Time Domain Astronomy
with the SKA

Takahiro AOKI (Yamaguchi Univ.)
2016-12-16, CTA-Japan Workshop

2SKA-Japan
EngineeringTransients
From Akahori’s slide @ several workshops

Radio Telescopes I’ve Operated
Yamaguchi 32 & 34 m

Nasu 20 m x 8 & 30 m

3

Talk
1. Introducing the SKA project
2. SKA Transient Science
3. Japanese possible contribution to the SKA

4

Square Kilometre Array (SKA)
SKA-MID (~GHz)

SKA-LOW (~MHz)

5

SKA Antennas @ IAU Hawaii

6

SKA-MID (~GHz)

SKA1: 133 antennas
SKA2: ~2000?

7

SKA-MID (~GHz)
Design
SKA1: 133 antennas
SKA2: ~2000?

Sensitivity
Smin ~ 0.5 μJy @ 6 hr integ.

SKA1 (0.95 – 1.76 GHz)SKA2 (0.35 – 13.8 GHz?)

8

9

SKA-LOW (~MHz)
Log-periodic dipole antenna
SKA1: 131,072 antennas
SKA2: ~ 3,000,000!!?

SKA-LOW (~MHz)10

SKA-LOW (~MHz)
DesignSensitivity
Smin ~ 6 μJy @ 30 min integ.

SKA1 (50 – 300 MHz)11

Dirty Image Quality Comparison
SKA1-MID

VLA A-conﬁg.

From Braun’s slide @ skaengcon16

12

Dirty Image Quality Comparison
SKA1-MID

VLA A+B+C+D

From Braun’s slide @ skaengcon16

13

Dirty Image Quality Comparison

From Braun’s slide @ skaengcon16

14

Dirty Image Quality Comparison

From Braun’s slide @ skaengcon1615Performance Comparison▶ SKA (Resulting) Concept: High Sensitivity & Wide Field of View
› Consisting of many small antennas(& Wide Band in SKA2?)› World’s highest sensitivity› World’s highest survey speed» Time Domain Radio Astronomy available!
» Transient science eﬀective
16

Project Roadmap

17

Next year: SKA1 CDR

2023 - 2028: SKA1

2028-… SKA2

McPherson’s slide @ skaengcon16

SKA Science Book

18

Transient Science in the Book
1.

The Transient Universe with the Square Kilometre Array

2.

The SKA View of Gamma-Ray Bursts

3.

Incoherent transient radio emission from stellar-mass compact objects in the SKA era

4.

SKA as a powerful hunter of jetted Tidal Disruption Events

5.

Fast Transients at Cosmological Distances with the SKA

6.

The SKA contribution to GRB cosmology

7.

Time domain studies of Active Galactic Nuclei with the Square Kilometre Array

8.

Core-collapse and Type Ia supernovae with the SKA

9.

Thermal radio emission from novae & symbiotics with the Square Kilometre Array

10.

Investigations of supernovae and supernova remnants in the era of SKA

11.

The SKA and the Unknown Unknowns

12.

Early Phase Detection and Coverage of Extragalactic and Galactic Black Hole X-ray
Transients with SKA

FRB?

Get them from www.skatelescope.org/books/

19

20

SKA1 Science Priority & Freq. Ranges

High priority @ SKA2(Band 5 unavailable in SKA1)High priority @ SKA1

From System Baseline Design 2.0

21Transients/Variables
Transients
CCSN

MergerSN Ia

TDEVariables
Magnetar

CVPulsar

AGNetc.

Transient!
Detection threshold
Intrinsically variable
Light Curve

No observational sense to distinguishtransients from variables

22

Observational Classification
Short duration (< 1 s)
Fast Radio Bursts (FRBs)
Extragalactic

Long duration (> 1 s)
Supernovae, AGN,…

…

FRB

Pulsars

Flare stars, X-ray binaries,…

…

Galactic

Time-series observation

Imaging observation

23

Luminosity

Phase Space

Pietka+, 2015

Frequency x Duration24

Phase Space

Luminosity

FRB

Pietka+, 2015

Frequency x Duration

25

Phase Space
Looking Back in Time:
FRB

Accretion-powered explosions

Luminosity

Fast radio bursts (FRBs)

The Power of Gravity:

Pietka+, 2015

Frequency x Duration

Variables

26

Phase Space

Luminosity

The Unknown in blank?
→ ‘Commensal’ survey?
Pietka+, 2015

Frequency x Duration

27

Luminosity

Phase Space

Short
DurationTransients(< sec)Long
DurationTransients(> sec)Pietka+, 2015

Frequency x Duration

Luminosity

Phase Space

28

GRB
Afterglow

Short
DurationTransients(< sec)Pietka+, 2015

Frequency x Duration

GAMMA-RAY BURSTS

29

30

Gamma-ray Bursts
NS-NS/BH merger?
(Short-duration GRB)Oγ
After days

Collapse of a massive star?
(Long-duration GRB)RGRB Afterglow: Issues in RadioLow Detection RateOrphan Afterglows
Undiscovered▶ GRB follow-up results› X-ray: 93% detected› Optical: 75% detected› Radio: 30% detected

On-axis GRB afterglow:
30% radio detected〇 Simulated GRBs

Orphan/oﬀ-axis GRBA
(99% of population):
Undiscovered in radio● 9 GHz Detections ~ 0.1 mJy

On-axis GRB: 1% of the all GRBs
Italian SKA White Book››

Radio detection: 30% of on-axis GRBs
Radio detection: 0.3% of population›Need for the high sensitive
SKA-MID31

GRB Afterglow: Why Radio?
▶ Revealing Blast Wave

▶ Revealing Jet Particles &Kinetic EnergyMagnetism› Bright in radio at the spherical› Reverse shock observation

outﬂow phase› Need for immediate follow-ups
within several hours› Energy estimation easy!
Swift

8 hr
AMI
robotic follow-up

First observation
Anderson+ 2014

Burlon 201532

GRB Afterglow: Why SKA?
GRB
全母集団を解明〇 Simulated
GRBs● 9 GHz Detections

33

GRB Afterglow: Why SKA?
GRB
全母集団を解明〇 Simulated
GRBs

9 GHz

● 9 GHz Detections

Burlon, 2015

4 GHz
1.4 GHz
SKA1-MID

Italian SKA White Book

12 hr, 5σthreshold

200 MHz▶ Almost all the GHz afterglows detectable using SKA-MID▶ However, MHz afterglows undetectable using SKA-LOW…
34

Rare events

Orphan GRBA Surveys

Aoki+ 2014

Faint events35

Rare events

Orphan GRBA Surveys

Aoki+ 2014

Faint events

SKA is a powerful hunter of these sources!

36

Unknown Transients
Fast Radio Bursts

Long Duration Transients

1 ms duration, 1 Jy intensity

Minutes duration

Lorimer+ 2007 (Parkes)

Stewert+ 2015 (LOFAR)

37

Performance Comparison▶ SKA (Resulting) Concept: High Sensitivity & Wide Field of View
› Consisting of many small antennas(& Wide Band in SKA2?)› World’s highest sensitivity› World’s highest survey speed» Time Domain Radio Astronomy available!
» Transient science eﬀective
38

Requirements
Commensal System

Robotic Follow-up System

Commensal System
Swift

8 hr
AMI
robotic follow-up

First observation
Anderson+ 201439

Japanese Contribution?
▶ VLBI Follow-up

VLBI = Very Long Baseline Interferometry40▶ The slide design is based on an SKA oﬃcial (?) templatebut slightly customized.
▶ The SKA webpage: www.skatelescope.org