Supporting material for Lecture 3:

Gamma-Ray Bursts and their counterparts

Light extinction: Atmospheric absorptionGalactic extinction by dust and gas

GRBs are brief flashes of soft -ray radiation (100 keV), discovered in the 1970’s, the origin of which was not known until 1997

CGRO-BATSE

Early Multiwavelength Counterparts

(z = 0.937)

Bloom et al. 2008

(z = 6.29)

(z = 1.6)

atmospheric extinction

The amount of atmospheric extinction depends on the altitude of an object, being lowest at the zenith and at a maximum near the horizon. It is calculated by multiplying the standard atmospheric extinction curve by the mean airmass calculated over the duration of the observation:

Airmass = sec(z), z = zenith angle

Spectrum of star HD144470: the only line produced in the Stellar atmosphere is He 7065, the rest are telluric

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The Milky Way in Infrared (2MASS survey)Note the Galactic Plane

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Extinction curves of our Galaxy and Magellanic Clouds

2175 Å: graphite or PAH?

Dust suppression along given sight lines is estimated fromCOBE Infrared maps:

Schlegel, Finkbeiner, Davis 1998, ApJ, 500, 525

Neutral gas in our Galaxy absorbs thru photoelectric effect. This is predominantly neutral hydrogen (HI): the Lyman limitoccurs at 912 Å = 13.6 eV

At frequencies higher than 13.6 eV part of the X-ray flux is Absorbed, in a frequency-dependent way

Morrison & McCammon (1983, ApJ, 270, 119) have computed this dependence in the 0.03 - 10 keV energy interval, taking into account cosmic abundances

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One = 21 cm (1420 MHz) photon is emitted when the proton And electron spins flip from parallel to antiparallel.

Hydrogen atom

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Radio and far infrared images of M81 (3.6 Mpc)

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The Antennae(22 Mpc)

White: opticalBlue: radio (21cm)

High-z QSO spectra (Becker et al. 2001)

The Intergalactic mediumAbsorbs radiation:

Lyman alpha forestAnd Lyman continuumIn high redshift quasars:intervening absorption byClouds of neutral hydrogen

Elihu Boldt

The Extreme Universe: Some Views From Here

Closing lecture, 3rd INTEGRAL Workshop: The Extreme Universe, Taormina, September 14-18 1998Astrophysical Letters & Communications Vol. 37, 1999

arXiv:astro-ph/9902040