The origin of lithium (Li) and its production process have long been an unsettled question in cosmology and astrophysics. Candidates environments of Li production events or sites suggested by previous studies include big bang nucleosynthesis, interactions of energetic cosmic rays with interstellar matter, evolved low mass stars, novae, and supernova explosions.Chemical evolution models and observed stellar Li abundances suggest that at least half of the present Li abundance may have been produced in red giants, asymptotic giant branch (AGB) stars, and novae [1][2][3] . However, no direct evidence for the supply of Li from stellar ob- High-resolution spectra (R = 90, 000-60, 000) of V339 Del were obtained at four epochs after its outburst (+38, +47, +48, and +52 d). These spectra contain a series of broad emission lines originating from neutral hydrogen (H I, Balmer series) and other permitted transitions of neutral or singly ionized species (e.g., Fe II, He I, Ca II). These emission lines are usually seen in post-outburst spectra of classical novae. Most of these broad emission lines are accompanied by sharp and blue-shifted multiple absorption lines at their blue edges. The typical radial velocity (v rad ) of these highly blue-shifted absorption lines is ∼ −1, 000 km s −1 . Figure 1- There are no Na I D doublet lines, which are often found to be the strongest absorption features in novae within a few weeks after their outbursts 8,10 . We interpret this as indicating that the ionization state of the ejected gas has evolved into a higher stage of excitation before our observing epochs (5-7 weeks). The observed spectral energy distribution of this nova indicates that the shape of the continuous radiation had entered a very hot stage (effective temperature >100,000 K) within 5 weeks after the explosion 11 . Other observed characteristics of this nova (e.g., light curves, optical and UV emission lines) show that it is a typical Fe II nova with a CO white dwarf (WD) 12,13 .Among these absorption line systems, we have noticed two remarkable pairs of absorption features near 312 nm. These correspond to the absorption components originating from transitions 3 at ∼313 nm. These pairs are marked as A, B and C, D, respectively, in Figure 1- The transition probability of the 7 Be II line at 313.0583 nm (log gf = −0.178) is twice as large as that of the 7 Be II at 313.1228 nm (log gf = −0.479) 14 . Due to saturation effects, the ratio of their equivalent widths is expected to be in the range between 2 (no saturation) to 1 (complete saturation). The measured ratios are 1.1 ± 0.3 and 1.6 ± 0.4 for the components at v rad = −1, 268and −1, 103 km s −1 , respectively. These are within the range expected for the doublet, although the values contain some errors ( ∼ < ±25%) due mainly to the uncertainty in the continuum placement.The weaker component at v rad = −1, 268 km s −1 has a ratio closer to complete saturation. This can 4 be interpreted as resulting from the fact that the absorbing gas cloud moving with v rad = −1, 268 km s...

We report spectroscopic observations of the resonance lines of singly ionized 7 Be in the blue-shifted absorption line systems found in the post-outburst spectra of two classical novae -V5668 Sgr (Nova Sagittarii 2015 No. 2) and V2944 Oph (Nova Ophiuchi 2015). The unstable isotope, 7 Be, should has been created during the thermonuclear runaway (TNR) of these novae and decays to form 7 Li within a short period (a half-life of 53.22 days). Confirmations of 7 Be are the second and the third ones following the first case found in V339 Del by Tajitsu et al. (2015). The blue-shifted absorption line systems in both novae are clearly divided into two velocity components, both of which contain 7 Be. This means that the absorbing gases in both velocity components consist of products of TNR. We estimate amounts of 7 Be produced during outbursts of both novae and conclude that significant 7 Li should have been created. These findings strongly suggest that the explosive production of 7 Li via the reaction 3 He(α,γ) 7 Be and subsequent decay to 7 Li occurs frequently among classical novae and contributes to the process of the Galactic Li enrichment.

The Andromeda Galaxy recurrent nova M31N 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. With a measured recurrence period of =  P 351 13 rec days (we believe the true value to be half of this) and a white dwarf very close to the Chandrasekhar limit, M31N 2008-12a has become the leading pre-explosion supernova type Ia progenitor candidate. Following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground-and space-based follow-up programs. In this paper we present the 2015 detection, visible to near-infrared photometry and visible spectroscopy, and ultraviolet and X-ray observations from the Swiftobservatory. The LCOGT 2 m (Hawaii) discovered the 2015 eruption, estimated to have commenced at August 28.28±0.12 UT. The 2013-2015 eruptions are remarkably similar at all wavelengths. New early spectroscopic observations reveal short-lived emission from material with velocities ∼13,000 km s −1 ,

We present optical (B, V, R c , I c and y) and near-infrared (J, H, and K s ) photometric and spectroscopic observations of a classical nova V1280 Scorpii for five years from 2007 to 2011. Our photometric observations show a declining event in optical bands shortly after the maximum light, which took about 250 days to recover. This event was most probably caused by dust formation. The event was accompanied by a short (∼30 days) re-brightening episode (∼2.5 mag in V), which suggests that there had been some re-ignition of the surface nuclear burning. After 2008, the y band observations show a very long plateau at around y = 10.5 for more than 1000 days until April 2011 (∼1500 days after the maximum light). The nova had taken a very long time (∼50 months) to enter the nebular phase, according to a clear detection of both [O iii] 4959 and 5007 and is still continuing to generate the wind caused by H-burning.This finding suggests that historically V1280 Sco is evolving at its slowest ever measured rate. The interval from the maximum light (2007 February 16) to the beginning of the nebular phase is longer than any previously known slow novae: V723 Cas (18 months), RR Pic (10 months), or HR Del (8 months). It suggests that the mass of a white dwarf in the V1280 Sco system might be 0.6 M or lower. The distance, based on our measurements of the expansion velocity combined with the directly measured size of the dust shell, is estimated to be 1.1 ± 0.5 kpc.