Search

Neutral hydrogen (H i ) is the primary component of the cool interstellar medium (ISM) and is the reservoir of fuel for star formation. Owing to the sensitivity of existing radio telescopes, our understanding of the evolution of the ISM in galaxies remains limited, as it is based on only a few hundred galaxies detected in H i beyond the local Universe. With the high sensitivity of the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we carried out a blind H i search, the FAST Ultra-Deep Survey, which extends to redshifts up to 0.42 and a sensitivity of 50 μ Jy beam ^−1 . Here, we report the first discovery of six galaxies in H i at z > 0.38. For these galaxies, the FAST angular resolution of ∼4′ corresponds to a mean linear size of $\sim 1.3\,{h}_{70}^{-1}\,$ Mpc. These galaxies are among the most distant H i emission detections known, with one having the most massive H i content ( ${10}^{10.93\pm 0.04}\,{h}_{70}^{-2}\,{M}_{\odot }$ ). Using recent data from the DESI survey and new observations with the Hale, Big Telescope Alt-azimuth, and Keck telescopes, optical counterparts are detected for all galaxies within the 3 σ positional uncertainty ( $0.5\,{h}_{70}^{-1}\,$ Mpc) and 200 km s ^−1 in recession velocity. Assuming that the dominant source of H i is the identified optical counterpart, we find evidence of evolution in the H i content of galaxies over the last 4.2 Gyr. Our new high-redshift H i galaxy sample provides the opportunity to better investigate the evolution of cool gas in galaxies. A larger sample size in the future will allow us to refine our knowledge of the formation and evolution of galaxies.

During routine survey imaging, the reactivated Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE-R) serendipitously caught the Type II supernova SN 2023ixf in Messier 101 on the rise, starting day 3.6 through day 10.9, and again on the decline at late times from days 211 through 213 and days 370 through 372. We have considered these mid-IR data together with observations from the ultraviolet (UV) through the near-IR, when possible. At day 3.6 we approximated the optical emission with a hot, ∼26,630 K blackbody, with a notable UV excess inferred to result from strong supernova (SN) shock interaction with circumstellar matter (CSM). In the IR, however, a clear excess is also obvious, and we fit it with a cooler, ∼1620 K blackbody with a radius of ∼2.6 × 10 ^15 cm, consistent with dust in the progenitor’s circumstellar shell likely heated by the UV emission from the CSM interaction. On day 10.8, the light detected was consistent with SN ejecta-dominated emission. At late times we also observed a clear NEOWISE-R excess, which could arise either from newly formed dust in the inner ejecta or in the contact discontinuity between the forward and reverse shocks, or from more distant pre-existing dust grains in the SN environment. Furthermore, the large 4.6 μ m excess at late times can also be explained by the emergence of the carbon monoxide 1–0 vibrational band. SN 2023ixf is the best-observed SN II in the mid-IR during the first several days after the explosion and one of the most luminous such SNe ever seen.

We present the discovery and analysis of SN 2022oqm, a Type Ic supernova (SN) detected

Over recent decades, robotic (or highly automated) searches for supernovae (SNe) have discovered several thousand events, many of them in quite nearby galaxies (distances < 30 Mpc). Most of these SNe, including some of the best-studied events to date, were found before maximum brightness and have associated with them extensive follow-up photometry and spectroscopy. Some of these discoveries are so-called “SN impostors,” thought to be superoutbursts of luminous blue variable stars, although possibly a new, weak class of massive-star explosions. We conducted a Snapshot program with the Hubble Space Telescope (HST) and obtained images of the sites of 31 SNe and four impostors, to acquire late-time photometry through two filters. The primary aim of this project was to reveal the origin of any lingering energy for each event, whether it is the result of radioactive decay or, in some cases, ongoing late-time interaction of the SN shock with preexisting circumstellar matter, or the presence of a light echo. Alternatively, lingering faint light at the SN position may arise from an underlying stellar population (e.g., a host star cluster, companion star, or a chance alignment). The results from this study complement and extend those from Snapshot programs by various investigators in previous HST cycles.

We follow our first paper with an analysis of the ensemble of the extensive preexplosion ground- and space-based infrared observations of the red supergiant (RSG) progenitor candidate for the nearby core-collapse supernova SN 2023ixf in Messier 101, together with optical data prior to the explosion obtained with the Hubble Space Telescope (HST). We have confirmed the association of the progenitor candidate with the supernova (SN), as well as constrained the metallicity at the SN site, based on SN observations with instruments at Gemini-North. The internal host extinction to the SN has also been confirmed from a high-resolution Keck spectrum. We fit the observed spectral energy distribution (SED) for the star, accounting for its intrinsic variability, with dust radiative-transfer modeling, which assumes a silicate-rich dust shell ahead of the underlying stellar photosphere. The star is heavily dust obscured, likely the dustiest progenitor candidate yet encountered. We found median estimates of the star’s effective temperature and luminosity of 2770 K and 9.0 × 10 ^4 L _⊙ , with 68% credible intervals of 2340–3150 K and (7.5–10.9) × 10 ^4 L _⊙ , respectively. The candidate may have a Galactic RSG analog, IRC −10414, with a strikingly similar SED and luminosity. Via comparison with single-star evolutionary models we have constrained the initial mass of the progenitor candidate from 12 M _⊙ to as high as 14 M _⊙ . We have had available to us an extraordinary view of the SN 2023ixf progenitor candidate, which should be further followed up in future years with HST and the James Webb Space Telescope.

We present early-time ground-based optical follow-up observations of GRB 180418A, which was discovered by both Swift/BAT and Fermi/GBM. Its broadband afterglow was well monitored by Swift/XRT and ground-based optical telescopes. The optical light curve of GRB 180418A can be modeled by forward shock (FS) plus reverse shock (RS). We fit the light curves with standard external shock models and derive the physical properties of the outflow. It is found that the ratio R _B ≡ ε _B _, _r / ε _B _, _f is 11.22, indicating a moderate degree of magnetization in the RS region. The reported duration of GRB 180418A, T _90 , lies in the intermediate region between short and long gamma-ray bursts (GRBs). We further discuss the classification of GRB 180418A, and calculate ε = E _γ _,iso,52 / E _p _, _z _,2 values of 0.026 and 0.018 (assuming the redshift z is 1.0 and 1.5, respectively), which is closer to short GRBs (SGRBs) in the ε - T _90, _z plane. If GRB 180418A is an SGRB, it is the only reported SGRB thus far with RS emission in optical light curves. In order to compare the properties of GRB 180418A, we collected three SGRBs that may have RS emission (GRBs 060313, 090426, and 210207B) and also 22 long GRBs (LGRBs) with RS emission. We find that the parameters of LGRBs are in a wider range than those of SGRBs. Also, SGRBs appear to have very small R _B values, but the results are generally similar to those of LGRBs. The fitting parameters of GRB 180418A are generally consistent with those of the other three SGRBs, implying that GRB 180418A may belong to the category of SGRBs.

We present an analysis of ground-based and JWST observations of SN 2022pul, a peculiar “03fg-like” (or “super-Chandrasekhar”) Type Ia supernova (SN Ia), in the nebular phase at 338 days postexplosion. Our combined spectrum continuously covers 0.4–14 μ m and includes the first mid-infrared spectrum of a 03fg-like SN Ia. Compared to normal SN Ia 2021aefx, SN 2022pul exhibits a lower mean ionization state, asymmetric emission-line profiles, stronger emission from the intermediate-mass elements (IMEs) argon and calcium, weaker emission from iron-group elements (IGEs), and the first unambiguous detection of neon in a SN Ia. A strong, broad, centrally peaked [Ne ii ] line at 12.81 μ m was previously predicted as a hallmark of “violent merger” SN Ia models, where dynamical interaction between two sub- M _Ch white dwarfs (WDs) causes disruption of the lower-mass WD and detonation of the other. The violent merger scenario was already a leading hypothesis for 03fg-like SNe Ia; in SN 2022pul it can explain the large-scale ejecta asymmetries seen between the IMEs and IGEs and the central location of narrow oxygen and broad neon. We modify extant models to add clumping of the ejecta to reproduce the optical iron emission better, and add mass in the innermost region (

We present optical photometry for the afterglow of GRB 221009A, in some respects the most extraordinary gamma-ray burst (GRB) ever observed. Good quality in the R -band light curve is obtained, covering 0.32–19.57 days since the Fermi-Gamma-Ray Burst Monitor trigger. We find that a weak bump emerges from the declining afterglow at t ≈ 11 days; a supernova (SN) may be responsible. We use a smooth broken power-law and ^56 Ni model to fit the light curve. The best-fitting results reveal that the SN ejected a total mass of M _ej = 3.70 M _⊙ , a ^56 Ni mass of M _Ni = 0.23 M _⊙ , and a kinetic energy of ${E}_{\mathrm{SN},{\rm{K}}}=2.35\times {10}^{52}\,\mathrm{erg}$ . We also compare GRB 221009A with other GRB–SN events based on a GRB-associated SN sample and find that only SN 2003lw and SN 2011kl can be obviously revealed in the afterglow of GRB 221009A by setting these objects at its distance. This suggests that a supernova (SN 2022xiw) is possibly obscured by the brighter afterglow emission from GRB 221009A.

We present comprehensive optical observations of SN 2021gmj, a Type II supernova (SN II) discovered within a day of explosion by the Distance Less Than 40 Mpc survey. Follow-up observations show that SN 2021gmj is a low-luminosity SN II (LL SN II), with a peak magnitude M _V = −15.45 and an Fe ii velocity of ∼1800 km s ^−1 at 50 days past explosion. Using the expanding photosphere method, we derive a distance of ${17.8}_{-0.4}^{+0.6}$ Mpc. From the tail of the light curve we obtain a radioactive nickel mass of ${M}_{{}^{56}\mathrm{Ni}}$ = 0.014 ± 0.001 M _⊙ . The presence of circumstellar material (CSM) is suggested by the early-time light curve, early spectra, and high-velocity H α in absorption. Analytical shock-cooling models of the light curve cannot reproduce the fast rise, supporting the idea that the early-time emission is partially powered by the interaction of the SN ejecta and CSM. The inferred low CSM mass of 0.025 M _⊙ in our hydrodynamic-modeling light-curve analysis is also consistent with our spectroscopy. We observe a broad feature near 4600 Å, which may be high-ionization lines of C, N, or/and He ii . This feature is reproduced by radiation-hydrodynamic simulations of red supergiants with extended atmospheres. Several LL SNe II show similar spectral features, implying that high-density material around the progenitor may be common among them.

The afterglows of gamma-ray bursts are believed to have originated from a relativistic jet, which is driven by the merger of compact binary objects or the core collapse of massive stars. Some of their jets may consist of two components: a faster (but narrower) jet and a slower (but wider) jet. The light curves produced by the interaction between the two-component jet and the surrounding medium typically exhibit a chromatic break in multiple bands. For GRB 191221B, the optical light curve of the afterglow exhibits a plateau from 33 to 143 s, followed by a steeper decay that is consistent with the characteristics of reverse shock from an arbitrarily magnetized ejecta. The flattening at ∼10 ks exhibits chromaticity relative to the X-ray afterglow. We propose that the two-component jet scenario can explain this observational result: For the X-ray afterglow, the narrow jet forward shock is dominated until ∼10 ks, and then both the narrow and wide components contribute comparable flux from the forward shock. For the optical afterglow, the first 2 ks is dominated by the narrow jet reverse shock emission (the plateau from 33 to 143 s is due to the jet being magnetized). Between 2 and 10 ks, the forward shock of the narrow jet dominates the optical afterglow, then transitions to wide component forward shock dominance, causing a chromatic plateau. For radio afterglow, the data are only presented after 10 ^5 s, which is dominated by the wide jet forward shock emission.

We present extensive photometric and spectroscopic observations of the nearby Type Ia supernova (SN) 2023wrk at a distance of about 40 Mpc. The earliest detection of this SN can be traced back to a few hours after the explosion. Within the first few days, the light curve shows a bump feature, while the B − V color is blue and remains nearly constant. The overall spectral evolution is similar to that of an SN 1991T/SN 1999aa-like SN Ia, while the C ii λ 6580 absorption line appears to be unusually strong in the first spectrum taken at t ≈ −15.4 days after the maximum light. This carbon feature disappears quickly in subsequent evolution but it reappears at around the time of peak brightness. The complex evolution of the carbon line and the possible detection of Ni iii absorption around 4700 Å and 5300 Å in the earliest spectra indicate macroscopic mixing of fuel and ash. The strong carbon lines are likely related to the collision of SN ejecta with unbound carbon, consistent with the predictions of pulsational delayed-detonation or carbon-rich circumstellar-matter interaction models. Among those carbon-rich SNe Ia with strong C ii λ 6580 absorption at very early times, the line-strength ratio of C ii to Si ii and the B − V color evolution are found to exhibit large diversity, which may be attributed to different properties of unbound carbon and outward-mixing ^56 Ni.

We present extensive observations and analysis of supernova (SN) SN 2021dbg, utilizing optical photometry and spectroscopy. For approximately 385 days following the explosion, SN 2021dbg exhibited remarkable luminosity, surpassing most Type II SNe (SNe II). This initial high luminosity is potentially attributed to interaction between the ejected material and the surrounding circumstellar material (CSM), as evidenced by the pronounced interaction signatures observed in its spectra. The subsequent high luminosity is primarily due to the significant ^56 Ni mass (0.17 ± 0.05 M _⊙ ) produced in the explosion. Based on the flux of flash emission lines detected in the initial spectra, we estimate that the CSM mass near the progenitor amounted to ∼(1.0–2.0) × 10 ^−3 M _⊙ , likely resulting from intense stellar wind activity 2–3 yr preceding the explosion. Considering the bolometric light curve, nebular spectrum modeling, and mass-loss rate, we suggest that the progenitor of SN 2021dbg was a red supergiant (RSG) with a mass of ∼20 M _⊙ and a radius of 1200 R _⊙ . This RSG featured a thick hydrogen shell, which may have contained a region with a sharp decrease in material density, electron density, and temperature, contributing to its layered structure. This object demonstrates mixed features of Type IIP and IIL SNe, making it a transitional event linking the above two subclasses of SNe II.

We present optical and near-infrared (NIR) observations of SN 2022crv, a stripped-envelope supernova in NGC 3054, discovered within 12 hr of explosion by the Distance Less Than 40 Mpc Survey. We suggest that SN 2022crv is a transitional object on the continuum between Type Ib supernovae (SNe Ib) and Type IIb supernovae (SNe IIb). A high-velocity hydrogen feature (∼ −20,000 to −16,000 km s ^−1 ) was conspicuous in SN 2022crv at early phases, and then quickly disappeared. We find that a hydrogen envelope of ∼10 ^−3 M _⊙ can reproduce the observed behavior of the hydrogen feature. The lack of early envelope cooling emission implies that SN 2022crv had a compact progenitor with an extremely low amount of hydrogen. A nebular spectral analysis shows that SN 2022crv is consistent with the explosion of a He star with a final mass of ∼4.5–5.6 M _⊙ that evolved from a ∼16 to 22 M _⊙ zero-age main-sequence star in a binary system with ∼1.0–1.7 M _⊙ of oxygen finally synthesized in the core. In order to retain such a small amount of hydrogen, the initial orbital separation of the binary system is likely larger than ∼1000 R _⊙ . The NIR spectra of SN 2022crv show a unique absorption feature on the blue side of the He i line at ∼1.005 μ m. This is the first time such a feature has been observed in SNe Ib/IIb, and it could be due to Sr II. Further detailed modeling of SN 2022crv can shed light on the progenitor and the origin of the mysterious absorption feature in the NIR.

Abstract The most recent outbreak of 2019 novel coronavirus, named as COVID-19, caused pneumonia epidemic in Wuhan with 2121 deaths cases as of February 20th 2020. Identification of effective antiviral agents to combat the novel coronavirus is urgently needed. Citrus fruit peel or wild citrus are rich in flavonoids, and clinically documented for roles in relief of cough and promotion of digestive health. Therefore, citrus fruits are assumed to possess antivirus activities or enhance the host immunity. A previous study found that hesperetin could act as a high potent inhibitor of SARS-CoV 3CLpro. We determined six flavonoid compounds’ content in three citrus species by using LC–MS technique. The content of naringin and naringenin was at higher levels in pummelo. Hesperetin and hesperidin were highly accumulated in mandarin and sweet orange. The subsequent in vitro and in vivo experiments indicated that naringin could inhibit the expression of the proinflammatory cytokines (COX-2, iNOS, IL-1β and IL-6) induced by LPS in Raw macrophage cell line, and may restrain cytokine through inhibiting HMGB1 expression in a mouse model. The results revealed that naringin may have a potential application for preventing cytokine storm. We simulated molecular docking to predict the binding affinity of those flavonoids to bind Angiotensin-converting enzyme 2 (ACE 2), which is a receptor of the coronavirus. Consideration of the potential anti-coronavirus and anti-inflammatory activity of flavonoids, the citrus fruit or its derived phytochemicals are promising in the use of prevention and treatment of SARS-CoV-2 infection. Graphical Abstract

We present six epochs of optical spectropolarimetry of the Type II supernova (SN) 2023ixf ranging from ∼2 to 15 days after the explosion. Polarimetry was obtained with the Kast double spectrograph on the Shane 3 m telescope at Lick Observatory, representing the earliest such observations ever captured for an SN. We observe a high continuum polarization p _cont ≈ 1% on days +1.4 and +2.5 before dropping to 0.5% on day +3.5, persisting at that level up to day +14.5. Remarkably, this change coincides temporally with the disappearance of highly ionized “flash” features. The decrease of the continuum polarization is accompanied by a ∼70° rotation of the polarization position angle (PA) as seen across the continuum. The early evolution of the polarization may indicate different geometric configurations of the electron-scattering atmosphere as seen before and after the disappearance of the emission lines associated with highly ionized species (e.g., He ii , C iv , and N iii ), which are likely produced by elevated mass loss shortly prior to the SN explosion. We interpret the rapid change of polarization and PA from days +2.5 to +4.5 as the time when the SN ejecta emerge from the dense asymmetric circumstellar material (CSM). The temporal evolution of the continuum polarization and the PA is consistent with an aspherical SN explosion that exhibits a distinct geometry compared to the CSM. The rapid follow-up spectropolarimetry of SN 2023ixf during the shock ionization phase reveals an exceptionally asymmetric mass-loss process leading up to the explosion.

Precision contact probes have a huge demand in industrial manufacturing due to their high accuracy. However, the passive measurement mode of the existing probe easily causes wear of the probe ball and loss of accuracy during continuous contact scanning. In this paper, a PZT(piezoelectric actuators)-driven flexible probe is proposed with the dynamic time-domain function of the system response from low frequency to high drive frequency. The low-frequency measurement mode is established based on the linear response of the triangle wave. In order to avoid the trajectory nonlinearity of the stylus ball driven by PZT, the nonlinear mapping of the PZT hysteresis model is constructed by the BP neural network, and the linearly weighted particle swarm optimization (PSO) algorithm is used to realize the suppression of the response nonlinearity. Finally, the measurement experiment of the PZT-driven probe is conducted to reveal the measurement characteristics of low-frequency mode as well as measurement capability compared with commercial sensors.

We combine our dynamical modeling black-hole mass measurements from the Lick AGN Monitoring Project 2016 sample with measured cross-correlation time lags and line widths to recover individual scale factors, f , used in traditional reverberation-mapping analyses. We extend our sample by including prior results from Code for AGN Reverberation and Modeling of Emission Lines ( caramel ) studies that have utilized our methods. Aiming to improve the precision of black-hole mass estimates, as well as uncover any regularities in the behavior of the broad-line region (BLR), we search for correlations between f and other AGN/BLR parameters. We find (i) evidence for a correlation between the virial coefficient ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\sigma })$ and black-hole mass, (ii) marginal evidence for a similar correlation between ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma })$ and black-hole mass, (iii) marginal evidence for an anticorrelation of BLR disk thickness with ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\mathrm{FWHM}})$ and ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\mathrm{FWHM}})$ , and (iv) marginal evidence for an anticorrelation of inclination angle with ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\mathrm{FWHM}})$ , ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma })$ , and ${\mathrm{log}}_{10}({f}_{\mathrm{mean},\sigma })$ . Last, we find marginal evidence for a correlation between line-profile shape, when using the root-mean-square spectrum, ${\mathrm{log}}_{10}{(\mathrm{FWHM}/\sigma )}_{\mathrm{rms}}$ , and the virial coefficient, ${\mathrm{log}}_{10}({f}_{\mathrm{rms},\sigma })$ , and investigate how BLR properties might be related to line-profile shape using caramel models.

When discovered, SN 2017egm was the closest (redshift z = 0.03) hydrogen-poor superluminous supernova (SLSN-I) and a rare case that exploded in a massive and metal-rich galaxy. Thus, it has since been extensively observed and studied. We report spectroscopic data showing strong emission at around He i λ 10830 and four He i absorption lines in the optical. Consequently, we classify SN 2017egm as a member of an emerging population of helium-rich SLSNe-I (i.e., SLSNe-Ib). We also present our late-time photometric observations. By combining them with archival data, we analyze high-cadence ultraviolet, optical, and near-infrared light curves spanning from early pre-peak (∼−20 days) to late phases (∼+300 days). We obtain its most complete bolometric light curve, in which multiple bumps are identified. None of the previously proposed models can satisfactorily explain all main light-curve features, while multiple interactions between the ejecta and circumstellar material (CSM) may explain the undulating features. The prominent infrared excess with a blackbody luminosity of 10 ^7 –10 ^8 L _⊙ detected in SN 2017egm could originate from the emission of either an echo of a pre-existing dust shell or newly formed dust, offering an additional piece of evidence supporting the ejecta–CSM interaction model. Moreover, our analysis of deep Chandra observations yields the tightest-ever constraint on the X-ray emission of an SLSN-I, amounting to an X-ray-to-optical luminosity ratio ≲10 ^−3 at late phases (∼100–200 days), which could help explore its close environment and central engine.

We have conducted photometric and spectroscopic observations of the peculiar Type Ia supernova (SN Ia) 2016ije that was discovered through the Tsinghua-NAOC Transient Survey. This peculiar object exploded in the outskirts of a metal-poor, low-surface brightness galaxy (i.e., M _g = −14.5 mag). Our photometric analysis reveals that SN 2016ije is subluminous ( ${M}_{B,\max }$ = −17.65 ± 0.06 mag) but exhibits relatively broad light curves (Δ m _15 ( B ) = 1.35 ± 0.14 mag), similar to the behavior of SN 2002es. Our analysis of the bolometric light curve indicates that only 0.14 ± 0.04 M _⊙ of ^56 Ni was synthesized in the explosion of SN 2016ije, which suggests a less energetic thermonuclear explosion when compared to normal SNe Ia, and this left a considerable amount of unburned materials in the ejecta. Spectroscopically, SN 2016ije resembles other SN 2002es-like SNe Ia, except that the ejecta velocity inferred from its carbon absorption line (∼4500 km s ^−1 ) is much lower than that from silicon lines (∼8300 km s ^−1 ) at around the maximum light. Additionally, most of the absorption lines are broader than other 02es-like SNe Ia. These peculiarities suggest the presence of significant unburned carbon in the inner region and a wide line-forming region along the line of sight. These characteristics suggest that SN 2016ije might originate from the violent merger of a white dwarf binary system, when viewed near an orientation along the iron-group-element cavity caused by the companion star.

We search the archival Zwicky Transient Facility public survey for rapidly evolving transient (RET) candidates based on well-defined criteria between 2018 May and 2021 December. The search yielded 19 bona fide RET candidates, corresponding to a discovery rate of ∼5.2 events per year. Even with a Galactic latitude cut of 20°, eight of the 19 events (∼42%) are Galactic, including one with a light-curve shape closely resembling that of the GW170817 kilonova (KN). An additional event is a nova in M31. Four out of the 19 events (∼21%) are confirmed extragalactic RETs (one confirmed here for the first time) and the origin of six additional events cannot be determined. We did not find any extragalactic events resembling the GW170817 KN, from which we obtain an upper limit on the volumetric rate of GW170817-like KNe of R ≤ 2400 Gpc ^−3 yr ^−1 (95% confidence). These results can be used for quantifying contaminants to RET searches in transient alert streams, specifically when searching for KNe independently of gravitational-wave and gamma-ray-burst triggers.

We present observations of SN 2022joj, a peculiar Type Ia supernova discovered by the Zwicky Transient Facility. SN 2022joj exhibits an unusually red g _ZTF − r _ZTF color at early times and a rapid blueward evolution afterward. Around maximum brightness, SN 2022joj shows a high luminosity ( ${M}_{{g}_{\mathrm{ZTF}},\max }\simeq -19.7$ mag), a blue broadband color ( g _ZTF − r _ZTF ≃ −0.2 mag), and shallow Si ii absorption lines, consistent with those of overluminous, SN 1991T-like events. The maximum-light spectrum also shows prominent absorption around 4200 Å, which resembles the Ti ii features in subluminous, SN 1991bg-like events. Despite the blue optical-band colors, SN 2022joj exhibits extremely red ultraviolet minus optical colors at maximum luminosity ( u − v ≃ 0.6 mag and uvw 1 − v ≃ 2.5 mag), suggesting a suppression of flux at ∼2500–4000 Å. Strong C ii lines are also detected at peak. We show that these unusual spectroscopic properties are broadly consistent with the helium-shell double detonation of a sub-Chandrasekhar mass ( M ≃ 1 M _⊙ ) carbon/oxygen white dwarf from a relatively massive helium shell ( M _s ≃ 0.04–0.1 M _⊙ ), if observed along a line of sight roughly opposite to where the shell initially detonates. None of the existing models could quantitatively explain all the peculiarities observed in SN 2022joj. The low flux ratio of [Ni ii ] λ 7378 to [Fe ii ] λ 7155 emission in the late-time nebular spectra indicates a low yield of stable Ni isotopes, favoring a sub-Chandrasekhar mass progenitor. The significant blueshift measured in the [Fe ii ] λ 7155 line is also consistent with an asymmetric chemical distribution in the ejecta, as is predicted in double-detonation models.

Nebular-phase observations of peculiar Type Ia supernovae (SNe Ia) provide important constraints on progenitor scenarios and explosion dynamics for both these rare SNe and the more common, cosmologically useful SNe Ia. We present observations from an extensive ground- and space-based follow-up campaign to characterize SN 2022pul, a super-Chandrasekhar mass SN Ia (alternatively “03fg-like” SN), from before peak brightness to well into the nebular phase across optical to mid-infrared (MIR) wavelengths. The early rise of the light curve is atypical, exhibiting two distinct components, consistent with SN Ia ejecta interacting with dense carbon–oxygen (C/O)-rich circumstellar material (CSM). In the optical, SN 2022pul is most similar to SN 2012dn, having a low estimated peak luminosity ( M _B = −18.9 mag) and high photospheric velocity relative to other 03fg-like SNe. In the nebular phase, SN 2022pul adds to the increasing diversity of the 03fg-like subclass. From 168 to 336 days after peak B -band brightness, SN 2022pul exhibits asymmetric and narrow emission from [O i ] λ λ 6300, 6364 (FWHM ≈ 2000 km s ^−1 ), strong, broad emission from [Ca ii ] λ λ 7291, 7323 (FWHM ≈ 7300 km s ^−1 ), and a rapid Fe iii to Fe ii ionization change. Finally, we present the first ever optical-to-MIR nebular spectrum of an 03fg-like SN Ia using data from JWST. In the MIR, strong lines of neon and argon, weak emission from stable nickel, and strong thermal dust emission (with T ≈ 500 K), combined with prominent [O i ] in the optical, suggest that SN 2022pul was produced by a white dwarf merger within C/O-rich CSM.

Contact scanning probes have higher accuracy than non-contact probes in industrial applications. But changes of the measured surface and adjustment of velocity and acceleration may cause random measurement deviations, which are mainly determined by dynamic characteristics of the probe system. To realize the prediction of measurement deviations related to scanning parameters, this paper proposes a simpler detection method of dynamic performance. In this article, the dynamic response characteristics of the probe to diverse external stimuli are studied theoretically and experimentally on the basis of the original probe design. Under different scanning variables including the amplitude, spacing and shape of the surface, velocity and acceleration, the integration of the second-order vibration model and external excitation forms the theoretical basis for quantitative analysis of the system response, and numerical simulation and three sets of experiments are designed to effectively verify the deviation distribution of the system response caused by different scanning parameters in the time and frequency domains.

The process of seed germination is crucial not only for the completion of the plant life cycle but also for agricultural production and food chemistry; however, the underlying metabolic regulation mechanism involved in this process is still far from being clearly revealed. In this study, one indica variety (Zhenshan 97, with rapid germination) and one japonica variety (Nipponbare, with slow germination) in rice were used for in-depth analysis of the metabolome at different germination stages (0, 3, 6, 9, 12, 24, 36, and 48 h after imbibition, HAI) and exploration of key metabolites/metabolic pathways. In total, 380 annotated metabolites were analyzed by using a high-performance liquid chromatography (HPLC)-based targeted method combined with a nontargeted metabolic profiling method. By using bioinformatics and statistical methods, the dynamic changes in metabolites during germination in the two varieties were compared. Through correlation analysis, coefficient of variation analysis and differential accumulation analysis, 74 candidate metabolites that may be closely related to seed germination were finally screened. Among these candidates, 29 members belong to the ornithine–asparagine–polyamine module and the shikimic acid–tyrosine–tryptamine–phenylalanine–flavonoid module. As the core member of the second module, shikimic acid’s function in the promotion of seed germination was confirmed by exogenous treatment. These results told that nitrogen flow and antioxidation/defense responses are potentially crucial for germinating seeds and seedlings. It deepens our understanding of the metabolic regulation mechanism of seed germination and points out the direction for our future research.