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.
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.
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.
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)
118902770
A search for wide visual companions of exoplanet host stars: The Calar Alto Survey
We have carried out a search for co-moving stellar and substellar companions around 18 exoplanet host stars with the infrared camera MAGIC at the 2.2 m Calar Alto telescope, by comparing our images with images from the all sky surveys 2MASS, POSS I and II. Four stars of the sample namely HD80606, 55 Cnc, HD46375 and BD–10°3166, are listed as binaries in the Washington Visual Double Star Catalogue (WDS). The binary nature of HD80606, 55 Cnc, and HD46375 is confirmed with both astrometry as well as photometry, thereby the proper motion of the companion of HD46375 was determined here for the first time.We derived the companion masses as well as the longterm stability regions for additional companions in these three binary systems. We can rule out further stellar companions around all stars in the sample with projected separations between 270AU and 2500AU, being sensitive to substellar companions with masses down to ∼60 MJup (S /N = 3). Furthermore we present evidence that the two components of the WDS binary BD–10°3166 are unrelated stars, i.e this system is a visual pair. The spectrophotometric distance of the primary (a K0 dwarf) is ∼67 pc, whereas the presumable secondary BD–10°3166B (a M4 to M5 dwarf) is located at a distance of 13 pc in the foreground. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
3235867
On the possibility of ground-based direct imaging detection of extra-solar planets: the case of TWA-7 ?
We show that ground-baseddirect imaging detection of extra-solar planets is possible with current technology. As an example, we present evidence for a possible planetary compan- ion to the young T Tauri star 1RXSJ104230.3 334014 (=TWA- 7), discovered by ROSAT as a member of the nearby TW Hya association. In an HST NICMOS F160W image, an object is detected that is more than 9 mag fainter than TWA-7, located 2:4450:035 00 south-east at a position angle of 142:241:34. One year later using the ESO-NTT with the SHARP speckle camera, we obtained H- and K-band detections of this faint ob- ject at a separation of 2:536 0:077 00 and a position angle of 139:3 2:1. Given the known proper motion of TWA-7, the pair may form a proper motion pair. If the faint object orbits TWA-7, then its apparent magnitudes of H=16:42 0:11 and K=16:340:15 mag yield absolute magnitudes consistent with a 10 6:5 yr old 3 Mjup mass object according to the non- gray theory by Burrows et al. (1997). At 55 pc, the angular separation of 2:5 00 corresponds to 138 AU, clearly within typical disk sizes. However, position angles and separations are slightly more consistent with a background object than with a companion.
115154823
Balanced Hermitian metrics from SU(2)-structures
We study the intrinsic geometrical structure of hypersurfaces in six-manifolds carrying a balanced Hermitian SU(3)-structure, which we call balanced SU(2)-structure. We provide sufficient conditions, in terms of suitable evolution equations, which imply that a five-manifold with such structure can be isometrically embedded as a hypersurface in a balanced Hermitian SU(3)-manifold. Any five-dimensional compact nilmanifold has an invariant balanced SU(2)-structure, and we show how some of them can be evolved to give new explicit examples of balanced Hermitian SU(3)-structures. Moreover, for n=3,4, we present examples of compact solvmanifolds endowed with a balanced SU(n)-structure such that the corresponding Bismut connection has holonomy equal to SU(n).
123499216
New silicon microstrip detectors optimized for tracker alignment
The resolution of tracking systems based on layers of silicon microstrips is comparable to the stability of the structures on which they are mounted. Environmental changes during operation will misalign the modules out of their nominal positions. A straight laser beam that sequentially traverses consecutive layers of microstrips can be used as an artificial track to align them. For such a laser track to reach the last sensor, high transmittance of microstrips to infrared (IR) light is needed. We have simulated the passage of a coherent beam of light through a microstrip detector and identified the minimum set of changes to the design that boosts its transmittance. The simulation has been validated against real microstrip detector samples.
120064071
Semitransparent amorphous silicon sensors for the CMS alignment: an in-depth study
Abstract Semitransparent amorphous silicon sensors have been proposed as the 2D positioning sensors for the link system of the CMS alignment. An in-depth study of the actual performance of these sensors is here reported.
139842026
Test Results of the Semi-transparent Amorphous Silicon Sensors for the Link System of CMS
120520890
Silicon microstrip detectors for future tracker alignment systems
Abstract The next experiments at particles colliders will demand stability of the tracking systems to the level of few microns. The available technology cannot provide a supporting structure able to guarantee this degree of stability in working condition, when environmental changes will misalign the detectors out of their nominal position. Based on the successful experience of AMS and CMS tracker systems, we propose to use infrared laser beams traversing consecutive layers of silicon detectors to align them with respect to the beams. For such a laser track to reach the last sensor, high transmittance of microstrip sensors to infrared (IR) light is needed. We simulated the passage of a coherent beam of light through a microstrips detector and we identified the minimum set of changes to the design and technology that boost its transmittance while still respecting its tracking capabilities. The first prototypes are in process at IMB-CNM clean room facilities. We held the fabrication process at an intermediate step and we performed the first measurements of transmittance and reflectance on the sensors.