Data mining using the INTErnational Gamma-Ray  

   Astrophysics Laboratory (INTEGRAL) Observatory

mc logo    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


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.



Emrah Kalemci
emrah PI....

Graduate Students:

Sirin Caliskan

sirin Project: Searching for Redshifted 2.2 MeV line from Neutron Stars.

Isil Erdeve
isil Project: Searching for high energy emission from isolated neutron stars.



1. Year Progress Report (Sept 2005- Sept 2006)


Publications related to the project

Refereed articles:

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.

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




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.