Observational aspects of Cosmological Transient Objects

Poonam ChandraRoyal Military College of Canada

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

Supernovae and Gamma Ray Bursts: Stellar deaths

8MΘ ≤ M ≤ 30MΘ

Supernova

M ≥ 30MΘ

Gamma Ray Burst

Supernovae

Circumstellar interaction in supernovae

CS wind

Explosion center

Reverse Shock

Forward Shock

Ejecta

• 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

• 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

• 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

• More fundamental properties, such as microphysics of acceleration of electron, equipartition energy density distribution.

Radio

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

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

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

Peak radio and X-ray luminosities

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.

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

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

Absorption Mechanism: SN 2006jd (Chandra et al. 2012b)

FLAT DENSITY PROFILE -1.45, Chandra et al. 2012b

X-ray light curves (Chandra et al. 2012b)

TWO SEPARATE KINDS OF

TYPE IIN SUPERNOVAE!!!!

Gamma Ray Bursts

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

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)

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

GRB 070125: Scintillation (fireball >2 microarcsec) (Chandra et al. 2008)

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)

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

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.

Multiwaveband modeling of GRB 090423 (Chandra et al. 2010)

Last Chandrameasurement

Multiwaveband modeling using Yost et al. 2004

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)

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

Swift Complications: Redshift

35

Median Swift redshift 2X higher. Shifts tjet to later times.

From Palli Jakobssson webpageComplete to November 2009

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

Inverse-Compton in X-rays: GRB 070125 (Chandra et al. 2008)

Detection rate in radio – 30% (Chandra et al. 2012, accepted in ApJ)

Post Swift detection rate– 30% (redshift independent) (Chandra et al. 2012 )

(Chandra et al. 2012, accepted in ApJ)

Radio detectability of GRB afterglows

• Dependence on fluence• Dependence on Isotropic Energy• Dependence on X-ray flux• Dependence on optical flux

(Chandra et al. 2012, accepted in ApJ)

(Chandra et al. 2012, accepted in ApJ)

(Chandra et al. 2012, accepted in ApJ)

Future of GRB Physics: A seismic shift in radio afterglow studies

• Expanded Very Large Array (EVLA)• 20 times more sensitive than the VLA.

(Chandra et al. 2012, accepted in ApJ)

SHB

XRFSN-GRB

LGRB

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

Future: Atacama Large Millimeter Array (ALMA)

Accurate determination of kinetic energy

Future: ALMA Debate between wind versus ISM solved

• 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)

• 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)

• 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).

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).

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(Chandra et al. 2012, accepted in ApJ)

Density

Kinetic Energy Redshift

Collaborators

• Dale Frail• Roger Chevalier• Alak Ray• Alicia Soderberg• Shri Kulkarni• Brad Cenko• Claes Fransson• Nikolai Chugai• Edo Berger