The Library

ULTRACAM observations of two accreting white dwarf pulsators

Tools

Copperwheat, C. M., Marsh, T. R., Dhillon, V. S., Littlefair, S. P., Woudt, P. A. (Patrick A.), 1970-, Warner, Brian, Steeghs, D. (Danny), 1972-, Gänsicke, B. T. (Boris T.) and Southworth, J. (John). (2009) ULTRACAM observations of two accreting white dwarf pulsators. Monthly Notices of the Royal Astronomical Society, Vol.393 (No.1). pp. 157-170. ISSN 0035-8711

Preview

Text
WRAP_Steeghs_ULTRACAM_0810.5528v1.pdf - Accepted Version
Download (2287Kb) | Preview

Official URL: http://dx.doi.org/10.1111/j.1365-2966.2008.14163.x

Abstract

In this paper, we present high time-resolution observations of GW Librae (GW Lib) and SDSS J161033.64-010223.3 (SDSS 1610) - two cataclysmic variables which have shown periodic variations attributed to non-radial pulsations of the white dwarf (WD). We observed both these systems in their quiescent states with ULTRACAM on the Very Large Telescope (VLT) and the University of Cape Town Photometer on the SAAO 1.9m telescope, and detect the strong pulsations modes reported by previous authors. The identification of further periodicities in GW Lib is limited by the accretion-driven flickering of the source, but in the case of SDSS 1610 we identify several additional low-amplitude periodicities. In both the sources, we find the pulsation modes to be stronger in amplitude at bluer wavelengths. In the case of SDSS 1610, there is evidence to suggest that the two primary signals have a different colour dependence, suggesting that they may be different spherical harmonic modes. We additionally observed GW Lib during several epochs following its 2007 dwarf nova outburst, using ULTRACAM on the VLT and the Auxiliary Port Imager on the William Herschel Telescope. This is the first time a dwarf nova containing a pulsating WD has been observed in such a state. We do not observe any periodicities, suggesting that the heating of the WD had either switched-off the pulsations entirely, or reduced their relative amplitude in flux to the point where they are undetectable. Further observations 11 months after the outburst taken with RATCam on the Liverpool Telescope still do not show the pulsation modes previously observed, but do show the emergence of two new periodic signals, one with a frequency of 74.86 +/- 0.68 cycles d(-1) (P = 1154 s) and a g '-band amplitude of 2.20 per cent +/- 0.18 and the other with a frequency of 292.05 +/- 1.11 cycles d(-1) (P = 296 s) and a g ' amplitude of 1.25 per cent +/- 0.18. In addition to the WD pulsations, our observations of GW Lib in quiescence show a larger amplitude modulation in luminosity with a period of approximately 2.1 h. This has previously been observed, and its origin is unclear: it is unrelated to the orbital period. We find this modulation to vary over the course of our observations in phase and/or period. Our data support the conclusion that this is an accretion-related phenomenon, which originates in the accretion disc.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Dwarf novae, Stellar oscillations, White dwarf stars, Cataclysmic variable stars
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley-Blackwell Publishing, Inc
ISSN:	0035-8711
Date:	11 February 2009
Volume:	Vol.393
Number:	No.1
Number of Pages:	14
Page Range:	pp. 157-170
Identification Number:	10.1111/j.1365-2966.2008.14163.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Science and Technology Facilities Council (Great Britain) (STFC), National Research Foundation (South Africa), University of Cape Town
Grant number:	ST/F002599/1 (STFC), PP/D002370/1 (STFC), PP/E001777/1 (STFC)
Related URLs:	Other Repository
References:	Araujo-Betancor S., G¨ansicke B. T., Hagen H.-J., Marsh T. R., Harlaftis E. T., Thorstensen J., Fried R. E., Schmeer P., Engels D., 2005, A&A, 430, 629 Arras P., Townsley D. M., Bildsten L., 2006, ApJ, 643, L119 Bradley P. A., 1998, Balt. Astron., 7, 111 Breger M. et al., 1993, A&A, 271, 482 Clemens J. C., 1993, Balt. Astron., 2, 407 Dhillon V. S. et al., 2007, MNRAS, 378, 825 Efron B., 1979, Ann. Stat., 7, 1 Efron B., Tibshirani R. J., 1993, An Introduction to the Bootstrap. Chapman & Hall, New York G¨ansicke B. T., 2000, Rev. Modern Astron., 13, 151 G¨ansicke B. T. et al., 2003, ApJ, 594, 443 Gehrz R. D., Truran J.W.,Williams R. E., Starrfield S., 1998, PASP, 110, 3 Gianninas A., Bergeron P., Fontaine G., 2006, AJ, 132, 831 Gianninas A., Bergeron P., Fontaine G., 2007, in Napiwotzki R., Burleigh M. R., eds, ASP Conf. Ser. Vol. 372, 15th EuropeanWorkshop on White Dwarfs. Astron. Soc. Pac., San Francisco, p. 577 Godon P., Sion E. M., Cheng F., G¨ansicke B. T., Howell S., Knigge C., Sparks W. M., Starrfield S., 2004, ApJ, 602, 336 Godon P., Sion E. M., Cheng F., Long K. S., G¨ansicke B. T., Szkody P., 2006, ApJ, 642, 1018 Kleinman S. J. et al., 1998, ApJ, 495, 424 Kuulkers E., Knigge C., Steeghs D., Wheatley P. J., Long K. S., 2002, in G¨ansicke B. T., Beuermann K., Reinsch K., eds, ASP Conf. Ser. Vol. 261, The Physics of Cataclysmic Variables and Related Objects. Astron. Soc. Pac., San Francisco, p. 443 Littlefair S. P. et al., 2008, MNRAS, 388, 1582 Long K. S., Froning C. S., G¨ansicke B., Knigge C., Sion E. M., Szkody P., 2003, ApJ, 591, 1172 Mukadam A. S., Montgomery M. H., Winget D. E., Kepler S. O., Clemens J. C., 2006, ApJ, 640, 956 Neustroev V. V., 2002, A&A, 382, 974 Neustroev V. V., Zharikov S., Tovmassian G., Shearer A., 2005, MNRAS, 362, 1472 O’Donoghue D., 1995, Balt. Astron., 4, 519 Patterson J. et al., 2002, PASP, 114, 721 Sion E. M. et al., 2003, ApJ, 592, 1137 Steele I. A. et al., 2004, in Oschmann J. M., Jr, ed., Proc. SPIE Conf. Vol. 5489. Ground-based Telescopes. SPIE, Bellingham, WA, p. 679 Szkody P., G¨ansicke B. T., Howell S. B., Sion E. M., 2002, ApJ, 575, L79 Szkody P. et al., 2007a, AJ, 134, 185 Szkody P. et al., 2007b, ApJ, 658, 1188 Thorstensen J. R., Patterson J., Kemp J., Vennes S., 2002, PASP, 114, 1108 Tovmassian G. et al., 2003, PASP, 115, 725 Tovmassian G. H., Zharikov S. V., Neustroev V. V., 2007, ApJ, 655, 466 Townsley D. M., Arras P., Bildsten L., 2004, ApJ, 608, L105 van Zyl L., Warner B., O’Donoghue D., Sullivan D., Pritchard J., Kemp J., 2000, Balt. Astron., 9, 231 van Zyl L. et al., 2004, MNRAS, 350, 307 Warner B., 1995, Cataclysmic Variable Stars. Cambridge Astrophysics Series. Cambridge Univ. Press, Cambridge, New York Warner B., O’Donoghue D., 1987, MNRAS, 224, 733 Warner B., van Zyl L., 1998, in Deubner F.-L., Christensen-Dalsgaard J., Kurtz D., eds, Proc. IAU Symp. 185, New Eyes to See Inside the Sun and Stars. Kluwer, Dordrecht, p. 321 Watson R. D., 1988, Ap&SS, 140, 255 Woudt P. A., Warner B., 2002, Ap&SS, 282, 433 Woudt P. A., Warner B., 2004, MNRAS, 348, 599 Wu Y., Goldreich P., 1999, ApJ, 519, 783
URI:	http://wrap.warwick.ac.uk/id/eprint/28628