Highspeed photometry of outbursting AM CVn stars

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High-speed photometryof outbursting AM CVn stars
Patrick A. Woudt (UCT), Brian Warner, Joe
Patterson and the CBA

• Three new AM CVns discovered recently all fall
  into the category
• of high/low state AM CVns (2003aw, SDSS J1240,
  2QZ J1427)
• 2003aw high-speed photometry and Psh
• The 2005 May outburst of SDSS J1240
  determination of Psh
• Photometry and spectroscopy of the new AM CVn
  star 2QZ J1427

• Dwarf Nova Oscillations and Quasi-Periodic
  Oscillations in AM CVn stars
• DNOs and QPOs in AM CVn stars
• The 175-s modulation in V803 Cen

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2003aw The 2003 (discovery) outburst.
Maximum brightness V 15.0 mag (2004
outburst) Psh 2041.5 0.3 s (confirmed
in the 2004 outburst) Pcycl 16 h, amplitude gt
0.4 mag
re-brightening
cycling state
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• The 2005 May outburst of SDSS J1240
• Observed with the SAAO 74-in UCT CCD
• Peak of the outburst could have been missed
• Cycling phase (Pcycl 7 hr, amplitude gt 0.26
  mag) similar in behaviour to V803 Cen, CR Boo,
  2003aw, but at shorter (very poorly determined!)
• period

SDSS J1240 in outburst (2005 May)
SDSS J1240 at quiescence (Woudt, Warner
Pretorius 2004)
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• The 2005 May outburst of SDSS J1240
• Psh 2253.2 0.1 s
• Porb 2241.3 0.1 s (Roelofs et al. 2005)

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• The new outbursting AM CVn star 2QZ J1427
• Outburst reported on 2005 Jan 23 (ROTSE III,
  Rykoff et al. ATel 403)
• QSO (blazar) or CV?
• Reached 15.2 mag at peak brightness, lasting
  3 - 4 days

Outburst spectrum very similar to CP Eri
He I 5875
Outburst spectrum 2QZ J1427 (HET LRS)
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• The new outbursting AM CVn star 2QZ J1427
• Observed with the SAAO 74-in
• and the UCT CCD in 2005 May
• V 20.2 mag
• In the SDSS, u-g -0.25 mag.

Fourier Transform 2QZ J1427 15 May 2005 and 16
May 2005. From combined FT Porb 2194 4 s.
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• The new outbursting AM CVn star 2QZ J1427
• 2QZ J1427 in quiescence strange spectrum?

No, clearly an AM CVn system!
Quiescent spectrum of 2QZ J1427 (2dF QSO
survey).
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Outbursting AM CVn stars similarities and
differences
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• Dwarf Nova Oscillations and Quasi-periodic
  oscillations in AM CVn systems
• Dwarf Nova Oscillations (DNOs)
• Periods in the range of 4 to 50 seconds
• Fairly low-coherence
• Quasi-Periodic Oscillations (QPOs)
• Periods in the range of 60 to 1000 seconds
• Even lower coherency (typically 5-10 cycles)
• DNOs and QPOs observed in AM CVn systems
• DNOs AM CVn (26.2 s Patterson et al.
  1979,1992), CR Boo (19-22 s Patterson,

Low Inertia Magnetic Accretor (LIMA) Warner
Woudt (2002). Picture from Hellier (2004)
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• Dwarf Nova Oscillations and Quasi-periodic
  oscillations in AM CVn systems
• PQPO/PDNO 15 (similar to the ratio of the
  two-QPOs seen in low-mass
• X-ray binaries).

• CR Boo PDNO 21.6 s
• PQPO 291 s

WWP (2003) Pretorius (2004)
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• Dwarf Nova Oscillations and Quasi-periodic
  oscillations in AM CVn systems
• The 175-s photometric modulation in V803 Cen

Run S4035 (ODonoghue Kilkenny 1989)
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• Dwarf Nova Oscillations and Quasi-periodic
  oscillations in AM CVn systems
• The 175-s photometric modulation in V803 Cen

• CBA data 2001 April.
• lpDNO strong during cycling phase

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• Dwarf Nova Oscillations and Quasi-periodic
  oscillations in AM CVn systems
• The 175-s photometric modulation in V803 Cen

Reprocessing from the precessing disk?
Runs S6731/S6735/S6740 (2003 January UCT CCD)
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• Dwarf Nova Oscillations and Quasi-periodic
  oscillations in AM CVn systems
• The 175-s modulation of V803 Cen
• Pulsation? No!
• Period changes too much (ODonoghue et al. 1987)
• Seen during outburst, when dominated by accretion
  luminosity
• Dwarf Nova Oscillations?
• Period changes during return to quiescence
  (varies with dM/dt)
• Observed during outburst
• Does not fit the period-luminosity relation
• longer period Dwarf Nova Oscillations?
• Generally behaves like a DNO
• Accretion not onto the rapidly spinning
  equatorial belt, but onto
• the differentially rotating main body of the
  white dwarf primary
• Implication is that the primary is probably
  weakly magnetic
• If DNOs are found, they will be around 45 s.

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• Dwarf Nova Oscillations and Quasi-periodic
  oscillations in AM CVn systems
• Studying rapid oscillations of AM CVns with SALT
  and SALTICAM/PFIS

SALTICAM and PFIS will be able to take
continuous (no dead-time) photometry and
spectroscopy/ spectropolarimetry at 0.1 s.