Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Eran  Ofek   Weizmann  Institute  of  Science  

   

ULTRASAT   Exploring  the  UV  transient  sky  

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

What is ULTRASAT

Capabilities

Science motivation highlight

SN shock cooling and breakout

GW EM counterpart

…

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Weizmann-Caltech led proposed small space mission (~$100M)

PIs: Waxman & Kulkarni

JPL, ISA, IAI, ElOp

Exploring the UV transient sky

Designed to:

SN shock cooling and breakout discovery & alerts

Studying SN progenitors and physics

Search & alert for GW EM counterparts in the UV

Explore the transient sky (e.g., variability, TDE, GRB, QSO)

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

33 cm f/1 Schmidt

NUV band (220-280 nm)

δ-d CCD (QE~70%)

Lim mag. 21.8 AB (3x300s; 5σ)

30 mag arcsec2 (in 3 months)

FWHM ~24’’

FOV: 235 deg2

Volumetric rate: ~380 X GALEX

~12 X ZTF

~0.2 LSST (but in NUV)

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

GEO +300km

Avoiding geocoronal lines

Observing continuously 24/7

Direct & continuous communication

All data transmission

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

For several weeks - All sky survey to 22.8 AB mag.

Continuous observing of the same FOV for 6 months

Switching to opposite hemisphere after 6 months

Mission life time: 2yr

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Pointings

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Image transmission (

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

SN shock breakout & cooling

GW EM counterpart search

TDE, GRB, QSO, variability...

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Shock breakout

occurs when τ~c/v

Measure R*, E/M, composition

R*/c  

di ffu

sio n   t-­‐4/3  

L~R*2  

log  t   ~30  min   ~1  day  

Lu m in os ity

 

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

SN shock cooling – some observations

2008D (?)

(Soderberg+08)

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

What can we learn?

Stellar radius

Explosion energetics (E/M)

Composition

Complications: Wind/CSM

but can derive CSM mass

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Accuracy?

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Why UV?

The rise time in optical >> rise time in UV

Therefore, by the time optical reach max light -> T complicated physics

Removing the degeneracy between E/M and R* requires UV observations

Probe the temperature

Brighter in UV in earlier times

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

Expectations

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

The advantages of a large FOV UV

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

The advantages of a large FOV UV

1. LIGO/VIRGO error regions ~100 deg2

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

The advantages of a large FOV UV

2. Ground based observatory can follow up on 1/16 of the ToO within 20min.

ULTRASAT – can access ~48% of the sky within 20min

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

3. EM counterpart properties highly uncertain. However, models predicts UV +blue counterpart at early times

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

TDE (>100 event/yr)

GRB (a few/yr)

QSO monitoring >20,000

Stellar monitoring >200,000

Subtraction

Eran Ofek

Big Data Dec 17, 2015

ΩB  =  0.0447  ±  0.0016  

Larson+10  

ULTRASAT capabilities have the potential to revolutionize transient research