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![Page 1: Observational aspects of Cosmological Transient Objects Poonam Chandra Royal Military College of Canada.](https://reader030.fdocuments.in/reader030/viewer/2022032804/56649e575503460f94b4f376/html5/thumbnails/1.jpg)
Observational aspects of Cosmological Transient Objects
Poonam ChandraRoyal Military College of Canada
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Outline• Supernovae and Gamma Ray Bursts –
Introduction• Supernovae : Physics from multiwaveband
observations• Ongoing and Future projects• Gamma Ray Bursts – afterglows• Multiwaveband modeling of afterglows• Importance of radio observations• Future of GRB afterglows in view of ALMA and
EVLA
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Supernovae and Gamma Ray Bursts: Stellar deaths
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8MΘ ≤ M ≤ 30MΘ
Supernova
M ≥ 30MΘ
Gamma Ray Burst
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Supernovae
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Circumstellar interaction in supernovae
CS wind
Explosion center
Reverse Shock
Forward Shock
Ejecta
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• Trace back the history of the progenitor star since wind velocity ~10 km/s and ejecta speeds ~10,000 km/s.
•Supernova observed one year after explosion gives information about the progenitor star 1000 years before explosion!!!
Forward Shock
Reverse Shock
CS wind
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• X-ray and Radio emission
• Information about the mass loss rate of the star, density of the shocked ejecta, temperatures, density of the CSM
Radio
X-ray
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• Radio absorption process.
• Synchrotron self absorption (SSA): magnetic field, size of the shell.
• Free-free absorption (FFA): Mass loss rate of the progenitor star.
FFA
SSA
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• More fundamental properties, such as microphysics of acceleration of electron, equipartition energy density distribution.
Radio
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GMRT
VLA
Synchrotron cooling break at
4 GHz
Frequency
FluxmJy
Synchrotron cooling break
at ~5.5 GHz
GMRT
VLA
Frequency
FluxmJy
SN 1993JChandra et al. 2004a, 2004b
On day 3200
B=330 mG
On day 3770
B=280 mG
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SN 2010jl: Chandra Observations
Chandra et al. 2012a
Dec 2010
Oct 2011
Column density=3E+23 cm-2
Column density=1E+24 cm-2Temperature 80 KeV
Speed 7000 km/s
External X-ray absorption
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Ongoing and future project: Type IIn Supernovae
• Suggested by Schlegel 1990.• Unusual optical characteristics:
– Very high bolometric and Ha luminosities– Ha emission, a narrow peak sitting atop of broad
emission– Slow evolution and blue spectral continuum
• Late infrared excess• Indicative of dense circumstellar medium.• Very diverse in nature
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Peak radio and X-ray luminosities
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Multiwaveband Study
• Radio: circumstellar medium characteristics
• X-ray: Shock temperature, ejecta structure.
• Optical: Temporal evolution, chemical composition, explosion, distance
• IR: circumstellar dust nebula surrounding SN.
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Multiwaveband campaign to understand Type IIn supernovae
• Observe all the Type IIN supernovae with the Very Large Array within 150 Mpc distance (PI: Chandra).
• If bright enough, do spectroscopy with XMM-Newton (PI: Chandra).
• Follow radio bright and/or Swift detected Type IIN supernova with ChandraXO. Get spectroscopy, separate from nearby contamination (PI: Chandra).
• If detected in radio, follow with Swift-XRT (PI: Soderberg).
• NIR photometry with PAIRITEL (PI: Soderberg).
Chandra, Soderberg, Chevalier, Fransson, Chugai
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SN Days Detection Distance ATel2005kd 640-1173 Y 64 11822006jd 404-1030 Y 79 12972007gy 72-418 N - -2007nx 22-372 N - -2007pk 2-342 N 71 12712007rt 49-329 N 96 13592008B 21 N 78 13662008J 254-336 N 66 -2008S 8-308 N 5.6 13822008X 12 N 27 14102008aj 6-300 N 108 1409
2008am 40-337 N - 14082008be 27-268 N 123 14702008bk 4-13 N 4 1452,55,652008bm 252 N - 1865,692008cg 39-222 N - 15942008cu 156 N 152 -2008en 132 N 160 -2008es 130 N - 17762008gm 52 N 50 -2008ip 5-124 N 65 18912009ay 15 N 95 -2009dn 55 N - -2009fs 7 N - 2070
VLA
obse
rvati
ons
of T
ype
IIn s
uper
nova
e
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Absorption Mechanism: SN 2006jd (Chandra et al. 2012b)
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FLAT DENSITY PROFILE -1.45, Chandra et al. 2012b
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X-ray light curves (Chandra et al. 2012b)
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TWO SEPARATE KINDS OF
TYPE IIN SUPERNOVAE!!!!
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Gamma Ray Bursts
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Gamma Ray Bursts
• AG is synchrotron emission produced by electrons accelerated in a relativistic shock interacting with the circumburst medium.
• Entire temporal and spectral evolution is governed by simple physical parameters– Blast kinetic energy: Ek
– Circumburst density: n(r)– Shock microphysics: p,εe,εb
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Multiwaveband modeling• Long lived afterglow with powerlaw decays• Spectrum broadly consistent with the synchrotron.
• Measure Fm, nm, na, nc and obtain Ek (Kinetic energy), n (density), ee, eb (micro parameters), theta (jet break), p (electron spectral index).
GRB 070125 (Chandra et al. 2008)GRB 090423 (Chandra et al. 2010)
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Radio Observations
• Late time follow up- accurate calorimetry Eg. 970528 Frail et al.
• Scintillation- constraint on size (GRB 070125)• VLBI- fireball expansion (GRB 030329)• Density structure: wind-type versus constant
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GRB 070125: Scintillation (fireball >2 microarcsec) (Chandra et al. 2008)
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Detectable at high redshifts in radio bands due to negative K-correction
• Effect was first noted by Ciardi & Loeb (2000)
• Steep synchrotron self-absorption (ν2) partially counteracts dL
2 diming
• Time dilation (1+z) helps to probe the early epoch of reverse shock
• From z=2 to z=10 flux density drops only 40%
28
Frail et al. (2006)
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Reverse shock emission from GRB 090423 (Chandra et al. 2010)
Reverse shock seen in GRB 050904 (z=6.26) too
RS seen in PdBI data too on day 1.87
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GRB 090423 (Chandra et al. 2010)
• Highest redshift GRB at z=8.2• Highest redshift object of any kind known in
our Universe.• Must have exploded just 630 million years
after the Big Bang.
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Multiwaveband modeling of GRB 090423 (Chandra et al. 2010)
Last Chandrameasurement
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Multiwaveband modeling using Yost et al. 2004
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Swift Era: Missing Jets?
Fewer than 10% of all Swift X-ray light curves show breaks consistent with a jet-like outflow.
Koceveski & Butler (2008)
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Swift Complications: Soft Energy Response
• 15-350 keV BAT bandpass provides limited spectral coverage
• Often miss Epeak
• Leads to large uncertainties in Eγ,iso
Abdo et al., 2009
GRB 090902B
Swift
energy response
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Swift Complications: Redshift
35
Median Swift redshift 2X higher. Shifts tjet to later times.
From Palli Jakobssson webpageComplete to November 2009
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Swift Complications: Energy Injection
• Bright flares and long-lived plateau phases in X-ray afterglows
• Can inject significant amount of energy into forward shock (Ek)
Falcone et al. 2005
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Inverse-Compton in X-rays: GRB 070125 (Chandra et al. 2008)
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Detection rate in radio – 30% (Chandra et al. 2012, accepted in ApJ)
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Post Swift detection rate– 30% (redshift independent) (Chandra et al. 2012 )
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(Chandra et al. 2012, accepted in ApJ)
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Radio detectability of GRB afterglows
• Dependence on fluence• Dependence on Isotropic Energy• Dependence on X-ray flux• Dependence on optical flux
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(Chandra et al. 2012, accepted in ApJ)
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(Chandra et al. 2012, accepted in ApJ)
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(Chandra et al. 2012, accepted in ApJ)
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Future of GRB Physics: A seismic shift in radio afterglow studies
• Expanded Very Large Array (EVLA)• 20 times more sensitive than the VLA.
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(Chandra et al. 2012, accepted in ApJ)
SHB
XRFSN-GRB
LGRB
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ALMA. What can we expect?
• Years of (painful) mm/submm work at BIMA, OVRO, PdBI, JCMT, IRAM 30-m, CSO and CARMA.
• A 30% detection rate. – Radio & optical selected sample– ~2.5 mJy at t=7-14 days (too late)
47
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Future: Atacama Large Millimeter Array (ALMA)
Accurate determination of kinetic energy
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Future: ALMA Debate between wind versus ISM solved
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• Swift had expected to find many RS
• At most, 1:25 optical AG have RS
• Does not explain why prompt radio emission is seen more frequently.
• About 1:4 radio AG may be RS
• Possible Explanation: The RS spectral peak is shifted out of the optical band to lower frequencies
50
Kul
karn
i et
al.
(199
9)
Reverse shock in radio GRBs Chandra et al. (to be submitted)
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• Swift had expected to find many RS
• At most, 1:25 optical AG have RS
• Does not explain why prompt radio emission is seen more frequently.
• About 1:4 radio AG may be RS
• Possible Explanation: The RS spectral peak is shifted out of the optical band to lower frequencies
51
Kul
karn
i et
al.
(199
9)
Reverse shock in radio GRBs Chandra et al. (to be submitted)
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• mm emission from RS if observed few hours after the burst is bright, redshift-independent as effects of time-dilation compensates for frequency-redshift. (no extinction or scintillation). ALMA will be ideal with 75 uJy/4 min sensitivity.
52
Inoue, Omukai, Ciardi (2007)
Reverse shock emission from high-z GRBs and implications for future observations
Inoue, Omuka & Ciardi (2006).
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Molecular and Atomic Absorption Lines
• Optical/NIR spectroscopy of bright GRB AGs has measured Z, Tg, n and ΔV of high z SF
• ALMA (z>5)– HD 112 um (Pop III coolant)– [OI] 63.2 um (higher Z coolant)– [CII] 158 um (will replace CO)– H2 28.3 um (too hard?)
• ALMA (z=1-4)– CO lower transitions– HCN, HCO+, etc
• Eventually the AG goes away
– Probe global galaxy properties– Image dust and line emission Inoue, Omuka & Ciardi (2006).
53
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(Chandra et al. 2012, accepted in ApJ)
Density
Kinetic Energy Redshift
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Collaborators
• Dale Frail• Roger Chevalier• Alak Ray• Alicia Soderberg• Shri Kulkarni• Brad Cenko• Claes Fransson• Nikolai Chugai• Edo Berger