supporting material for lecture 3: gamma-ray bursts and their counterparts light extinction:
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Supporting material for Lecture 3: Gamma-Ray Bursts and their counterparts Light extinction: Atmospheric absorption Galactic 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. - PowerPoint PPT PresentationTRANSCRIPT
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