The Transient Universe: AY 250 Spring 2007 The Transient Universe AY 250 Geoff Bower.

The Transient Universe: AY 250 Spring 2007

The Transient UniverseAY 250

Geoff Bower


Bayeux tapestrycommemorating SN of 1066


What is Transient Astronomy?



• What isn’t?– 20/43 astronomical phenomena (from Harwit

1984) involve or were discovered by transient or variable phenomena.


PhenomenaTransient Phenomena

(Harwit 1984)• Stars• Planets• Novae• Comets• Moons• Rings• Galactic clusters• Clusters of galaxies• Interplanetary matter• Asteroids• Multiple stars• Variable stars with nebulosity• Planetary nebulae• Globular clusters• Ionized gas clouds• Giants/main sequence stars• Cosmic rays• Pulsating variables• White dwarfs• Galaxies• Cosmic expansion

• Interstellar dust• Novae/supernovae• Galaxies with/without gas• Supernova remnants• Radio galaxies• Magnetic variables• Flare stars• Interstellar magnetic fields• X-ray stars• X-ray background• Quasars• Microwave background• Masers• Infrared stars• X-ray galaxies• Pulsars• Gamma-ray background• Infrared galaxies• Superluminal sources• Gamma-ray bursts• Unidentified radio sources



• What isn’t?– 20/43 astronomical phenomena (from Harwit

1984) involve or were discovered by transient or variable phenomena.

• The study of variable and ephemeral phenomena in the sky…


What is Transient Astronomy? II• Where the timescale of variability is comparable to or less than a human

graduate student timescale.– Giant pulses (nanoseconds)– Long wavelength radio afterglows (years)

• Transient in flux– Undetectable to detectable– Gamma-ray bursts

• Variable in flux– Exoplanet transits (milli) to a galactic supernova (mega-mega)– But solar variability?

• Variable in position– Asteroids, KBOs– Astrometry?

• Variable in spectrum, polarization– Exoplanet radial velocities?

• Variable particle emission


Solar Transient Activity

Nita et al 2004


What is Transient Astronomy? III

• Answer is clearly human and telescope-dependent• The bigger the telescope, the longer the timescale the

more transient phenomena• Critical from antiquity to the present in advancing our

understanding of the Universe

Bayeux tapestrycommemorating SN of 1066


Three Important Examples in Current Astronomy

• Supernovae– Discovered in antiquity– Understood in modern era along with nucleosynthesis, stellar life

cycle– Probes of the geometry of the Universe

• Gamma-ray bursts– Discovered in modern era through military technology– Understood with advent of new telescopes– Probes of star formation at high redshift

• Pulsars– Discovered in modern era with new telescope– Understood through accumulation of examples– Probes of general relativity, interstellar medium, nuclear

equation of state


Examples of Transients That Will Become Critical

• Killer asteroids• Exoplanets

– Stellar transits as probe of size

– Radio emission as probe of magnetic and stellar winds

• Gravity waves– A generation of non-

detections– Black hole & NS mergers

• Neutrino sources– SN 1987A

• SETI


Examples of Transients That Will Become Critical


Expansion of Parameter Space Discovery

• Cosmic Discovery, Harwit 1984• Parameter space

– Sensitivity– wavelength– angular resolution – spectral resolution– time resolution– polarization – particle mode


Trends of Discovery(Harwit)

• Most important discoveries result from substantial technological innovation

• Following a new technique, discovery follows quickly• Novel instrument soon exhausts its capacity for

discovery• New discoveries are often made by physicists or

engineers from outside astronomy• Many discoveries involve military technology• Instruments used in the discovery were often

constructed by the discoverer• Discoveries often occur by chance


How Much Is Left to Be Discovered?

• Harwit 1984 makes counting arguments that suggest 10 – 30% of all discoveries have been made

• Time scale for discoveries are centuries to millenia


A New Generation of Telescopes

Radio Optical Gamma-ray

LOFARMWALWA

ATAEVLAALMASKA

Pan StarrsLSST

KAITPAIRITELROTSE III

SwiftGLAST


Radio

• MWA• LWA• LOFAR

• ATA• EVLA• ALMA• SKA


New Radio Characteristics

• Powerful survey capacity

• Orders of magnitude in sensitivity increase

• Rapid slewing

• All sky view

• Re-play mode

• High time resolution

• Increased frequency domain


Radio Survey SpeedSKA

ATA-350+


Optical

• KAIT• PAIRITEL • ROTSE III• Raptor

• Pan Starrs• LSST• Kepler


Robotic Telescopes

• Robotic follow-up telescopes– KAIT, PAIRITEL,

ROTSE– Follow-up on time

scale

• Wide field of view search telescopes– Raptor (>1000 sq deg

FOV)


Monster Survey Telescopes

• SDSS• Pan Starrs• LSST


High Energy

• Swift• GLAST


New High Energy Capabilities

• Rapid, accurate localization– 1 deg <1 arcmin

• Much greater sensitivity– 50 times sensitivity of EGRET


Particle & Gravity Wave Telescopes

• LIGO-II• LISA

• Auger• IceCube


Issues in Transient Discovery

• How to find transients– Telescope/wavelength specific search strategies– What is the optimal telescope for transient discovery?– What is the optimal search strategy?– Matched filter analysis– How does discovery change in the era of the VO?– Dealing with volume of data (10 PB/year for LSST)

• How to identify/classify transients– Multi-wavelength coordination– Decision making strategies

• What response should be made– Machine-to-machine communication– Number of transients will be large– Is it useful to me?


Example of Flare Star/Asteroid/Optical Flash

Confusion• Flare stars and asteroids dominate the foreground in the

optical• Rejection of foregrounds by motion, optical color,

spectral feature, multiwavelength behavior, catalog identification, parallax

• LSST will catalog all s.s. objects > 200 m

Vestrand et al


Course Overview


Course Details

• New time– TuTh 11:00-12:30

• Office hours– 621 Campbell

• No exams• Reading (see syllabus)• Student presentations

• http://astro.berkeley.edu/~gbower/TU_S07

http://astro.berkeley.edu/~gbower/TU_S07

The Transient Universe: AY 250 Spring 2007 The Transient Universe AY 250 Geoff Bower.

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