17710652
Colliding Clouds: The Star Formation Trigger of the Stellar Cluster around BD +40 4124
We present BIMA and SCUBA observations of the young cluster associated with BD +40 4124 in the dense molecular gas tracer CS J = 2 → 1 and the continuum dust emission at λ = 3.1 mm and 850 μm. The dense gas and dust in the system are aligned in a long ridge morphology extending ~0.4 pc with 16 gas clumps of estimated masses ranging from 0.14 to 1.8 M☉. A north-south variation in the CS center line velocity can be explained with a two-cloud model. We posit that the BD +40 4124 stellar cluster formed from a cloud-cloud collision. The largest line widths occur near V1318 Cyg S, a massive star affecting its natal environment. In contrast, the dense gas near the other, more evolved, massive stars displays no evidence for disruption; the material must either be processed into the star, dissipate, or relax fairly quickly. The more evolved low-mass protostars are more likely to be found near the massive stars. If the majority of low-mass stars are coeval, the seemingly evolved low-mass protostars are not older: the massive stars have eroded their structures. Finally, at the highest resolution, the λ = 3.1 mm dust emission is resolved into a flattened structure 3100 × 1500 AU with an estimated mass of 3.4 M☉. The continuum and CS emission are offset by 11 from the southern binary source. A simple estimate of the extinction due to the continuum emission structure is AV ~ 700 mag. From the offset and because the southern source is detected in the optical, the continuum emission is from a previously unknown very young, intermediate-mass, embedded stellar object.
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.
119415475
Nonequilibrium relaxation in neutral BCS superconductors: Ginzburg-Landau approach with Landau damping in real time
We present a field-theoretical method to obtain consistently the equations of motion for small amplitude fluctuations of the order parameter directly in real time for a homogeneous, neutral BCS superconductor. This methodallows to study the nonequilibrium relaxation of the order parameter as an initial value problem. We obtain the Ward identities and the effective actions for small phase the amplitude fluctuations to one-loop order. Focusing on the long wavelength, low-frequency limit near the critical point, we obtain the time-dependent Ginzburg-Landau effective action to one-loop order, which is nonlocal as a consequence of Landau damping. The nonequilibrium relaxation of the phase and amplitude fluctuations is studied directly in real time. The long-wavelength phase fluctuation (Bogoliubov-Anderson-Goldstone mode) is overdamped by Landau damping and the relaxation time scale diverges at the critical point, revealing critical slowing down.
6278628
Search for the standard model Higgs Boson produced in association with top quarks using the full CDF data set.
A search is presented for the standard model Higgs boson produced in association with top quarks using the full Run II proton-antiproton collision data set, corresponding to 9.45 fb(-1), collected by the Collider Detector at Fermilab. No significant excess over the expected background is observed, and 95% credibility-level upper bounds are placed on the cross section σ(ttH → lepton + missing transverse energy+jets). For a Higgs boson mass of 125 GeV/c(2), we expect to set a limit of 12.6 and observe a limit of 20.5 times the standard model rate. This represents the most sensitive search for a standard model Higgs boson in this channel to date.
125260045
Evidence of sigma particle in J / psi ---> omega pi pi
118643961
AGE AND MASS CONSTRAINTS FOR A YOUNG MASSIVE CLUSTER IN M31 BASED ON SPECTRAL ENERGY DISTRIBUTION FITTING
VDB0-B195D is a massive, blue star cluster in M31. It was observed as part of the Beijing-Arizona-Taiwan-Connecticut (BATC) Multicolor Sky Survey using 15 intermediate-band filters covering a wavelength range of 3000-10000 A. Based on aperture photometry, we obtain its spectral energy distribution (SED) as defined by the 15 BATC filters. We apply previously established relations between the BATC intermediate-band and the Johnson-Cousins UBVRI broadband systems to convert our BATC photometry to the standard system. A detailed comparison shows that our newly derived VRI magnitudes are fully consistent with previous results, while our new B magnitude agrees to within 2{sigma}. In addition, we determine the cluster's age and mass by comparing its SED (from 3000 to 20000 A, comprising photometric data in the 15 BATC intermediate bands, optical broadband BVRI, and Two Micron All Sky Survey near-infrared JHK{sub s} data) with theoretical stellar population synthesis models, resulting in age and mass determinations of 60.0 {+-} 8.0 Myr and (1.1-1.6) x 10{sup 5} M{sub sun}, respectively. This age and mass confirms previous suggestions that VDB0-B195D is a young massive cluster in M31.
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.