10656237
Rotation periods of Post-T Tauri stars in Lindroos systems
We present a rotational study of Post-T Tauri stars (PTTSs) in Lindroos systems, defined as binaries with early type primaries on the main-sequence (MS) and late-type secondaries on the pre-main-sequence (PMS) phase. The importance of this study in comparison with previous ones is that the Lindroos sample is not X-ray selected so we avoid a possible bias towards fast rotators. In this preliminary study we have monitored eleven stars in the UBVRI bands during two campaigns of ten consecutive nights each. Eight of the observed PTTSs show periodic modulations in their lightcurves and the derived periods range from 1.9 d to 8.0 d. The comparison of these results with theoretical rotational tracks based on disk-star locking theory shows that star-disk decoupling times of 1−20 Myr could reproduce the rotational properties of the targets, assuming an initial rotation period of ∼ 8d and a mass of 1M� . We have studied the rotation-activity relations of Lindroos PTTSs and compared them with those found in other groups of PMS and zero-age main-sequence (ZAMS) ∼1 Mstars. The Lindroos sample displays activity-rotation relations very similar to those found in TTSs. It contains a mixture of very active stars, with LX/Lbol ratios close to the saturation level of -3, and less active (unsaturated) stars. This could be the result of different star-disk decoupling times. Future monitoring of a larger and unbiased sample of PTTS will be important to confirm the significance of these results.
118556816
The stellar content of the young open cluster Trumpler 37
With an apparent cluster diameter of 1.5° and an age of 4 Myr, Trumpler 37 is an ideal target for photometric monitoring of young stars as well as for the search of planetary transits, eclipsing binaries and other sources of variability. The YETI consortium has monitored Trumpler 37 throughout 2010 and 2011 to obtain a comprehensive view of variable phenomena in this region. In this first paper we present the cluster properties and membership determination as derived from an extensive investigation of the literature. We also compared the coordinate list to some YETI images. For 1872 stars we found literature data. Among them 774 have high probability of being member and 125 a medium probability. Based on infrared data we re-calculate a cluster extinction of 0.9–1.2 mag. We can confirm the age and distance to be 3–5 Myr and870 pc. Stellar masses are determined from theoretical models and the mass function is fitted with a power-law index of α = 1.90 (0.1–0.4 M⊙) and α = 1.12 (1–10 M⊙). (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
118040393
A Search for Wide (Sub)Stellar Companions Around Extrasolar Planet Host Stars
We present an overview of our ongoing systematic search for wide (sub)stellar companions around the stars known to host rad‐vel planets. By using a relatively large field of view and going very deep, our survey can find all directly detectable stellar and massive brown dwarf companions (m>40 MJup) within a 1000 AU orbit.
118472064
Coordinated Multiwavelength Observations of V410Tau
In November 2001 we undertook a coordinated observing campaign to study the connection between X-ray and optical variability in the weak-line T Tauri star V410Tau. The observing plan included three 15 ksec observations with Chandra using the Advanced CCD Imaging Spectrometer for Spectroscopy scheduled for different phases of the known 1.87 d starspot cycle. Photometric and spectroscopic monitoring of V410Tau involving telescopes on three different continents was scheduled simultaneously with the Chandra exposures.
118032689
The Variable Star One-shot Project, and its little child: Wikimbad
The Variable Star One-shot Project (VSOP) aimed at providing to the world-wide stellar community the necessary one-shot spectrum of unstudied variable stars, too often classified as such by an analysis of photometric data only. The VSOP has established an new kind of observational model, where all steps from observations to spectral analysis, are automatized (or are underway to be fully automatized). The project is centralized on a collaborative wiki website. The VSOP operational model is very successful, data is continously flowing and being analyszed, and VSOP is now a worldwide open collaboration of people with very different and complementary skills and expertise. The idea of a central wiki website has been extended by one of us to propose a new service to the whole astronomical community, called Wikimbad. Wikimbad is an open wiki website aimed at collecting, organizing and making publicly available all kind of reduced and published astronomical data. Its strengths and a comparison with the Virtual Observatory are discussed. See: this http URL and this http URL
17464041
The T Tauri star RX J1608.6-3922 -not an eclipsing binary but a spotted single star
High-resolution spectroscopy and photometric monitoring of the pre-main sequence star RX J1608.6-3922 shows that it is not an eclipsing binary, as previously claimed. Radial velocity measurements covering suitable time spans in order to detect a spectroscopic binary with the claimed period of about 7 days have been performed. The scatter of the radial velocity does not exceed 2.4 km s -1 , defining an upper mass limit of 24 $M_{{\tiny Jupiter}}$ for any eclipsing companion orbiting this star with the claimed period. Photometric observations of RX J1608.6-3922 in 7 consecutive nights (i.e. as long as the claimed orbital period) reveal brightness variations of the order of 0.2 mag with a period of 3.6 days. The shape of the detected light curve differs from a light curve of the star recorded in 1996. The small variations of the radial velocity, the variable shape of the light curve, as well as ($B-V$) color variations suggest that the flux of RX J1608.6-3922 is modulated by spots on the stellar surface with a rotational period of 3.6 days. The stellar activity of this star seems to be highly variable, taking into account the variable shape of the light curve, with an amplitude varying from 0.5 to 0.2 mag in a few years, as well as hints for a variable H α equivalent width.
26141595
First investigation of a novel 2D position-sensitive semiconductor detector concept
This paper presents a first study of the performance of a novel 2D position-sensitive microstrip detector, where the resistive charge division method was implemented by replacing the metallic electrodes with resistive electrodes made of polycrystalline silicon. A characterization of two proof-of-concept prototypes with different values of the electrode resistivity was carried out using a pulsed Near Infra-Red laser. The experimental data were compared with the electrical simulation of the sensor equivalent circuit coupled to simple electronics readout circuits. The good agreement between experimental and simulation results establishes the soundness of resistive charge division method in silicon microstrip sensors and validates the developed simulation as a tool for the optimization of future sensor prototypes. Spatial resolution in the strip length direction depends on the ionizing event position. The average value obtained from the protype analysis is close to 1.2% of the strip length for a 6 MIP signal.
119795166
2D position sensitive microstrip sensors with charge division along the strip: Studies on the position measurement error
Abstract Position sensitivity in semiconductor detectors of ionizing radiation is usually achieved by the segmentation of the sensing diode junction in many small sensing elements read out separately as in the case of conventional microstrips and pixel detectors. Alternatively, position sensitivity can be obtained by splitting the ionization signal collected by one single electrode amongst more than one readout channel with the ratio of the collected charges depending on the position where the signal was primary generated. Following this later approach, we implemented the charge division method in a conventional microstrip detector to obtain position sensitivity along the strip. We manufactured a proof-of-concept demonstrator where the conventional aluminum electrodes were replaced by slightly resistive electrodes made of strongly doped poly-crystalline silicon and being readout at both strip ends. Here, we partially summarize the laser characterization of this first proof-of-concept demonstrator with special emphasis on the study on how the different noise sources are affecting the device position error along the strip.
12971013
Measurement of residual nucleus cross sections and recoil energies in p + Fe collisions at 300, 500, 750, 1000 and 1500 MeV
The production of residual nuclei in p + Fe collisions has been measured at GSI on the FRS facility by means of the reverse kinematic techniques at 300, 500, 750, 1000 and 1500 MeV/A. The cross‐sections larger than 0.01 mb of all isotopes with Z larger than 8 have been obtained. Velocity distributions were also measured. Comparisons to models describing spallation reactions and some empirical formulae often used in astrophysics are presented. These data are directly used to calculate impurety production and DPAs in a thin window as foreseen in spallation sources or accelerator‐driven systems.
16989103
First test of tiltmeters for the link system of CMS
In this note we present first tests done with the tiltmeters proposed as the key elements of the Laser Level systems to be used in the CMS alignment system. The reponse of the sensors under moderated longitudinal and transversal tilts is studied and intrinsic perform ance is extracted.
121731391
Revised and extended level scheme of the doubly-odd nucleus 188Ir
High-spin states in the doubly odd $Z=77$ nucleus $^{188}\mathrm{Ir}$ were studied using the reaction $^{186}\mathrm{W}$($^{7}\mathrm{Li}$, $5n$) at 59 MeV and the GASP spectrometer for \ensuremath{\gamma}-ray detection. The level structures recently suggested to be built on the known 4.1(3) ms isomeric state of this nucleus have been considerably revised and extended and an isomer with a lifetime of 17.7(2) ns has been identified within the main decay sequence. In addition two rotational bands built on low spin states below the ms isomer have been observed for the first time. The basic features of the excitation scheme of $^{188}\mathrm{Ir}$ are discussed within the Hartree-Fock-Bogoliubov theory within the Lipkin-Nogami approach with the finite-range density-dependent Gogny force.