Direct detection of exoplanet host star companion γ Cep B and revised masses for both stars and the sub-stellar object

Context. The star γ Cep is known as a single-lined spectroscopic triple system at a distance of 13.8 pc, composed of a K1 III-IV primary star with V = 3.2 mag, a stellar-mass companion in a 66-67 year orbit (Torres 2007, ApJ, 654, 1095), and a substellar companion with M_p sin i = 1.7 M_(Jup) that is most likely a planet (Hatzes et al. 2003, ApJ, 599, 1383). Aims. We aim to obtain a first direct detection of the stellar companion, to determine its current orbital position (for comparison with the spectroscopic and astrometric data), its infrared magnitude and, hence, mass. Methods. We use the Adaptive Optics camera CIAO at the Japanese 8 m telescope Subaru on Mauna Kea, Hawaii, with the semi-transparent coronograph to block most of the light from the bright primary γ Cep A, and to detect at the same time the faint companion B. In addition, we also used the IR camera Ω Cass at the Calar Alto 3.5 m telescope, Spain, to image γ Cep A and B by adding up many very short integrations (without AO). Results. γ Cep B is clearly detected on our CIAO and Ω Cass images. We use a photometric standard star to determine the magnitude of B after PSF subtraction in the Subaru image, and the magnitude difference between A and B in the Calar Alto images, and find an average value of K = 7.3 ± 0.2 mag. The separations and position angles between A and B are measured on 15 July 2006 and 11 and 12 Sept. 2006, B is slightly south of west of A. Conclusions. By combining the radial velocity, astrometric, and imaging data, we have refined the binary orbit and determined the dynamical masses of the two stars in the γ Cep system, namely 1.40 ± 0.12 M_☉ for the primary and 0.409 ± 0.018 M_☉ for the secondary (consistent with being a M4 dwarf). We also determine the minimum mass of the sub-stellar companion to be M_p sin i = 1.60 ± 0.13 M_(Jup)

Direct detection of exoplanet host star companion gamma Cep B and revised masses for both stars and the sub-stellar object

The star gamma Cep is known as a single-lined spectroscopic triple system at a distance of 13.8 pc, composed of a K1 III-IV primary star with V = 3.2 mag, a stellar-mass companion in a 66--67 year orbit (Torres 2006), and a substellar companion with M_p sin i = 1.7 M_Jup that is most likely a planet (Hatzes et al. 2003). We aim to obtain a first direct detection of the stellar companion, to determine its current orbital position (for comparison with the spectroscopic and astrometric data), its infrared magnitude and, hence, mass. We use the Adaptive Optics camera CIAO at the Japanese 8m telescope Subaru on Mauna Kea, Hawaii, with the semi-transparent coronograph to block most of the light from the bright primary gamma Cep A, and to detect at the same time the faint companion B. In addition, we also used the IR camera Omega-Cass at the Calar Alto 3.5m telescope, Spain, to image gamma Cep A and B by adding up many very short integrations (without AO). gamma Cep B is clearly detected on our CIAO and Omega-Cass images. We use a photometric standard star to determine the magnitude of B after PSF subtraction in the Subaru image, and the magnitude difference between A and B in the Calar Alto images, and find an average value of K = 7.3 \pm 0.2 mag. The separations and position angles between A and B are measured on 15 July 2006 and 11 and 12 Sept 2006, B is slightly south of west of A. By combining the radial velocity, astrometric, and imaging data, we have refined the binary orbit and determined the dynamical masses of the two stars in the gamma Cep system, namely 1.40 \pm 0.12 M_sun for the primary and 0.409 \pm 0.018 M_sun for the secondary (consistent with being a M4 dwarf). We also determine the minimum mass of the sub-stellar companion to be M_p sin i = 1.60 \pm 0.13 M_Jup

V1647 Orionis (IRAS 05436-0007) : A New Look at McNeil's Nebula

We present a study of the newly discovered McNeil's nebula in Orion using the JHKs-band simultaneous observations with the near-infrared (NIR) camera SIRIUS on the IRSF 1.4m telescope. The cometary infrared nebula is clearly seen extending toward north and south from the NIR source (V1647 Orionis) that illuminates McNeil's nebula. The compact nebula has an apparent diameter of about 70 arcsec. The nebula is blue (bright in J) and has a cavity structure with two rims extending toward north-east and north-west. The north-east rim is brighter and sharp, while the north-west rim is diffuse. The north-east rim can be traced out to ~ 40 arcsec from the location of the NIR source. In contrast, no cavity structure is seen toward the south, although diffuse nebula is extended out to ~ 20 arcsec. New NIR photometric data show a significant variation in the magnitudes (> 0.15 mag) of the source of McNeil's nebula within a period of one week, that is possibly under the phase of eruptive variables like FUors or EXors.Comment: 13 pages, 5 figures in JPEG format. Accepted for the publication in PASJ Letter

A New Galactic Extinction Map of the Cygnus Region

We have made a Galactic extinction map of the Cygnus region with 5' spatial resolution. The selected area is 80^\circ to 90^\circ in the Galactic longitude and -4^\circ to 8^\circ in the Galactic latitude. The intensity at 140 \mum is derived from the intensities at 60 and 100 \mum of the IRAS data using the tight correlation between 60, 100, and 140 \mum found in the Galactic plane. The dust temperature and optical depth are calculated with 5' resolution from the 140 and 100 \mum intensity, and Av is calculated from the optical depth. In the selected area, the mean dust temperature is 17 K, the minimum is 16 K, and the maximum is 30 K. The mean Av is 6.5 mag, the minimum is 0.5 mag, and the maximum is 11 mag. The dust temperature distribution shows significant spatial variation on smaller scales down to 5'. Because the present study can trace the 5'-scale spatial variation of the extinction, it has an advantage over the previous studies, such as the one by Schlegel, Finkbeiner, & Davis, who used the COBE/DIRBE data to derive the dust temperature distribution with a spatial resolution of 1^\circ. The difference of Av between our map and Schlegel et al.'s is \pm 3 mag. A new extinction map of the entire sky can be produced by applying the present method.Comment: 27 pages, 14 figures, accepted for publication in Ap

Site-Specific Cleavage by Topoisomerase 2: A Mark of the Core Centromere.

In addition to its roles in transcription and replication, topoisomerase 2 (topo 2) is crucial in shaping mitotic chromosomes and in ensuring the orderly separation of sister chromatids. As well as its recruitment throughout the length of the mitotic chromosome, topo 2 accumulates at the primary constriction. Here, following cohesin release, the enzymatic activity of topo 2 acts to remove residual sister catenations. Intriguingly, topo 2 does not bind and cleave all sites in the genome equally; one preferred site of cleavage is within the core centromere. Discrete topo 2-centromeric cleavage sites have been identified in α-satellite DNA arrays of active human centromeres and in the centromere regions of some protozoans. In this study, we show that topo 2 cleavage sites are also a feature of the centromere in Schizosaccharomyces pombe, the metazoan Drosophila melanogaster and in another vertebrate species, Gallus gallus (chicken). In vertebrates, we show that this site-specific cleavage is diminished by depletion of CENP-I, an essential constitutive centromere protein. The presence, within the core centromere of a wide range of eukaryotes, of precise sites hypersensitive to topo 2 cleavage suggests that these mark a fundamental and conserved aspect of this functional domain, such as a non-canonical secondary structure

The human Mis12 complex is required for kinetochore assembly and proper chromosome segregation

During cell division, kinetochores form the primary chromosomal attachment sites for spindle microtubules. We previously identified a network of 10 interacting kinetochore proteins conserved between Caenorhabditis elegans and humans. In this study, we investigate three proteins in the human network (hDsn1Q9H410, hNnf1PMF1, and hNsl1DC31). Using coexpression in bacteria and fractionation of mitotic extracts, we demonstrate that these proteins form a stable complex with the conserved kinetochore component hMis12. Human or chicken cells depleted of Mis12 complex subunits are delayed in mitosis with misaligned chromosomes and defects in chromosome biorientation. Aligned chromosomes exhibited reduced centromere stretch and diminished kinetochore microtubule bundles. Consistent with this, localization of the outer plate constituent Ndc80HEC1 was severely reduced. The checkpoint protein BubR1, the fibrous corona component centromere protein (CENP) E, and the inner kinetochore proteins CENP-A and CENP-H also failed to accumulate to wild-type levels in depleted cells. These results indicate that a four-subunit Mis12 complex plays an essential role in chromosome segregation in vertebrates and contributes to mitotic kinetochore assembly