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The dwarf nova BZ U Ma

The dwarf nova BZ U Ma

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The dwarf nova BZ U Ma

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  1. The dwarf nova BZ UMa Simultaneous photometry and echelle-spectroscopy during the 2005 January Outburst MNRAS, 2006, Coming Soon Vitaly Neustroev (NUI Galway), S.Zharikov and R.Michel

  2. BZ UMa • Period: 97.8 min • Outburst cycle: > 300d • Min: V≈16-17 (17.8) • Max: V≈10.5-11.5 • Very strong Balmer emission lines

  3. Spectrum

  4. Doppler Tomography • April, 2004. Quiescence: Hα

  5. Observations • OAN SPM (Mexico) • Photometry: 2005 Jan 12-13 and 15-17 • Echelle-spectroscopy: 2005 Jan 15-17

  6. Light Curve

  7. Light Curve

  8. Light Curve

  9. Light Curve

  10. Colours

  11. Line profiles

  12. FWHM, Fluxes and EW of Hα

  13. Doppler Tomography • April, 2004. Quiescence: Hα

  14. Doppler Tomography • Jan 15, 2005. Preoutburst: Hα

  15. Doppler Tomography • Jan 16, 2005. Outburst, 1st stage: Hα

  16. Doppler Tomography • Jan 16, 2005. Outburst, 3rd stage: Hα

  17. Doppler Tomography • Jan 17, 2005. Outburst, Decline: Hα

  18. Doppler Tomography • Jan 17, 2005. Outburst, Decline: Hβ

  19. Doppler Tomography • Jan 17, 2005. Outburst, Decline: He I 5876

  20. Inside-Out or Outside-In outburst? • The only way to be sure of the outburst type is from eclipse profile observations during outbursts and BZ UMa is not an eclipsed system. • A very low mass-transfer rate for BZ UMa (≤1015 g/s) implies that theoretically, its outbursts should be of an inside-out type.

  21. Line profiles

  22. Line profiles

  23. Line profiles

  24. Summary • We reported simultaneous photometric and echelle-spectroscopic observations of the dwarf nova BZ UMa during which we were lucky to catch the system at the onset of an outburst. • Using Doppler tomography we found that the unusual emission distribution detected in quiescence held during the outburst. • On the base of the spectral changes during the rising stage we conclude that the 2005 January outburst of BZ UMa was of the inside-out type. • Nevertheless, a highly asymmetrical light curve with a “jump” shows that this outburst cannot easily be fit into the framework of the current Disc Instability Model.