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Spectroscopy and Doppler tomography of BZ Ursae Majoris in quiescence  [PDF]
V. V. Neustroev,A. Medvedev,S. Turbin,N. Borisov
Physics , 2001,
Abstract: We present the first results of time-resolved spectroscopic observations of little-studied dwarf nova BZ Ursae Majoris in quiescence.
The system parameters of DW Ursae Majoris  [PDF]
S. Araujo-Betancor,C. Knigge,K. S. Long,D. W. Hoard,P. Szkody,B. Rodgers,K. Krisciunas,V. S. Dhillon,R. I. Hynes,J. Patterson,J. Kemp
Physics , 2002, DOI: 10.1086/345098
Abstract: We present new constraints on the system parameters of the SW Sextantis star DW Ursae Majoris, based on ultraviolet (UV) eclipse observations with the Hubble Space Telescope. Our data were obtained during a low state of the system, in which the UV light was dominated by the hot white dwarf (WD) primary. Eclipse analysis, using the full Roche lobe geometry, allows us to set firm limits on the masses and radii of the system components and the distance between them: 0.67 \leq M_1/M_sun \leq 1.06, 0.008 \leq R_1/R_sun \leq 0.014, M_2/M_sun > 0.16, R_2/R_sun > 0.28 and a/R_sun > 1.05. For q = M_2/M_1 < 1.5 the inclination must satisfy i > 71 degrees. Using Smith & Dhillon's mass-period relation for CV secondaries, our estimates for the system parameters become M_1/M_sun = 0.77 \pm 0.07, R_1/R_sun = 0.012 \pm 0.001, M_2/M_sun = 0.30 \pm 0.10, R_2/R_sun = 0.34 \pm 0.04, q =0.39 \pm 0.12, i = 82 \pm 4 degrees and a/R_sun = 1.14 \pm 0.06. We have also estimated the spectral type of the secondary, M3.5 \pm 1.0, and distance to the system, d =930 \pm 160 pc, from time-resolved I- and K-band photometry. Finally, we have repeated Knigge et al.'s WD model atmosphere fit to the low-state UV spectrum of DW UMa in order to account for the higher surface gravity indicated by our eclipse analysis. In this way we obtained a second estimate for the distance, d = 590 \pm 100 pc, which allows us to obtain a second estimate for the spectral type of the secondary, M7 \pm 2.0. We conclude that the true value for the distance and spectral type will probably be in between the values obtained by the two methods.
A BVRcIc Survey of W Ursae Majoris Binaries  [PDF]
Dirk Terrell,John Gross,Walter R. Cooney Jr
Physics , 2012, DOI: 10.1088/0004-6256/143/4/99
Abstract: We report on a BVRcIc survey of field W Ursae Majoris binary stars and present accurate colors for 606 systems that have been observed on at least three photometric nights from a robotic observatory in southern Arizona. Comparison with earlier photometry for a subset of the systems shows good agreement. We investigate two independent methods of determining the interstellar reddening, although both have limitations that can render them less effective than desired. A subset of 101 systems shows good agreement between the two reddening methods.
CCD Photometry of SW Ursae Majoris during the 1996 Superoutburst  [PDF]
I. Semeniuk,A. Olech,T. Kwast,M. Nalezyty
Physics , 1997,
Abstract: We present CCD R photometry of SW Ursae Majoris - an SUUMa type cataclysmic variable - obtained during its April 1996 superoutburst. The mean value of the superhump period derived from our observations is 0.05818(+/-2) days (83.8 min). The analysis of times of superhump maxima gives clear evidence for the increase of the superhump period with dPsh/dt=0.000089.
Radial velocity study of the CP star Epsilon Ursae Majoris  [PDF]
N. A. Sokolov
Physics , 2009, DOI: 10.1111/j.1745-3933.2008.00419.x
Abstract: In this Letter, the radial velocity variability of the chemically peculiar star Epsilon Ursae Majoris ($\epsilon$ UMa) from the sharp cores of the hydrogen lines is investigated. This study is based on the ELODIE archival data obtained at different phases of the rotational cycle. The star exhibits low-amplitude radial velocity variations with a period of P=5.0887 d. The best Keplerian solution yields an eccentricity e=0.503 and a minimum mass ~14.7$M_{\rm Jup}$ on the hypothesis that the rotational axis of $\epsilon$ UMa is perpendicular to the orbital plane. This result indicate that the companion is the brown-dwarf with the projected semi-amplitude variation of the radial velocity $K_{\rm 2}$=135.9 km/sec and the sine of inclination times semi-major axis $a_{2}$sin(i)=0.055 au.
A Multicolour Photometric Study of the neglected eclipsing binary FT Ursae Majoris  [PDF]
Jin-Zhao Yuan
Physics , 2011, DOI: 10.1088/1674-4527/11/10/004
Abstract: The multicolour photometric observations of the neglected eclipsing binary FT Ursae Majoris (FT UMa) were obtained in 2010. The 2003 version of Wilson-Devinney code was used to analyze the light curves in $B$, $V$, and $R$ bands simultaneously. Based on the spectroscopic mass ratio $q=0.984$ published by Pribulla et al., it is found that FT UMa is an evolved contact binary with a contact degree of 15.3%. The low amplitude of light variations, $\sim 0.15$ mag, arises mainly from a moderately low inclination angle of $i=62.^{\circ}80$ and almost identical components in size rather than the light dilution of a third component, which contributes light of only $\sim 10%$
OAO/MITSuME Photometry of Dwarf Novae: I SU Ursae Majoris  [PDF]
Akira Imada,Hideyuki Izumiura,Daisuke Kuroda,Kenshi Yanagisawa,Toshihiro Omodaka,Ryo Miyanoshita,Nobuyuki Kawai,Daisaku Nogami
Physics , 2013, DOI: 10.1093/pasj/65.4.87
Abstract: We report on simultaneous $g'$, $R_{\rm c}$ and $I_{\rm c}$ photometry of SU Ursae Majoris during 2011 December - 2012 February using OAO/MITSuME. Our photometry revealed that quiescence is divided into three types based on the magnitude and color. Quiescent light curves showed complicated profiles with various amplitudes and time scales. Although no superoutbursts were observed during our run, five normal outbursts occurred with intervals of 11 - 21 d. The shapes of the normal outbursts were characteristic of the outside-in type. During the rising phase of a normal outburst, the light curve showed periodic modulations with a period of ${\sim}$ 0.048111(354) d, but the origin of this peirod was unclear. We examined daily averaged color-color diagram and found that two cycles exist. This implies that the thermal limit cycle in SU UMa is complicated. We newly discovered that $g'-R_{\rm c}$ becomes red about 3 days prior to an outburst. Although the working mechanism on this reddening is unclear, we propose two possibilities: one is that the inner portion of the accretion disk is filled by matter and obscures the central white dwarf, and the other is that the stagnation effect works in the outer region of the accretion disk.
S 10943 Vulpeculae: A New ROSAT Selected Dwarf Nova, probably of SU Ursae Majoris Subclass  [PDF]
G. A. Richter,J. Greiner,P. Kroll
Physics , 1998,
Abstract: We have identified the ROSAT all-sky survey source RX J1953.1+2115 with a newly discovered dwarf novae (named S 10943 Vulpeculae) with a recurrence time of 83.6 days. With the expected period of ~2.8 hrs (based on the measured superhump period of 2.871 hrs) S 10943 Vul would be the SU Ursae Majoris star with the second largest superhump (and orbital) period known (together with TU Men).
A T8.5 Brown Dwarf Member of the Xi Ursae Majoris System  [PDF]
Edward L. Wright,M. F. Skrutskie,J. Davy Kirkpatrick,Christopher R. Gelino,Roger L. Griffith,Kenneth A. Marsh,Tom Jarrett,M. J. Nelson,H. J. Borish,Gregory Mace,Amanda K. Mainzer,Peter R. Eisenhardt,Ian S. McLean,John J. Tobin,Michael C. Cushing
Physics , 2012, DOI: 10.1088/0004-6256/145/3/84
Abstract: The Wide-field Infrared Survey Explorer has revealed a T8.5 brown dwarf (WISE J111838.70+312537.9) that exhibits common proper motion with a solar-neighborhood (8 pc) quadruple star system - Xi Ursae Majoris. The angular separation is 8.5 arc-min, and the projected physical separation is about 4000 AU. The sub-solar metallicity and low chromospheric activity of Xi UMa A argue that the system has an age of at least 2 Gyr. The infrared luminosity and color of the brown dwarf suggests the mass of this companion ranges between 14 and 38 Jupiter masses for system ages of 2 and 8 Gyr respectively.
Observations of the SW Sextantis star DW Ursae Majoris with the Far Ultraviolet Spectroscopic Explorer  [PDF]
D. W. Hoard,Paula Szkody,Cynthia S. Froning,Knox S. Long,Christian Knigge
Physics , 2003, DOI: 10.1086/378605
Abstract: We present an analysis of the first far-ultraviolet observations of the SW Sextantis-type cataclysmic variable DW Ursae Majoris, obtained in November 2001 with the Far Ultraviolet Spectroscopic Explorer. The time-averaged spectrum of DW UMa shows a rich assortment of emission lines (plus some contamination from interstellar absorption lines including molecular hydrogen). Accretion disk model spectra do not provide an adequate fit to the far-ultraviolet spectrum of DW UMa. We constructed a light curve by summing far-ultraviolet spectra extracted in 60-sec bins; this shows a modulation on the orbital period, with a maximum near photometric phase 0.93 and a minimum half an orbit later. No other periodic variability was found in the light curve data. We also extracted spectra in bins spanning 0.1 in orbital phase; these show substantial variation in the profile shapes and velocity shifts of the emission lines during an orbital cycle of DW UMa. Finally, we discuss possible physical models that can qualitatively account for the observed far-ultraviolet behavior of DW UMa, in the context of recent observational evidence for the presence of a self-occulting disk in DW UMa and the possibility that the SW Sex stars may be the intermediate polars with the highest mass transfer rates and/or weakest magnetic fields.
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