Data mining using the INTErnational
Gamma-Ray
Astrophysics
Laboratory (INTEGRAL) Observatory
FP 6 Marie Curie
International Reintegration Grant
Acronym : INDAM
Short title: INtegral DAta Mining
PI : Dr.
Emrah Kalemci
Supervisor: Prof. Ali Alpar
Start: September
1st, 2005
End: August
31st, 2007
Contract No: MIRG-CT-2005-017203
Projects
People Reports Publications Events
Summary
INTEGRAL (INTErnational Gamma Ray Astrophysics Laboratory) is one of
the major astronomical
satellites of the European Space Agency (ESA). With its two main
instruments working
in the hard X-ray to Gamma-ray band (20 keV – 10 MeV), it
provides unprecedented imaging (12
arcmin FWHM angular resolution with the IBIS instrument) and spectral
capability (2 keV energy
resolution at 1 MeV with the SPI instrument). This project covers five
main projects that
uses INTEGRAL data : Gamma-ray polarization with
SPI, imaging and spectral studies of SN1006,
search for red-shifted 2.2 MeV (neutron capture on Hydrogen) nuclear
lines from selected neutron
stars, search for hard X-ray emission from isolated neutron stars, and
finally radiation damage studies of
SPI. All these projects are being done in collaboration with instrument
teams, especially with the SPI team
at Centre d'Etude Spatiale des Rayonnements (CESR), Toulouse, France.
The major objectives
of the project are:1. Detecting the redshifted 2.2 MeV line from
4U1820-30, or other bright neutron star
(like Sco X-1), determining the mass to radius (M/R) ratio and
constraining the equation state, as well as
determining the spin of the neutron star, 2. imaging SN1006 with JEM-X
above 10 keV, and with ISGRI
above 20 keV, determining the inner structure, and dominant X-ray
emission mechanism using INTEGRAL
imaging and spectroscopy. Detecting 511 keV positron annihilation line
using SPI, 3. measuring polarization
fraction and angle of a GRB in the FOV of INTEGRAL, and constraining
GRB mechanisms, 4. characterizing
the effects of radiation damage on SPI detectors between annealings,
searching for long term effects,
5. characterizing hard X-ray emission properties isolated neutron stars
to make quantitative comparisons
between different types and investigate evolutionary scenarios between
them. With the funding this project supplies,
researchers have attended SPI co-I meetings and visited CESR for close
collaboration, a fast and large storage raid
array for effective analysis of the INTEGRAL and other astronomical
instruments' data has been purchased and
maintained at Sabanci. Two PhD students were funded, workshops have
been organized. The main deliverables
of the project have been several refereed publications.
Projects under IRG
Gamma-ray
polarization with SPI and ISGRI:
See "Search for polarization
from the prompt gamma-ray emission of GRB041219A with SPI on INTEGRAL",
published in ApJS
in 2007 for detailed information on polarization studies with SPI.
The results are not very constraining, even though GRB 041219 was
one of
the brightest and longest bursts ever observed. The polarization
measuerements critically depend on the modeling of scattered events in
the
detectors, and even with the bright burst the signal to noise ratio is
low. For persistent sources, systematic effects that come from modeling
will dominate the errors. For Crab, each pointing needs to be simulated
independently (for the method we use to measure polarization) and
it will take a very long time to finish the simulations and understand
the systematic effects. For the purposes of the MC project
polarization
studies have finished.
Similar methods employed for the SPI polarization has been employed to
measure polarization from solar flares wıth the RHESSI instrument.
Details can be found in "Gamma-Ray Polarimetry of
Two X-Class Solar Flares",
published in ApJ in 2006.
Imaging and
spectral studies of SN 1006 with INTEGRAL:
a. X-ray observations of SN 1006 with
INTEGRAL:
SN 1006 has 30' diameter and an extended source for
both ISGRI and JEM-X. Analysis of extended sources is difficult with
coded mask
instruments, but with the help of the instrument teams we welcomed this
challenge. The idea was to image the source above 20 keV and
differentiate between the synchrotron and bremsstrahlung possibilities
for the hard X-ray emission through morphological analysis. With JEM-X,
with 750 ks exposure (~200 ks effective on time) the source was
detected between 2.4 keV and 8.2 keV, which was the first detection of
an extended
object. The source was not detected with ISGRI above 20 keV. The
estimates for the synchrotron and bremsstrahlung flux made before the
project
has started needed to be updated after the non-detection of the limbs
with TeV observations, and it was not surprising to have no detection
with ISGRI
with 750 ks of exposure. For details, see
"X-Ray Observations of SN 1006 with Integral", published in
ApJ in 2006. After our succesful
proposal in INTEGRAL AO4 we had obtained 2.5 Ms more data on the
source. The results were quite disappointing. Not only the source has
not
been detected with ISGRI (even with reduced low energy limit of
17 keV), it has not been detected with JEM-X, despite our earlier
detection with
less exposure time. The software and the JEM-X module has changed in
between and the instrument team is reanalyzing the data to understant
what had heppened. For the purposes of IRG, all the analysis has
finished and we wait for the contribution of the instrument team on
JEM-X. The
fianl ISGRI results weakly constrain some synchrotron emission models.
This work will be submitted for publication soon.
b. Search for positron annihilation
radiation from SN 1006 with INTEGRAL:
Supernovae Type Ia are promising candidates for the
source of positrons in the Galaxy. The recent results on the
distribution and overall flux of
positrons, along with the simulations of positron transport from
supernovae indicate that 30-60% of the positrons may come from supernova
remnants. However, the simulations assume a ceratin escape fraction
from the remnant which has not been determined explicitly. SN 1006, with
its well studied properties is a very good candidate to search for
positron annihilation radiation and place limits on the escape fraction
of positrons.
But, since it is a relatively young supernova, and the ISM around it is
not dense, the thermalization of escaped positrons may not have
happened yet.
In this case, to be able to see positron annihilation radiation, the
escaped positrons must be prevented to leak to the ISM by shocks. Our
first attempt
with 1 Ms exposure time to detect positron annihilation line has failed
(see "Searching for
annihilation radiation from SN
1006 with SPI on INTEGRAL",
2006,
ApJL) . The new dataset which has also been analyzed (total of
3.5 Ms) also yielded
null results, while weakly constraining escape fraction to be less than
12%. One reason for no detection that the positrons may leak to
the ISM efficiently and has not been thermalized yet. The analysis and
the
results are also being prepared for submission to the ApJ.
Redshifted 2.2 MeV
line searches from neutron stars:
The search for the redshifted 2.2 MeV line
relies on the excellent spectral capability of the SPI instrument. The
neutrons liberated during deceleration
either recombine with protons [H(n,γ)D] producing Gamma-rays at
2.2 MeV in the radially thin neutron star atmosphere (dr <<RNS),
or
suffer charge exchange on atmospheric 3He. Any nuclear (or atomic) line
created at the surface of a neutron star will be gravitationally
redshifted,
and broadened due to rotation and relativistic effects. The redshift
and broadening of nuclear and atomic lines have been modeled in detail
(Ozel &Psaltis, 2003, ApJL, 582, p31). With my graduate student
Sirin Caliskan, we first concentrated on H1820-30, a neutron star
believed
to be accreting from a helium white dwarf. There are two reasons to
choose this source; first the accreting material may be extremely
rich in heavy
nuclei (hence the neutrons) as the companion is a white dwarf, second
it is observed many times with INTEGRAL with the GCDE and the GPS,
so abundant data are available. In addition to the already existing
database, we submitted a Key program proposal for INTEGRAL and obtained
more observation time on the source. The detection and study of such a
line have three major contributions to gamma-ray astronomy and compact
object science: 1. It will reveal information about the density and
content of the accreting material, and the nuclear processes at the
neutron star
atmosphere. 2. It will determine the spin period of this source, which
has not been determined yet. The detection of the spin frequency will
help studies
to determine the relation between spin and the observed KHz
quasi-periodic oscillations (QPOs). 3. Most importantly, thanks to the
superior energy
resolution of SPI, the study can determine (M/R)NS to less than 1%
uncertainty, constraining the equation of state of neutron stars
strongly.
So far, a significant fraction of the dataset is analyzed, and we have
not been able to obtain a significant detection of a gamma-ray line
that could be a
redshifted 2.2 MeV radiation. The analysis is complicated for a variety
of reasons: the energy of the line is not known, the width of the line
is not known,
due to missing detectors the entire dataset cannot be analyzed at once,
there are artificial electronic noise right at where the redshifted
line would be
expected. Based on the detected kHz QPOs, the source may be
spinning extremely rapidly, whilst broadening the line beyond the
sensitivity of SPI on
INTEGRAL. Once we finish analyzing the enitre dataset, we will at least
have some upper limits.
In 2005, a giant outburst followed by a smaller outburst has been
observed from the high mass X-ray binary A0535+262. During the giant
outburst the
source was too close to the Sun, and only RHESSI could observe the
source. Boggs & Smith searched for redshifted 2.2 MeV line and
reported
upper limits. During the weaker outburst, the source was observed with
INTEGRAL. We have collaborated with the PI of the observation Dr.
Kretscmar
and analyzed the data with SPI and alse searched for a redshifted line.
SPI is more sensitive than RHESSI, however, the source was significantly
weaker during INTEGRAL observations than that of RHESSI. We have
obtained slightly lower upper limits for a redshifted 2.2 MeV line
with SPI on INTEGRAL. A paper on our results will be submitted to the
ApJ.
Characterizing
high energy emission of isolated neutron stars:
High energy emission (above 50 keV) has first been detected for the AXP
1E1841-045 (Kuiper, M. et al., 2004, ApJ, 613, p1173) with the HEXTE
instrument on RXTE, and also INTEGRAL. This has been an exciting
development for the AXPs, which are believed to have very high magnetic
fields (~1015
Gauss). Later, almost all AXPs and SGRs turned out to be emitters
of persistent high energy emission. It looks like strong magnetic
fields are responsible
for the emission, however the exact mechanism is not certain. To be
able to understand what really causes this high energy emission, and
also to aid
studies of evolutionary scenarios for isolated neutron stars, we have
decided to characterize the hard X-ray emission properties of all types
of isolated
neutron stars (CCOs, RRATs, DTNs). My graduate student Isil Erdeve
analyzed all available ISGRI data from CCOs and found upper limits for
emission
between 20 keV and 300 keV. The upper limits are an order of magnitude
lower than the hard X-ray flux observed in AXPs. Along with the
new results
on period and period derivative measurements of CCOs, lack of high
energy emission also supports low magnetic field, propeller type
emission. The results
will be presented in an article submitted to the ApJ.
Radiation
damage of SPI:
SPI is subject to strong radiation in space, and the performance of the
detector suffers from hole trapping caused by the radiation damage. The
hole trapping
causes incomplete charge collection, which shifts the centroid of
nuclear lines in the spectrum to lower energies, and also broaden the
lines, and increase the
background in the continuum through a low energy tail. In principle, as
long as the line shift as a function of position of interaction in the
detector is known,
the spectrum can be corrected to help maintain Gaussian shape, reduce
line width, and replace source counts in the line. One can use the TTP
information in
the PSD data word in SPI to obtain the line shift as a function of
position of interaction. We have applied this technique to determine
the line shifts, and devised a
correction method. The average gain in FWHM before and after the first
annealing is 0.97 keV in quadrature, which is quite significant. There
have been many
annealings since the first annealing, and with this method, we continue
to characterize radiation damage effects between annealings. However,
due to a software
bug at ISDC, a large chunk of the raw data has PSD_DATA word
incorrectly set. Before ISDC fixes this problem (which requires
reanalyzing the entire
raw spacecraft data) we can only work up to revolution 219. There have
been four annealings and characterization is underway.
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People
Emrah Kalemci
PI....
Graduate Students:
Sirin
Caliskan
Project: Searching for
Redshifted 2.2 MeV line from Neutron Stars.
Isil
Erdeve
Project: Searching for high energy
emission from isolated neutron stars.
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Reports
1. Year Progress
Report (Sept 2005- Sept 2006)
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Publications related to the project
Refereed
articles:
1. E. Kalemci,
S. E. Boggs, C. Kouveliotou, M. Finger, and M. G. Baring,"Search for polarization
from the prompt gamma-ray emission of GRB041219A with SPI on INTEGRAL"
, 2007, ApJS, 169, 75
2. E. Kalemci,
S. P. Reynolds, S. E. Boggs, N. Lund, J. Chenevez, M. Renaud, J. Rho,
"X-Ray Observations of SN 1006 with Integral", 2006, ApJ, 644, 274.
3. E. Kalemci,
S. E. Boggs, P. A. Milne, S. P. Reynolds, "Searching for
annihilation radiation from SN 1006 with SPI on INTEGRAL", 2006,
ApJL, 640, L55.
4. S. E. Boggs, W.
Coburn, E. Kalemci, "Gamma-Ray Polarimetry of
Two X-Class Solar Flares", 2006, ApJ, 638,
p1129.
5. Matthieu, R. et al., "Imaging extended sources
with coded mask telescopes: Application to the INTEGRAL IBIS/ISGRI
instrument",2006, A &
A, 456, 389.
Refereed conference
proceedings:
1. E. Kalemci et al., "SN 1006 with INTEGRAL", 2006, to
appear in the Proceedings of the 6th INTEGRAL Workshop, Moscow, Russia.
2. E. Kalemci et al., "Polarization measurement of GRB 041219a
with SPI", 2006, to appear in the Proceedings of the 6th
INTEGRAL Workshop, Moscow, Russia.
3. S. Caliskan, E. Kalemci, S. E. Boggs, "Search
for redshifted 2.2 MeV line from 4U1820-30" , 2006, to
appear in the Proceedings of the 6th INTEGRAL Workshop, Moscow, Russia.
SPI co-I meeting presentations
1. E. Kalemci et al., “Search
for polarization in the prompt emission of GRB 041219 using SPI”,
Toulouse,
November 2005.
2. C.
Wunderer & S. Boggs, “Update on 1.4-1.6 MeV noise
features,” SPI Scientific Team Meeting,
MPE, Garching, Germany, March
2006.
3. E. Kalemci et
al., “Search
for polarization in the prompt emission of GRB 041219 using SPI, the
end”, Toulouse,
October 2007.
4.
S. Caliskan, E. Kalemci, S.Boggs, “Search for
redshifted 2.2 MeV line from accreting neutron stars”, Toulouse,
October 2007 .
5. E. Kalemci,
“SPI related
activities at Sabanci
University”,
MPE,
Garching, March 2007.
6. S.
Caliskan, E. Kalemci,
S.Boggs, “Search for redshifted 2.2 MeV line from A0535+26 during
an outburst”, Garching, March 2007.
Articles in
preparation
1. E.
Kalemci et al., "X-ray and Gamma-ray observations of SN 1006 with
INTEGRAL", 2007, to be submitted to ApJ.
2. I.
Erdeve, E. Kalemci, A. Alpar, "Hard X-ray flux upper limits of central
compact objects in supernova remnants", 2007, to be submitted to ApJ.
3. S.
Caliskan, E. Kalemci, S. Boggs, P. Kretchmar, "Search
for redshifted 2.2 MeV line from A0535+26 during an outburst with SPI
on INTEGRAL", 2007, to be
submitted to ApJ.
Public
outreach (Turkish)
1. Astronominin vahsi batisi, gama
isinlarinda uzay ve INTEGRAL, 2007, TUBITAK Bilim ve Teknik, Sayı
476.
2. Kara delikleri gozlemek,
2007, Bilim ve Utopya
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Events
Workshops
1. High
Energy Astrophysics Workshop, September 2006, Sabanci University
2. ASTRONS
and INDAM Workshop, July 2007, Sabanci Un. Karakoy Comm. Center
Public
outreach
1. Space
instrumentation for astrophysics,
2006, presentation given at Bilkent Nanotechnology Center and Middle
East Technical University.
2. Gorunmeyeni anlamak I, kara
delikler, 2007,
presentation at the TUBITAK Observation Fair, Uludag, Bursa.
3. Gorunmeyeni anlamak II,
karanlik madde, karanlik enerji, 2007, presentation at
the TUBITAK Observation Fair, Uludag, Bursa.
4. Turkiye'de uzay astronomisi,
2007, Ilk ve Ortaogretim Kurumlari, Astronomi Bulusmasi III, panel
presentation for k12 at Yuzyil Isik Schools, Istanbul.
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