The dwarf nova The dwarf nova BZ BZ UUMaMa

Simultaneous photometry and Simultaneous photometry and echelle-spectroscopy during the echelle-spectroscopy during the

2005 January Outburst2005 January Outburst

MNRAS, 2006, Coming SoonMNRAS, 2006, Coming Soon

Vitaly Neustroev (NUI Galway), S. Zharikov and R. Michel

BZ UMaBZ UMa

Period: 97.8 minPeriod: 97.8 min Outburst cycle: > 300Outburst cycle: > 300dd

Min: VMin: V≈16-17 (17.8)≈16-17 (17.8) Max: VMax: V≈10.5-11.5≈10.5-11.5 Very strong Balmer emission linesVery strong Balmer emission lines

SpectrumSpectrum

Doppler TomographyDoppler Tomography

April, 2004. Quiescence: HApril, 2004. Quiescence: Hαα

ObservationsObservations

OAN SPM (Mexico)OAN SPM (Mexico) Photometry: 2005 Jan 12-13 and 15-Photometry: 2005 Jan 12-13 and 15-

1717 Echelle-spectroscopy: 2005 Jan 15-Echelle-spectroscopy: 2005 Jan 15-

1717

Light CurveLight Curve

Light CurveLight Curve

Light CurveLight Curve

Light CurveLight Curve

ColoursColours

Line profilesLine profiles

FWHM, Fluxes and EW of FWHM, Fluxes and EW of HHαα

Doppler TomographyDoppler Tomography

April, 2004. Quiescence: HApril, 2004. Quiescence: Hαα

Doppler TomographyDoppler Tomography

Jan 15, 2005. Preoutburst: HJan 15, 2005. Preoutburst: Hαα

Doppler TomographyDoppler Tomography

Jan 16, 2005. Outburst, 1Jan 16, 2005. Outburst, 1stst stage: H stage: Hαα

Doppler TomographyDoppler Tomography

Jan 16, 2005. Outburst, 3Jan 16, 2005. Outburst, 3rdrd stage: H stage: Hαα

Doppler TomographyDoppler Tomography

Jan 17, 2005. Outburst, Decline: HJan 17, 2005. Outburst, Decline: Hαα

Doppler TomographyDoppler Tomography

Jan 17, 2005. Outburst, Decline: HJan 17, 2005. Outburst, Decline: Hββ

Doppler TomographyDoppler Tomography

Jan 17, 2005. Outburst, Decline: HJan 17, 2005. Outburst, Decline: He I e I 58765876

Inside-Out or Outside-In Inside-Out or Outside-In outburst?outburst?

The only way to be sure of the The only way to be sure of the outburst type is from eclipse profile outburst type is from eclipse profile observations during outbursts and observations during outbursts and BZ UMa is not an eclipsed system.BZ UMa is not an eclipsed system.

A very low mass-transfer rate for BZ A very low mass-transfer rate for BZ UMa (≤10UMa (≤101515 g/s) implies that g/s) implies that theoretically, its outbursts should be theoretically, its outbursts should be of an inside-out type.of an inside-out type.

Line profilesLine profiles

Line profilesLine profiles

Line profilesLine profiles

SummarySummary We reported simultaneous photometric and echelle-We reported simultaneous photometric and echelle-

spectroscopic observations of the dwarf nova BZ spectroscopic observations of the dwarf nova BZ UMa during which we were lucky to catch the UMa during which we were lucky to catch the system at the onset of an outburst. system at the onset of an outburst.

Using Doppler tomography we found that the Using Doppler tomography we found that the unusual emission distribution detected in unusual emission distribution detected in quiescence held during the outburst.quiescence held during the outburst.

On the base of the spectral changes during the On the base of the spectral changes during the rising stage we conclude that the 2005 January rising stage we conclude that the 2005 January outburst of BZ UMa was of the inside-out type. outburst of BZ UMa was of the inside-out type.

Nevertheless, a highly asymmetrical light curve with Nevertheless, a highly asymmetrical light curve with a “jump” shows that this outburst cannot easily be a “jump” shows that this outburst cannot easily be fit into the framework of the current Disc Instability fit into the framework of the current Disc Instability Model.Model.