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We report the results of an unsupervised decomposition of the local stellar halo in the chemodynamical space spanned by the abundance measurements from APOGEE DR17 and GALAH DR3. In our Gaussian mixture model, only four independent components dominate the halo in the solar neighborhood, three previously known, Aurora, Splash, and Gaia-Sausage/Enceladus (GS/E), and one new, Eos. Only one of these four is of accreted origin, namely, the GS/E, thus supporting the earlier claims that the GS/E is the main progenitor of the Galactic stellar halo. We show that Aurora is entirely consistent with the chemical properties of the so-called Heracles merger. In our analysis in which no predefined chemical selection cuts are applied, Aurora spans a wide range of [Al/Fe] with a metallicity correlation indicative of a fast chemical enrichment in a massive galaxy, the young Milky Way. The new halo component dubbed Eos is classified as in situ given its high mean [Al/Fe]. Eos shows strong evolution as a function of [Fe/H], where it changes from being the closest to GS/E at its lowest [Fe/H] to being indistinguishable from the Galactic low-α population at its highest [Fe/H]. We surmise that at least some of the outer thin disk of the Galaxy started its evolution in the gas polluted by the GS/E, and Eos is evidence of this process.

We present BVRI and unfiltered (Clear) light curves of 70 stripped-envelope supernovae (SESNe), observed between 2003 and 2020, from the Lick Observatory Supernova Search (LOSS) follow-up program. Our SESN sample consists of 19 spectroscopically normal SNe Ib, two peculiar SNe Ib, six SNe Ibn, 14 normal SNe Ic, one peculiar SN Ic, ten SNe Ic-BL, 15 SNe IIb, one ambiguous SN IIb/Ib/c, and two superluminous SNe. Our follow-up photometry has (on a per-SN basis) a mean coverage of 81 photometric points (median of 58 points) and a mean cadence of 3.6 d (median of 1.2 d). From our full sample, a subset of 38 SNe have pre-maximum coverage in at least one passband, allowing for the peak brightness of each SN in this subset to be quantitatively determined. We describe our data collection and processing techniques, with emphasis toward our automated photometry pipeline, from which we derive publicly available data products to enable and encourage further study by the community. Using these data products, we derive host-galaxy extinction values through the empirical colour evolution relationship and, for the first time, produce accurate rise-time measurements for a large sample of SESNe in both optical and infrared passbands. By modeling multiband light curves, we find that SNe Ic tend to have lower ejecta masses and lower ejecta velocities than SNe Ib and IIb, but higher 56Ni masses.

In this work, BV RI light curves of 55 Type II supernovae (SNe II) from the Lick Observatory Supernova Search program obtained with the Katzman Automatic Imaging Telescope and the 1 m Nickel telescope from 2006 to 2018 are presented. Additionally, more than 150 spectra gathered with the 3 m Shane telescope are published. We conduct an analyse of the peak absolute magnitudes, decline rates, and time durations of different phases of the light and colour curves. Typically, our light curves are sampled with a median cadence of 5.5 days for a total of 5093 photometric points. In average V-band plateau declines with a rate of 1.29 mag (100 days) −1 , which is consistent with previously published samples. For each band, the plateau slope correlates with the plateau length and the absolute peak magnitude: SNe II with steeper decline have shorter plateau duration and are brighter. A time-evolution analysis of spectral lines in term of velocities and pseudoequivalent widths is also presented in this paper. Our spectroscopic sample ranges between 1 and 200 days post-explosion and has a median ejecta expansion velocity at 50 days post-explosion of 6500 km s −1 (Hα line) and a standard dispersion of 2000 km s −1 . Nebular spectra are in good agreement with theoretical models using a progenitor star having a mass < 16 M . All the data are available to the community and will help to understand SN II diversity better, and therefore to improve their utility as cosmological distance indicators.