• X. Chen

Articles written in Journal of Astrophysics and Astronomy

• X-ray Time Lags in TeV Blazars

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.

• Pumping Mechanisms for SiO Masers around VX Sgr

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.

• Massive Star Formation: Accreting from Companion

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.

• Outward Motions of SiO Masers around VX Sgr

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.

• Discovery of a Faint Eclipsing Binary GSC 02265-01456

When observing the transiting extrasolar planets, we found a new eclipsing binary named GSC 02265-01456. The 𝑉 and 𝑅c 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.

• Photometric Analysis and Period Investigation of the EW Type Eclipsing Binary V441 Lac

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.

• Journal of Astrophysics and Astronomy

Current Issue
Volume 40 | Issue 2
April 2019

• Continuous Article Publication

Posted on January 27, 2016

Since January 2016, the Journal of Astrophysics and Astronomy has moved to Continuous Article Publishing (CAP) mode. This means that each accepted article is being published immediately online with DOI and article citation ID with starting page number 1. Articles are also visible in Web of Science immediately. All these have helped shorten the publication time and have improved the visibility of the articles.