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We present an analysis of very early high-resolution spectroscopic observations of the Type II supernova (SN) 2024ggi, a nearby SN that occurred in the galaxy NGC 3621 at a distance of 7.24 Mpc (\\(z\\approx0.002435\\)). These observations represent the earliest high-resolution spectra of a Type II SN ever made. We analyzed the very early-phase spectroscopic evolution of SN 2024ggi obtained in a short interval at 20.6 and 27.8 h after its discovery, or 26.6 and 33.8 h after the SN first light. Observations were obtained with the high-resolution spectrograph MIKE (\\(R \\approx 22600 - 28000\\)) at the 6.5 m Magellan Clay Telescope, located at the Las Campanas Observatory, on the night of April 12, 2024 UT. We analyzed the evolution of ions of HI, HeI, HeII, NIII, CIII, SiIV, NIV and CIV detected across the spectra. We modeled these features with multiple Gaussian and Lorentzian profiles, and estimated their velocities and full widths at half maximum (FWHMs). The spectra show asymmetric emission lines of HI, HeII, CIV, and NIV that can be described by narrow Gaussian cores with broader Lorentzian wings, and symmetric narrow emission lines of HeI, NIII, and CIII. The emission lines of HeI are detected only in the first spectrum, indicating the rapid ionization of HeI to HeII. The narrow components of the emission lines show a systematic blueshift relative to their zero-velocity position, with an increase of \\(\\sim18\\) km s\\(^{-1}\\) in the average velocity between the two epochs. The broad Lorentzian components show a blueshift in velocity relative to the narrow components, and a significant increase in the average velocity of \\(\\sim103\\) km s\\(^{-1}\\). Such a rapid evolution and significant ionization changes in a short period of time were never observed before, and are probably a consequence of the radiative acceleration generated in the SN explosion.

The purpose is to develop a non-viral gene delivery system that meets the requirements of colloidal stability of DNA complexes expressed in terms of no particle aggregation under physiologic conditions. The system should be used to transfect cardiovascular tissues. We used a strategy based on the formation of polyelectrolyte nanoparticles by deposition of alternatively charged polyelectrolytes onto a DNA core. Polyelectrolytes were transfer RNA as well as the synthetic polyanion, polyvinyl sulfate (PVS), and the polycation polyethylenimine (PEI). The PEI/DNA complex formed the DNA core. We observed that the DNA is condensed by polycations and further packaged by association with a polyanion. These nanoparticles exhibited negative surface charge and low aggregation tendency. In vivo rat carotid artery experiments revealed high transfection efficiency, not only with the reporter gene but also with the gene encoding human urokinase plasminogen activator (Hu-uPA). Hu-uPA is one of the proteins involved in the recovery of the blood vessels after balloon catheter injury and therefore clinically relevant. A strategy for in vivo gene transfer is proposed that uses the incorporation of polyanions as RNA or PVS into PEI/DNA complexes in order to overcome colloidal instability and to generate a negative surface charge. The particles proved to be transfectionally active in vascular gene transfer.

We use the {\\it Gaia} EDR3 to explore the Galactic supernova remnant SNR G272.2-3.2, produced by the explosion of a Type Ia supernova (SNIa), about 7,500 years ago, to search for a surviving companion. From the abundances in the SNR ejecta, G272.2-3.2 is a normal SN Ia. The {\\it Gaia} parallaxes allow to select the stars located within the estimated distance range of the SNR, and the {\\it Gaia} proper motions to study their kinematics. From the {\\it Gaia} EDR3 photometry, we construct the HR diagram of the selected sample, which we compare with the theoretical predictions for the evolution of possible star companions of SNIa. We can discard several proposed types of companions by combining kinematics and photometry. We can also discard hypervelocity stars. We focus our study on the kinematically most peculiar star, {\\it Gaia} EDR3 5323900215411075328 (hereafter MV-G272), a 8.9 \\(\\sigma\\) outlier in proper motion. It is of M1-M2 stellar type. Its trajectory on the sky locates it at the center of the SNR, 6,000--8,000 years ago, a unique characteristic among the the sample. Spectra allow a stellar parameters determination and a chemical abundance analysis. In conclusion, we have a candidate to be the surviving companion of the SN Ia that resulted in SNR G272.2-3.2. It is supported by its kinematical characteristics and its trajectory within the SNR. This opens the possibility of a single-degenerate scenario for a SN Ia with an M-type dwarf companion.

We present optical photometry and spectroscopy of the superluminous SN 2002gh from maximum light to \\(+204\\) days, obtained as part of the Carnegie Type II Supernova (CATS) project. SN 2002gh is among the most luminous discovered supernovae ever, yet it remained unnoticed for nearly two decades. Using Dark Energy Camera archival images we identify the potential SN host galaxy as a faint dwarf galaxy, presumably having low metallicity, and in an apparent merging process with other nearby dwarf galaxies. We show that SN 2002gh is among the brightest hydrogen-poor SLSNe with \\(M_{V} = -22.40 \\pm 0.02\\), with an estimated peak bolometric luminosity of \\(2.6 \\pm 0.1 \\times 10^{44}\\) erg s\\(^{-1}\\). We discount the decay of radioactive nickel as the main SN power mechanism, and assuming that the SN is powered by the spin down of a magnetar we obtain two alternative solutions. The first case, is characterized by significant magnetar power leakage, and \\(M_{\\mathrm{ej}}\\) between 0.6 and 3.2 \\(M_{\\odot}\\), \\(P_{\\mathrm{spin}} = 3.2\\) ms, and \\(B = 5 \\times 10^{13}\\) G. The second case does not require power leakage, resulting in a huge ejecta mass of about 30 \\(M_{\\odot}\\), a fast spin period of \\(P_{\\mathrm{spin}} \\sim 1\\) ms, and \\(B\\sim 1.6 \\times 10^{14}\\) G. We estimate a zero-age main-sequence mass between 14 and 25 \\(M_{\\odot}\\) for the first case and of about 135 \\(M_{\\odot}\\) for the second case. The latter case would place the SN progenitor among the most massive stars observed to explode as a SN.

We present optical and IR observations from maximum light until around 600 d of SN 2022jli, a peculiar SE SN showing two maxima, each one with a peak luminosity of about 3 x 10^{42} erg/s and separated by 50 d. The second maximum is followed by periodic undulations with a period of P ~ 12.5 days. The spectra and the photometric evolution of the first maximum are consistent with the behaviour of a standard SE SN with an ejecta mass of 1.5 +/- 0.4 Msun, and a nickel mass of 0.12 +/- 0.01 Msun. The optical spectra after 400 d correspond to a standard SN Ic event, and at late times SN 2022jli exhibits a significant drop in the optical luminosity implying that the physical phenomena that produced the secondary maximum has ceased to power the SN light curve. One possibility is that the second maximum is powered by a magnetar with an initial spin period of P=48.5 ms and a magnetic field of B = 8.5x10^{14} G, while the light curve periodic undulations could be produced by accretion of material from a companion star onto the neutron star in a binary system. The near-IR spectra shows clear 1st CO overtone emission from about 190 d after the first maximum, and it becomes undetected at 400 d. A significant near-IR excess from hot dust emission is detected at 238 d produced by either newly formed dust in the SN ejecta or due to a strong near-IR dust echo. Depending on the assumptions of the dust composition, the estimated dust mass is 2-16 x 10^{-4} Msun. The magnetar power of the second maximum can fit in a more general picture where magnetars are the power source of super-luminous SNe, could produce their frequent bumps and undulations, and where pulsars could produce the late time excess observed in some SE SNe. The detection of CO and the potential detection of dust formed in the ejecta of SN2022jli are important to understand the formation molecules and dust in the ejecta of SE SNe.

We assess the robustness of the two highest rungs of the \"cosmic distance ladder\" for Type Ia supernovae and the determination of the Hubble-Lemaître constant. In this analysis, we hold fixed Rung 1 as the distance to the LMC determined to 1 % using Detached Eclipsing Binary stars. For Rung 2 we analyze two methods, the TRGB and Cepheid distances for the luminosity calibration of Type Ia supernovae in nearby galaxies. For Rung 3 we analyze various modern digital supernova samples in the Hubble flow, such as the Calán-Tololo, CfA, CSP, and Supercal datasets. This metadata analysis demonstrates that the TRGB calibration yields smaller \\(H_0\\) values than the Cepheid calibration, a direct consequence of the systematic difference in the distance moduli calibrated from these two methods. Selecting the three most independent possible methodologies/bandpasses (\\(B\\), \\(V\\), \\(J\\)), we obtain \\(H_{0}=69.9 \\pm 0.8\\) and \\(H_{0} =73.5 \\pm 0.7\\) km s\\(^{-1}\\) Mpc\\(^{-1}\\) from the TRGB and Cepheid calibrations, respectively. Adding in quadrature the systematic uncertainty in the TRGB and Cepheid methods of 1.1 and 1.0 km s\\(^{-1}\\) Mpc\\(^{-1}\\), respectively, this subset reveals a significant 2.0 \\(\\sigma\\) systematic difference in the calibration of Rung 2. If Rung 1 and Rung 2 are held fixed, the different formalisms developed for standardizing the supernova peak magnitudes yield consistent results, with a standard deviation of 1.5 km s\\(^{-1}\\) Mpc\\(^{-1}\\), that is, Type Ia supernovae are able to anchor Rung 3 with 2 % precision. This study demonstrates that Type Ia supernovae have provided a remarkably robust calibration of R3 for over 25 years.

We present high-cadence optical, ultraviolet (UV), and near-infrared data of the nearby (\\(D\\approx23\\) Mpc) Type II supernova (SN) 2021yja. Many Type II SNe show signs of interaction with circumstellar material (CSM) during the first few days after explosion, implying that their red supergiant (RSG) progenitors experience episodic or eruptive mass loss. However, because it is difficult to discover SNe early, the diversity of CSM configurations in RSGs has not been fully mapped. SN 2021yja, first detected within \\({\\approx}5.4\\) hours of explosion, shows some signatures of CSM interaction (high UV luminosity, radio and x-ray emission) but without the narrow emission lines or early light curve peak that can accompany CSM. Here we analyze the densely sampled early light curve and spectral series of this nearby SN to infer the properties of its progenitor and CSM. We find that the most likely progenitor was an RSG with an extended envelope, encompassed by low-density CSM. We also present archival Hubble Space Telescope imaging of the host galaxy of SN 2021yja, which allows us to place a stringent upper limit of \\({\\lesssim}9\\ M_\\odot\\) on the progenitor mass. However, this is in tension with some aspects of the SN evolution, which point to a more massive progenitor. Our analysis highlights the need to consider progenitor structure when making inferences about CSM properties, and that a comprehensive view of CSM tracers should be made to give a fuller view of the last years of RSG evolution.

We present panchromatic observations and modeling of the Calcium-rich supernova 2019ehk in the star-forming galaxy M100 (d\\(\\approx\\)16.2 Mpc) starting 10 hours after explosion and continuing for ~300 days. SN 2019ehk shows a double-peaked optical light curve peaking at \\(t = 3\\) and \\(15\\) days. The first peak is coincident with luminous, rapidly decaying \\(\\textit{Swift}\\)-XRT discovered X-ray emission (\\(L_x\\approx10^{41}~\\rm{erg~s^{-1}}\\) at 3 days; \\(L_x \\propto t^{-3}\\)), and a Shane/Kast spectral detection of narrow H\\(\\alpha\\) and He II emission lines (\\(v \\approx 500\\) km/s) originating from pre-existent circumstellar material. We attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at \\(r<10^{15}\\) cm and the resulting cooling emission. We calculate a total CSM mass of \\(\\sim\\) \\(7\\times10^{-3}\\) \\(\\rm{M_{\\odot}}\\) with particle density \\(n\\approx10^{9}\\,\\rm{cm^{-3}}\\). Radio observations indicate a significantly lower density \\(n < 10^{4}\\,\\rm{cm^{-3}}\\) at larger radii. The photometric and spectroscopic properties during the second light curve peak are consistent with those of Ca-rich transients (rise-time of \\(t_r =13.4\\pm0.210\\) days and a peak B-band magnitude of \\(M_B =-15.1\\pm0.200\\) mag). We find that SN 2019ehk synthesized \\((3.1\\pm0.11)\\times10^{-2} ~ \\rm{M_{\\odot}}\\) of \\({}^{56}\\textrm{Ni}\\) and ejected \\(M_{\\rm ej} = (0.72\\pm 0.040)~\\rm{M_{\\odot}}\\) total with a kinetic energy \\(E_{\\rm k}=(1.8\\pm0.10)\\times10^{50}~\\rm{erg}\\). Finally, deep \\(\\textit{HST}\\) pre-explosion imaging at the SN site constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (~10 \\(\\rm{M_{\\odot}}\\)) in binaries that lost most of their He envelope or white dwarfs. The explosion and environment properties of SN 2019ehk further restrict the potential WD progenitor systems to low-mass hybrid HeCO WD + CO WD binaries.

We present a comprehensive dataset of optical and near-infrared photometry and spectroscopy of type~Ia supernova (SN) 2016hnk, combined with integral field spectroscopy (IFS) of its host galaxy, MCG -01-06-070, and nearby environment. Properties of the SN local environment are characterized by means of single stellar population synthesis applied to IFS observations taken two years after the SN exploded. SN 2016hnk spectra are compared to other 1991bg-like SNe Ia, 2002es-like SNe Ia, and Ca-rich transients. In addition, abundance stratification modelling is used to identify the various spectral features in the early phase spectral sequence and the dataset is also compared to a modified non-LTE model previously produced for the sublumnious SN 1999by. SN 2016hnk is consistent with being a sub-luminous (M\\(_{\\rm B}=-16.7\\) mag, s\\(_{\\rm BV}\\)=0.43\\(\\pm\\)0.03), highly reddened object. IFS of its host galaxy reveals both a significant amount of dust at the SN location, as well as residual star formation and a high proportion of old stellar populations in the local environment compared to other locations in the galaxy, which favours an old progenitor for SN 2016hnk. Inspection of a nebular spectrum obtained one year after maximum contains two narrow emission lines attributed to the forbidden [Ca II] \\(\\lambda\\lambda\\)7291,7324 doublet with a Doppler shift of 700 km s\\(^{-1}\\). Based on various observational diagnostics, we argue that the progenitor of SN 2016hnk was likely a near Chandrasekhar-mass (\\(M_{\\rm Ch}\\)) carbon-oxygen white dwarf that produced 0.108 \\(M_\\odot\\) of \\(^{56}\\)Ni. Our modeling suggests that the narrow [Ca II] features observed in the nebular spectrum are associated with \\(^{48}\\)Ca from electron capture during the explosion, which is expected to occur only in white dwarfs that explode near or at the \\(M_{\\rm Ch}\\) limit.

Hydrogen-rich, core-collapse supernovae are typically divided into four classes: IIP, IIL, IIn, and IIb. In general, interaction with circumstellar material is only considered for Type IIn supernovae. However, recent hydrodynamic modeling of IIP and IIL supernovae requires circumstellar material to reproduce their early light curves. In this scenario, IIL supernovae experience large amounts of mass loss before exploding. We test this hypothesis on ASASSN-15oz, a Type IIL supernova. With extensive follow-up in the X- ray, UV, optical, IR, and radio we present our search for signs of interaction, and the mass-loss history indicated by their detection. We find evidence of short-lived intense mass-loss just prior to explosion from light curve modeling, amounting in 1.5 M\\(_{\\odot}\\) of material within 1800 R\\(_{\\odot}\\) of the progenitor. We also detect the supernova in the radio, indicating mass-loss rates of \\(10^{-6}-10^{-7}\\) M\\(_{\\odot}\\) yr\\(^{-1}\\) prior to the extreme mass-loss period. Our failure to detect the supernova in the X-ray and the lack of narrow emission lines in the UV, optical, and NIR do not contradict this picture and place an upper limit on the mass-loss rate outside the extreme period of \\(<10^{-4}\\) M\\(_{\\odot}\\) yr\\(^{-1}\\). This paper highlights the importance gathering comprehensive data on more Type II supernovae to enable detailed modeling of the progenitor and supernova which can elucidate their mass-loss histories and envelope structures and thus inform stellar evolution models.