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The absolute magnitudes of Cepheids and the extragalacticdistance scale
Feast, Michael
It is pointed out that a Cepheid period-luminosity relation with a zero-point from Hipparcos trigonometrical parallaxes and a consistent reddening system zero-point implies that some recent estimates of H_0 based on the Cepheid scale should be increased by ~8 per cent. This result avoids using the distance to the Large Magellanic Cloud (LMC) as an…
CCD photometry of variable stars in the Magellanic Clouds - VI. The eclipsing binary HV982 in the Large Magellanic Cloud
Guinan, E. F.; Pritchard, J. D.; Tobin, W. +1 more
Using improved techniques, high-quality CCD uvbyVI photometry has been obtained for the eclipsing binary HV982 in the Large Magellanic Cloud (LMC). International Ultraviolet Explorer ultraviolet spectrophotometry was also obtained. These data have been analysed using the Wilson-Devinney synthetic light-curve code and Kurucz low-metallicity model a…
Phase-resolved Hubble Space Telescope ultraviolet spectroscopy of V795 HER
Prinja, R. K.; Mason, K. O.; Howell, S. B. +2 more
We present highly time-resolved HST FOS UV spectroscopy of the nova-like binary V795 Her. Several key results emerge. For the first time we find a strong 2.6-h signature in the variability of the UV lines. The HST data reveal no evidence of a 4.8-h `period', in contrast to our previous IUE observations. This, and differences in the spectral line c…
SBF distances to Leo and Virgo using the HST
Morris, P. W.; Shanks, T.
We use archive HST WFPC2 data for three elliptical galaxies (NGC 3379 in the Leo I group, and NGC 4472 and 4406 in the Virgo cluster) to determine their distances using the surface brightness fluctuation (SBF) method as described by Tonry & Schneider. A comparison of the HST results with the SBF distance moduli found by Ciardullo et al. shows …
Beta Cephei type variability in the ultraviolet spectrum and radial velocity of PHL 346
Dufton, P. L.; van Leeuwen, F.; Keenan, F. P. +4 more
International Ultraviolet Explorer low-resolution and optical moderate-resolution spectra are presented for the high galactic latitude beta Cephei type star, PHL 346. Variability is identified in both the ultraviolet flux and the radial velocity with periods and phases consistent with those previously deduced from optical photometry. The similarit…
Two serendipitous low-mass LMC clusters discovered with HST1
Elson, Rebecca A. W.; Sigurdsson, Steinn; Gilmore, Gerard F. +1 more
We present V and I photometry of two open clusters in the LMC down to V~26. The clusters were imaged with the Wide Field and Planetary Camera 2 (WFPC2) on board the Hubble Space Telescope (HST), as part of the Medium Deep Survey Key Project. Both are low-luminosity (M_V~-3.5), low-mass (M~10^3 Msolar) systems. The chance discovery of these two clu…
The stellar content of a spiral arm of NGC 4321
Dolphin, Andrew E.; Hodge, Paul W.; Wyder, Ted K.
The effects of the passage of a spiral arm through the disc of the giant Virgo Sc galaxy NGC 4321 are investigated with Hubble Space Telescope WFPC2 images in two colours. Concentrating on a portion of the southern spiral arm of NGC 4321, we have applied a new program to solve for the star formation histories in the arm and interarm regions separa…
The Cepheid period-luminosity zero-point from HIPPARCOS trigonometrical parallaxes
Catchpole, R. M.; Feast, M. W.
Hipparcos trigonometrical parallaxes of Cepheid variables are used to derive a zero-point for the period-luminosity (PL) relation. Adopting a slope from the Large Magellanic Cloud (LMC), the relation is found to be <M_V>=-2.81 log P-1.43. The standard error of the zero-point is 0.10 mag. Together with metallicity corrections this corresponds…
Cross-correlation characteristics of OB stars from IUE spectroscopy
Howarth, Ian D.; Prinja, Raman K.; Siebert, Kaj W. +1 more
We present a catalogue of homogeneous measures of the linewidth parameter, v_esin i, for 373 O-type stars and early B supergiants (including the separate components of 25 binary and three triple systems), produced by cross-correlating high-resolution, short-wavelength IUE spectra against a `template' spectrum of tauSco. We also tabulate terminal v…
Galactic kinematics of Cepheids from HIPPARCOS proper motions
Feast, Michael; Whitelock, Patricia
The Hipparcos proper motions of 220 Galactic Cepheids, together with relevant ground-based photometry, have been analysed. The effects of Galactic rotation are very clearly seen. Mean values of the Oort constants, A=14.82+/-0.84 km s^-1 kpc^-1, and B=-12.37+/-0.64 km s^-1 kpc^-1, and of the angular velocity of circular rotation at the Sun, Omega_o…