Gaia view of low-mass star formation

Understanding how young stars and their circumstellar disks form and evolve is key to explain how planets form. The evolution of the star and the disk is regulated by different processes, both internal to the system or related to their environment. The former include accretion of material onto the central star, wind emission, and photoevaporation of the disk due to high-energy radiation from the central star. These are best studied spectroscopically, and the distance to the star is a key parameter in all these studies. Here we present new estimates of the distance to a complex of nearby star-forming clouds obtained combining TGAS distances with measurement of extinction on the line of sight. Furthermore, we show how we plan to study the effects of the environment on the evolution of disks with Gaia, using a kinematic modelling code we have developed to model young star-forming regions.Comment: 4 pages, 1 figure. To appear in the Proceedings of IAU Symposium 330: Astrometry and Astrophysics in the Gaia Sk

Searching for physics beyond the Standard Model in the decay B+ -> K+K+pi-

The observation potential of the decay B+ -> K+K+pi- with the ATLAS detector at LHC is described in this paper. In the Standard Model this decay mode is highly suppressed, while in models beyond the Standard Model it could be significantly enhanced. To improve the selection of the K+K+pi- final state, a charged hadron identification using Time-over-Threshold measurements in the ATLAS Transition Radiation Tracker was developed and used.Comment: 12 pages, 4 figures, 1 tabl

X-Shooter spectroscopy of young stellar objects in Lupus. Atmospheric parameters, membership and activity diagnostics

A homogeneous determination of basic stellar parameters of young stellar object (YSO) candidates is needed to confirm their evolutionary stage, membership to star forming regions (SFRs), and to get reliable values of the quantities related to chromospheric activity and accretion. We used the code ROTFIT and synthetic BT-Settl spectra for the determination of the atmospheric parameters (Teff and logg), the veiling, the radial (RV) and projected rotational velocity (vsini), from X-Shooter spectra of 102 YSO candidates in the Lupus SFR. We have shown that 13 candidates can be rejected as Lupus members based on their discrepant RV with respect to Lupus and/or the very low logg values. At least 11 of them are background giants. The spectral subtraction of inactive templates enabled us to measure the line fluxes for several diagnostics of both chromospheric activity and accretion. We found that all Class-III sources have H$\alpha$ fluxes compatible with a pure chromospheric activity, while objects with disks lie mostly above the boundary between chromospheres and accretion. YSOs with transitional disks displays both high and low H$\alpha$ fluxes. We found that the line fluxes per unit surface are tightly correlated with the accretion luminosity ($L_{\rm acc}$) derived from the Balmer continuum excess. This rules out that the relationships between $L_{\rm acc}$ and line luminosities found in previous works are simply due to calibration effects. We also found that the CaII-IRT flux ratio, $F_{8542}/F_{8498}$, is always small, indicating an optically thick emission source. The latter can be identified with the accretion shock near the stellar photosphere. The Balmer decrement reaches instead, for several accretors, high values typical of optically thin emission, suggesting that the Balmer emission originates in different parts of the accretion funnels with a smaller optical depth.Comment: 28 pages, 26 figures, accepted by A&

Mapping young stellar populations towards Orion with Gaia DR1

We use the first data release of the Gaia mission to explore the three dimensional arrangement and the age ordering of the many stellar groups towards the Orion OB association, aiming at a new classification and characterization of the stellar population. We make use of the parallaxes and proper motions provided in the Tycho Gaia Astrometric Solution (TGAS) sub-set of the Gaia catalogue, and of the combination of Gaia and 2MASS photometry. In TGAS we find evidence for the presence of a young population, at a parallax $\varpi \sim 2.65 \, \mathrm{mas}$, loosely distributed around some known clusters: 25 Ori, $\epsilon$ Ori and $\sigma$ Ori, and NGC 1980 ($\iota$ Ori). The low mass counterpart of this population is visible in the color-magnitude diagrams constructed by combining Gaia and 2MASS photometry. We study the density distribution of the young sources in the sky. We find the same groups as in TGAS, and also some other density enhancements that might be related to the recently discovered Orion X group, the Orion dust ring, and to the $\lambda$ Ori complex. We estimate the ages of this population and we infer the presence of an age gradient going from 25 Ori (13-15 Myr) to the ONC (1-2 Myr). We confirm this age ordering by repeating the Bayesian fit using the Pan-STARRS1 data. The estimated ages towards the NGC 1980 cluster span a broad range of values. This can either be due to the presence of two populations coming from two different episodes of star formation or to a large spread along the line of sight of the same population. Our results form the first step towards using the Gaia data to unravel the complex star formation history of the Orion region in terms of the different star formation episodes, their duration, and their effects on the surrounding interstellar medium.Comment: 17 pages, 17 figure

Pengaruh Tata Ruang Kelas dan Media Visual terhadap Minat Belajar Fisika Peserta Didik Kelas VIII MTs Madani Alauddin Paopao

Penelitian ini bertujuan untuk menggambarkan pengaruh tata ruang kelas dan media visual terhadap minat belajar fisika peserta didik kelas VIII MTs Madani Alauddin Paopao. Populasi dalam penelitian ini adalah peserta didik kelas VIII MTs Madani Alauddin Pao-pao sebanyak 49 orang dan sampel pada penelitian ini berjumlah 49 orang. Instrumen pengumpulan data yang digunakan adalah lembar observasi untuk penataan ruang kelas dan media visual dan angket untuk minat belajar fisika. Data tersebut kemudian di analisis dengan menggunakan regresi berganda. Berdasarkan hasil penelitian dan analisis deskriptif diperoleh skor rata-rata tata ruang kelas adalah 62 termasuk dalam kategori cukup dan skor rata-rata penggunaan media visual adalah 56 termasuk dalam kategori cukup,serta skor rata-rata minat belajar fisika adalah 61 termasuk dalam kategori tinggi. Adapun hasil analisis inferensial menunjukkan nilai Fhitung adalah 585,9 sedangkan Ftabel pada taraf signifikansi 5% adalah 3,20. Dengan demikian, nilai Fhitung lebih besar dari pada nilai Ftabel dan hipotesis nol ditolak, artinya terdapat pengaruh yang signifikan antara tata ruang kelas dan media visual teradap minat belajar fisika peserta didik kelas VIII MTs Madani Alauddin Paopao

Pengaruh Gaya Kepemimpinan Transformasional Dan Iklim Organisasi Terhadap Komitmen Organisasi

This study aimed to determine the effect of transformational leadership style and organizational climate on organizational commitment. Subjects were employees and lecturers at the University of Setia Budi Surakarta as many as 65 people. Data analysis used regression analysis techniques. Analisisis results showed a correlation coefficient (R) of 0.760 with F of 42.386 p = 0.000 (p <0.01) which means that there was a highly significant correlation between transformational leadership and organizational climate on organizational commitment. Determinant coefficient (R2) of 57.8%, this indicates that the variables of transformational leadership and organizational commitment affected organizational climate by 57.8% and 42.2% were influenced by other variables

DNA sequencing with MspA: molecular dynamics simulations reveal free-energy differences between sequencing and non-sequencing mutants

MspA has been identified as a promising candidate protein as a component of a nanopore-based DNA-sequencing device. However the wildtype protein must be engineered to incorporate all of the features desirable for an accurate and efficient device. In the present study we have utilized atomistic molecular dynamics to perform umbrella-sampling calculations to calculate the potential of mean force (PMF) profiles for translocation of the four DNA nucleotides through MspA. We show there is an energetic barrier to translocation of individual nucleotides through a mutant that closely resembles the wildtype protein, but not through a mutant engineered for the purpose of sequencing. Crucially we are able to quantify the change in free energy for mutating key residues. Thus providing a quantitative characterisation of the energetic impact of individual amino acid sidechains on nucleotide translocation through the pore of MspA

X-shooter spectroscopy of young stellar objects in Lupus: Lithium, iron, and barium elemental abundances

With the purpose of performing a homogeneous determination of elemental abundances for members of the Lupus T association, we analyzed three chemical elements: lithium, iron, and barium. The aims were: to derive the Li abundance for ~90% of known class II stars in the Lupus I, II, III, IV clouds; to perform chemical tagging of a region where few Fe abundance measurements have been obtained in the past, and no determination of the Ba content has been done up to now. We also investigated possible Ba enhancement, as this element has become increasingly interesting in the last years following the evidence of Ba over-abundance in young clusters, the origin of which is still unknown. Using X-shooter@VLT, we analyzed the spectra of 89 cluster members, both class II and III stars. We measured the strength of the Li line and derived the abundance of this element through equivalent width measurements and curves of growth. For six class II stars we also measured the Fe and Ba abundances using the spectral synthesis and the code MOOG. The veiling contribution was taken into account for all three elements. We find a dispersion in the strength of the Li line at low Teff and identify three targets with severe Li depletion. The nuclear age inferred for these highly Li-depleted stars is around 15 Myr, which exceeds the isochronal one. As in other star-forming regions, no metal-rich members are found in Lupus, giving support to a recent hypothesis that the Fe abundance distribution of most of the nearby young regions could be the result of a common and widespread star formation episode involving the Galactic thin disk. We find that Ba is over-abundant by ~0.7 dex with respect to the Sun. Since current theoretical models cannot reproduce this Ba abundance pattern, we investigated whether this unusually large Ba content might be related to effects due to stellar parameters, stellar activity, and accretion.Comment: 15 pages, 14 figures, 3 tables; accepted for publication in A&A; abstract shortene