We present the first results of an ensemble and systematic survey of oscillation mode variability in pulsating hot B subdwarf (sdB) and white dwarf stars observed with the original Kepler mission. The satellite provides uninterrupted high-quality photometric data with a time baseline that can reach up to 4 yr collected on pulsating stars. This is a unique opportunity to characterize long-term behaviors of oscillation modes. A mode modulation in amplitude and frequency can be independently inferred by its fine structure in the Fourier spectrum, from the sLSP, or with prewhitening methods applied to various parts of the light curve. We apply all these techniques to the sdB star KIC 3527751, a long-period-dominated hybrid pulsator. We find that all the detected modes with sufficiently large amplitudes to be thoroughly studied show amplitude and/or frequency variations. Components of three identified quintuplets around 92, 114, and 253 μHz show signatures that can be linked to nonlinear interactions according to the resonant mode coupling theory. This interpretation is further supported by the fact that many oscillation modes are found to have amplitudes and frequencies showing correlated or anticorrelated variations, a behavior that can be linked to the amplitude equation formalism, where nonlinear frequency corrections are determined by their amplitude variations. Our results suggest that oscillation modes varying with diverse patterns are a very common phenomenon in pulsating sdB stars. Close structures around main frequencies therefore need to be carefully interpreted in light of this finding to secure a robust identification of real eigenfrequencies, which is crucial for seismic modeling. The various modulation patterns uncovered should encourage further developments in the field of nonlinear stellar oscillation theory. It also raises a warning to any long-term project aiming at measuring the rate of period change of pulsations caused by stellar evolution, or at discovering stellar (planetary) companions around pulsating stars using timing methods, as both require very stable pulsation modes.

Cosmic ray (CR) physics has entered a precision-driven era. With the latest AMS-02 nuclei data (boron-to-carbon ratio, proton flux, helium flux and antiproton-to-proton ratio), we perform a global fitting and constrain the primary source and propagation parameters of cosmic rays in the Milky Way by considering 3 schemes with different data sets (with and withoutp/p data) and different propagation models (diffusion-reacceleration and diffusion-reacceleration-convection models). We find that the data set withp/p data can remove the degeneracy between the propagation parameters effectively and it favors the model with a very small value of convection (or disfavors the model with convection). The separated injection spectrum parameters are used for proton and other nucleus species, which reveal the different breaks and slopes among them. Moreover, the helium abundance, antiproton production cross sections and solar modulation are parametrized in our global fitting. Benefited from the self-consistence of the new data set, the fitting results show a little bias, and thus the disadvantages and limitations of the existed propagation models appear. Comparing to the best fit results for the local interstellar spectra (φ = 0) with the VOYAGER-1 data, we find that the primary sources or propagation mechanisms should be different between proton and helium (or other heavier nucleus species). Thus, how to explain these results properly is an interesting and challenging question.

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).

Many experiments have confirmed spectral hardening at a few hundred GeV in the spectra of cosmic ray (CR) nuclei. Three different origins have been proposed: primary source acceleration, propagation, and the superposition of different kinds of sources. In this work, a broken power law has been employed to fit each of the spectra of cosmic ray nuclei from AMS-02 directly, for rigidities greater than 45 GeV. The fitting results of the break rigidity and the spectral index differences less than and greater than the break rigidity show complicated relationships among different nuclear species, which cannot be reproduced naturally by a simple primary source scenario or a propagation scenario. However, with a natural and simple assumption, the superposition of different kinds of sources could have the potential to explain the fitting results successfully. Spectra of CR nuclei from a single future experiment, such as DAMPE, will provide us the opportunity to do cross checks and reveal the properties of the different kinds of sources.

Multidrug resistance (MDR) is a major cause for incurable breast cancer. Salvianolic acid A (SAA), the hydrophilic polyphenolic derivative of Salvia miltiorrhiza Bunge (Danshen/Red Sage), was examined for cytotoxicities to MDR MCF-7 human breast cancer cells and their parental counterparts. We have shown that SAA inhibited proliferation, caused cell cycle arrest at the S phase, and induced apoptosis dose dependently to the two kinds of cancer cells. However, the resistant cells were significantly susceptible to the inhibition of SAA compared with the parental cells. SAA increased the level of reactive oxygen species (ROS) by 6.2-fold in the resistant cells, whereas the level of SAA-induced ROS changed only by 1.6-fold in their parental counterparts. Thus, the data showed that the selective cytotoxicity resulted from the hypersensitivity of the resistant cells to the strongly elevated ROS by SAA. In addition, SAA-triggered apoptosis was associated with increased caspase-3 activity, disrupted mitochondrial membrane potential, downregulated Bcl-2 expression, and upregulated Bax expression in the resistant cells. Moreover, SAA downregulated the level of P-glycoprotein, which was overexpressed in the resistant cells. This indicated that SAA modulated MDR. Furthermore, SAA showed higher antitumor activity than did doxorubicin in xenografts established from the resistant cells. The present work raised a possibility that SAA might be considered a potential choice to overcome MDR for the selective susceptibility of the resistant breast cancer cells to SAA treatment.