than ENSO. The study elucidates the interannual variability of Chl-a and the overall influence of associated extreme events in the SEAS.

Google Trends Data: A Potential New Tool for Monitoring the Opioid Crisis

Introduction: There is a need to strengthen the standard surveillance of the opioid overdose crisis in the USA. The role of Google Trends (GT) was explored in this context. Methods: In this study, a systemic GT search was done for a period from January 2004 to December 2018. “Naloxone” and “drug overdose” were chosen as search inputs. By using locally weighted scatterplot smoothing, we locally regressed and smoothed the relative search data generated by the GT search. We conducted a changepoint analysis (CPA) to detect significant statistical changes in the “naloxone” trend from 2004 to 2018. Cross-correlation function analyses were done to examine the correlation between 2 time series: year-wise relative search volume (RSV) for “naloxone” and “drug overdose” with the age-adjusted drug overdose mortality rate. Pearson’s correlation was performed for the state-wise age-adjusted mortality rate due to drug overdose and RSV for “naloxone” and “drug overdose.” Results: Smoothed and regressed GT of “naloxone” were similar to the “opioid overdose” trend published by the National Center for Health Statistics. The CPA showed 2 statistically significant points in 2011 and 2015. CPA of year-wise RSV for “naloxone” and “drug overdose” showed significantly positive correlation with the age-adjusted drug overdose mortality at lag zero. State-wise RSV for “naloxone” and “drug overdose” too showed a strong and significant positive correlation with the state-wise mortality data. Discussion/Conclusion: Inexpensive, publicly accessible, real-time GT data could supplement and strengthen the monitoring of opioid overdose epidemic if used in conjunction with the existing official data sources.

High Throughput Mapping of Single Molecules' Redox Potentials on Electrode.

By synchronizing electrochemical potential scanning with a single-molecule localization super-resolution fluorescence microscope, kinetic fluorescence changes of hundreds of single molecular redox events were tracked simultaneously with high throughput, and subsequent cross-correlation function analysis mapped single molecules' redox potentials (times) out on the imaging area from site to site in unprecedented detail by extracting electrochemically induced fluorescence change from apparently random fluorescence on/off blinking. This work paves the way toward mapping redox states at single-molecule levels in high throughput in chemical and biological systems.

Effects of the El Niño Southern Oscillation (ENSO) on fish assemblages in a Neotropical floodplain

We evaluated the association between the El Nino Southern Oscillation (ENSO), an important climatic phenomenon on Earth, with water level variation and fish assemblage attributes (i.e., abundance, species richness and structure of the assemblage) of the Parana (dammed) and Ivinhema (undammed) rivers, located in the upper Parana River floodplain, Brazil. Cross-Correlation Function analyses were performed using the Oceanic Nino Index (ONI; which indexed ENSO events) as the influential time series on water level and fish assemblage attributes time series. ONI were positively associated with water level and with most of the fish assemblage attributes tested, but these patterns differed between the two rivers. This indicates that El Nino events affect the structure of the fish assemblages, mainly in the Ivinhema River, which presented more assemblage attributes associated with ONI. In addition, dams may play a regulatory effect over the water level of the Parana River, which probably explains the different patterns of assemblage attributes in both rivers. Thus, ENSO events are associated with the composition and structure of the fish assemblages in the studied area, and their effects are apparently minimized in the Parana River due to the presence of upstream dams.

Time Correction of Ocean-Bottom Seismometers Using Improved Ambient Noise Cross Correlation of Multicomponents and Dual-Frequency Bands

Abstract An effective approach was developed for identifying and correcting ocean-bottom seismometer (OBS) time errors through improving ambient noise cross-correlation function (NCCF) analysis and combination with other methods. Significant improvements were illustrated through analyzing data from a passive-source seismic experiment in the southwestern sub-basin of the South China Sea. A novel method was first developed that can effectively identify errors in the sampling frequency of the OBS instruments. The traditional NCCF method was then expanded by increasing the analyzed data spectrum from a single-frequency band to dual-frequency band pairs, thus doubling the number of available data points and substantially improving the time correction quality. For data with relatively low signal-to-noise ratios, the average time errors were reduced from the original average values of 60–80 ms by the conventional methods to &amp;lt;40  ms using the improved approaches. The new multistep procedure developed in this study has general applicability to analysis of other OBS experiments. The demonstrated significant improvements in the data quality are critical for advancing seismic tomography and other modern marine geophysical studies that require high accuracy in the OBS data.

Dust reverberation mapping of Z229–15

ABSTRACTWe report results of the dust reverberation mapping (DRM) on the Seyfert 1 galaxy Z229–15 at z = 0.0273. Quasi-simultaneous photometric observations for a total of 48 epochs were acquired during the period 2017 July to 2018 December in B, V, J, H and Ks bands. The calculated spectral index (α) between B and V bands for each epoch was used to correct for the accretion disc (AD) component present in the infrared light curves. The observed α ranges between −0.99 and 1.03. Using cross-correlation function analysis we found significant time delays between the optical V and the AD corrected J, H and Ks light curves. The lags in the rest frame of the source are $12.52^{+10.00}_{-9.55}$ d (between V and J), $15.63^{+5.05}_{-5.11}$ d (between V and H) and $20.36^{+5.82}_{-5.68}$ d (between V and Ks). Given the large error bars, these lags are consistent with each other. However, considering the lag between V and Ks bands to represent the inner edge of the dust torus, the torus in Z229–15 lies at a distance of 0.017 pc from the central ionizing continuum. This is smaller than that expected from the radius luminosity (R−L) relationship known from DRM. Using a constant α = 0.1 to account for the AD component, as is normally done in DRM, the deduced radius (0.025 pc) lies close to the expected R−L relation. However, usage of constant α in DRM is disfavoured as the α of the ionizing continuum changes with the flux of the source.