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We present highly sampled photometry of the supernova (SN) 2023ixf, a Type II SN in M101, beginning 2 days before its first known detection. To gather these data, we enlisted the global Unistellar Network of citizen scientists. These 252 observations from 115 telescopes show the SN's rising brightness associated with shock emergence followed by gradual decay. We measure a peak $M_{V}$ = -18.18 $\pm$ 0.09 mag at 2023-05-25 21:37 UTC in agreement with previously published analyses., Comment: 4 pages, 1 figure

We constructed a comprehensive model atom for NeI -- NeII using the most up-to-date atomic data available and evaluated the non-local thermodynamic equilibrium (NLTE) line formation for NeI and NeII in classical 1D models representing the atmospheres of B-type stars. We find that the large NLTE strengthening of the NeI lines corresponding to the 2p$^5$3p $-$ 2p$^5$3s transitions array occurs due to extremely small photoionization cross-sections of 2p$^5$3s levels that leads to strong overpopulation of these levels relative to their LTE populations. The deviations from LTE for the most NeII lines are small and do not exceed 0.11~dex in the absolute value. We analysed 20 lines of NeI and 13 lines of NeII for twenty-four B-type stars in the temperature range of 10\,400 $\le$ \Teff\ $\le$ 33\,400~K. For five stars, the NLTE leads to consistent abundances of NeI and NeII, while the difference in LTE abundance can reach up to 0.50~dex. The using of the experimental oscillator strengths recently measured by Piracha et al. (2015) leads to smaller line-by-line scatter for the most investigated stars. The averaged neon abundance in twenty-four B-type stars in solar neighborhood is 8.02$\pm$0.05. This value may provide indirect constraints on solar photospheric neon abundance., Comment: 20 pages, 9 figures, accepted to Astrophysical Journal

We present a model atom for C I - C II - C III - C IV using the most up-to-date atomic data and evaluated the non-local thermodynamic equilibrium (NLTE) line formation in classical 1D atmospheric models of O-B-type stars. Our models predict the emission lines of C II 9903~\AA\ and 18535~\AA\ to appear at effective temperature \Teff~$\geq$~17\,500~K, those of C II 6151~\AA\ and 6461~\AA\ to appear at \Teff~$>$~25\,000~K, and those of C III 5695, 6728--44, 9701--17~\AA\ to appear at \Teff~$\geq$~35\,000~K (log~$g$=4.0). Emission occurs in the lines of minority species, where the photoionization-recombination mechanism provides a depopulation of the lower levels to a greater extent than the upper levels. For C II 9903 and 18535~\AA, the upper levels are mainly populated from C III reservoir through the Rydberg states. For C III 5695 and 6728--44~\AA, the lower levels are depopulated due to photon losses in UV transitions at 885, 1308, and 1426--28~\AA\ which become optically thin in the photosphere. We analysed the lines of C I, C II, C III, and C IV for twenty-two O-B-type stars with temperature range between 15\,800 $\leq$~\Teff~$\leq$ 38\,000~K. Abundances from emission lines of C I, C II and C III are in agreement with those from absorption ones for most of the stars. We obtained log~$\epsilon_{\rm C}$=8.36$\pm$0.08 from twenty B-type stars, that is in line with the present-day Cosmic Abundance Standard. The obtained carbon abundances in 15~Mon and HD~42088 from emission and absorption lines are 8.27$\pm$0.11 and 8.31$\pm$0.11, respectively., Comment: 22 pages, 11 figures

We present a list of weak emission lines (WELs) observed in a sharp-lined B3 V star {\iota} Her (HD 160762) using high resolution (R = 65000) and high SN (~1300) spectral data. The list covers a spectral region between 4900A and 10000A. We register 207 WELs in this star and identified 190 lines including ten ions (nine elements). Emission lines of C II, N I, Cr II, Mn II, and Ni II have been identified among normal B-type stars for the first time. 17 emission lines remain unidentified. We compare our list with the published list of WELs for 3 Cen A (Wahlgren and Hubrig 2004) and found that numbers of detected emission lines reflect differences in abundance between these two stars. We detect 13 C I emission lines in iota Her (normal in C), while only one C I emission line is found in 3 Cen A (deficient in C). Many emission lines of P II and Cu II have been detected in 3 Cen A (overabundant in both P and Cu), while no emission line of these ions has been found in {\iota} Her. Many emission lines of Fe II are visible in the shorter wavelength side of 6000 A in iota Her, while these emission lines are missing in 3 Cen A. Close inspections of spectral data of 3 Cen A reveal that apparently missing Fe II lines appear as absorption lines in this star. Because these two stars have nearly the same atmospheric parameters (Teff and log g), a physical interpretation which is independent on these two parameters is needed to account for this observation., Comment: 13 pages, 7 figures

Abundances of 21 elements in two 3He stars HD 185330 and 3 Cen A have been analysed relative to the well studied sharp-lined B3 V star iota Her. Six elements (P, Ti, Mn, Fe, Ni, and Br) are over-abundant in these two peculiar stars, while six elements (C, O, Mg, Al, S, and Cl) are under-abundant. Absorption lines of the two rarely observed heavy elements Br II and Kr II are detected in both stars and these elements are both over-abundant. The centroid wavelengths of the Ca II infrared triplet lines in these stars are red-shifted relative to those lines in iota Her and the presence of heavy isotopes of Ca (mass number 44 - 46) in these two stars are confirmed. In spite of these similarities, there are several remarkable differences in the abundance pattern between these two stars. N is under-abundant in HD 185330, as in many Hg-Mn stars, while it is significantly over-abundant in 3 Cen A. P and Ga are both over-abundant in 3 Cen A, while only P is over-abundant and no trace of absorption line of Ga II can be found in HD 185330. Large over-abundances of Kr and Xe are found in both stars, while the abundance ratios Kr / Xe are significantly different between them (-1.4 dex in HD 185330 and +1.2 dex in 3 Cen A). Some physical explanations are needed to account for these qualitative differences., Comment: 12 pages,13 figures, accepted for publication in PASJ

Previously unrecognized weak emission lines originating from high excitation states of Si II (12.84 eV) and Al II (13.08 eV) are detected in the red region spectra of slowly rotating early B-type stars. We surveyed high resolution spectra of 35 B-type stars covering spectral sub-types between B1 and B7 near the main sequence and found the emission line of SiII at 6239.6 A in all 13 stars having spectral sub-types B2 and B2.5. There are 17 stars belonging to sub-type B3 and seven stars among them are found to show the emission line of Si II. The emission line of Al II at 6243.4 A is detected in a narrower temperature range (Teff between 19000K and 23000 K) in nine stars. Both of these emission lines are not detected in cooler (Teff < 16000 K) stars in our sample. The emission line of Si II at 6239.6 A shows a single-peaked and symmetric profile and the line center has no shift in wavelength with respect to those of low excitation absorption lines of Si II. Measured half width of the emission line is the same as those of rotationally broadened low excitation absorption lines of Si II. These observations imply that the emitting gas is not circumstellar origin, but is located at the outermost layer of the atmosphere, covering the whole stellar surface and co-rotates with the star., Comment: 6 pages, 4 figures, 2 tables, accepted for publication in Publ. Astron. Soc. Japan