Bi-site time-series photometric and high-resolution spectroscopic observations were made for the double-mode high-amplitude δ Scuti star VX Hya. The fundamental frequency f 0 = 4.4763 c days −1 , the first overtone f 1 = 5.7897 c days −1 and 23 harmonics and linear combinations of f 0 and f 1 are detected by pulsation analysis. From the spectroscopic data, we get [Fe/H] = −0.2 ± 0.1 dex. The period change rate of the fundamental mode is obtained by using the Fourier-phase diagram method, which gives the value of (1/P 0 )(dP 0 /dt) = (1.81 ± 0.09) × 10 −7 yr −1 . With these results from the observations, we perform theoretical explorations with the stellar evolution code MESA, and constrain the models by fitting f 0 , f 1 , and (1/P 0 )(dP 0 /dt) within 3σ deviations. The results show that the period change of VX Hya could be ascribed to the evolutionary effect. The stellar parameters of VX Hya could be derived as: the mass 2.385 ± 0.025 M , the luminosity log(L/L ) = 1.93 ± 0.02 and the age (4.43 ± 0.13) × 10 8 years. VX Hya is found to locate at the post-main-sequence stage with a helium core and a hydrogen-burning shell on the H−R diagram.

Based on the precise nuclei data released by AMS-02, we study the spectra hardening of both the primary (proton, helium, carbon, oxygen, and the primary component of nitrogen) and the secondary (anti-proton, lithium, beryllium, boron and the secondary component of nitrogen) cosmic ray (CR) nuclei. With the diffusion-reacceleration model, we consider two schemes to reproduce the hardening in the spectra: (i) A high-rigidity break in primary source injection; (ii) A high-rigidity break in diffusion coefficient. The global fitting results show that both schemes could reproduce the spectra hardening in current status. More precise multi-TV data (especially the data of secondary CR species) is needed if one wants to distinguish these two schemes. In our global fitting, each of the nuclei species is allocated an independent solar modulation potential and a re-scale factor (which accounts for the isotopic abundance for primary nuclei species and uncertainties of production cross section or inhomogeneity of CR sources and propagation for secondary nuclei species). The fitting values of these two parameter classes show us some hints on some new directions in CR physics. All the fitted re-scale factors of primary nuclei species have values that systematically smaller than 1.0, while that of secondary nuclei species are systematically larger than 1.0. Moreover, both the re-scale factor and solar modulation potential of beryllium have values which are obviously different from other species. This might indicate that beryllium has the specificity not only on its propagation in the heliosphere, but also on its production cross section. All these new results should be seriously studied in the future.

We analyze the photometric data and spectroscopic data that collect on the δ Scuti star AE UMa. The fundamental and the first overtone frequencies are confirmed as f 0 = 11.62560 c d −1 and f 1 = 15.03124 c d −1 , respectively, from the frequency content by analyzing of the 40 nights light curve spanning from 2009 to 2012. Additionally, another 37 frequencies are identified as either the harmonics or the linear combinations of the fundamental and the first overtone frequencies, among which 25 are newly detected. The rate of period change of the fundamental mode is determined as (1/P 0 )(dP 0 /dt) = 5.4(±1.9) × 10 −9 yr −1 as revealed from the O − C diagram based on the 84 newly determined times of maximum light combined with those derived from the literature. The spectroscopic data suggests that AE UMa is a population I δ Scuti star. With these physical properties, we perform theoretical explorations based on the stellar evolution code MESA on this target, considering that the variation of pulsation period is caused by secular evolutionary effects. We finally constraint the AE UMa with the physical parameters as: the mass of 1.805 ± 0.055 M ⊙ , the radius of 1.647 ± 0.032 × 10 11 cm, the luminosity of 1.381 ± 0.048 (log L/L ⊙ ) and the age of 1.055 ± 0.095 × 10 9 yr. AE UMa can be the (Pop. I) δ Scuti star that locates just after the second turn-off of its evolutional track leaving the main sequence, a star in the phase of the Hertzsprung Gap with a helium core and a hydrogen-burning shell.

Recently, DAMPE has released its first results on the high-energy cosmic-ray electrons and positrons (CREs) from about 25 GeV to 4.6 TeV, which directly detect a break at ∼ 1 TeV. This result gives us an excellent opportunity to study the source of the CREs excess. In this work, we used the data for proton and helium flux (from AMS-02 and CREAM),p/p ratio (from AMS-02), positron flux (from AMS-02) and CREs flux (from DAMPE without the peak signal point at ∼ 1.4 TeV) to do global fitting simultaneously, which can account the influence from the propagation model, the nuclei and electron primary source injection and the secondary lepton production precisely. For extra source to interpret the excess in lepton spectrum, we consider two separate scenarios (pulsar and dark matter annihilation via leptonic channels) to construct the bump ( > ∼ 100 GeV) and the break at ∼ 1 TeV. The result shows: (i) in pulsar scenario, the spectral index of the injection should be νpsr ∼ 0.65 and the cut-off should be Rc ∼ 650 GV; (ii) in dark matter scenario, the dark matter particle's mass is mχ ∼ 1208 GeV and the cross section is σv ∼ 1.48 × 10 −23 cm 3 s −1 . Moreover, in the dark matter scenario, the ττ annihilation channel is highly suppressed, and a DM model is built to satisfy the fitting results. * jsniu@itp.ac.cn † tli@itp.ac.cn arXiv:1712.00372v4 [astro-ph.HE] 26 Apr 2018[1] J. Chang, "Dark matter particle explorer: The first chinese cosmic ray and hard gamma-ray detector in space,"Chinese Journal of Space Science 34, 550 (2014).

The variability of young stellar objects is mostly driven by star-disk interactions. In long-term photometric monitoring of the accreting T Tauri star GI Tau, we detect extinction events with typical depths of DṼ 2.5 mag that last for days to months and often appear to occur stochastically. In 2014-2015, extinctions that repeated with a quasi-period of 21 days over several months are the first empirical evidence of slow warps predicted by magnetohydrodynamic simulations to form at a few stellar radii away from the central star. The reddening is consistent with =  R 3.85 0.5 V and, along with an absence of diffuse interstellar bands, indicates that some dust processing has occurred in the disk. The 2015-2016 multiband light curve includes variations in spot coverage, extinction, and accretion, each of which results in different traces in color-magnitude diagrams. This light curve is initially dominated by a month-long extinction event and a return to the unocculted brightness. The subsequent light curve then features spot modulation with a 7.03 day period, punctuated by brief, randomly spaced extinction events. The accretion rate measured from U-band photometry ranges from´-1.3 10 8 to´-1.1 10 10 M e yr −1 (excluding the highest and lowest 5% of high-and low-accretion rate outliers), with an average of4.7 -10 9 M e yr −1 . A total of 50% of the mass is accreted during bursts of >´-12.8 10 9 M e yr -1, which indicates limitations on analyses of disk evolution using single-epoch accretion rates.