Time-domain%20astronomy%20on%20the%20WHT

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

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CK Vul Nova Vulpeculae 1670

• classical nova?
• late thermal pulse?
• merger?
• sub-Chandra SN?

(Hevelius 1670, Phil. Trans. 5, 2087)
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Same constellation - 337 years later
IPHAS 6 weeks
AAVSO
IPHAS pre-eruption H?
(Wesson et al. 2008, ApJL 688, 21)
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V458 Vul Nova Vulpeculae 2007
WHT/INT H? 2007-2009
IPHAS pre-eruption H?
(Wesson et al. 2008, ApJL 688, 21)
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V458 Vul Nova Vulpeculae 2007
ISIS radial velocities
shortest-period PN nucleus Porb98.1min ? likely
a binary white dwarf
(Rodríguez-Gil et al. submitted)
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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
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SDSS10350551 The first definite BD donor
VLT spectroscopy eclipsing, P82min
(Southworth et al. 2006, MNRAS 373, 687)
WHT/ULTRACAM photometry M20.0550.002
(Littlefair et al. 2006, Science 314, 1578)
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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)
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SDSS12575428 a WD NS/BH binary

• cool, high-mass white dwarf with a large radial
  velocity amplitude
• unseen companion is a NS or BH, at d48pc, this
  is the closest
• supernova remnant known

(Badenes et al. 2009, ApJ 707, 971)
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SDSS12575428 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,
arxiv1002.4677)
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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. MmSAI 79, 562 Parsons et al.
2010, MNRAS 402, 2591)
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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. MmSAI 79, 562 Parsons et al.
2010, MNRAS 402, 2591)
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Eclipsing WD low-mass companions
SDSS UKIDSS
extending the observed M-R relation to very
low stellar masses
SDSS UKIDSS
WDM6
WHT/ ACAM
(Burleigh et al. in prep., Gänsicke et al. in
prep)
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Asteroseismology
WHT/ULTRACAM
PG0014027
(Jeffery et al. 2005, MNRAS 362, 66)
Pulsation frequency spectrum provides information
about mass, core composition, envelope mass,
rotation rate, magnetic field
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V455 And the time-domain family pack
V455 AndHS23313905
Porb

• eclipsing
• brown dwarf
• pulsating WD
• rapidly rotating WD
• magnetic WD
• warped accretion disc

WHT/ULTRACAM
WD pulsations
WD spin
2xWD spin
(Araujo-Betancor et al. 2005, AA 430, 629)
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Ultrafast spectroscopy
QUCam spectroscopy
15800 spectra 2sec exposure time no deadtime
(Steeghs et al. in prep)
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The anomalous X-ray pulsar 4U 014261
WHT/ULTRACAM
RXTE
P8.687s
g27.2 i23.7
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)
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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)
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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)
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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 WDMS
• 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

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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 V20 (GAIA limit)

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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