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We present early-phase good-cadence (hour-to-day) simultaneous multiband ( ugi and vrz bands) imaging of the nearby supernova SN 2024ggi, which exploded in the nearby galaxy NGC 3621. A quick follow-up was conducted within less than a day after the explosion and continued for ∼23 days. The uvg band light curves display a rapid rise (∼1.4 mag day ^−1 ) to maximum in ∼4 days and absolute magnitude M _g ∼ −17.75 mag. The postpeak decay rate in redder bands is ∼0.01 mag day ^−1 . Different colors (e.g., u − g and v − r ) of SN 2024ggi are slightly redder than SN 2023ixf. A significant rise (∼12.5 kK) in blackbody temperature (optical) was noticed within ∼2 days after the explosion, which successively decreased, indicating shock break out inside a dense circumstellar medium surrounding the progenitor. Using semianalytical modeling, the ejecta mass and progenitor radius were estimated as 1.2 M _☉ and ∼550 R _☉ . The archival deep images ( g , r , i , and z bands) from the Dark Energy Camera Legacy Survey were examined, and a possible progenitor was detected in each band (∼22–22.5 mag) and had a mass range of 14–17 M _☉ .

We present a catalog of dust clouds at high Galactic latitude based on the Planck 857 GHz dust emission data. Using a clustering hierarchical algorithm, 315 dust clouds at high Galactic latitudes are identified. Additionally, using the optical and ultraviolet extinction of 4 million and 1 million stars, respectively, provided by Sun et al., we derive the distances and physical properties for 190 high Galactic latitude dust clouds and the ultraviolet excess ratios for 165 of them. Through the study of color excess ratios, this work confirms that molecular clouds with large Galactic distances and low extinction likely have a higher proportion of small-sized dust grains. In addition, clouds with well-defined distances in the catalog are used to trace the Local Bubble, showing good consistency with the boundary of the Local Bubble from the literature.

SN 2023ixf, recently reported in the nearby galaxy M101 at a distance of 6.85 Mpc, was one of the closest and brightest core-collapse supernovae in the last decade. In this work, we present multiwavelength photometric observation of SN 2023ixf with the Multi-channel Photometric Survey Telescope (Mephisto) in the uvgr bands and with the twin 50 cm telescopes in the griz bands. We find that the bolometric luminosity reached the maximum value of 3 × 10 ^43 erg s ^−1 at 3.9 days after the explosion and fully settled onto the radioactive tail at ∼90 days. The effective temperature decreased from 3.2 × 10 ^4 K at the first observation and approached a constant of ∼(3000–4000) K after the first 2 months. The evolution of the photospheric radius is consistent with a homologous expansion with a velocity of 8700 km s ^−1 in the first 2 months, and it shrunk subsequently. Based on the radioactive tail, the initial nickel mass is about M _Ni ∼ 0.098 M _⊙ . The explosion energy and the ejecta mass are estimated to be E ≃ (1.0–5.7) × 10 ^51 erg and M _ej ≃ (3.8–16) M _⊙ , respectively. The peak bolometric luminosity is proposed to be contributed by the interaction between the ejecta and the circumstellar medium (CSM). We find a shocked CSM mass of M _CSM ∼ 0.013 M _⊙ , a CSM density of ρ _CSM ∼ 2.5 × 10 ^−13 g cm ^−3 , and a mass-loss rate of the progenitor of $\dot{M}\sim 0.022\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ .

Supernova (SN) 2023ixf was discovered on 2023 May 19. The host galaxy, M101, was observed by the Hobby–Eberly Telescope Dark Energy Experiment collaboration over the period 2020 April 30–2020 July 10, using the Visible Integral-field Replicable Unit Spectrograph (3470 ≲ λ ≲ 5540 Å) on the 10 m Hobby–Eberly Telescope. The fiber filling factor within ±30″ of SN 2023ixf is 80% with a spatial resolution of 1″. The r < 5.″5 surroundings are 100% covered. This allows us to analyze the spatially resolved preexplosion local environments of SN 2023ixf with nebular emission lines. The two-dimensional maps of the extinction and the star formation rate (SFR) surface density (Σ _SFR ) show weak increasing trends in the radial distributions within the r < 5.″5 regions, suggesting lower values of extinction and SFR in the vicinity of the progenitor of SN 2023ixf. The median extinction and that of the surface density of SFR within r < 3″ are E ( B − V ) = 0.06 ± 0.14, and ${{\rm{\Sigma }}}_{\mathrm{SFR}}={10}^{-5.44\pm 0.66}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}\,{\mathrm{arcsec}}^{-2}.$ There is no significant change in extinction before and after the explosion. The gas metallicity does not change significantly with the separation from SN 2023ixf. The metal-rich branch of the R _23 calculations indicates that the gas metallicity around SN 2023ixf is similar to the solar metallicity (∼ Z _☉ ). The archival deep images from the Canada–France–Hawaii Telescope Legacy Survey (CFHTLS) show a clear detection of the progenitor of SN 2023ixf in the z band at 22.778 ± 0.063 mag, but nondetections in the remaining four bands of CFHTLS ( u , g , r , i ). The results suggest a massive progenitor of ≈22 M _☉ .

Modern large-scale photometric surveys have provided us with multiband photometries of billions of stars. Determining the stellar atmospheric parameters, such as the effective temperature ( T _eff ) and metallicities ([Fe/H]), absolute magnitudes ( M _G ), distances ( d ), and reddening values ( E ( G _BP − G _RP )) is fundamental to study the stellar populations, structure, kinematics, and chemistry of the Galaxy. This work constructed an empirical stellar library that maps the stellar parameters to multiband photometries from a data set with Gaia parallaxes, LAMOST atmospheric parameters, and optical to near-infrared photometry from several photometric surveys. Based on the stellar library, we developed a new algorithm, SPar (Stellar Parameters from multiband photometry), which fits the multiband stellar photometries to derive the stellar parameters ( T _eff , [Fe/H], M _G , d , and E ( G _BP − G _RP )) of the individual stars. The algorithm is applied to the multiband photometric measurements of a sample of stars selected from the SMSS survey, which have stellar parameters derived from the spectroscopic surveys. The stellar parameters derived from multiband photometries by our algorithm are in good agreement with those from the spectroscopic surveys. The typical differences between our results and the literature values are 170 K for T _eff , 0.23 dex for [Fe/H], 0.13 mag for M _G , and 0.05 mag for E ( G _BP − G _RP ). The algorithm proved to be robust and effective and will be applied to the data of future large-scale photometric surveys such as the Mephisto and CSST surveys.