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Observational aspects of Cosmological Transient Objects Poonam Chandra Royal 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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8M Θ ≤ M ≤ 30M Θ Supernova M ≥ 30M Θ 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 FluxmJyFluxmJy Synchrotron cooling break at ~ 5.5 GHz GMRT VLA Frequency FluxmJyFluxmJy SN 1993J Chandra 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-2 Temperature 80 KeV Speed 7000 km/s External X-ray absorption
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Suggested by Schlegel 1990. Unusual optical characteristics: – Very high bolometric and H luminosities – H 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). 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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VLA observations of Type IIn supernovae
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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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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: E k – Circumburst density: n(r) – Shock microphysics: p, ε e, ε b
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Long lived afterglow with powerlaw decays Spectrum broadly consistent with the synchrotron. Measure F m, m, a, c and obtain E k (Kinetic energy), n (density), e, b (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 ( ν 2 ) partially counteracts d L 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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Last Chandra measurement
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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 E peak Leads to large uncertainties in E γ,iso Abdo et al., 2009 GRB 090902B Swift energy response
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Swift Complications: Redshift 35 Median Swift redshift 2X higher. Shifts t jet to later times. From Palli Jakobssson webpage Complete 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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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 XRF SN-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 Kulkarni et al. (1999) 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 Kulkarni et al. (1999) 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, T g, n and Δ V 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) – H 2 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
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