8106823
THE X-RAY ORIGIN OF HERBIG AeBe SYSTEMS: NEW INSIGHTS
We present a statistical study of the X-ray emission toward 22 Herbig AeBe stars (HAEBE) using the Chandra archive. We probe the origin of the X-rays toward Herbig stars: are they intrinsic?This question is addressed by correlations between the physical stellar properties and the X-ray emission. There is a weak correlation between the continuum radio emission at λ = 3.6 cm and L X, which suggests that the X-ray emission depends upon the source. On the other hand, no correlation was found with the stellar rotational period, but that only excludes solar-like magnetic activity as the origin of the X-rays. Most importantly, the X-ray luminosity of HAEBE has a different distribution from that of T Tauri stars, suggesting that X-ray emission from an unseen late-type star companion can be ruled out with an 80% confidence level. This implies that the HAEBE must have magnetic activity. In addition, we report the observation of five sources for the first time, in three detections.
17153677
Dense Molecular Gas in a Young Cluster around MWC 1080: Rule of the Massive Star
We present CS -->J = 2→ 1,13CO -->J = 1→ 0, and C18O -->J = 1→ 0, observations with the 10 element Berkeley Illinois Maryland Association (BIMA) array toward the young cluster around the Be star MWC 1080. These observations reveal a biconical outflow cavity with size ~0.3 and 0.05 pc for the semimajor and semiminor axis and ~45° position angle. These transitions trace the dense gas, which is likely the swept-up gas of the outflow cavity, rather than the remaining natal gas or the outflow gas. The gas is clumpy; 32 clumps are identified. The identified clumps are approximately gravitationally bound and consistent with a standard isothermal sphere density, which suggests that they are likely collapsing protostellar cores. The gas kinematics suggests that velocity gradients exist that imply effects from the inclination of the cavity and MWC 1080. The kinematics of dense gas has also been affected by either outflows or stellar winds from MWC 1080, and lower mass clumps are possibly under stronger effects from MWC 1080 than higher mass clumps. In addition, low-mass cluster members tend to be formed in the denser and more turbulent cores, compared to isolated low-mass star-forming cores. This results from the contributions of nearby forming massive stars, such as outflows or stellar winds. Therefore, we conclude that in clusters like the MWC 1080 system, effects from massive stars dominate the star-forming environment in both the kinematics and dynamics of the natal cloud and the formation of low-mass cluster members. This study provides insights into the effects of MWC 1080 on its natal cloud, and suggests a different low-mass star-forming environment in clusters compared to isolated star formation.
124550490
Study of $J/ψ → ωp\overline{p}$ at BESIII
14222346
Extended radio emission after the soft X-ray maximum of the NOAA 9077 AR solar flare on July 10, 2000
An extended radio emission after a soft X-ray (SXR) maximum was detected in the active region NOAA 9077 by several observatories for the solar flare after 21:42 UT on July 10, 2000. Also some radio fine structures before the enduring radio emission were observed with the 1.0-2.0 GHz spectrometer of Beijing Astronomical Observatory (BAO) in the same time. We apply a shear-driven quadrupolar reconnection model (SQR) to analyze the fine structures and the related radio emission. We find that the footpoint shear motion of the flux loop is accompanied with the emerging up of the loop during the reconnection process. We tentatively interpret the extended radio emission as the nonthermal radiation caused by a new reconnection process between emerging flux loop and pre-existing overarching loop after the soft X-ray maximum.
5366774
Observation of spontaneous emitted X-ray betatron radiation in beam-plasma interactions
An experiment is being carried out at the Stanford Linear Accelerator Center (SLAC) to see if an ion channel can wiggle a beam of ultra-relativistic electrons to produce X-ray radiation. The goal is to create an intense source of undulator radiation using a plasma wiggler in the 1-10 keV range and also to determine the suitability of such an electrostatic wiggler to create a coherent beam of X-rays via the ion channel laser mechanisml. Here we give some of the scaling laws for the power and frequency distribution of the spontaneous emission from sending an electron beam through such an ion channel. Some initial experimental observations are also presented.
119218666
Forming Habitable Planets Around Dwarf Stars: Application to OGLE-06-109L
Dwarf stars are believed to have a small protostar disk where planets may grow up. During the planet formation stage, embryos undergoing type I migration are expected to be stalled at an inner edge of the magnetically inactive disk (a crit ~ 0.2-0.3 AU). This mechanism makes the location around a crit a sweet spot for forming planets. In dwarf stars with masses ~0.5 M ☉, a crit is roughly inside the habitable zone of the system. In this paper, we study the formation of habitable planets due to this mechanism using model system OGLE-06-109L, which has a 0.51 M ☉ dwarf star with two giant planets in 2.3 and 4.6 AU observed by microlensing. We model the embryos undergoing type I migration in the gas disk with a constant disk-accretion rate (). Giant planets in outside orbits affect the formation of habitable planets through secular perturbations at the early stage and secular resonance at the late stage. We find that the existence and the masses of the habitable planets in the OGLE-06-109L system depend on both and the speed of type I migration. If planets are formed earlier, so that is larger (~10–7 M ☉ yr–1), terrestrial planets cannot survive unless the type I migration rate is an order of magnitude less. If planets are formed later, so that is smaller (~10–8 M ☉ yr–1), single and high-mass terrestrial planets with high water contents (~5%) will be formed by inward migration of outer planet cores. A slower-speed migration will result in several planets via collisions of embryos, and thus their water contents will be low (~2%). Mean motion resonances or apsidal resonances among planets may be observed if multiple planets survive in the inner system.
55072733
Source Region of the Decameter–Hectometric Type II Radio Burst: Shock–Streamer Interaction Region
D–H type II radio bursts are widely thought to be caused by coronal mass ejections (CMEs). However, it is still unclear where the exact source of the type IIs on the shock surface is. We identify the source regions of the decameter–hectometric (D–H) type IIs based on imaging observations from SOHO/LASCO and the radio dynamic spectrum from Wind/Waves. The analysis of two well-observed events suggests that the sources of these two events are located in the interaction regions between shocks and streamers, and that the shocks are enhanced significantly in these regions.