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V445 Puppis – a unique helium nova

V445 Puppis – a unique helium nova. The near infrared evolution of V445 Puppis A distance determination from the expansion parallax The nature of the binary. Collaborators: Patrick Woudt (Univ. of Cape Town, RSA) Danny Steeghs (Univ. of Warwick, UK)

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V445 Puppis – a unique helium nova

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  1. V445 Puppis – a unique helium nova • The near infrared evolution of V445 Puppis • A distance determination from the expansion parallax • The nature of the binary Collaborators: Patrick Woudt (Univ. of Cape Town, RSA) Danny Steeghs (Univ. of Warwick, UK) Margaritha Karovska (Center for Astrophysics, USA) Brian Warner (Univ. of Cape Town, RSA) Derck Smits (Univ. of South Africa, RSA) Paul Groot (Radboud Univ. Nijmegen, NL) Gijs Nelemans (Radboud Univ. Nijmegen, NL) Gijs Roelofs (Radboud Univ. Nijmegen, NL) Tom Marsh (Warwick Univ., UK) Takahiro Nagayama (Kyoto Univ, Japan) Tim O’Brien (Univ. of Manchester, UK) Image: J(IRSF),H(IRSF), Ks(IRSF)3.4' x 3.4' colour-composite of V445 Puppis (taken on 22/03/05).

  2. V445 Puppis: the outburst in 2000 • Last nova of the previous • millenium • Discovered by K. Kanatsu • (8.6 mag on 28 November 2000) • Outburst between September and • 28 November 2000 (HJD 2451876) • Slow nova (outburst lasted • ~7 months) Ashok & Banerjee (2003) Wagner et al. (2001) • Carbon-rich ejecta, helium • (He I), no hydrogen! More on the outburst of V445 Puppis in the subsequent talk by Mariko Kato

  3. V445 Pup: outburst & model • Proposed as the first observed helium nova (Kato & Hachisu 2003; • Ashok & Banerjee 2003). Various unique aspects: • Hydrogen-deficient (Wagner et al. 2001) • Enriched in carbon and helium (e.g. Ashok & Banerjee 2003) • The initially formed optically thin dust shell has developed in an optically thick shell (Henden et al. 2001) • Shell still obscures the nova (6 years later)… See our IRSF/SIRIUS photometry • One of a kind! • From modelling of the optical outburst light curve, Kato & Hachisu (2003) deduced the following (model-dependent) parameters: • Helium shell flash on the surface of the white dwarf primary • Mass-transferring binary with massive primary (recurrent nova models) • Mass of the primary: M1 > 1.33 MSun • Mass transfer rate (dM/dt) is several times 10-7 MSun/yr • Nova recurrence time (tr) is ~ 70 years • M1 and tr in their models depend sensitively on the assumed distance: • d = 640 pc (1.33 MSun and 61 year); d = 700 pc (1.35 MSun and 84 year)

  4. V445 Pup: nature of the binary • In Kato & Hachisu’s models of a helium nova, the nature of the companion is ill-constrained. • The companion can be: • a white dwarf the binary would be an AM CVn cataclysmic variable (binary period can be as short as ~5 minutes) • a helium star helium cataclysmic (Iben & Tutukov 1991) • a normal companion (accreting hydrogen-rich material) but with a very high accretion rate → hydrogen-burning on the surface of the white dwarf primary (hydrogen processed in to helium) Supersoft source (strong X-ray emission… not observed!) • After many helium shell flashes, the helium nova with a massive primary • (as the models suggest, but model-dependent) could end up • as a supernova Ia, or an accretion-induced collapsed neutron star.

  5. V445 Pup: (slow) near-infrared evolution • Near infrared photometry with the InfraRed Survey Facility (IRSF) • Since 22 March 2002, continuous monitoring (~ once per 1-2 months) 22/03/02 19/06/02 28/08/02 04/11/02 14/05/03 26/04/04 02/02/99 2MASS pre-outburst 5-year light curve obtained thanks to many observers at IRSF in service mode.

  6. HJD 245 2515 – 245 2665 • HJD 245 2712 – 245 3324 • HJD 245 3365 – 245 3644 • HJD 245 3669 – 245 4172 Rapid change in (J – H) colour over the 610-day period (blue dots) due to the appearance of He I at 1.0830 micron as seen in the infrared spectra of Lynch et al. (2004). He I recombination lines require ionising photons with E > 24.59 eV. AV = 1.8 mag

  7. V445 Pup: resolving the nova shell Optical imaging of V445 Puppis in the V-band using the 6.5-m Magellan telescope in excellent seeing conditions (FWHM ~ 0.6") Data obtained: 17 December 2003 (3 years after the outburst) V445 Puppis appears extended and elongated! 5"

  8. Expansion parallax: • For an expanding nova shell, the distance to the nova can be determined from • high-angular resolution imaging (→ expansion on the sky) and (preferably) integral • field unit spectroscopy (→ measure the velocity of the expanding material). • Complications: • complex (non-spherically symmetric) geometry • unknown inclination (convert radial into • tangential velocities) • Modelling of the shell geometry important. • → distance error ~10% • d distance (kpc) • Δt time since outburst (in days) • vexp expansion velocity (km/s) • α angular radius (in arcsec) The bipolar shell of the slow nova HR Del (Harman & O’Brien 2003)

  9. V445 Pup: the nova shell at high resolution • VLT + NAOS/CONICA • 4 epochs of K-band imaging • - (E1) 25 March 2005 • (E2) 06 December 2005 • (E3) 06 October 2006 • (E4) 03 March 2007 • Good seeing (~0.6") • Achieved FWHM ~ 0.11" • Expanding bipolar nova shell Deconvolution: M. Karovska (CfA) • Knots at extremes of • major axis • Viewing dust disk/torus • nearly edge-on Field of view: 1.6" x 1.6"

  10. clear (uniform?) expansion along the knots (knot-to-knot): • epoch 1 to epoch 2, 257 days: 0.28" • epoch 1 to epoch 3, 561 days: 0.66" • epoch 1 to epoch 4, 709 days: 0.83" • → 0.215" per year along the major axis (from centre) V445 Pup: angular expansion of the nova shell March 2005 (E1) October 2006 (E3) March 2007 (E4) 1.6" x 1.6" December 2005 (E2) 3.5" x 3.5"

  11. V445 Pup: optical (long-slit) spectroscopy Magellan + IMACS: Dec 2003 • Dominant lines: • [O II] 7320, 7330 Å • [O III] 4959, 5007 Å • He I recombination lines • No hydrogen lines! • Multiple velocity components: • -1600, -900, +800 km/s Presence of [O III] 4363 Å and [O II] 7320/7330 Å indicates a high temperature

  12. V445 Pup: optical (IFU) spectroscopy Magellan + IMACS: Jan 2006 and 2007 He I (7065 Å) – 3000 km/s – 2000 km/s – 1000 km/s 0 km/s + 1000 km/s + 2000 km/s + 3000 km/s Clear (radial) velocity structure in each line: NE lobe: -1270 km/s and +1140 km/s(–65 km/s) SW lobe: -760 km/s and +1720 km/s(+480 km/s)

  13. V445 Pup: hydrogen deficient • IFU line profile across the central column • black: centred on He I at 7065 Å • red: centred on Hα at 6563 Å • Blue- and redshifted components on either • side of the shell→ bi-conical outflow? • Opening angle? Inclination? No evidence for any hydrogen.

  14. V445 Pup: expansion parallax Opening angle of the cone of 14° and an inclination of 3.5° w.r.t. plane of the sky, and an outflow velocity of ~5000 km/s gives a distance of 4.9 ± 0.5 kpc (from the expansion parallax). Estimate of the opening angle of the cone from imaging (~14°). Varying over time? ↓ d ~ 4.9 ± 0.5 kpc

  15. V445 Pup: continuous outflow • Velocity profile relatively • unchanged over 2 year • period. • → Continued post-nova outflow • at similar velocities consistent • with escape velocity of WD. • Redshifted component heavily • obscured by dust in • the shell.

  16. V445 Pup: expansion parallax A distance of 4.9 kpc, would imply a distance modulus (m – M) = 13.4 mag. The pre-outburst magnitude of V445 Puppis is V = 14.5 mag and the galactic foreground extinction AV ~ 1.8 mag → MV ~ -0.7 mag Note: pre-existing dust around V445 Puppis? • Candidate helium nova progenitors: • white dwarf + white dwarf absolute magnitude (V-band): about +7 mag • white dwarf + helium star absolute magnitude (V-band): about -1 mag • white dwarf + normal companion (accreting hydrogen-rich material at high accretion rates)… but no X-rays detected, nor any hydrogen. absolute magnitude (V-band): –2 to +3 mag

  17. V445 Pup: conclusions (so far) • Clearly detected an expanding, bipolar nova shell with an strongly obscuring • dust disk/torus perpendicular to the ejecta. • Distance from expansion parallax: 4.9 ± 0.5 kpc • - strong limits on the nature of the companion; not a WD+WD binary • - Model must be tested rigorously (allow for changing shell structure) • No previous outburst observed in the CfA plate archives (1890 – 1960) • - Recurrent nova? Time scale? • Evolution of V445 Puppis is still ongoing • - continued near-infrared (IRSF) monitoring • Supernova Ia progenitor? • - New distance estimate must be compared with Kato’s models • to check for compatibility with the massive WD models • White dwarf / helium star binary? When the dust clears, an orbital period • must be obtained using high-speed photometry! Eclipsing?

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