Date post: | 15-Jan-2016 |
Category: |
Documents |
View: | 217 times |
Download: | 0 times |
Long Wavelength Array
Exploring the Transient Universe Exploring the Transient Universe with the Long Wavelength Arraywith the Long Wavelength Array
(LWA:(LWA: http://lwa.nrl.navy.mil)
Greg Taylor (KIPAC / NRAO / UNM)
for the Southwest Consortium (UNM, NRL, UT, LANL)
Wavelengths longer than 3 meters“Long Wavelengths” (LW) Frequencies below 90 MHz
Long Wavelength Array
The 2004 Dec. 27 Giant FlareThe 2004 Dec. 27 Giant Flare
Swift was ~ 5o from the sun
It’s distance ≈ 15 kpc
Eiso ~ (2-9)1046 erg
Eiso,spike / Eiso,tail ~ 300
Expanding radio afterglow
(Palmer et al. 2005)
Long Wavelength Array
From Cameron et al. 2005
Radio Afterglow has a Steep Spectrum ~ -0.6 at t+7 days down to at least 220 MHz
Flux > 1 Jy at early times and low frequencies.
Visible out to ~ 1 Mpc
Long Wavelength Array
Image EvolutionImage Evolution
VLA 8.5 GHzTaylor et al. 2005, astro-ph/0504363
Long Wavelength Array
Growth of the Radio AfterglowGrowth of the Radio Afterglow
VLA8.5 GHz
Size att+7 days1016 cm
Velocity tot + 30 days~ 0.8 c
Decrease in vexp
Long Wavelength Array
400 km
1 “LWA Station” = 256 antennas Full LWA: 50 stations spread across NM
LWA Overview:LWA Overview:Far Larger than the VLAFar Larger than the VLA
100 m
State of N
ew M
exico
Y
VLA
Long Wavelength Array
Phased DevelopmentPhased Development
Time Phase Description Acronym
2004 0 Existing 74 MHz VLA VLA74
2004-2006 I Long Wavelength Development Array LWDA
2006-2009 II 9 station Long Wavelength Intermediate Array
LWIA
2008-2010 III LWA Core LWAC
2010-2012 IV High Resolution LWA LWA
2010- V LW Operations and Science Center LWOSC
Long Wavelength Array
Full LWA SpecificationsFull LWA Specifications
Frequency range, bandwidth 20-80 MHz, 0.05-3.0 MHz Total collecting area @ 20 MHz 106 m2 @ 60 MHz 105 m2 Angular resolution @ 20 MHz 8” @ 60 MHz 2” Pointing/frequency conversion ti me < 1 ms Sky coverage < 60° zenith distance Sensitivity ( =3 MHz, t=8 hr) @ 20 MHz ~3 mJy @ 60 MHz ~1 mJy Polarization Full Field of view @ 20 MHz ~12° @ 60 MHz ~3° Number of instantaneous baselines 1300 Time resolution 10 ms
Long Wavelength Array
Another recently discovered type of transient Another recently discovered type of transient radio source:radio source:
CGRT J1745-3009 (Hyman et al. 2005)• A periodic flaring to ~1 Jy at 76 min intervals during several months in 2002 • No obvious IR or X-ray counterpart• Tb ~ 1016 K, most likely a coherent emitter• New type of radio source?
Long Wavelength Array
1 10 102 103 104 105 106
Frequency (MHz)
107
106
105
104
103
102
10
LWA Range (deca-meter wave)
Centimeter waves
Millimeter waves
Detecting Extra solar Planets Detecting Extra solar Planets
LWA may detect emission from extra-solar “Jupiters” in outburst. Jupiter exhibits bursts of ~105 Jy at ~ 40 MHz.
~40 MHz
. Interaction of Jupiter’s magnetospherewith the Solar Wind
Bri
ghtn
ess
Long Wavelength Array
Low Frequency Transient Sources Low Frequency Transient Sources
• Radio afterglows (GRBs, SNe, magnetars, …)
• Extra-Solar planets
• Ultra-High Energy Cosmic-ray showers
• Prompt GRB and/or SNe emission
• Giant pulses from pulsars
• Microquasars
• AGN flares
• Microlensing events
• LIGO events?
• Evaporating black holes?
• …
Falcke et al. 2005
Long Wavelength Array
SUMMARYSUMMARY
Opportunity– A pathfinder Long Wavelength (LW) system demonstrates we can finally “see”
through the ionosphere at high sensitivity below 100 MHz. The Long Wavelength Array (LWA) project
– A Long Wavelength system more than 10X size and 100X the power of a recently developed LW VLA pathfinder system.
– A 400 km, completely electronic radio-telescope to be built in NM by the Southwest Consortium, providing arcsecond resolution below 100 MHz.
Goals:– Detection and Monitoring of Transient Sources, Cosmic Evolution, Particle
Acceleration, and Ionospheric Physics
The Long Wavelength Array will open the last poorly explored region of the spectrum - the potential for new discoveries will be high!