Transcript New Alternative Methods of GRB Detection

Alternative Detections of
Gamma Ray Bursts
René Hudec2 and Rudolf Slosiar1
1 Slovak Union of Amateur Astronomers, Bojnice,
Slovak Republic
2 Astronomical Institute, Academy of Sciences of the
Czech Republic, CZ-251 65 Ondrejov, Czech Republic
Image credit: NASA
Alternative GRB Detections
•By Ionospheric Response
•By Bright Prompt Optical Emission
•By Promt X-ray Emission
Indirect detection of GRBs
by ionospheric response
Introduction
• We report on the independent and indirect
detection of GRBs by their ionospheric response
(SID – Sudden Ionospheric Disturbance)
observed at VLF (Very Low Frequency).
• Although few such detections have been already
reported in the past, the capability of such
alternative and indirect investigations of GRBs
still remains to be investigated in more details.
We present and discuss the examples of further
such VLF/SID detections.
Previous VLF detections of GRBs
• SGR1806: Detection of a Sudden
Ionospheric Disturbance. Campbell et al.,
GCN 2932, 2003.
• GRB030329 observed as a Sudden
Ionospheric Disturbance (SID) P.W.
Schnoor GCN 2176, 2003.
Physics behind ionospheric
detection I
• The solar particle stream, solar wind, shapes and
controls the Earths‚ magnetic envelope - the
magnetosphere- and increases heat in the aurora zones.
But not all ionospheric variability is caused by solar or
geomagnetic disturbances. The ionosphere is not a
constant 'mirror in the sky'. The E layer (100-200 km
above ground) and the F1 layer (170-200 km) usually
behave in regular, solar-controlled way, but the F2 layer
(250-350 km) does not.
• It is the F2 layer, which has the greatest density of free
electrons, and is potentially the most effective reflector of
radio waves. (Rishbeth, Nature Vol. 418, 4 July 2002)
Physics behind ionospheric
detection II
• The ionossperic D layer plays in the GRB detections an
important role, as the detection of X-ray and gamma-ray
triggers is based on the measuremeńt (monitoring) of
reflected radio waves from this layer. The ionospheric D
layer is not transparent for radio VLF waves (frequencies
3kHz to 30 kHz) and behaves like a mirror.
• If the transmitter is at large distance (800 to 2000 km)
then the radio waves are guided like in a waveguide
consisting of the D layer and the earth surface.
• Any change in the quality of this waveguide results then
in the signal change in the SID monitor. The change can
be positive but in some cases such as the sudden phase
anomaly also negative.
Typical ionospheric behaviour
This picture shows the typical behaviour of the ionosphere during one day.
Note the different behavior at night with absence of the D layer.
The plot from the SID monitor
during the period of enhanced solar
activity
Dec 6, 2006
Demonstration of the
possibility and
sensitivity of the
method. Four Solar
Flares (SF) are visible
with intensities M6, C6,
C2, C4, exactly
corresponding to the
measurements by the
GOES satellite. The
peak related to the SF
C4 occurs around
15:03UT, which is
nearly the detection
time of GRB060124A, on
Jan 24, 2006, confirming
that even at the time of
the decay of the D
ionospheric layer
reliable measurements
are feasible.
SGR1806-20: A sharp spike, then renormalization of the ionosphere (Howe, 2004)
The SID receiver and cross loop
antenna
2-channel receiver used to eliminate false
triggers
Instrumentation used for the
indirect detection of GRB 060124A.
The antenna size is 75 x 75 cm
Inexpensive instrumentation suitable
for easy duplication for other sites
The detection of GRB 060124A
GRB_TIME: 15:54:51.82 UT
SID trigger detection 15:56:31 +/- 5sec
Swift BAT LCT
The detection of GRB 060124A
2500
2000
1500
1000
500
0
16:40 16:42 16:44 16:46 16:48 16:50 16:52 16:54 16:56 16:58 17:00 17:02 17:04 17:06 17:08 17:10 17:12 17:14 17:16 17:18 17:20 17:22 17:24 17:26 17:28
For comparison: SID from
C2-class solar flare erupted from
sunspot 958
GRB080319D – possible
detection
GRB_TIME: 17:05:09.34 UT
SID signal: 17:05:41 +/- 5sec
Swift BAT LCT
GRB080320A – possible
detection
Swift BAT LCT
GRB_TIME: 04:37:38.46 UT
SID signal: 04:38:59 +/- 5sec.
Emitter Tavolara (Sardinia)
Emitter Sainte
Asise (France)
Speculations
• In the both recent cases of possible
detection
of
GRB080319D
and
GRB080320A, some structure appeared
afterwards, resembling a propagation
ionospheric wave
• Further observations are necessary to
confirm this hypothesis
GRB Induced Propagating
Ionospheric Waves
Speed: 300 to 1200m/s
Possible GRB080319D Induced
Propagating Ionospheric Waves
warningnotvirusscannedzygo.zip
For illustration: Recent Earthquake
May 29, 2008, at 15:46 UT (during yesterday talk of
Claudio)
Ionospheric waves can be triggered both from
outside (space radiation) but also from inside (e.g.
earthquakes)
Distance BojniceIsland (epicentre)
2680 km
4095
3071
mV
SID disturbance
detected with delay of
74 min
Hence mean speed of
propagation of the
ionospheric wave
was 603 m/s
(In Vulcano, the wave
arrived during talk of
Anatoly)
2048
1024
0
00:00:03 UT
05:19:51 UT
10:39:39 UT
TIME
15:59:27 UT
21:19:15 UT
Discussion
The conditions to detect GRB with SID monitor in VLF
•
•
•
The presence of the D layer of the ionosphere
The suitable combination of the GRB position (RA, DEC) and time and hence
direction and angle of the incoming gamma-ray radiation in relation to the D
layer and observing site.
The fluence and duration of the GRB.
The detection statistics
•
•
•
The recent detection rate of GRBs is about 130 in a year.
For one observing station, the number of GRBs occuring during the presence
of a D layer and in the field of view is about 20
This is ideal number, the real one is less than 10 due to occassional nonavailability of transmitters and other technical and observational issues.
Discussion II
• If the ionospheric detection of GRBs will
be definitely confirmed, a dedicated
experiment could be considered, namely a
dedicated emitter
GRB Detection by Bright OT
Emission
• A small fraction of GRBs is accompanied
by bright optical prompt emission (OT)
• This emission can be as bright as mag 6,
and perhaps even brighter
• Such triggers can be detected in optical
light, independently on gamma-ray
detection
GRB080319B
For ~ 1 minute
Brighter in
optical light
than mag 6
Naked eye visibility at z ~ 0.75
Indication exists that
some OT may be as
bright as mag 4 at
early times
Prompt optical
emission of
GRB060117
Images by WF lens 70 mm aperture at the Czech
FRAM RT in Argentina (related to Auger).
Peak 11.5 mag 2 min after
GRB, decline 1.4 mag in
2 min
Methods to detect bright OTs
of GRBs
• Wide-field monitoring systems, CCD
(preferably All-Sky)
• Wide-field monitoring systems, photographic
(secondary use of meteor patrol)
• Archival Astronomical Plates
• Always sophisticated s/w needed to find and
to verify the triggers
• Problem: (1) large background (2) typically,
we have to look for 1 new object among 10
000 - 100 000 stars: job for informatics
students
CONCAM All
Sky Optical
Monitoring
Lim mag 4….5
i.e. not enough for
most scientific goals
Price 10x more than
the alternative system
shown before
Vulcano Workshop 2008
27
Peleng 8 mm fisheye lens (1:3,5-1:16)
that provides a 24
mm circular 180°
field of view, and
a CANON EOS
350D digital CCD
camera
Digital CCD
all-sky
monitoring
lim mag ~11
Karlovy Vary
Observatory,
CZ
Vulcano Workshop 2008
28
All Sky CCD Camera, Sonneberg Observatory, 7K x 4K CCD and f/3.5 FE lens.
Lim mag
10 in 1 Leiden
min integration
10/11/2004
Sterrewacht
Lunch Talk time.
29
CCD Sky Patrol
Test Images
Sonneberg lim
mag 14 - 15
Vulcano Workshop 2008
30
How the
OTs of
GRBs
should
look like?
Example of fast
OT found duration less
than 5 minutes
… and that’s
expected
Vulcano Workshop 2008
Results promisingonly 1 OT per plate
found (typically)
31
Another short OT
example, mag < 10
OT
Comparison plate: no OT
Vulcano Workshop 2008
Optical Transient
Analyses - OT in
Triangulum, Sonneberg
Astrograph Plate, 6 mag
above plate limit
real object of unknown
The searches for
analogous OTs are
difficult since the plates
contains typically 100
000 – 1 000 000 star
images
32
Problem: backround triggers
simulating OTs
The OTs of (unknown) astrophysical origin have been confirmed also
by CCD observations (Brno 60 cm CCD telescope, Filip Hroch)
Stars elongated, OT image not elongated – short OT
April 27-May 1, 2005
38. Variable Stars Conference
ValMez 2006
33
GRB Detections By Prompt Xray emission
• So far most GRB are detected by their
gamma-ray emission
• Most of the GRBs exhibit also X-ray emission
• Hence the GRBs can be detected also in Xrays (as independent detections)
• This goal requires sensitive all-sky
monitoring
• Obvious solution is offered by X-ray All-Sky
Monitors with Lobster Eye Optics
LE lens
arrangement
according to
Angel
The front wiew of the mini - lobster module,
Schmidt arrangement, based on 100 micron
thick plates spaced by 300 microns, 23 x 23
mm each
The X-ray measurement at 8 keV in
comparison with mathematical simulation
measured
model
X-ray All
Sky Monitor
with LE
modules
Conclusions
• The independent and indirect detection of GRBs by their
ionospheric response (SID – Sudden Ionospheric
Disturbance) observed at VLF (Very Low Frequency) is
feasible.
• We present and discuss examples of such VLF/SID
detections of three GRB.
• The capability of such alternative and indirect
investigations of GRBs, as well as the possible
contribution to analyses of GRBs still remains to be
investigated in more details.
• The GRBs can be also (independently) detected in
optical light and in X-rays, based on suitable optical and
X-ray all-sky monitors
The End
GRB080319D – possible
detection
GRB080319D – possible
detection