Time-domain astronomy on the WHT
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Transcript of Time-domain astronomy on the WHT
Time-domain astronomy on the WHT
Boris Gänsicke
…or…Rare objects from wide-field surveys
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
CK Vul = Nova Vulpeculae 1670
(Hevelius 1670, Phil. Trans. 5, 2087)
- classical nova?- late thermal pulse?- merger?- sub-Chandra SN?
Same constellation - 337 years later
IPHAS pre-eruption HAAVSO
(Wesson et al. 2008, ApJL 688, 21)
IPHAS: 6 weeks
V458 Vul = Nova Vulpeculae 2007
IPHAS pre-eruption HWHT/INT H 2007-2009
(Wesson et al. 2008, ApJL 688, 21)
V458 Vul = Nova Vulpeculae 2007
(Rodríguez-Gil et al. submitted)
shortest-period PN nucleus: Porb=98.1min likely a binary white dwarf
ISIS radial velocities
The evolution of compact binary stars
White dwarf / main sequence binaries are the simplest CBs, yetpopulation models and observations used to disagree, e.g.no brown-dwarf donor confirmed until 2006
70% brown dwarf donors
SDSS1035+0551: The first definite BD donor
Twd~12000K
Sp(2)>L2
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)
Another BD donor dynamically confirmed
ISIS/QUCAM
(Tulloch et al. 2009, MNRAS 397L, 32)
628 spectra at 30sec exposure time
WD radial velocity = 34km/s
SDSS1257+5428 – a WD + NS/BH binary
(Badenes et al. 2009, ApJ 707, 971)
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
SDSS1257+5428 – a double white dwarf
ISIS spectroscopy
(Marsh et al. 2010, ApJL submitted, arxiv:1002.4677)
cool, very low-mass WD with a large radialvelocity amplitude, second high-mass WDvisible, rapidly rotating GWR progenitor“LISA-background source”
Basic stellar physics
(Ribas et al. MmSAI 79, 562 & Parsons et al. 2010, MNRAS 402, 2591)
low-mass stars white dwarfs
mass-radius relations are a strongprediction of stellar structure & evolutionmodels, but poorly probed/constrainedby observations
Basic stellar physics
(Ribas et al. MmSAI 79, 562 & Parsons et al. 2010, MNRAS 402, 2591)
low-mass stars white dwarfs
mass-radius relations are a strongprediction of stellar structure & evolutionmodels, but poorly probed/constrainedby observations
Eclipsing WD + low-mass companions
(Burleigh et al. in prep., Gänsicke et al. in prep)
SDSS & UKIDSS
SDSS & UKIDSS
WD+M6
WHT/ACAM
extending the observedM-R relation to very lowstellar masses
Asteroseismology
(Jeffery et al. 2005, MNRAS 362, 66)
WHT/ULTRACAM
Pulsation frequency spectrum provides information about mass, core composition, envelope mass, rotation rate, magnetic field…
PG0014+027
V455 And – the time-domain family pack
(Araujo-Betancor et al. 2005, A&A 430, 629)
V455 And=HS2331+3905
WHT/ULTRACAM
-eclipsing-brown dwarf-pulsating WD-rapidly rotating WD-magnetic WD-warped accretion disc
WD spin
WD pulsations
Porb
2xWD spin
Ultrafast spectroscopy
QUCam spectroscopy
67sec15800 spectra2sec exposure timeno deadtime
(Steeghs et al. in prep)
The anomalous X-ray pulsar 4U 0142+61
(Dhillon et al. 2005, MNRAS 363, 609)
WHT/ULTRACAM
RXTE
P=8.687sg=27.2i=23.7 60000+ 0.48sec exposures,
0.025sec dead-time
optical / X-ray modulation is in phase, not consistent with reprocessionfrom a disc most likely a magnetar
X-ray reprocessing in Sco-X1
(Munoz-Diarias et al. 2007, MNRAS 379, 1637)
WHT/ULTRACAM
RXTE
~11-16sec time X-ray/optical time-delay, consistent with X-ray reprocessing on the companion star
Planetary debris around white dwarfs
(Gänsicke et al. 2006, Science 314, 1908)
metal-rich debris from a tidally disruptedasteroid, real-time evolution of the debris disc is seen on time scales of years
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
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)
Summary
• 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 …
• Future surveys will continuously provide rare examples of stellar evolution (SDSS-III, PanSTARRS, and ultimately GAIA & LISA)
• The ING caters for a large and healthy community of time-domain astronomers addressing a wide range of scientific problems