Planets in exotic Locations Slide 2 Exotic I: Planets around
Pulsars Slide 3 Main sequence lifetime ~ 10 million years Helium
burning ~ 1 million years Carbon burning ~ 300 years Oxygen burning
~ 2/3 year Silicon burning ~ 2 days The Progenitors to Pulsars:
Exploding Massive stars The burning stages of massive stars After
Si burning the core collapses resulting in a supernova explosion.
What is left behind is a neutron star. These are Type II supernova
Slide 4 The Lighthouse Beacons of Pulsars Slide 5 Properties of
Neutron Stars (Pulsars) Progenitor Mass: 8-20 M sun Remnant mass:
< 3 M sun (otherwise it becomes a black hole) Pressure support:
Neutron degeneracy pressure Radius: ~10 km Density: 200 million
tons/cm 3 Magnetic field strength: ~ 10 13 Gauss Periods: 1.5
millisecs to 8.5 s Rotation period of B1937+21: P =
0.0015578064924327 0.0000000000000004 secs These are very stable
clocks! => timing method Slide 6 A shaky start: Nature 1991
Slide 7 Slide 8 1992: initial position of the pulsar used in the
barycentric motion of the Earth was off by 7 arcmin They detected
the eccentricity of the Earths orbit Slide 9 The (Really) First
Exoplanets: in 1992 Arecibo Radio-telescope Slide 10 98 d orbit
removed, 66 d orbit remains 66 d orbit removed, 98 d orbit remains
Slide 11 Slide 12 PSR 1257+12 system: Planet A: M = 0.02 M_Earth P
= 25.3 d ; a = 0.19 AU Planet B: M = 4.3 M_Earth P = 66.5 d ; a =
0.36 AU Planet C: M = 3.9 M_Earth P = 98.2 d ; a = 0.46 AU fourth
companion with very low mass and P~3.5 yrs Interaction between B
& C Confirms the planets and Establishes true masses! Slide 13
Planets C & D near 3:2 resonance => interact
gravitationally! Rasio et al. 1992 These effects were observed in
PSR 1257+12 (Wolszczan 1994) Very strong evidence that this
planetary system is real! Slide 14 Pulsar with a 0.3 Msun mass
companion in a 191 d orbit After removing the timing variations of
the stellar companion there are additional variations in the
residuals Slide 15 Phinney 1993: Period variations due to planet
14-400 Mearth with P > 15 yrs. Thorsett et al. 1993 : Variations
are consistent either with a planet at ~10 AU, or a star at ~50 AU
orbit This planet is uncertain. Currently there is only one pulsar
with planetary companions Slide 16 Origin of the Pulsar Planets
1.First Generation Planets: These rocks are remnants of planets
(maybe giant planets) that survived the supernova explosion
2.Second Generation Planets: Planets that formed in the debris disk
left behind after the supernova explosion (more likely) Debris disk
found around another pulsar fits this picture! Unfortunately, we
only have one example of a pulsar with planets, until we find more
such systems the nature of pulsar planets will be unknown. Slide 17
Exotic II: Pulsating white dwarfs & sdB stars and eclipsing WD
binaries (NN Ser & DP Leo) Slide 18 We Can Observe White Dwarfs
for Timing But first, what is a White Dwarf? The geriatric remains
of sun-like stars All stars with masses less than 8M will become
white dwarf stars Slide 19 The Timing Method With White Dwarf Stars
White Dwarf stars are extremely small (radius ~ Earth) Their mass
is comparable to the sun, so they are extremely dense Radial
velocity impossible on such broad spectral lines Observing
planetary transits is improbable Imaging studies have so far been
unsuccessful White Dwarf stars provide a few different stable
clocks Binary White Dwarf stars = eclipses Pulsating White Dwarf
stars = time of arrival of pulses WD Slide 20 Optical Light Curves
of ZZ Ceti Stars Searching for Planets Around Oscillating White
Dwarfs Mullally et al. (2008, ApJ, 676, 573) looked at a sample of
15 pulsating white dwarfs Slide 21 One white dwarf, GD 66 looks
promising: Arrival time variations consistent with a ~2 M Jup
companion in a 4.5 year orbitbut one has to be careful:
1.Evolutionary changes can cause period changes 2. Unstable modes
can cause period changes 3. Beating of modes can cause period
changes (WD stars tend to be multiperiodic pulsators). But the
amplitude of the mode shows variations Slide 22 Subdwarf B Stars
(sdB) sdB stars are believed to be core He-burning stars of 0.5 M
on the extended horizontal branch that have lost their envelope T
eff ~ 22.000 40.000 K Periods 100 250 secs V391 Peg Slide 23 sdB
stars sdB stars in the HR diagram: Slide 24 O-C for two pulsation
frequencies look the same Slide 25 Sub-stellar Objects in Strange
Places: The Sub-stellar companion to the sdB star HD 149382 found
with traditional radial velocity variations A 8-20 M Jup mass
object in a 2.9 d orbital periodso why is this interesting? P = 2.9
days a = 0.05 AU (assuming a 2 solar mass star) = 10 solar radii.
On giant branch: Stellar radius 10-50 R sun At one point this
companion was in the envelope of the star! Slide 26 Planets around
the cataclysmic eclipsing binary NN Ser White Dwarf: Mass: 0.535
Solar masses Temperature = 37000 K Orbital Period 3.12 hours M4
Dwarf companion: Mass: 0.11 Solar masses Temperature ~ 3000 K NN
Ser is an eclipsing system. If there are additional companions
around one or both stars this will change the expected time of the
eclipse. Mass transfer Not to scale! Slide 27 UT Case Study: NN
Serpentis Parsons et al. 2010, MNRAS 402 2591 Eclipses, which occur
every 3.120 hr, are the clock We observe this clock for any
deviations (for example, say we see 3.119 hr between eclipses, or
3.126 hr) Slide 28 One planet fit to the variations in the eclipse
timing: Two planet fit: P 1 = 15.5 years M 1 = 6.9 M Jup P 2 = 7.7
years M 2 ~ 2.2 M Jup 2:1 resonance Slide 29 These planets have to
be circumbinary planets: Formation scenarios: First or Second
Generation planets First Generation: Planets formed with stars, but
these would have to have survived the supernova explosion Second
Generation: Planets formed after the common envelope phase Are they
planets at all? Dynamical stability in question! X Slide 30 Planets
around the cataclysmic eclipsing binary DP Leo White Dwarf
companion with Mass > 1 Solar mass Companion is a cool star that
is transfering mass to the W.D. Orbital Period = 89 minutesDP Leo
is a post Common Envelope star (CE). During the evolution of the
W.D. the secondary was in the envelope of the companion star. Slide
31 Slide 32 Exotic III: Planets in globular and open clusters Slide
33 HST transit search for hot Jupiters in 47 Tuc Only 120 light
years across! Slide 34 Targets: 47 Tuc Main Sequence Stars (number
of usable targets ~34000) Telescope Time Allocation: 8.3 X 24
hours, continuous observation (120 X 96.4-min HST Orbits)
Observations schedule: 1999 July 3-11 Data Obtained: 636 F555W
Images (exposure time: 160 sec per image) 653 F814W Images
(exposure time: 160 sec per image) Number of Planetary Transits
expected: about 1% of Main Sequence Stars of the Solar
Neighbourhood host a Short-Period Planet ("Hot Jupiters") Transit
Probability for the Hot Jupiters: ~ 10% Therefore 1 Transit/1000
Stars is expected 30-40 Transits for the full surveyed Stellar
Sample are expected if the 47 Tuc Planet occurence is the same as
in Field Stars Results: No Planetary Transit Detected But:
dynamical environment and [Fe/H]=-0.7! HST transit search for hot
Jupiters in 47 Tuc Slide 35 An ancient planet in M4 orbiting a
pulsar/WD binary Timing residuals in pulsar PSR B1620-26 reveal a
high-mass companion Additional residuals point toward a 3 rd body,
could be planet orbiting both stars at large separation. HST
detected 2 nd body => WD Assuming co-planarity 3 rd body =
planet with ~2.5 Mjup with P~100yrs and age of 12.7 Gyrs! Slide 36
Slide 37 The Hyades Slide 38 Hyades stars have [Fe/H] = 0.2
According to V&F relationship 10% of the stars should have
giant planets, The Hyades Paulson, Cochran & Hatzes surveyed
100 stars in the Hyades According to V&H relationship should
have found 10 planets But found zero planets! Something is funny
about the Hyades. Is it their youth (650Myr) and activity level?
Slide 39 HD 166435 shows the same period in in photometry, color,
and activity indicators. This is not a planet! In 1996 Michel Mayor
announced at a conference in Victoria, Canada, the discovery of a
new 51 Peg planet in a 3.97 d. One problem The problem with active
stars: Slide 40 Exotic IV: HD 188753 Ab : an impossible Planet?
Slide 41 Konacki et al. 2005: An extrasolar giant planet in a close
triple-star system (aka the Tatooine planet search) HD 188753 A
& B: A planet ?? m sin i = 1.14 Mjup Another 3 rd star: P = 156
d P~26 yrs P=3.4 d This would be extremely interesting as
protoplanetary disk was truncated at ~1.3 AU, well inside the
ice-line! Capture scenario for 2 nd star? Slide 42 Eggenberger et
al. 2007: No evidence for HD 188753 Ab! Slide 43 Slide 44 Slide 45
Exotic V: HIP 13044 b: a planet from outside the Milky Way? Slide
46 Setiawan et al. (2010): HIP 13044, a highly evolved star, is
orbited by a giant planet with P=16.2 days J Setiawan et al.
Science 2010;330:1642-1644 Slide 47 ..and belongs to the Helmi
stellar stream that consists of stars that originally belonged to a
dwarf galaxy that merges with the Milky Way: HIP 13044 is extremely
metal-poor! Slide 48 We know little about about the RV behavior of
this type of star. HIP 13044 shows signs of variability of its
spectral lines: Im not convinced this is a real planet. Slide 49
Exotic Planets Summary: A multi-planet system around a milli-second
pulsar Candidates around pulsating white dwarfs (GD 66), one sdB
star (V 391 Peg) and eclipsing WD systems (NN Ser & DP Leo) No
planets in globular cluster 47 Tuc and open cluster Hyades, one
candidate in globular M4 Impossible planet HD 188753 Ab is not real
HIP 13044 b, a giant planet of extragalactic origin?
