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Time-domain astronomy on the WHT

Time-domain astronomy on the WHT. …or… Rare objects from wide-field surveys. Boris G änsicke. A few thoughts about time-domain astronomy. flares flickering outbursts eruptions explosions eclipses / transits motion. (minutes – hours) (msec – minutes) (days – months)

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Time-domain astronomy on the WHT

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  1. Time-domain astronomy on the WHT …or… Rare objects from wide-field surveys Boris Gänsicke

  2. A few thoughts about time-domain astronomy • flares • flickering • outbursts • eruptions • explosions • eclipses / transits • motion (minutes – hours) (msec – minutes) (days – months) (months – years) (months – years) (minutes – hours) (minutes – years) • stellar activity • stellar structure & evolution • binary evolution • exo-planets • accretion discs/processes • cosmology

  3. CK Vul = Nova Vulpeculae 1670 • classical nova? • late thermal pulse? • merger? • sub-Chandra SN? (Hevelius 1670, Phil. Trans. 5, 2087)

  4. Same constellation - 337 years later IPHAS: 6 weeks AAVSO IPHAS pre-eruption H (Wesson et al. 2008, ApJL 688, 21)

  5. V458 Vul = Nova Vulpeculae 2007 WHT/INT H 2007-2009 IPHAS pre-eruption H (Wesson et al. 2008, ApJL 688, 21)

  6. V458 Vul = Nova Vulpeculae 2007 ISIS radial velocities shortest-period PN nucleus: Porb=98.1min  likely a binary white dwarf (Rodríguez-Gil et al. submitted)

  7. The evolution of compact binary stars 70% brown dwarf donors White dwarf / main sequence binaries are the simplest CBs, yet population models and observations used to disagree, e.g. no brown-dwarf donor confirmed until 2006

  8. Twd~12000K Sp(2)>L2 SDSS1035+0551: The first definite BD donor VLT spectroscopy: eclipsing, P=82min (Southworth et al. 2006, MNRAS 373, 687) WHT/ULTRACAM photometry: M2=0.055±0.002 (Littlefair et al. 2006, Science 314, 1578)

  9. Another BD donor dynamically confirmed ISIS/QUCAM 628 spectra at 30sec exposure time WD radial velocity = 34km/s (Tulloch et al. 2009, MNRAS 397L, 32)

  10. SDSS1257+5428 – a WD + NS/BH binary • cool, high-mass white dwarf with a large radial velocity amplitude • unseen companion is a NS or BH, at d=48pc, this is the closest supernova remnant known (Badenes et al. 2009, ApJ 707, 971)

  11. SDSS1257+5428 – a double white dwarf ISIS spectroscopy cool, very low-mass WD with a large radial velocity amplitude, second high-mass WD visible, rapidly rotating  GWR progenitor “LISA-background source” (Marsh et al. 2010, ApJL submitted, arxiv:1002.4677)

  12. Basic stellar physics low-mass stars white dwarfs mass-radius relations are a strong prediction of stellar structure & evolution models, but poorly probed/constrained by observations (Ribas et al. MmSAI79, 562 & Parsons et al. 2010, MNRAS 402, 2591)

  13. Basic stellar physics low-mass stars white dwarfs mass-radius relations are a strong prediction of stellar structure & evolution models, but poorly probed/constrained by observations (Ribas et al. MmSAI79, 562 & Parsons et al. 2010, MNRAS 402, 2591)

  14. Eclipsing WD + low-mass companions SDSS & UKIDSS extending the observed M-R relation to very low stellar masses SDSS & UKIDSS WD+M6 WHT/ ACAM (Burleigh et al. in prep., Gänsicke et al. in prep)

  15. Asteroseismology WHT/ULTRACAM PG0014+027 (Jeffery et al. 2005, MNRAS 362, 66) Pulsation frequency spectrum provides information about mass, core composition, envelope mass, rotation rate, magnetic field…

  16. V455 And – the time-domain family pack V455 And=HS2331+3905 Porb • eclipsing • brown dwarf • pulsating WD • rapidly rotating WD • magnetic WD • warped accretion disc WHT/ULTRACAM WD pulsations 2xWD spin WD spin (Araujo-Betancor et al. 2005, A&A 430, 629)

  17. 67sec Ultrafast spectroscopy QUCam spectroscopy 15800 spectra 2sec exposure time no deadtime (Steeghs et al. in prep)

  18. The anomalous X-ray pulsar 4U 0142+61 WHT/ULTRACAM RXTE P=8.687s g=27.2 i=23.7 60000+ 0.48sec exposures, 0.025sec dead-time optical / X-ray modulation is in phase, not consistent with reprocession from a disc  most likely a magnetar (Dhillon et al. 2005, MNRAS 363, 609)

  19. X-ray reprocessing in Sco-X1 RXTE WHT/ULTRACAM ~11-16sec time X-ray/optical time-delay, consistent with X-ray reprocessing on the companion star (Munoz-Diarias et al. 2007, MNRAS 379, 1637)

  20. Planetary debris around white dwarfs metal-rich debris from a tidally disrupted asteroid, real-time evolution of the debris disc is seen on time scales of years (Gänsicke et al. 2006, Science 314, 1908)

  21. Time domain astronomy & wide-field surveys • all examples discussed here are rare objects found from • large-area surveys (e.g. PG, IPHAS, HQS, SDSS…) • usually identified from painful long-slit spectroscopic ID • programs • SDSS was a paradigm shift: co-ordinated deep multi-band • imaging plus MOS follow-up (10000 white dwarfs, 2000 WD+MS • binaries, 290 cataclysmic variables, 40000+ M-dwarfs…) • Future multi-colour surveys, in particular GAIA, need a similar • follow-up strategy to achieve maximum scientific impact, but… • … all time-domain science needs continued access to time-series • follow-up of new discoveries

  22. MOS requirements • low target density (a few to a few tens per square degree) •  multiplex with other target categories (as SDSS did) • broad wavelength coverage (~380-920nm) • intermediate spectral resolution (~2000) • complete down to V~20 (GAIA limit)

  23. Summary • The ING caters for a large and healthy community of • time-domain astronomers addressing a wide range of • scientific problems • Future surveys will continuously provide rare examples of • stellar evolution (SDSS-III, PanSTARRS, and ultimately • GAIA & LISA) • WHT is a leading and stable platform for time-domain • astronomy on all time scales, with a range of excellent • instruments: ISIS, ISIS/QUCAM, ACAM, ULTRACAM • … need to make sure that that expertise is kept …

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