Mssl astrophysics group start Terribly hot stars. Liz Puchnarewicz Mullard Space Science Laboratory, UCL -ray sources, missions

mssl astrophysics group

start

Terribly hot stars.

Liz Puchnarewicz

Mullard Space Science Laboratory, UCL

www.mssl.ucl.ac.uk/www_astro

-ray sources, missions and stars


introduction

-rays

models

breakthrough

new missions

Terribly hot stars.-ray sources, missions and stars

a brief history of -ray astronomy and a look at the -ray universe

models – collisions, hypernovae and others

finding -rays: mapping and measuring - SWIFT and MSSL’s UVOT

where do we see -rays? what does a g-ray burst look like?

bored

Beppo-SAX, with backup from Hubble, makes a real breakthrough


introduction

next

cosmic -ray sources had been expected for several years.

Cosmic rays + ISM supernovae

high-E electrons + mag field

-ray

CR

-ray


Introduction first crucial results

next

OSO-3

COS-B

SAS-2

• First significant detection of -rays from our galaxy.• 621 cosmic -rays

SAS-2 (NASA) and COS-B (ESA)

• first mapped the -ray sky

• detected the first point sources


Introduction first conclusions

next

1973

GRBs confirmed by SAS-2 and COS-B

BUT distance and origin were unknown

SO energy in burst unknown

SO concluded that sources were in our Galaxy, possibly reconnection of neutron star magnetic field lines with the ISM magnetic field (ie analogous to solar flares).


introduction

back to menu


-rays

next

• a -ray burst occurs about three times a day

• in seconds-to-minutes, it emits more energy than any other known phenomenon (apart from the Big Bang)

• they are distributed evenly over the sky

• they are very hard to study because they disappear before you can ‘catch’ them.

• they are very, very hot


-rays

back to menu

1. Extragalactic in origin

2. VERY energetic (up to 10 ergs) (only

surpassed by the Big Bang)

3. VERY quick (30msec to 1.6 hours) – so must be

emitted from a region only a few 10s of

kilometres across

So what are -rays?

53


models neutron star mergers

next

System emits radiation as neutron stars spiral inwards.

Merger occurs once every 10,000 to a million years in a galaxy.


models

next

A popular model for the origin of -ray bursts is in the merger of two neutron stars.


models the proton problem

next


models black hole forms

next

two stars

collide

Forms a black hole plus a disc

Relativistic jets emerge along disc axis


models where they might come from

back to menu

spatial distribution of counterparts

hypernovae

coalescing neutron stars

den

sity

of c

ou

nte

rpa

rts

distance from centre of host

coalescing neutron stars

hypernovae


Beppo-SAX

next


Beppo-Sax makes the breakthrough

next

8 hours after burst 2 days later


Beppo-SAX Hubble points to a galaxy

back to menu


new missions

next

New campaign strategies - SWIFT


new missions

next

Once a burst has been detected, the telescope will slew to position within seconds

X-ray positions to 2.5arcseconds

UVOT positions to 0.3arcseconds


campaigns

back to menu

* identify host galaxies uniquely by obtaining arcsec positions * measure redshift distribution to determine energetics, cosmological evolution, and GRB luminosity function * locate GRBs relative to host galaxies * constrain burst environment using X-ray absorption and optical reddening

* use optical/X-ray afterglow as high redshift beacons * measure Ly-alpha forest * use X-ray absorption to probe intergalactic/cluster medium * extend star formation rate observations to high redshift

Aims of the SWIFT mission


start again

the end

Liz Puchnarewicz

Mullard Space Science Laboratory, UCL

www.mssl.ucl.ac.uk/www_astro

Documents

Mssl astrophysics group start Terribly hot stars. Liz Puchnarewicz Mullard Space Science Laboratory, UCL -ray sources, missions