X-Shooter spectroscopy of young stellar objects: V - Slow winds in T Tauri stars

Disks around T Tauri stars are known to lose mass, as best shown by the profiles of forbidden emission lines of low ionization species. At least two separate kinematic components have been identified, one characterised by velocity shifts of tens to hundreds km/s (HVC) and one with much lower velocity of few km/s (LVC). The HVC are convincingly associated to the emission of jets, but the origin of the LVC is still unknown. In this paper we analyze the forbidden line spectrum of a sample of 44 mostly low mass young stars in Lupus and $\sigma$-Ori observed with the X-Shooter ESO spectrometer. We detect forbidden line emission of [OI], [OII], [SII], [NI], and [NII], and characterize the line profiles as LVC, blue-shifted HVC and red-shifted HVC. We focus our study on the LVC. We show that there is a good correlation between line luminosity and both L$_{star}$ and the accretion luminosity (or the mass-accretion rate) over a large interval of values (L$_{star}$ $\sim 10^{-2} - 1$ L$_\odot$; L$_{acc}$ $\sim 10^{-5} - 10^{-1}$ L$_\odot$; $\dot M_{acc}$ $\sim 10^{-11} - 10^{-7}$ M$_\odot$/yr). The lines show the presence of a slow wind ($V_{peak}10^8$ cm$^{-3}$), warm (T$\sim 5000-10000$ K), mostly neutral. We estimate the mass of the emitting gas and provide a value for the maximum volume it occupies. Both quantities increase steeply with the stellar mass, from $\sim 10^{-12}$ M$_\odot$ and $\sim 0.01$ AU$^3$ for M$_{star}$$\sim 0.1$ M$_\odot$, to $\sim 3 \times 10^{-10}$ M$_\odot$ and $\sim 1$ AU$^3$ for M$_{star}$$\sim 1$ M$_\odot$, respectively. These results provide quite stringent constraints to wind models in low mass young stars, that need to be explored further

X-Shooter spectroscopy of FU Tau A

We have analyzed a broad-band optical and near-infrared spectrum of FU Tau A, a presumed young brown dwarf in the Taurus star forming region that has intrigued both theorists and observers by its over-luminosity in the HR diagram with respect to standard pre-main sequence evolutionary models. The new data, obtained with the X-Shooter spectrograph at the Very Large Telescope, include an unprecedented wealth of information on stellar parameters and simultaneously observed accretion and outflow indicators for FU Tau A. We present the first measurements of gravity (log g = 3.5 +- 0.5), radial velocity (RV = 22.5 +- 2.9 km/s), rotational velocity (v sin(i) = 20 +- 5 km/s) and lithium equivalent width (W_Li = 430 +- 20 mAA) for FUTau A. From the rotational velocity and the published period we infer a disk inclination of i ~ 50^deg. The lithium content is much lower than theoretically expected for such a young very low mass object, adding another puzzling feature to this object's properties. We determine the mass accretion rate of FU Tau A from comparison of the luminosities of 24 emission lines to empirical calibrations from the literature and find a mean of log (dM/dt)_acc [M_sun/yr] = -9.9 +- 0.2. The accretion rate determined independently from modeling of the excess emission in the Balmer and Paschen continua is consistent with this value. The corresponding accretion luminosity is too small to make a significant contribution to the bolometric luminosity. The existence of an outflow in FU Tau A is demonstrated through the first detection of forbidden emission lines from which we obtain an estimate for the mass loss rate, log (dM/dt)_out [M_sun/yr] < -10.4. The mass outflow and inflow rates can be combined to yield (dM/dt)_out / (dM/dt)_acc ~ 0.3, a value that is in agreement with jet launching models.Comment: 12 pages, accepted for publication in A&

X-Shooter spectroscopy of young stellar objects - VI - HI line decrements

Hydrogen recombination emission lines commonly observed in accreting young stellar objects represent a powerful tracer for the gas conditions in the circumstellar structures. Here we perform a study of the HI decrements and line profiles, from the Balmer and Paschen lines detected in the X-Shooter spectra of a homogeneous sample of 36 T Tauri stars in Lupus, the accretion and stellar properties of which were already derived in a previous work. We aim to obtain information on the gas physical conditions to derive a consistent picture of the HI emission mechanisms in pre-main sequence low-mass stars. We have empirically classified the sources based on their HI line profiles and decrements. We identified four Balmer decrement types (classified as 1, 2, 3, and 4) and three Paschen decrement types (A, B, and C), characterised by different shapes. We first discussed the connection between the decrement types and the source properties and then compared the observed decrements with predictions from recently published local line excitation models. One third of the objects show lines with narrow symmetric profiles, and present similar Balmer and Paschen decrements (straight decrements, types 2 and A). Lines in these sources are consistent with optically thin emission from gas with hydrogen densities of order 10^9 cm^-3 and 5000<T<15000 K. These objects are associated with low mass accretion rates. Type 4 (L-shaped) Balmer and type B Paschen decrements are found in conjunction with very wide line profiles and are characteristic of strong accretors, with optically thick emission from high-density gas (log n_H > 11 cm^-3). Type 1 (curved) Balmer decrements are observed only in three sub-luminous sources viewed edge-on, so we speculate that these are actually reddened type 2 decrements. About 20% of the objects present type 3 Balmer decrements (bumpy), which cannot be reproduced with current models.Comment: 29 pages, accepted by A&

Numerical study of surface-induced reorientation and smectic layering in a nematic liquid crystal

Surface-induced profiles of both nematic and smectic order parameters in a nematic liquid crystal, ranging from an orienting substrate to "infinity", were evaluated numerically on base of an extended Landau theory. In order to obtain a smooth behavior of the solutions at "infinity" a boundary energy functional was derived by linearizing the Landau energy around its equilibrium solutions. We find that the intrinsic wave number of the smectic structure, which plays the role of a coupling between nematic and smectic order, strongly influences the director reorientation. Whereas the smectic order is rapidly decaying when moving away from the surface, the uniaxial nematic order parameter shows an oscillatory behavior close to the substrate, accompanied by a non-zero local biaxiality.Comment: LaTeX, 17 pages, with 4 postscript figure

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&

PENGARUH KINERJA KEUANGAN DAN UKURAN PERUSAHAAN TERHADAP HARGA SAHAM (Studi pada Perusahaan Perbankan yang Terdaftar di Bursa Efek Indonesia Tahun 2012-2014)

Penelitian ini dilakukan untuk menguji pengaruh Kinerja Keuangan dan Ukuran Perusahaan terhadap Harga Saham pada Perusahaan Perbankan yang terdaftar di Bursa Efek Indonesia tahun 2012 sampai 2014. Variabel yang digunakan adalah Capital Adequacy Ratio (CAR), Non Performing Loan (NPL), Return On Asset (ROA), Loan to Deposit Ratio (LDR), Firm Size (Ukuran Perusahaan). Teknik sampling yang digunakan adalah purposive sampling selama kurun waktu penelitian tahun 2012 sampai 2014. Data diperoleh berdasarkan publikasi Indonesian Capital Market Directory (ICMD 2015). Dan diperoleh jumlah sampel sebanyak 18 perusahaan. Teknik analisis yang digunakan adalah regresi berganda dengan persamaan kuadrat terkecil dan uji hipotesis menggunakan t-statistik untuk menguji koefisien regresi parsial serta f-statistik untuk menguji keberartian pengaruh secara bersama-sama dengan level of significance 5%. Selain itu juga dilakukan uji asumsi klasik yang meliputi uji normalitas, uji multikolinearitas, uji heteroskedastisitas, dan uji autokolerasi. Berdasarkan karakteristik keseluruhan data, tidak terjadi penyimpangan asumsi klasik, hal ini menunjukkan bahwa data yang tersedia telah memenuhi syarat untuk menggunakan model persamaan regresi linier berganda. Dari hasil penelitian menunjukkan bahwa variabel independen yang terdiri dari CAR, NPL, ROA, LDR, dan FIRM SIZE tahun 2012-2014 secara simultan mempunyai pengaruh signifikan terhadap harga saham. Adapun secara parsial, variabel ROA berpengaruh signifikan positif. Sedangkan variabel CAR, NPL, LDR dan FIRM SIZE berpengaruh signifikan negatif terhadap harga saham. Hasil uji R square pada penelitian ini menunjukkan bahwa variabel CAR, NPL, ROA, LDR, dan FIRM SIZE memiliki pengaruh 20,7% terhadap harga saham. Kata Kunci : CAR, NPL, ROA, LDR, Firm Size, Harga Saham

Tracking the Orbital and Super-orbital Periods of SMC X-1

The High Mass X-ray Binary (HMXB) SMC X-1 demonstrates an orbital variation of 3.89 days and a super-orbital variation with an average length of 55 days. As we show here, however, the length of the super-orbital cycle varies by almost a factor of two, even across adjacent cycles. To study both the orbital and super-orbital variation we utilize lightcurves from the Rossi X-ray Timing Explorer All Sky Monitor (RXTE-ASM). We employ the orbital ephemeris from Wojdowski et al. (1998) to obtain the average orbital profile, and we show that this profile exhibits complex modulation during non-eclipse phases. Additionally, a very interesting ``bounceback'' in X-ray count rate is seen during mid-orbital eclipse phases, with a softening of the emission during these periods. This bounceback has not been previously identified in pointed observations. We then define a super-orbital ephemeris (the phase of the super-orbital cycle as a function of date) based on the ASM lightcurve and analyze the trend and distribution of super-orbital cycle lengths. SMC X-1 exhibits a bimodal distribution of these lengths, similar to what has been observed in other systems (e.g., Her X-1), but with more dramatic changes in cycle length. There is some hint, but not conclusive evidence, for a dependence of the super-orbital cycle length upon the underlying orbital period, as has been observed previously for Her X-1 and Cyg X-2. Using our super-orbital ephemeris we are also able to create an average super-orbital profile over the 71 observed cycles, for which we witness overall hardening of the spectrum during low count rate times. We combine the orbital and super-orbital ephemerides to study the correlation between the orbital and super-orbital variations in the system.Comment: 10 pages, using emulateapj style. To be published in the Astrophysical Journa

A study of top polarization in single-top production at the LHC

This paper complements the study of single top production at the LHC aiming to estimate the sensitivity of different observables to the magnitude of the effective couplings. In a previous paper the dominant $W$-gluon fusion mechanism was considered, while here we extend the analysis to the subdominant (10% with our set of experimental cuts) s-channel process. In order to distinguish left from right effective couplings it is required to consider polarized cross-sections and/or include $m_b$ effects. The spin of the top is accessible only indirectly by measuring the angular distribution of its decay products. We show that the presence of effective right-handed couplings implies necessarily that the top is not in a pure spin state. We discuss to what extent quantum interference terms can be neglected in the measurement and therefore simply multiply production and decay probabilities clasically. The coarsening involved in the measurement process makes this possible. We determine for each process the optimal spin basis where theoretical errors are minimized and, finally, discuss the sensitivity in the s-channel to the effective right-handed coupling. The results presented here are all analytical and include $m_b$ corrections. They are derived within the narrow width approximation for the top.Comment: 30 pages, 14 figure

Discovery of Extremely Embedded X-ray Sources in the R Coronae Australis Star Forming Core

With the XMM-Newton and Chandra observatories, we detected two extremely embedded X-ray sources in the R Corona Australis (R CrA) star forming core, near IRS 7. These sources, designated as XB and XA, have X-ray absorption columns of ~3e23 cm-2 equivalent to AV ~180 mag. They are associated with the VLA centimeter radio sources 10E and 10W, respectively. XA is the counterpart of the near-infrared source IRS 7, whereas XB has no K-band counterpart above 19.4 mag. This indicates that XB is younger than typical Class I protostars, probably a Class 0 protostar or in an intermediate phase between Class 0 and Class I. The X-ray luminosity of XB varied between 29<log LX <31.2 ergs s-1 on timescales of 3-30 months. XB also showed a monotonic increase in X-ray brightness by a factor of two in 30 ksec during an XMM-Newton observation. The XMM-Newton spectra indicate emission from a hot plasma with kT ~3-4 keV and also show fluorescent emission from cold iron. Though the X-ray spectrum from XB is similar to flare spectra from Class I protostars in luminosity and temperature, the light curve does not resemble the lightcurves of magnetically generated X-ray flares because the variability timescale of XB is too long and because variations in X-ray count rate were not accompanied by variations in spectral hardness. The short-term variation of XB may be caused by the partial blocking of the X-ray plasma, while the month-long flux enhancement may be driven by mass accretion.Comment: 26 pages, 8 figures, To be published in ApJ in April 200