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Transcript
Supernovae Light Curves
Powered by Young Magnetars
The past/current (e.g. ROTSE, SNLS, SDSS,
Palomar Transient Factory,Pan-Starrs1) and future
(Dark Energy Survey, SkyMapper) supernovae
surveys probe large volumes, revealing a diversity of
supernovae not previously known.
We (Kasen & LB 2009; Woosley ‘09) explain very
bright (> 1044 erg sec-1) core collapse SNe as caused
by the birth of a 2-5 ms neutron star with 1014 G < B
< 1015 G.
Exciting times for Supernovae and Transients!
Palomar Transient Factory
(‘09; R=21, 3000 deg2, 5d)
Pan-Starrs1 (‘09; V=24,
50 deg2, 4d)
ROTSE (V=18, 200 deg2)
2005ap had photospheric spectra
2006gy (2006tf as well) had
evidence for interaction => IIn
(see Smith & McCray ‘07)
2008es: Lpeak=3x1044 erg sec-1
Miller et al. 2009
Gezari et al. 2009
Comparisons to other SNe
x100
Typical core collapse event
Rest et al 2009
Quimby’s Survey with ROTSE
• Evidence for two classes
– Type IIL = bright, no evidence for interaction
– Type IIn = bright, clear evidence for interaction
• Volume rate uncertain, but < 1% of Core Collapse
Simple Lightcurves (ala Arnett)
• Consider an ejected mass M that is expanding at
v, so R=vt, and has opacity Kappa
• Radiation diffusion time is >R/v=age until a time
• But before then the expansion is adiabatic and
when radiation-dominated=>
Luminosity Estimate
• The luminosity is
• During the adiabatic phase, T goes like 1/R, giving
• This provides an excellent estimate for the peak
luminosity of Type IIP SNe (1042-1043 erg s-1 )
where Ro is large for red giants (Popov ’93 is a
particularly nice paper).
Births of Magnetars!
• Studies of AXPs and SGRs reveal that ~10% of
NSs are born with 1014 G < B < 1015 G. If born
spinning at P=10msP10 spin-down will occur in:
• To substantially impact lightcurve, want this to
occur before diffusion kicks in, requiring
• In the range of magnetars (Kasen & L.B. ‘09;
Woosley ‘09) !!
Resetting the Entropy
• The deposition of spin-down energy resets the
interior entropy
• Where the available energy is the NS rotation
• As long as Ep>Esn(Ro/vtp), the entropy is reset, so
don’t need to have Ep~Esn to impact the lightcurve
Hot Bubble Formation
Magnetar spin-down time = 1 day
Kasen & L.B. ‘09
• Mej=5 M
• Esn=1051
ergs
• One month
•
•
•
•
Mej=5 M
Esn=1051 erg
Pi=5 ms
Dashed line is 1 M of
56Ni
• Expect to see swept up
shell in the
photospheric velocity
time evolution.
Kasen & L.B. ‘09
Peak Luminosity and Duration
imply Magnetar Properties
Kasen & L.B. ‘09
Mej=5 M
Mej=20 M
Radiation Hydrodynamics Examples
Kasen & L.B. ‘09
Bright Supernovae powered by
Magnetars
• We don’t need extreme rotation or B to modify the
core collapse event
• Maximum radiated luminosity is set by rotation,
and some expansion losses, to 1052 ergs.
• Events as bright as 2005ap and 2008es should be
<<10% of all core collapse events, as they require a
fast initial spin.
• Many ‘bright’ II L’s may be made this way.. As
more moderate spins can still brighten the event.