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Patrick A. Woudt

Publications and source records attributed to Patrick A. Woudt.

At least 55 records · Page 3Linked to original sources
arXiv2003

Extragalactic Large-Scale Structures behind the Southern Milky Way. IV. Redshifts Obtained with MEFOS

Abbreviated: As part of our efforts to unveil extragalactic large-scale structures behind the southern Milky Way, we here present redshifts for 764 galaxies in the Hydra/Antlia, Crux and Great Attractor region (266deg < l < 338deg, |b| < 10deg), obtained with the Meudon-ESO Fibre Object Spectrograph (MEFOS) at the 3.6-m telescope of ESO. The observations are part of a redshift survey of partially obscured galaxies recorded in the course of a deep optical galaxy search behind the southern Milky Way. A total of 947 galaxies have been observed, a small percentage of the spectra (N=109, 11.5%) were contaminated by foreground stars, and 74 galaxies (7.8%) were too faint to allow a reliable redshift determination. With MEFOS we obtained spectra down to the faintest galaxies of our optical galaxy survey, and hence probe large-scale structures out to larger distances (v <~ 30000 km/s) than our other redshift follow-ups. The most distinct large-scale structures revealed in the southern Zone of Avoidance are discussed in context to known structures adjacent to the Milky Way.

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arXiv2003

SDSS J161033.64-010223.3: A second Cataclysmic Variable with a Non-radially Pulsating Primary

We find from high speed photometry of the Sloan Digital Survey cataclysmic variable candidate SDSS J161033.64-010223.3 that it has a double humped modulation, which is probably orbital, with a period of 80.52 minutes, and shows strong ZZ Cet type pulsations. The largest amplitude oscillations have periods near 607, 345, 304 and 221 s. The amplitudes of some of the oscillations are seen to vary on time scales of hours, indicating modes with unresolved multiplets in which the splittings are ~1 d^-1. This is only the second dwarf nova found to have non-radial pulsations of its white dwarf primary.

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arXiv2003

AM CVn stars in the UCT CCD CV survey

High speed photometry of the helium-transferring binary ES Cet - taken over a two-year period (2001 October - 2003 October) - shows a very stable photometric period of 620.211437 +/- 0.000038 s, with a tentative indication of curvature in the O-C diagram suggesting a change in period at a rate of dP/dt ~ 1.6x10^-11. Phase-resolved spectroscopy of ES Cet obtained with the Hobby-Eberly Telescope shows a clear modulation on the photometric period. We have followed a newly identified AM CVn star (`2003aw') photometrically through its 2003 February/March outburst during which it varied in brightness over a range of V = 16.5 - 20.3; we find a superhump period of 2041.5 +/- 0.3 s. Questions are raised about the reality of the detected spin-up in RX J0806 (Hakala et al. 2003; Strohmayer 2003).

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arXiv2003

Accretion in Cataclysmic Variable stars

We consider accretion onto the white dwarfs in cataclysmic variables in relation to nova eruptions, dwarf nova outbursts, hibernation and non-radial oscillations.

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arXiv2003

The new AM CVn star in Hydra

High speed photometry of the new AM CVn star in Hya (previously known as SN2003aw), spectroscopically identified by Chornock & Filippenko, shows it to have a superhump period of 2041.5 +/- 0.3 s. We find a range of brightness from V ~ 16.5 to 20.3, presumably caused by variations in the rate of mass transfer. In the intermediate state the system cycles in brightness with a period of ~ 16 h and range >= 0.4 mag. There are sidebands to the principal frequencies in the Fourier transform which have constant frequency difference from the superhump harmonics.

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arXiv2003

Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic Variables: III. A New Kind of Dwarf Nova Oscillation, and Further Examples of the Similarities to X-Ray Binaries

We present measurements of the periods of Dwarf Nova Oscillations (DNOs) and Quasi-Periodic Oscillations (QPOs) in Cataclysmic Variable stars (CVs), many culled from published literature, but also others newly observed (in VZ Pyx, CR Boo, OY Car, Z Cha, AQ Eri, TU Men, HX Peg, CN Ori, V893 Sco, WX Hyi and EC2117-54). These provide data for 26 systems. We show that in general P_QPO ~ 15 P_DNO and that the correlation for CVs extends by three orders of magnitude lower in frequency the similar relationship found for X-Ray binaries. In addition, we have found that there is a second type of DNO, previously overlooked, which have periods ~ 4 times those of the regular DNOs (As well as those mined from publications, we have observed them in VW Hyi, OY Car, AQ Eri, V803 Cen, CR Boo, VZ Pyx, HX Peg and EC2117-54). Often both types of DNO coexist. Unlike the standard DNOs, the periods of the new type, which we refer to as longer period DNOs (lpDNOs), are relatively insensitive to accretion luminosity and can even appear in quiescence of dwarf novae. We interpret them as magnetically channelled accretion onto the differentially rotating main body of the white dwarf primary, rather than onto a rapidly slipping equatorial belt as in the case of the standard DNOs. This is supported by published measurements of v sin(i) for some of the primaries. Some similarities of the DNOs, lpDNOs and QPOs in CVs to the three types of QPO in X-Ray binaries (burst pulsation, high and low frequency QPOs) are noted.

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arXiv2003

High-speed photometry of the Recurrent Nova IM Normae

The recurrent nova IM Nor is found to have an orbital period of 2.462 h, shown by periodic dips in brightness. This is only the second recurrent nova known to have such a short period. We interpret the light curve as largely produced by a reflection effect from the heated face of the secondary star, probably with addition of a partial eclipse of the accretion disc.

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arXiv2003

Magnetic CVs in the UCT CCD CV Survey

An overview is given of all the magnetic CVs found in the UCT CCD CV Survey (Woudt & Warner 2001, 2002, 2003a). We have identified eight new candidate Intermediate Polars (IP), of which six are classical novae (RR Cha, DD Cir, AP Cru, V697 Sco, V373 Sct, and RX J1039.7-0507). The two other candidate IPs are Aqr1 (2236+0052) and RX J0944.5+0357. In addition, there are two probable Polars, namely V351 Pup (= Nova Puppis 1991) and FIRST J102347.6+003841.

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arXiv2003

RX J0944.5+0357: A Probable Intermediate Polar

From optical photometry the cataclysmic variable RX J0944.5+0357 is shown to have a double-peaked pulse profile with a period of ~2160 s. The two peaks vary rapidly in relative amplitude. Often most of the optical power is concentrated in the first harmonic of the 2160s modulation: RX J0944.5+0357 therefore probably belongs to the relatively rare class of two-pole accreting intermediate polars exemplified by YY Dra and V405 Aur.

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arXiv2003

High speed photometry of faint Cataclysmic Variables: III. V842 Cen, BY Cir, DD Cir, TV Crv, V655 CrA, CP Cru, V794 Oph, V992 Sco, EU Sct and V373 Sct

We present further results from a high speed photometric survey of faint cataclysmic variables. We find that V842 Cen (Nova Cen 1986 No. 2) is highly active, but with no evident orbital modulation. BY Cir (Nova Cir 1995) is an eclipsing system with an orbital period P(orb) of 6.76 h. TV Crv, an SU UMa type dwarf nova, is found to have P(orb) = 1.509 h from photometry at quiescence. DD Cir (Nova Cir 1999) is an eclipsing system with P(orb) = 2.339 h, a possible secondary eclipse, and a ~670 s photometric modulation. V655 CrA is highly active but shows no orbital modulation. The identification of V794 Oph is probably incorrect as we find no photometric variability. CP Cru (Nova Cru 1996) is an eclipsing system with P(orb) = 22.7 h. V992 Sco has P(orb) = 3.686 h from its periodic modulation. The supposed identification of EU Sct is probably incorrect. And finally, during one run V373 Sct (Nova Sct 1975) had a 258.3 s coherent periodicity, making it a candidate DQ Herculis star.

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arXiv2003

Dwarf Nova Oscillations and Quasi-Periodic Oscillations: Extension of the Two-QPO Diagram of X-Ray Binaries, and a new kind of DNO

Seventeen examples are given of Cataclysmic Variable (CV) stars possessing both Dwarf Nova Oscillations (DNOs) and Quasi-Periodic Oscillations (QPOs). These form an extension of the X-Ray Two-QPO correlation to frequencies three orders of magnitude lower. We draw attention to the existence of a second type of DNO in CVs, which is probably caused by magnetically channelled accretion onto the white dwarf.

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arXiv2002

RX J1039.7-0507: A New Intermediate Polar and Probable Recent Nova, possessing a large Reflection Effect

The ROSAT source RX J1039.7-0507, known from its optical spectrum to be a Cataclysmic Variable star, is shown from high speed photometry to have an orbital period of 1.574 h. The system has a nearly sinusoidal photometric modulation with a range of 1.1 mag which we interpret as the reflection effect caused by a very hot white dwarf primary. This suggests that a nova explosion occured on the primary in the relatively recent past. In addition, RX J1039.7-0507 has periodic signals at 1932.5 s and 721.9 s which, with the aid of other periods present at low amplitude, we interpret as an orbital sideband and the first harmonic of the primary's spin period. RX J1039.7-0507 is therefore an intermediate polar with a spin period of 1444 s (24.07 min).

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arXiv2002

Nova Scorpii 1941 (V697 Sco): A Probable Intermediate Polar

V697 Sco, the remnant of Nova Scorpii 1941 and currently at V ~ 20.0, is found from photometric observations to have the characteristics of an intermediate polar (IP) with an orbital period (Porb) of 4.49 h and a rotation period (Prot) of 3.31 h. It therefore appears to be a member of the rare class of IPs where Prot ~ Porb, which are probably discless systems. The prominence of the modulation at 0.5 Prot, and its orbital sidebands, indicates two-pole accretion.

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arXiv2002

The UCT Survey of Old Novae

We present a status report on our high speed photometric survey of faint Cataclysmic Variables, which is concentrating on old novae.

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arXiv2002

Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic Variables: II. A Low Inertia Magnetic Accretor Model

The Dwarf Nova Oscillations observed in Cataclysmic Variable (CV) stars are interpreted in the context of a Low Inertia Accretor model, in which accretion on to an equatorial belt of the white dwarf primary causes the belt to vary its angular velocity. The rapid deceleration phase is attributed to propellering. Evidence that temporary expulsion rather than accretion of gas occurs during this phase is obtained from the large drop in EUV flux. We show that the QPOs are most probably caused by a vertical thickening of the disc, moving as a travelling wave near the inner edge of the disc. This alternately obscures and `reflects' radiation from the central source, and is visible even in quite low inclination systems. A possible excitation mechanism, caused by winding up and reconnection of magnetic field lines, is proposed. We apply the model, deduced largely from VW Hyi observations, to re-interpret observations of SS Cyg, OY Car, UX UMa, V2051 Oph, V436 Cen and WZ Sge. In the last of these we demonstrate the existence of a 742 s period in the light curve, arising from obscuration by the travelling wave, and hence show that the two principal oscillations are a DNO and its reprocessed companion.

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arXiv2002

High speed photometry of faint Cataclysmic Variables: II. RS Car, V365 Car,] V436 Car, AP Cru, RR Cha, BI Ori, CM Phe and V522 Sgr

Short time scale photometric properties of eight faint Cataclysmic Variable (CV) stars are presented. Nova Carinae 1895 (RS Car) has a photometric modulation at 1.977 h which could be either an orbital or a superhump period. Nova Carinae 1948 (V365 Car) shows flickering, but any orbital modulation has a period in excess of 6 h. The nova-like variable and X-ray source V436 Car has an orbital modulation at P(orb) = 4.207 h, no detectable period near 2.67 h (which had previously given it a possible intermediate polar classification), and Dwarf Nova Oscillations (DNOs) at ~40 s. Nova Crucis 1936 (AP Cru) has a double humped ellipsoidal modulation at P(orb) = 5.12 h and a stable modulation at 1837 s characteristic of an intermediate polar. Nova Chamaeleontis 1953 (RR Cha) is an ecliping system with P(orb) = 3.362 h, but at times shows negative superhumps at 3.271 h and positive superhumps at 3.466 h. In addition it has a stable period at 1950 s, characteristic of an intermediate polar. BI Ori is a dwarf nova which we observed at quiescence and outburst without detecting any orbital modulation. CM Phe is a nova-like variable for which we confirm Hoard, Wachter & Kim-Quijano's (2001) value of P(orb) = 6.454 h. We have identified the remnant of Nova Saggitarii 1931 (V522 Sgr) with a flickering source ~2.2 mag fainter than the previously proposed candidate (which we find to be non-variable).

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arXiv2002

Dwarf Nova Oscillations and Quasi-Periodic Oscillations in Cataclysmic Variables: I. Observations of VW Hyi

From archived and recent high speed photometry of VW Hyi we find Dwarf Nova Oscillations (DNOs) occasionally present throughout outburst, evolving from 14.06 s period at maximum to > 40 s near the end of outburst. A relatively slow increase of period is followed by rapid increase and subsequent decrease. Quasi-periodic Oscillations (QPOs) are seen at periods of hundreds of seconds. For the first time, an evolution of QPO period is seen, steadily increasing during the final decline of an outburst. The occasional presence of two DNOs, separated in frequency by the QPO frequency, suggests reprocessing of the rotating DNO beam by a `wall' rotating progradely in the disc at the QPO period.

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