A non-main-sequence secondary in SY Cancri Smith, Robert Connon; Mehes, Otto; Vande Putte, Dave ...
Monthly notices of the Royal Astronomical Society,
06/2005, Volume:
360, Issue:
1
Journal Article
Peer reviewed
Open access
Simultaneous spectroscopic and photometric observations of the Z Cam type dwarf nova SY Cancri were used to obtain absolute flux calibrations. A comparison of the photometric calibration with a ...wide-slit spectrophotometric calibration showed that either method is equally satisfactory. A radial velocity study of the secondary star, made using the far-red Nai doublet, yielded a semi-amplitude of K2= 127 ± 23 km s−1. Taking the published value of 86 ± 9 km s−1 for K1 gives a mass ratio of q=M2/M1= 0.68 ± 0.14; this is very different from the value of 1.13 ± 0.35 quoted in the literature. Using the new lower mass ratio, and constraining the mass of the white dwarf to be within reasonable limits, then leads to a mass for the secondary star that is substantially less than would be expected for its orbital period if it satisfied a main-sequence mass–radius relationship. We find a spectral type of M0 that is consistent with that expected for a main-sequence star of the low mass we have found. However, in order to fill its Roche lobe, the secondary must be significantly larger than a main-sequence star of that mass and spectral type. The secondary is definitely not a normal main-sequence star.
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The Galactic population of Open Clusters provides an insight into star formation in the Galaxy. The open cluster catalogue by Dias et al. Astron. Astrophys. 389, 871 (2002) is a rich source of data, ...including kinematic information. This large sample made it possible to carry out a systematic analysis of 481 open cluster orbits, using parameters based on orbit eccentricity and separation from the Galactic plane. These two parameters may be indicative of origin, and we find them to be correlated. We also find them to be correlated with metallicity, another parameter suggested elsewhere to be a marker for origin in that high values of any of these two parameters generally indicate a low metallicity (Fe/H Solar<−0.2dex). The resulting analysis points to four open clusters in the catalogue being of extra-Galactic origin by impact of high velocity cloud on the disk: Berkeley21, 32, 99, and Melotte66, with a possible further four due to this origin (NGC2158, 2420, 7789, IC1311). A further three may be due to Galactic globular cluster impact on the disk i.e of internal Galactic origin (NGC6791, 1817, and 7044).
Prompted by the possibility that we have observed star formation triggered by globular cluster and dwarf spheroidal transits through galactic disks, we have examined kinematic evidence as to whether ...the superstar clusters in the Galactic bulge could have been formed from such transits. From their trajectores, we cannot exclude such a possibility. We note also that the high frequency of these transits may have generated rapid star formation at early times, and that remnant cluster cores may themselves nucleate further star formation.
A non-main-sequence secondary in SY Cancri Smith, Robert Connon; Mehes, Otto; Vande Putte, Dave ...
Monthly notices of the Royal Astronomical Society,
06/2005, Volume:
360, Issue:
1
Journal Article
Peer reviewed
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
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