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The comprehensive photometry and spectroscopy for the neglected eclipsing binary EUPegasi are presented. We determine its spectral type to be A3V. With the W-D program, the photometric solution was deduced from the four-color light curves. The results imply that EUPeg is a detached binary with a mass ratio of q = 0.3105(± 0.0011), whose components nearly fill their Roche lobes. The low-amplitude pulsation occurs around the secondary eclipse, which may be attributed to the more massive component. Three frequencies are preliminarily explored by the Fourier analysis. The pulsating frequency at f1 = 34.1 c d-1 is a p-mode pulsation. The orbital period may be undergoing a secular decrease, superimposed by a cyclic variation. The period decreases at a rate of dP/dt = -7.34 ± 1.06 d yr-1, which may be attributed to mass loss from the system due to stellar wind. The cyclic oscillation, with Pmod = 31.0 ± 1.4 yr and A = 0.0054 ± 0.0010 d, may be caused by the light-time effect due to the assumed third body. With its evolution, the pulsating binary EUPeg will evolve from the detached configuration to the semi-detached case. [ABSTRACT FROM AUTHOR]

We present photometry and spectroscopy data for V532Mon and GUOri, observed in 2011 and 2016. From the spectral observations, the spectral types are determined to be F5V for V532Mon and G0V for GUOri. With the 2015-version Wilson-Devinney program, the photometric solutions are simultaneously deduced from VR light curves (LCs). The intrinsic variability for V532Mon is found by comparing LCs in 2004 and 2011, while the asymmetric LCs for GUOri are modeled by a cool spot on the more massive component. The results imply that the two stars are A-type contact binaries. The mass ratios and fill-out factors are, respectively, q = 0.190(±0.006) and f = 43.7(±0.9)% for V532Mon and q = 0.455(±0.020) and f = 26.9(±1.3)% for GUOri. From the (O – C) curves, it is found that their orbital periods may be undergoing long-term variations. The rates of period change are dP/dt = -1.72(±0.05) × 10-7 dyr-1 for V532Mon and dP/dt = +1.45(±0.01) × 10-7 dyr-1 for GUOri. V532Mon with a decreasing period will evolve into a deep-contact binary, while GUOri with an increasing period may evolve into a broken-contact case. [ABSTRACT FROM AUTHOR]

In this study, new data concerning the EB-type eclipsing binary EG Cas are presented as observed using three telescopes in China. A spectral type of F0V was determined from the low-precision spectrum. By solving the radial velocity and BV light curves, the absolute parameters of this system are preliminarily deduced. The results imply that EG Cas is a semi-detached binary with the secondary star filling its Roche lobe. An unequal height between the light maxima (i.e., ≲0.02 mag) of the light curves is modeled with the addition of a magnetic dark spot on the surface of the less-massive component. Analyzing the O − C curve a secular decrease at is identified in the orbital period, which corresponds to a mass-loss rate of in the case of non-conserved evolution of the binary. From the spectral energy distribution, an excess in the infrared occurs in the WISE W4 band, which may be attributed to the circumstellar envelope due to mass loss via the stellar magnetic wind. With the ongoing mass transfer and loss, this kind of F-type near-contact binary will eventually evolve into an A-subtype contact binary, as predicted by the thermal relaxation oscillation theory. [ABSTRACT FROM AUTHOR]

Indium selenide (In2Se3) has attracted tremendous attention due to its favorable electronic features, broad tunable bandgap, high stability and other attractive properties. However, its further applications for nonlinear optics have not yet been fully explored. In this work, we demonstrate that few-layer α-In2Se3 nanosheets exhibit strong saturable absorption properties over a wide wavelength range covering 800, 1064 and 1550 nm. The few-layer α-In2Se3 nanosheets used for this experiment are fabricated via a simple ultrasonic exfoliation in liquid. Stable ultrafast mode-locking laser pulses are obtained from both ytterbium-doped and erbium-doped fiber laser systems operating at 1064 and 1550 nm, respectively. A pulse duration as short as 215 fs was achieved in the Er-doped fiber laser system. Stable output pulses over 6 h of operation were obtained in both laser systems. The pulse energy and peak power of the laser output pulses were increased by reducing the In2Se3 thickness. These results indicate that α-In2Se3 nanosheets with low layer numbers are promising candidates for broad ultrafast photonics devices, such as optical switchers, Q-switchers and mode lockers. [ABSTRACT FROM AUTHOR]