Speculative transients, GW counterparts, unnova

Speculative transients, GW counterparts, unnova

Exploring the Boundary Between
Neutron Stars and Black Holes!
Tony Piro
(Carnegie Observatories)
Experiments and Boutiques
August 28, 2015
Black Holes versus Neutron Stars
• Where do stellar
mass black holes
come from?
• Potential probe of
neutron star EOS
• Apparent
“compact object
desert” between
~2 and ~4 Msun.
What are
signatures of
events on either
side of divide?
Ozel et al. (2010, 2012)
Black holes don’t die quietly…
• Prior to BH
formation, NS emits
copious neutrinos
for ~few seconds
• Adjustment of the
envelope steepens
into a shock and
ejects H envelope
(Nadezhin ‘80)
• Dim, ~few month
long supernova
(Lovegrove &
Woosley ’13)
Lovegrove & Woosley (2013)
Shock Breakout Following BH Formation
Key properties:
• Low velocities
(~200-1000 km/s)
• T ~ 104 K
• Hydrogen-rich
composition,
devoid of burning
products
Key point: shock
ejects hydrogen
envelope so
helium core
becomes the BH!
(Kochanek ‘14)
Piro (2013)
Black Hole Formation Probability
Clausen, Piro, and Ott (2014)
Bad news:
Probability
function not
uniquely
determined
Good news:
No BHs below
M*~20 Msun is
robust
This implies at <10% of massive stars become BHs
This roughly matches the maximum mass observed
for Type II-P progenitors (Smartt et al.)
What if a long-lived NS is
produced in a NS merger?
Mej ~ 0.01Msun
Neutron
rich
B ~ 1014-1015 G
P ~ 1 ms
What if a long-lived NS is
produced in a NS merger?
Mej ~ 0.01Msun
νe + n → p + e-
np ~ n n
νe
νe
νe
Neutron
rich
νe
B ~ 1014-1015 G
P ~ 1 ms
Neutrinos make ejecta
composition more symmetric,
Ye ~ 0.5 (Metzger, Piro,
Quataert ‘09; Metzger &
Fernandez ‘14)
Magnetar-Powered Estimate
Assuming complete thermalization:
This gives peak Lth ~ Eth/td ~ 1045 erg/s!
Close-up of interior
e+/-
Iron-like ejecta
cools and
recombines
e+/-
Pulsar
wind
e+/-
e+/X-rays generated
via synchrotron
emission
Termination shock
creates spectrum of
non-thermal electrons
Metzger & Piro (2014)
Crab nebula
Close-up of ejecta wall
X-rays generated
via synchrotron
emission
X-rays
absorbed and
heat ejecta via
bound-free
interactions
Ionization
front
Thermal
photons
Metzger & Piro (2014)
Magnetar-Powered Estimate
Assuming complete thermalization:
This gives peak Lth ~ Eth/td ~ 1045 erg/s!
Physics missing!
• Non-thermal X-rays must travel through nebula
• X-ray heating depends on ionization state of ejecta
Early X-ray & Optical Emission
Metzger & Piro (2014)
Key properties:
• Blue transient
~10-100 times
brighter than SNe
• Peaks at ~1 day
• Non-thermal
X-rays have similar
luminosity and
timescale
GRB 080503
Perley, …, Piro, et al. (2009)
Optical/X-ray
Rebrightening
at t ~ 1 day
z = 0.561
GRB
080503
What is GRB 080503 explanation?
Problems with the kilonova explanation:
• Timescale too short (~1 day)
• Luminosity too high, unless hidden host at z < 0.2
• X-rays not explained
Benefits of the magnetar explanation:
• Timescale about right
• Luminosity roughly correct for z ~ 1
• X-rays expected
Late-time Synchrotron Radio Emission
Piro & Kulkarni (2013)
• Above ~ 1mJy for ~ 3 months
• For ASKAP, we expect ~4 above threshold over entire sky
Conclusions
Transient surveys can probe the boundary between NSs
and BHs over a wide range of wavelengths
X-rays and blue optical: ~day long burst from millisecond
magnetar following NS mergers (or AIC)
Optical: ~few day to week long shock breakout from proto-NS
neutrino losses
Radio: ~few month long brightening from long lasting plerion
emission following NS mergers (or AIC)
Many other possible signatures! Disk outflow-powered
(Kashiyama & Quataert ’15), fallback-powered (Dexter & Kasen
‘13), propeller-powered (Piro & Ott ’11)
NS/BH masses suggestion BHs made >20 Msun and by
less than ~10% of massive stars
Extra slides
Fallback accretion during supernovae
Piro & Ott (2011), Piro & Thrane (2012)
Neutron star spins up from
fallback accretion and
radiates accreted angular
momentum as GWs
GWs directly observe NS turning into a BH!
Detection with Advanced LIGO
Piro & Thrane (2012)
• Match-filtering
implies huge
detection distances
(~100 Mpc), but likely
unrealistic
• Injection recovery
with cross-power
based analysis and
density-based trackfinding algorithm
(Thrane et al. 2011)
Detection with Advanced LIGO
Piro & Thrane (2012)
• Match-filtering
implies huge
detection distances
(~100 Mpc), but likely
unrealistic
• Injection recovery
with cross-power
based analysis and
density-based trackfinding algorithm
(Thrane et al. 2011)
• Detectable with
Advanced LIGO
~10-20 Mpc
Recent Nearby Core Collapse SNe
Piro & Thrane (2012)
Recent Nearby Core Collapse SNe
Updated from Piro & Thrane (2012)
Connections to SN Progenitor Masses
Clausen, Piro, and Ott (2014)
• Lower limit at
~20
Msun roughly matches
the maximum mass for
observed Type II-P
progenitors
Smartt et al.
Impact on Chemical Enrichment
Clausen, Piro, and Ott (2014)
0.19
0.08
0.18
PBH,1
PBH,2
0.07
0.16
28Si/16O
20Ne/16O
0.17
0.15
0.14
0.06
0.05
⇤
MBH
0.13
PBH,1
0.12
0.11
10
⇤
MBH
0.04
PBH,2
20
30
40
50
⇤
MBH
60
[M ]
70
80
90
10
20
30
40
50
⇤
MBH
60
[M ]
70
80
The composition of material ejected by massive stars during their
life and death is impacted by which stars make BHs versus NSs
90