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We present a systematic analysis of the X-ray emission of a sample of 17 optically selected, X-ray-detected tidal disruption events (TDEs) discovered between 2014 and 2021. The X-ray light curves show a diverse range of temporal behaviors, with most sources not following the expected power-law decline. The X-ray spectra are mostly extremely soft and consistent with thermal emission from the innermost region of an accretion disk, which cools as the accretion rate decreases. Three sources show formation of a hard X-ray corona at late times. The spectral energy distribution shape, probed by the ratio (L BB/L X) between the UV/optical and X-ray, shows a wide range of L BB/L X ∈ (0.5, 3000) at early times and converges to disklike values of L BB/L X ∈ (0.5, 10) at late times. We estimate the fraction of optically discovered TDEs with L X ≥ 1042 erg s−1 to be at least 40% and show that X-ray loudness is independent of black hole mass. We argue that distinct disk formation timescales are unlikely to be able to explain the diverse range of X-ray evolution. We combine our sample with X-ray-discovered ones to construct an X-ray luminosity function, best fit by a broken power law, with a break at L X ≈ 1044 erg s−1. We show that there is no dichotomy between optically and X-ray-selected TDEs; instead, there is a continuum of early-time L BB/L X, at least as wide as L BB/L X ∈ (0.1, 3000), with optical/X-ray surveys selecting preferentially, but not exclusively, from the higher/lower end of the distribution. Our findings are consistent with unification models for the overall TDE population.

We conduct a systematic tidal disruption event (TDE) demographics analysis using the largest sample of optically selected TDEs. A flux-limited, spectroscopically complete sample of 33 TDEs is constructed using the Zwicky Transient Facility over 3 yr (from 2018 October to 2021 September). We infer the black hole (BH) mass (M BH) with host galaxy scaling relations, showing that the sample M BH ranges from 105.1 M ⊙ to 108.2 M ⊙. We developed a survey efficiency corrected maximum volume method to infer the rates. The rest-frame g-band luminosity function can be well described by a broken power law of ϕ(Lg)∝Lg/Lbk0.3+Lg/Lbk2.6−1 , with L bk = 1043.1 erg s−1. In the BH mass regime of 105.3 ≲ (M BH/M ⊙) ≲ 107.3, the TDE mass function follows ϕ(MBH)∝MBH−0.25 , which favors a flat local BH mass function ( dnBH/dlogMBH≈constant ). We confirm the significant rate suppression at the high-mass end (M BH ≳ 107.5 M ⊙), which is consistent with theoretical predictions considering direct capture of hydrogen-burning stars by the event horizon. At a host galaxy mass of M gal ∼ 1010 M ⊙, the average optical TDE rate is ≈3.2 × 10−5 galaxy−1 yr−1. We constrain the optical TDE rate to be [3.7, 7.4, and 1.6] × 10−5 galaxy−1 yr−1 in galaxies with red, green, and blue colors.

We present AT2020mrf (SRGe J154754.2+443907), an extra-galactic (z = 0.1353) fast blue optical transient (FBOT) with a rise time of t g,rise = 3.7 days and a peak luminosity of M g,peak = −20.0. Its optical spectrum around peak shows a broad (v ∼ 0.1c) emission feature on a blue continuum (T ∼ 2 × 104 K), which bears a striking resemblance to AT2018cow. Its bright radio emission (ν L ν = 1.2 × 1039 erg s−1; ν rest = 7.4 GHz; 261 days) is similar to four other AT2018cow-like events, and can be explained by synchrotron radiation from the interaction between a sub-relativistic (≳0.07–0.08c) forward shock and a dense environment ( Ṁ≲10−3M⊙yr−1 for v w = 103 km s−1). AT2020mrf occurs in a galaxy with M * ∼ 108 M ⊙ and specific star formation rate ∼10−10 yr−1, supporting the idea that AT2018cow-like events are preferentially hosted by dwarf galaxies. The X-ray luminosity of AT2020mrf is the highest among FBOTs. At 35–37 days, SRG/eROSITA detected luminous (L X ∼ 2 × 1043 erg s−1; 0.3–10 keV) X-ray emission. The X-ray spectral shape (f ν ∝ ν −0.8) and erratic intraday variability are reminiscent of AT2018cow, but the luminosity is a factor of ∼20 greater than AT2018cow. At 328 days, Chandra detected it at L X ∼ 1042 erg s−1, which is >200 times more luminous than AT2018cow and CSS161010. At the same time, the X-ray emission remains variable on the timescale of ∼1 day. We show that a central engine, probably a millisecond magnetar or an accreting black hole, is required to power the explosion. We predict the rates at which events like AT2018cow and AT2020mrf will be detected by SRG and Einstein Probe.

AT2022cmc was recently reported as the first on-axis jetted tidal disruption event (TDE) discovered in the last decade, and the fourth on-axis jetted TDE candidate known so far. In this work, we present NuSTAR hard X-ray (3–30 keV) observations of AT2022cmc, as well as soft X-ray (0.3–6 keV) observations obtained by NICER, Swift, and XMM-Newton. Our analysis reveals that the broadband X-ray spectra can be well described by a broken power law with f ν ∝ ν −0.5 (f ν ∝ ν −1) below (above) the rest-frame break energy of E bk ∼ 10 keV at the observer frame t obs = 7.8 and 17.6 days since discovery. At t obs = 36.2 days, the X-ray spectrum is consistent with either a single power law or a broken power law. By modeling the spectral energy distribution from radio to hard X-ray across the three NuSTAR observing epochs, we find that the submillimeter/radio emission originates from external shocks at large distances ≳1017 cm from the black hole, the UV/optical light comes from a thermal envelope with radius ∼1015 cm, and the X-ray emission is consistent with synchrotron radiation powered by energy dissipation at intermediate radii within the (likely magnetically dominated) jet. We constrain the bulk Lorentz factor of the jet to be of the order 10–100. Our interpretation differs from the model proposed by Pasham et al. where both the radio and X-rays come from the same emitting zone in a matter-dominated jet. Our model for the jet X-ray emission has broad implications on the nature of relativistic jets in other sources such as gamma-ray bursts.

This study aimed to investigate the preventive effects of isostrictiniin (ITN) from Nymphaea candida against acute lung injury (ALI) through lipopolysaccharide (LPS)-induced ALI mice and LPS-induced A549 cells. Compared with the model group, ITN (50 and 100 mg/kg) significantly reduced the lung indexes, W/D rates, BALF WBC counts, and total protein contents in ALI mice (p < 0.05), as well as the blood neu counts (p < 0.01), while increasing the blood lym counts (p < 0.01). ITN (50 and 100 mg/kg) also markedly decreased the lung tissue TNF-α, IL-6, IL-1β, MDA, and MPO activities in ALI mice (p < 0.01) and enhanced the SOD and GSH levels (p < 0.01). Additionally, ITN (50 and 100 mg/kg) significantly improved lung histopathological damage in ALI mice. Moreover, ITN (10 and 25 µM) significantly reduced the NO, PGE2, IL-1β, IL-6, TNF-α, and MDA levels in LPS-induced A549 cells (p < 0.01) while significantly increasing the SOD and GSH activities (p < 0.01). After LPS-induced A549 cells, the Keap1, p-JNK/JNK, p-ERK1/2/ERK1/2, p-P38/P38, p-IκBα/IκBα, and p-NF-κBp65/NF-κB p65 levels were significantly upregulated (p < 0.05), whereas the Nrf2 and HO-1 protein expressions were downregulated (p < 0.05). After treatment with ITN (25 μM), the changes in these relative protein expressions in LPS-induced A549 cells were significantly reversed (p < 0.05). The above results indicate that ITN has a better preventive effect against ALI, and its mechanisms are related to the regulation of the Keap1-Nrf2/HO-1 and MAPK/NF-κB signaling pathways.

Observations of the extragalactic (z = 0.0141) transient AT 2018cow established a new class of energetic explosions shocking a dense medium, producing luminous emission at millimeter and submillimeter wavelengths. Here we present detailed millimeter- through centimeter-wave observations of a similar transient, ZTF 20acigmel (AT 2020xnd), at z = 0.2433. Using observations from the NOrthern Extended Millimeter Array and the Very Large Array, we model the unusual millimeter and radio emission from AT 2020xnd under several different assumptions and ultimately favor synchrotron radiation from a thermal electron population (relativistic Maxwellian). The thermal electron model implies a fast but subrelativistic (v ≈ 0.3c) shock and a high ambient density (n e ≈ 4 × 103 cm−3) at Δt ≈ 40 days. The X-ray luminosity of L X ≈ 1043 erg s−1 exceeds simple predictions from the radio and UVOIR luminosity and likely has a separate physical origin, such as a central engine. Using the fact that month-long luminous (L ν ≈ 2 × 1030 erg s−1 Hz−1 at 100 GHz) millimeter emission appears to be a generic feature of transients with fast (t 1/2 ≈ 3 days) and luminous (M peak ≈ −21 mag) optical light curves, we estimate the rate at which transients like AT 2018cow and AT 2020xnd will be detected by future wide-field millimeter transient surveys such as CMB-S4 and conclude that energetic explosions in dense environments may represent a significant population of extragalactic transients in the 100 GHz sky.

2D materials, such as graphene, black phosphorous and transition metal dichalcogenides, have gained persistent attention in the past few years thanks to their unique properties for optoelectronics. More importantly, introducing 2D materials into silicon photonic devices will greatly promote the performance of optoelectronic devices, including improvement of response speed, reduction of energy consumption, and simplification of fabrication process. Moreover, 2D materials meet the requirements of complementary metal‐oxide‐semiconductor compatible silicon photonic manufacturing. A comprehensive overview and evaluation of state‐of‐the‐art 2D photonic integrated devices for telecommunication applications is provided, including light sources, optical modulators, and photodetectors. Optimized by unique structures such as photonic crystal waveguide, slot waveguide, and microring resonator, these 2D material‐based photonic devices can be further improved in light‐matter interactions, providing a powerful design for silicon photonic integrated circuits. 2D materials have gained persistent attention in the past few years and they meet the requirements of complementary metal‐oxide‐semiconductor compatible silicon photonic manufacturing. A comprehensive overview of fabrication and evaluation of state‐of‐the‐art 2D photonic integrated devices for telecommunication applications is provided, including light sources, optical modulators, and photodetectors in on‐chip devices.

Structural health monitoring (SHM) is critical to maintaining safe and reliable civil infrastructure, but the optimal design of an SHM sensing system, i.e., optimal sensor placement (OSP), remains a complex challenge. Based on the existing literature, this paper presents a comprehensive review of OSP strategies for SHM. It covers the key steps in OSP, from evaluation criteria to efficient optimization algorithms. The evaluation criteria are classified into six groups, while the optimization algorithms are roughly categorized into three classes. The advantages and disadvantages of each group of methods have been summarized, aiming to benefit the OSP strategy selection in future projects. Then, the real-world implementation of OSP on bridges, high-rise buildings, and other engineering structures, is presented. Based on the current progress, the challenges of OSP are recognized; its future development directions are recommended. This study equips researchers/practitioners with an integrated perspective on state-of-the-art OSP. By highlighting key developments, persistent challenges, and prospects, it is expected to bridge the gap between theory and practice.

The host galaxies of tidal disruption events (TDEs) have been shown to possess peculiar properties, including high central light concentrations, unusual star formation histories, and “green” colors. The ubiquity of these large-scale galaxy characteristics among TDE host populations suggests that they may serve to boost the TDE rate in such galaxies by influencing the nuclear stellar dynamics. We present the first population study of integral field spectroscopy for 13 TDE host galaxies across all spectral classes and X-ray brightnesses with the purpose of investigating their large-scale properties. We derive the black hole masses via stellar kinematics (i.e., the M–σ relation) and find masses in the range 5.0≲log(MBH/M⊙)≲8.0 , with a distribution dominated by black holes with M BH ∼ 106 M ⊙. We find one object with M BH ≳ 108 M ⊙, above the “Hills mass”, which if the disrupted star was of solar type, allows a lower limit of a ≳ 0.16 to be placed on its spin, lending further support to the proposed connection between featureless TDEs and jetted TDEs. We also explore the level of rotational support in the TDE hosts, quantified by (V/σ) e , a parameter that has been shown to correlate with the stellar age and may explain the peculiar host-galaxy preferences of TDEs. We find that the TDE hosts exhibit a broad range in (V/σ) e following a similar distribution as E + A galaxies, which have been shown to be overrepresented among TDE host populations.

In this work, we use the Jansky Very Large Array Sky Survey to compile the first sample of six radio-selected tidal disruption events (TDEs) with transient optical counterparts. While we still lack the statistics to do detailed population studies of radio-selected TDEs, we use these events to suggest trends in host galaxy and optical light-curve properties that may correlate with the presence of radio emission and hence can inform optically selected TDE radio follow-up campaigns. We find tentative trends that radio-selected TDEs tend to have faint and cool optical flares, as well as host galaxies with low supermassive black hole masses, although larger samples are required to establish these trends as statistically significant. Our radio-selected TDEs also tend to have more energetic, larger radio-emitting regions than radio-detected, optically selected TDEs. We consider possible explanations for these trends, including by invoking super-Eddington accretion and enhanced circumnuclear media. Finally, we constrain the radio-emitting TDE rate to be ≳10 Gpc−3 yr−1.