We use Monte Carlo/Fokker–Planck simulations to study the X-ray time lags. Our results show that soft lags will be observed as long as the decay of the flare is dominated by radiative cooling, even when acceleration and cooling time scales are similar. Hard lags can be produced in the presence of a competitive achromatic particle energy loss mechanism if the acceleration process operates on a time scale such that particles are slowly moved towards higher energy while the flare evolves. In this type of scenario, the 𝛾-ray/X-ray quadratic relation is also reproduced.

VX Sgr, a semi-regular variable, is a red giant star with intense SiO maser emission at 43 GHz. The pumping mechanism of the circumstellar SiO masers has been controversial for decades since its discovery. In order to pursue this long-standing problem further, we have carried out simultaneous VLBA observations of two 7 mm SiO masers at five epochs in about two years. We present relatively aligned 𝑣 = 1 and 𝑣 = 2, 𝐽 = 1-0 SiO maser maps and discuss the dominant pumping mechanism, which may be epoch dependent or a combination of both mechanisms.

We report the possible accretion from companion in the massive star forming region (G350.69–0.49). This region seems to be a binary system composed of a diffuse object (possible nebulae or UC HII region) and a Massive Young Stellar Object (MYSO) seen in Spitzer IRAC image. The diffuse object and MYSO are connected by the shock-excited 4.5 𝜇m emission, suggesting that the massive star may form through accreting material from the companion in this system.

We report the proper motions of SiO maser features around VX Sgr from the two-epoch VLBA observations (2006 December 15 and 2007 August 19). The majority of maser feature activities show a trend of outward motions. It is consistent with our previous finding that the outflow may play an important role for SiO maser pumping.

When observing the transiting extrasolar planets, we found a new eclipsing binary named GSC 02265-01456. The 𝑉 and 𝑅_c observations were carried out for this binary. The photometric light curves of the two bands were simultaneously analyzed using the W–D code. The solutions show that GSC 02265-01456 is an extremely low mass ratio (𝑞 = 0.087) overcontact binary system with a contact degree of 𝑓 = 82.5%. The difference between the two maxima of the light curve can be explained by a dark spot on the primary component.

Four color light curves of the EW type eclipsing binary V441Lac were presented and analyzed by the W--D code. It is found that V441Lac is an extremely low mass ratio $(q = 0.093 \pm 0.001)$ semi-detached binary with the less massive secondary component filling the inner Roche lobe. Two dark spots on the primary component were introduced to explain the asymmetric light curves. By analyzing all times of light minimum, we determined that the orbital period of V441 Lac is continuously increasing at a rate of ${\rm d}P/{\rm d}t = 5.874(\pm 0.007)\times 10^{--7} {\rm d yr}^{--1}$. The semidetached Algol type configuration of V441 Lac is possibly formed by a contact configuration destroyed shallow contact binary due to mass transfer from the less massive component to the more massive one predicted by the thermal relaxation oscillation theory.