Tidal Disruption Research Articles

Tidal Deformation and Dissipation Processes in Icy Worlds

Abstract Tidal interactions play a key role in the dynamics and evolution of icy worlds. The intense tectonic activity of Europa and the eruption activity on Enceladus are clear examples of the manifestation of tidal deformation and associated dissipation. While tidal heating has long been recognized as a major driver in the activity of these icy worlds, the mechanism controlling how tidal forces deform the different internal layers and produce heat by tidal friction still remains poorly constrained. As tidal forcing varies with orbital characteristics (distance to the central planet, eccentricity, obliquity), the contribution of tidal heating to the internal heat budget can strongly change over geological timescales. In some circumstances, the tidally-produced heat can result in internal melting and surface activity taking various forms. Even in the absence of significant heat production, tidal deformation can be used to probe the interior structure, the tidal response of icy moons being strongly sensitive to their hydrosphere structure. In the present paper, we review the methods to compute tidal deformation and dissipation in the different layers composing icy worlds. After summarizing the main principle of tidal deformation and the different rheological models used to model visco-elastic tidal response, we describe the dissipation processes expected in rock-dominated cores, subsurface oceans and icy shells and highlight the potential effects of tidal heating in terms of thermal evolution and activity. We finally anticipate how data collected by future missions to Jupiter’s and Saturn’s moons could be used to constrain their tidal response and the consequences for past and present activities.

Tidal Effects on Dissolved Organic Matter Dynamics in a Brackish Water Front Adjacent to Yangtze River Estuary

A brackish water front, where river water meets seawater, is a hotspot for biogeochemical processes. In this study, we examined the quantity and composition of dissolved organic matter (DOM) over a 24 h tidal cycle at a brackish water front near the Yangtze River estuary. Utilizing elemental analysis, fluorescence and ultraviolet spectroscopy, and ultra-high-resolution mass spectrometry, we observed rapid fluctuations in DOM throughout the tidal cycle. The dissolved organic carbon (DOC) and total nitrogen (TN) concentrations ranged from 0.70 to 1.5 mg/L and 0.43 to 0.94 mg/L, respectively. Water samples during low tide exhibited a higher fractional abundance of CHON (17.2 ± 0.1% vs. 14.6 ± 0.4%), CHOS (14.6 ± 4.5% vs. 9.1 ± 3.1%), and CHONS (1.6 ± 0.5% vs. 0.5 ± 0.3%) formulas, and a higher aromatization and average molecular weight, which is consistent with a stronger terrestrial influence. In contrast, at high tide, the water samples contained a greater abundance of CHO compounds (75.7 ± 3.8% vs. 66.5 ± 4.1%), a humic-like fluorescent C1 component, and carboxyl-rich alicyclic molecules (CRAMs), indicating a greater release of refractory DOM from resuspended sediments. However, variations in the DOC concentrations and several optical spectral parameters did not correlate with the changes in the salinity and tidal height. The results of the principal component analysis revealed different controls on specific fractions of DOM that are related to variable DOM sources or biogeochemical processes. The complexity of DOM dynamics underscores the necessity of elucidating DOM compositions at varying levels to enhance our understanding of carbon cycling in estuarine and coastal ecosystems.

Correction to: On the relative importance of shocks and self-gravity in modifying tidal disruption event debris streams

Correction to: On the relative importance of shocks and self-gravity in modifying tidal disruption event debris streams

Resonant capture of stars by Black Hole Binaries: Extreme eccentricity excitation

Abstract Massive black hole (MBH) binaries in galactic nuclei are one of the leading sources of ∼ mHz gravitational waves (GWs) for future missions such as LISA. However, the poor sky localization of GW interferometers will make it challenging to identify the host galaxy of MBH mergers absent an electromagnetic counterpart. One such counterpart is the tidal disruption of a star that has been captured into mean motion resonance with the inspiraling binary. Here we investigate the production of tidal disruption events (TDEs) through capture into, and subsequent evolution in, orbital resonance. We examine the full nonlinear evolution of planar autoresonance for stars that lock in to autoresonance with a shrinking MBH binary. Capture into the 2:1 resonance is guaranteed for any realistic astrophysical parameters (given a relatively small MBH binary mass ratio), and the captured star eventually attains an eccentricity e ≈ 1, leading to a TDE. Stellar disks can be produced around MBHs following an active galactic nucleus episode, and we estimate the TDE rates from resonant capture produced when a secondary MBH begins inspiralling through such a disk. In some cases, the last resonant TDE can occur within a decade of the eventual LISA signal, helping to localize the GW event.

The Effects of Tide on Seepage and Deformation Behaviors of Coastal Foundation Pit

The Effects of Tide on Seepage and Deformation Behaviors of Coastal Foundation Pit

Mapping of water spread dynamics of a tropical Ramsar wetland of India for conservation and management.

Wetlands are dynamic ecosystems vital for sustaining ecological health and development at regional and global scales. Geospatial tools have emerged as essential for managing wetland ecosystems. This study assessed the spatiotemporal dynamics of water spread in the Point Calimere Wetland, a coastal Ramsar site located along the Bay of Bengal, India, from 1984 to 2023. The analysis based on Global Surface Water Explorer (GSWE) and Normalized Difference Water Index (NDWI) derived from Landsat 5, 7, and 8 data revealed that 21% of the total wetland area showed an increasing trend. In comparison, 5.7% of the area showed a decreasing trend of surface water coverage, largely driven by erosion and climatic variability. The mean water spread increased from 119.47 km2 (2000-2003) to 160.88 km2 (2020-2023), with notable seasonal fluctuations. Among all seasons, the monsoon with the highest surge (41.1%) in water dynamics reported the largest water spread in 2020-2023 (221.87 km2). A moderate positive and negative relationship was noted between rainfall and water spread (r = 0.35) and temperature and water spread (r = - 0.43). A marked increase in habitat patches and edge density between 2000-2003 and 2020-2023 indicates the wetland's vulnerability to changing climatic conditions and the critical role of seawater intrusion, shoreline changes, and tidal forces in shaping its hydrological dynamics. The data presented on the historical water dynamics in this study is invaluable for the conservation planning and management of wetlands to support the associated coastal biodiversity and livelihood of the dependent communities.

Black Hole Mass and Optical Radiation Mechanism of the Tidal Disruption Event AT 2023clx

We present the optical light curves of the tidal disruption event AT 2023clx in the declining phase, observed with Mephisto. Combining our light curve with the ASAS-SN and ATLAS data in the rising phase, and fitting the composite multi-band light curves with MOSFiT, we estimate black hole mass for AT 2023clx is between 105.67 and 105.82 M ⊙. This event may be caused by either a full disruption of a 0.1 M ⊙ star, or a partial disruption of a 0.99 M ⊙ star, depending on the data adopted for the rising phase. Based on those fit results and the non-detection of soft X-ray photons in the first 90 days, we propose that the observed optical radiation is powered by stream-stream collision. We speculate that the soft X-ray photons may gradually emerge in 100–600 days after the optical peak, when the debris is fully circularized into a compact accretion disk.

Late-time Radio Brightening and Emergence of a Radio Jet in the Changing-look AGN 1ES 1927+654

We present multifrequency (5–345 GHz) and multiresolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic nuclei (CL-AGNs). The source was first designated a CL-AGN after an optical outburst in late 2017 and has since displayed considerable changes in X-ray emission, including the destruction and rebuilding of the X-ray corona in 2019–2020. Radio observations prior to 2023 show a faint and compact radio source typical of a radio-quiet AGN. Starting in 2023 February, 1ES 1927+654 began exhibiting a radio flare with a steep exponential rise, reaching a peak 60 times previous flux levels, and has maintained this higher level of radio emission for over a year to date. The 5–23 GHz spectrum is broadly similar to gigahertz-peaked radio sources, which are understood to be young radio jets less than ∼1000 yr old. Recent high-resolution Very Long Baseline Array observations at 23.5 GHz now show resolved extensions on either side of the core, with a separation of ∼0.15 pc, consistent with a new and mildly relativistic bipolar outflow. A steady increase in the soft X-ray band (0.3–2 keV) concurrent with the radio may be consistent with jet-driven shocked gas, though further observations are needed to test alternate scenarios. This source joins a growing number of CL-AGNs and tidal disruption events that show late-time radio activity, years after the initial outburst.

Towards submesoscale eddy detection in SDGSAT-1 data through deep learning

ABSTRACT In coastal regions, the formation of submesoscale eddies is frequently influenced by factors including topography, tidal forces, and ocean currents. These eddies are often challenging to detect owing to the limited spatial resolution of altimeters and restricted observation areas. Equipped with a multispectral imager (MSI) specialized in coastal and offshore environments, SDGSAT-1 supports the sustainable development goals. It generates extensive data concerning nearshore resources. However, the multispectral data from SDGSAT-1 exhibit image blurring and indistinct eddy boundaries due to the imaging conditions of remote sensing satellites. This challenge impedes conventional deep learning models from directly identifying these features. Consequently, we developed a multispectral eddy detection network (MEDNet). Given the characteristics of remote sensing images, we employ a linear stretching technique to enhance eddy information in SDGSAT-1 images. Additionally, we propose a multispectral eddy horizontal flip technique (MEHFT) to address the imbalance between cyclonic and anticyclonic eddies in remote sensing imagery. To direct the network’s focus towards critical areas, we incorporate a multi-branch stacking construct and an SPPCSPC module to enhance eddy feature extraction. Experimental results demonstrate that our method achieves high accuracy (mAP of 90.42%) in the dataset, surpassing competing object detection models.

Stability of evolving cluster of stars and exotic matter

AbstractThis paper discusses the phenomenon of evolving spherically symmetric cluster of stars in the presence of an exotic matter. To discuss evolutionary mechanism, we use the Starobinsky model of f(R) gravity as exotic matter and the structure scalars as evolutional parameters. We study various evolution modes such as isotropic pressure, quasi-homologous evolution, density homogeneity, and geodesic nature. The stability of homogeneous density of baryonic and non-baryonic matter is discussed using dissipation, tidal forces, anisotropic pressures, expansion and shear-effects. It is observed that the dark matter has remarkable impact on the evolutionary changes. Also, it is shown that the dissipation factor produces density inhomogeneity in expanding clusters with shear effects. We observe that high curvature geometry enhances quasi-homologous evolution in the presence of shear. We use star Her X-1 as test star to discuss physical behavior of Starobinsky model. It is found that the density of dark matter overcomes the density of matter for large values of dark matter parameter n.

A candidate of high-z central tidal disruption event in quasar SDSS J000118.70+003314.0

Abstract We report a high-redshift (z = 1.404) tidal disruption event (TDE) candidate in SDSS J000118.70+003314.0 (SDSS J0001),which is a quasar with apparent broad Mg ii emission line. The long-term variability in its nine-year photometric ugriz-band light curves, obtained from the SDSS Stripe82 and the PHOTOOBJALL databases, can be described by the conventional TDE model. Our results suggest that the TDE is a main-sequence star with mass of $1.905_{-0.009}^{+0.023}{\rm M_\odot }$ tidally disrupted by a black hole (BH) with mass $6.5_{-2.6}^{+3.5}\times 10^7{\rm M_\odot }$. The BH mass is about 7.5 times smaller than the virial BH mass derived from the broad Mg ii emission line, which can be explained by non-virial dynamic properties of broad emission lines from TDEs debris. Furthermore, we examine the probability that the event results from intrinsic variability of quasars, which is about 0.009%, through applications of the DRW/CAR process. Alternative explanations for the event are also discussed, such as the scenarios of dust obscurations, microlensing and accretion. Our results provide clues to support that TDEs could be detectable in broad line quasars as well as in quiescent galaxies, and to indicate the variability of some active galactic nuclei may be partly attributed to central TDEs.

From one-dimensional to three-dimensional: effect of lateral inhomogeneity on tidal gravity and its implications for lithospheric strength

From one-dimensional to three-dimensional: effect of lateral inhomogeneity on tidal gravity and its implications for lithospheric strength

NGTS-EB-7, an eccentric, long-period, low-mass eclipsing binary

ABSTRACT Despite being the most common types of stars in the Galaxy, the physical properties of late M dwarfs are often poorly constrained. A trend of radius inflation compared to evolutionary models has been observed for earlier type M dwarfs in eclipsing binaries, possibly caused by magnetic activity. It is currently unclear whether this trend also extends to later type M dwarfs below the convective boundary. This makes the discovery of lower mass, fully convective, M dwarfs in eclipsing binaries valuable for testing evolutionary models – especially in longer-period binaries where tidal interaction between the primary and secondary is negligible. With this context, we present the discovery of the NGTS-EB-7 AB system, an eclipsing binary containing a late M dwarf secondary and an evolved G-type primary star. The secondary star has a radius of $0.125\pm 0.006$ R$_{\odot }$, a mass of $0.096^{+0.003}_{-0.004}$ M$_{\odot }$ and follows a highly eccentric (e = $0.71436\pm 0.00085$) orbit every $193.35875\pm 0.00034$ d. This makes NGTS-EB-7 AB the third longest-period eclipsing binary system with a secondary smaller than 200 ${\rm M}_{\rm J}$ with the mass and radius constrained to better than 5 per cent. In addition, NGTS-EB-7 is situated near the centre of the proposed LOPS2 southern field of the upcoming PLATO mission, allowing for detection of the secondary eclipse and measurement of the companion’s temperature. With its long-period and well-constrained physical properties – NGTS-EB-7 B will make a valuable addition to the sample of M dwarfs in eclipsing binaries and help in determining accurate empirical mass/radius relations for later M dwarf stars.

Detection of a Highly Ionized Outflow in the Quasiperiodically Erupting Source GSN 069

Quasiperiodic eruptions (QPEs) are high-amplitude, soft X-ray bursts recurring every few hours, associated with supermassive black holes. Many interpretations for QPEs were proposed since their recent discovery in 2019, including extreme mass ratio inspirals and accretion disk instabilities. But, as of today, their nature still remains debated. We perform the first high-resolution X-ray spectral study of a QPE source using the Reflection Grating Spectrometers' gratings on board XMM-Newton, leveraging nearly 2 Ms of exposure on GSN 069, the first discovered source of this class. We resolve several absorption and emission lines including a strong line pair near the N vii rest-frame energy, resembling the P-Cygni profile. We apply photoionization spectral models and identify the absorption lines as an outflow blueshifted by 1700−2900 km s−1, with a column density of about 1022 cm−2 and an ionization parameter log(ξ /erg cm s−1) of 3.9−4.6. The emission lines are instead redshifted by up to 2900 km s−1, and likely originate from the same outflow that imprints the absorption features, and covers the full 4π sky from the point of view of GSN 069. The column density and ionization are comparable to the outflows detected in some tidal disruption events, but this outflow is significantly faster and has a strong emission component. The outflow is more highly ionized when the system is in the phase during which QPEs are present, and from the limits, we derive on its location, we conclude that the outflow is connected to the recent complex, transient activity of GSN 069, which began around 2010.

Numerical investigation of nonlinear interaction between salinity- and sediment-induced stratification in highly turbid estuaries and coastal seas

ABSTRACT In highly turbid estuaries and coastal seas where freshwater rivers meet the salty ocean, both salinity-induced stratification (SaIS) and sediment-induced stratification (SeIS) are crucial in shaping total estuarine stratification. This study investigates the nonlinearity emerging from the interaction between SaIS and SeIS using a one-dimensional water column model over an erodible bed, driven by a longitudinal salinity gradient and oscillating tidal currents. The results reveal that total stratification deviates significantly from a simple addition of SaIS under clearwater conditions and SeIS under freshwater conditions, indicating a highly nonlinear interaction. The complex spatial and temporal patterns of the nonlinearity arise from the differing source-sink dynamics of salt and sediment. SaIS reduces SeIS during flood but intensifies it during ebb, whereas SeIS consistently strengthens SaIS. This nonlinearity, which exhibits notable flood-ebb asymmetry, is relatively insensitive to changes in tidal forcing compared to salinity gradient forcing, due to the conflicting effects of tidal currents on salinity straining, sediment diffusion, and turbulent mixing. These findings highlight the necessity of incorporating sediment's modulation of classical strain-induced periodic stratification due to salinity gradients in numerical models to improve predictions of buoyancy and stability in highly turbid estuarine and coastal systems.

A binary system in the S cluster close to the supermassive black hole Sagittarius A*

AbstractHigh-velocity stars and peculiar G objects orbit the central supermassive black hole (SMBH) Sagittarius A* (Sgr A*). Together, the G objects and high-velocity stars constitute the S cluster. In contrast with theoretical predictions, no binary system near Sgr A* has been identified. Here, we report the detection of a spectroscopic binary system in the S cluster with the masses of the components of 2.80 ± 0.50 M⊙ and 0.73 ± 0.14 M⊙, assuming an edge-on configuration. Based on periodic changes in the radial velocity, we find an orbital period of 372±3 days for the two components. The binary system is stable against the disruption by Sgr A* due to the semi-major axis of the secondary being 1.59±0.01 AU, which is well below its tidal disruption radius of approximately 42.4 AU. The system, known as D9, shows similarities to the G objects. We estimate an age for D9 of $$2.{7}_{-0.3}^{+1.9}\,\times \,1{0}^{6}$$ 2 . 7 − 0.3 + 1.9 × 1 0 6 yr that is comparable to the timescale of the SMBH-induced von Zeipel-Lidov-Kozai cycle period of about 106 yr, causing the system to merge in the near future. Consequently, the population of G objects may consist of pre-merger binaries and post-merger products. The detection of D9 implies that binary systems in the S cluster have the potential to reside in the vicinity of the supermassive black hole Sgr A* for approximately 106 years.

A Brief Review of Hydrodynamic Circulation in the Mediterranean Gulfs

In this paper, a brief review regarding the hydrodynamic circulation of the Mediterranean gulfs is presented. Studies concerning the hydrodynamics of the Mediterranean gulfs with significant environmental and commercial importance were gathered as an initial insight of studies in the Mediterranean microtidal environment. Numerical models, field measurements, and satellite images are the methods used by the investigators for the description and prediction of the circulation in the gulfs. The basic hydrodynamic characteristics of the gulfs are mainly defined by the wind action and less by tide and baroclinicity. Most of the gulfs are characterized by a cyclonic wind-driven circulation, since the tidal effect remains weak in the Mediterranean basin. However, tidal resonance and strong currents are evident in the shallow coastal areas as well as in the wider area of straits. Basic gulfs’ characteristics are summarized in a table that gives an overview of the main Mediterranean gulfs, which can be especially useful for young researchers or new hydroenvironmental studies in the Mediterranean marine and coastal environment.

Io's tidal response precludes a shallow magma ocean.

Io experiences tidal deformation due to its eccentric orbit around Jupiter, which provides a primary energy source for Io's ongoing volcanic activity and infrared emission1. The amount of tidal energy dissipated within Io is enormous and has been hypothesized to support the large-scale melting of Io's interior and the formation of a global subsurface magma ocean. If Io has a shallow global magma ocean, its tidal deformation would be much larger than in the case of a more rigid, mostly solid interior2. Here we report the measurement of Io's tidal deformation, quantified by the gravitational tidal Love number k2, enabled by two recent flybys of the Juno spacecraft. By combining Juno3,4 and Galileo5-7 Doppler data from the Deep Space Network and astrometric observations, we recover Re(k2) of 0.125±0.047 (1σ) and the tidal dissipation parameter Q of 11.4±3.6 (1σ). These measurements confirm that a shallow global magma ocean in Io does not exist and are consistent with Io having a mostly solid mantle2. Our results indicate that tidal forces do not universally create global magma oceans, which may be prevented from forming due to rapid melt ascent, intrusion, and eruption8,9, so even strong tidal heating - like that expected on several known exoplanets and super-Earths10 - may not guarantee the formation of magma oceans on moons or planetary bodies.

The first all-sky survey of star-forming galaxies with eROSITA. Scaling relations and a population of X-ray luminous starbursts

In this work, we present the results from a study of X-ray normal galaxies, that is, galaxies not harbouring active galactic nuclei (AGN), using data from the first complete all-sky scan of the X-ray survey (eRASS1) obtained with eROSITA on board the Spectrum-Roentgen-Gamma observatory. eRASS1 provides the first unbiased X-ray census of local normal galaxies, thus allowing us to study the X-ray emission (0.2-8.0 ) from X-ray binaries (XRBs) and the hot interstellar medium in the full range of stellar population parameters present in the local Universe. By combining the updated version of the Heraklion Extragalactic Catalogue (HECATE v2.0) value-added catalogue of nearby galaxies (Distance ; lesssim \,200$Mpc) with the X-ray data obtained from eRASS1, we studied the integrated X-ray emission from normal galaxies as a function of their star-formation rate ( ), stellar mass ( ), metallicity, and stellar population age. After applying stringent optical and mid-infrared activity classification criteria, we constructed a sample of 18790 bona fide star-forming galaxies (HEC-eR1 galaxy sample) with measurements of their integrated X-ray luminosity (using each galaxy's D$_ $) over the full range of stellar population parameters present in the local Universe. By stacking the X-ray data in bins, we studied the correlation between the average X-ray luminosity and the average stellar population parameters. We also present updated and -metallicity scaling relations based on a completely blind galaxy sample and accounting for the scatter dependence on the The average X-ray spectrum of star-forming galaxies is well described by a power law ($ $) and a thermal plasma component ($kT = 0.70^ $). We find that the integrated X-ray luminosity of the individual HEC-eR1 star-forming galaxies is significantly elevated (reaching $10^ $) with respect to what is expected from the current standard scaling relations. The observed scatter is also significantly larger. This excess persists even when we measured the average luminosity of galaxies in and metallicity bins, and it is stronger (up to $ sim 2$ dex) towards lower s. Our analysis shows that the excess is not the result of the contribution by hot gas, low-mass XRBs, background AGN, low-luminosity AGN (including tidal disruption events), or stochastic sampling of the XRB X-ray luminosity function. We find that while the excess is generally correlated with lower metallicity galaxies, its primary driver is the age of the stellar populations. Our analysis reveals a sub-population of very X-ray luminous starburst galaxies with higher specific SFRs (sSFRs), lower metallicities, and younger stellar populations. This population drives upwards the X-ray scaling relations for star-forming galaxies and has important implications for understanding the population of XRBs contributing in the most X-ray luminous galaxies in the local and high-redshift Universe. These results demonstrate the power of large blind surveys such eRASS1, which can provide a more complete picture of the X-ray emitting galaxy population and their diversity, revealing rare populations of objects and recovering unbiased underlying correlations.

DalROMS-NWA12 v1.0, a coupled circulation–ice–biogeochemistry modelling system for the northwest Atlantic Ocean: development and validation

Abstract. This study presents DalROMS-NWA12 v1.0, a coupled ocean circulation–sea ice–biogeochemistry modelling system for the northwest Atlantic Ocean (NWA) in which the circulation and biogeochemistry modules are based on ROMS (Regional Ocean Modeling System). The circulation module is coupled to a sea ice module based on the Community Ice CodE (CICE), and the physical ocean state simulated by the circulation module drives the biogeochemical module. Study of the biological carbon pump in the NWA is one of the main intended applications of this model. Global atmospheric and ocean reanalyses are used to force DalROMS-NWA12 at the sea surface and as part of its lateral boundary input, respectively. The modelling system is also forced by tides, riverine freshwater input, and continental runoff. The physical ocean state and sea ice from two simulations of the period 2015–2018, with and without nudging of the simulated temperature and salinity towards a blend of observations and reanalysis, are examined in this study. Statistical comparisons between model results and observations or reanalyses show that the control (nudged) simulation outperforms the prognostic (un-nudged) simulation in reproducing the paths of the Gulf Stream and the West Greenland Current, as well as propagation of the estuarine plume in the Gulf of St. Lawrence. The prognostic simulation performs better in simulating the sea ice concentration. The biogeochemical module, which is run only in the control simulation, performs reasonably well in reproducing the observed spatiotemporal variations in oxygen, nitrate, alkalinity, and total inorganic carbon. To examine the effects of tides and sea ice on the physical fields in the study area, results of simulations from which either component is absent are compared to results of the prognostic simulation. In the absence of tides, Ungava Bay in summer experiences a simulated surface salinity that is higher by up to ∼7 psu than in the simulation with tides, as well as experiencing changes in horizontal distributions of surface temperature and sea ice. Without coupling to the sea ice module, the circulation module produces summertime sea surface temperatures that are higher by up to ∼5 °C in Baffin Bay.