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From BeppoSAX to INTEGRAL: Wide Field Camera results on the Galactic Plane and INTEGRAL prospective
Nuclear Physics B (Proc. Suppl.) 132 (2004) 580–583 www.elsevierphysics.com
From BeppoSAX to INTEGRAL: Wide Field Camera results on the Galactic Plane and INTEGRAL prospective F. Capitanioa , A. Bazzanoa, M. Cocchia , L. Nataluccia , P. Ubertinia , J.J.M. in ’t Zandbc and J. Heisebc a
Istituto di Astrofisica Spaziale e Fisica Cosmica, CNR, Via del Fosso del Cavaliere 100, 00133 Roma, Italy b c
Astronomical Institute, Utrecht University, P.O. Box 80000, NL-3508 TA Utrecht, The Nethelands,
SRON National Institute for Space Research, Sorbonnelaan 2,NL -3584 CA Utrecht, The Nethelands
During 6 years of the BeppoSAX operational life, the Wide Field Camera observations covered almost the full sky providing a coverage of the Galactic Plane at different epochs. We analysed the longest Wide Field Camera pointing in the Galactic Plane in different energy bands in order to predict sources detection with INTEGRAL instruments. In fact, about 30 % of INTEGRAL Core Programme (CP) observing time is dedicated to a survey of the Galactic Plane with the aim to detect new sources, trigger TOO observations for CP and General Observer programme and to map the diffuse emission. Here we focus on producing a map containing all sources detected by BeppoSAX along the Galactic Plane for comparison with the same IBIS/INTEGRAL exposed sky region.
1. INTRODUCTION Ffor the first AO, the 35% of the INTEGRAL satellite Observing Time is devoted to a regular survey of the Galactic plane and to periodic Galactic centre deep exposures. Moreover, during the operational life of BeppoSAX [1], the Wide Field Camera (WFCs) secondary mode observations covered all the Galactic Plane. We choose a sample of these observations to generate a WFC map of the Galactic plane. The aim of this work is to predict persistent, though variable, source detection along the Core Programme INTEGRAL observations with IBIS, the coded mask imager on board INTEGRAL. 2. WFC GALACTIC PLANE OBSERVATIONS The two identical Wide Field Camera (WFCs) [3] on board BeppoSAX mapped the sky in the energy range 1.8 - 28 keV during 1996-2002. The instrument design is based on the coded mask principle using multi-wire proportional counters. The two WFCs were mounted in opposite directions and perpendicular to the pointing direction 0920-5632/$ – see front matter © 2004 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2004.04.128
of the Narrow Field Instruments (NFI), looking at different sky zones during any NFI pointing. They each had a 40 × 40 degrees field of view, a 5’ angular resolution and about 20 % spectral resolution (FWHM) at 6 keV. In this way, during the 6 years of the BeppoSAX operational life, the WFCs secondary mode observations covered most of the sky. Moreover, two times a year (autumn and spring), the WFCs observed, as primary BeppoSAX instrument, the Galactic Centre region with an average of one day per week [2]. The time in this program correspond to 8 % of the total devoted observing time. Twelve campaigns were carried out amounting to a total net exposure up to 6 Msec. The large field of view coupled with the good angular resolution resulted in an unprecedented simultaneous observation of a large fraction (almost 50 %) of the low-mass X-ray binaries population in our Galaxy. 3. THE INTEGRAL GRAMME
CORE
PRO-
INTEGRAL [6] is a ESA medium-sized scientific mission devoted to γ-rays that was launched
F. Capitanio et al. / Nuclear Physics B (Proc. Suppl.) 132 (2004) 580–583
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Table 1 List of X-ray Galactic Sources detected by WFC (18 - 28 keV) Source name GRO J1744-28 SAX J1747.0-2853 SAX J1750.8-2900 KS 1731-260 GX 1+4 GX 3+1 4U 1820-303 GRS 1758-25 GX 5-1 GX 9+9 GX 9+1 RX J1829.4-2347 GX 13+1 GX 17+2 4U 1823-00 4U 1916-05 Aql X-1 Ser X-1 X1908+075 EXO 1908+092 GRS 1915+105 4U 1957+115 KS 1947+300 4U 1954+31 Cyg X-1 Cyg X-3 Cyg X-2 SS Cyg Cas-A A0114+650 Crab 4U 0614+091 Vela X-1 Cen X-3 1E 1145.1-6141 GX 301-2 4U 1254-690 4U 1323-619 Cen X-2 4U 1416-62 4U 1543-62 4U 1626-67 Cir X-1 4U 1556-60 XTE J1550-564 Nor X-2 4U 1608-522 4U 1636-536 4U 1624-49 Nor X-1 GX 339-4 GX 340+0 4U 1705-44 OAO 1657-419 GRO J1655-40 4U 1735-44 4U 1700-37 GX 349+2 GX 354-0 GRS 1724-308 GRS 1737-31 1E 1740.7-2943 SLX 1744-299 SLX 1744-300 A 1742-294
l (deg)
b (deg)
0.04 0.20 0.45 1.06 1.94 2.29 2.79 4.52 5.07 8.51 9.07 9.27 13.52 16.44 29.93 31.34 35.73 36.13 41.91 43.77 45.39 51.31 66.10 68.40 71.33 79.83 87.32 90.54 111.74 125.71 184.55 200.88 263.06 292.11 295.51 300.11 303.46 307.03 309.98 313.04 321.74 321.78 322.11 324.14 325.93 327.40 330.91 332.90 334.92 336.91 338.96 339.59 343.33 344.39 345.00 346.06 347.77 349.10 354.32 356.28 357.57 359.11 359.27 359.28 359.56
0.31 -0.23 -0.96 3.66 4.81 0.80 -7.92 -1.36 -1.02 9.05 1.15 -6.09 0.11 1.28 5.80 -8.47 -4.14 4.85 -0.81 0.49 -0.22 -9.31 2.08 1.92 3.06 0.69 -11.31 -7.11 -2.16 2.56 -5.80 -3.35 3.93 0.34 -0.01 -0.03 -6.42 0.43 -2.77 -1.60 -6.33 -13.12 0.05 -5.97 -1.81 2.19 -0.84 -4.81 -0.26 0.25 -4.33 -0.07 -2.32 0.33 2.46 -6.99 2.15 2.75 -0.14 2.33 -0.10 -0.12 -0.91 -0.90 -0.39
Obs. flux (10−3 cts s−1 cm−2 ) 91 ±1 19±1 7±2 34 ±2 11 ±2 81 ±2 85 ±3 18 ±2 247 ±3 55 ±4 159 ±4 19 ±3 79 ±5 1311 ±5 60 ±3 19 ±2 716 ±5 385 ±4 21 ±2 30 ±3 1288 ±7 65 ±6 27 ±1 38 ±2 579 ±4 510 ±7 166±2 7±1 6±1 5±1 397±2 5±2 142 ±2 23 ±2 6±2 40 ±2 15±1 7±1 13 ±1 13±1 9±1 8±1 239±2 7±1 26±2 17 ±1 18±2 46±1 17±2 10 ±1 22±3 119±8 19±4 21±3 451 ±9 64±5 92±6 211±4 49±2 19±2 9±2 9±2 9±2 8±1 11±1
Figure 1. Schematic view of two consecutive INTEGRAL GPS scans.
on 2002, October 17th . It consists of two main γ-rays instruments: a Spectrometer (SPI) and an Imager (IBIS) covering the 15 keV - 10 MeV band complemented by two monitor instruments in the X-ray domain (JEM-X, 3-35 keV) and optical range (OMC, 550-850 nm). INTEGRAL has been designed to complement our knowledge following the results of the Compton γ-ray Observatory (CGRO) and Granat-SIGMA mission. The INTEGRAL Core Programme observing time consists in part of guaranteed time observations for the INTEGRAL Science Working Team [5]. The Core Programme is characterised by three elements: - the scanning of the Galactic Plane (GPS): it is done to provide frequent monitoring of the plane in order to detect transient sources. In fact, the γ-ray sky in the INTEGRAL energy range is dominated by the extreme variability of many sources. Another reason is to build up time-resolved maps of the Galactic Plane in continuum and diffuse line emission; - deep survey of the Galactic centre, called the Galactic Centre Deep Exposure (GCDE), which is driven by the following objectives: mapping line emission from nucleosynthesis radioisotopes (e.g. 26 Al, 44 Ti, 511 keV), mapping continuum emission of the Galactic ridge, and performing deep imaging and spectroscopic studies of the central region of the Galaxy; - pointed observations of a few selected sources: part of the Core Programme observing time is reserved to perform target of opportunity
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Figure 2. Wide Field Camera Galactic Plane Map (18 - 28 keV). For sources location in the GC region see Fig. 3
Galactic Plane (Fig. 1). Each subsequent scan is shifted by 27.5 degrees in galactic longitude. On the contrary, the galactic centre region is observed using a set of four rectangular pointing grids each with a pitch of 2.4 degrees [5]. 4. GALACTIC PLANE MAP
Figure 3. Zoom on the Galactic Center region (18 - 28 keV). For sources location see table 1.
(”TOOs”) observations for transient events which have either been detected during the INTEGRAL’s GPS and GCDE or triggered by other instruments at different wavelengths. The scans during the GPS are performed every three orbits by performing a ”slew and stare” maneuver of spacecraft along the visible part of the Galactic Plane with latitude extent ±10 degrees. The angular distance between subsequent exposures (2200 seconds each) along the scan part is 6 degrees. The scan is performed as a sawtooth with inclination of 21 degrees respect to the
The INTEGRAL Galactic Centre Deep Exposure of the Core Programme is thus comparable to the BeppoSAX Core Programme investigations, both in coverage and exposure time. The secondary WFC observations covered all the Galactic Plane with an exposure depending on different sky positions. From all the longest WFC Observing Periods (OP) (100 ks), we selected those with low galactic longitude (-10 < l < +10), covering all the Galactic Plane with at least one WFC observation. For the (GCDE) region we used also a sample of 100 ks primary WFC OP. We analysed all the selected OP with the SAX WFC Data Analysis System, extracting the images for the whole energy range and for the highest band (18 - 28 keV). This band was selected for direct comparison between WFC and IBIS [4], the coded mask γ-rays telescope on board INTEGRAL satellite. We generated a list of the X-ray galactic sources in two different energy ranges. In Tab. 1 we report the source list of the highest en-
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.00
0
15
.00
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F. Capitanio et al. / Nuclear Physics B (Proc. Suppl.) 132 (2004) 580–583
CygX-3 .00
0
5.0
CygX-1
00
80
75
.00
0
KS 1947+300 70
.00
0
-5 . 00 0
65
Figure 4. The Cygnus zone from the Galactic Plane map of the WFC data (18 - 28 keV)
ergy range (18 - 28 keV). The Galactic Plane map between 18- 28 keV is shown in 2: we plotted (in galactic coordinates) all the detected sources as a filled circle with the radius representing (logarithmic scale) the average flux corresponding to different detections in all the OP sampled. Besides predicting persistent, though variable, source detection with IBIS along the Core Programme INTEGRAL observations, the same set of data is currently used to perform archival searches of new sources discovered by INTEGRAL. As an example we show in Fig.4 the image of the Cygnus region extracted from the WFC Galactic Plane map that has been used for the first GPS of INTEGRAL satellite. For comparison we show in Fig. 5 the equivalent image from IBIS. REFERENCES 1. Boella, G., Butler R.C., Perola, C. et al., 1997, A&AS, 122,299 2. In ’t Zand, J.M., 2001, ESA SP-459, 463, September 2001, Proceeding of the 4th INTEGRAL workshop 3. Jager, R., Mels, W.A., Brinkman, A.C. et al.,
.00
0
Figure 5. IBIS (ISGRI) image of the Cygnus zone between 20-40 keV. The image has been produced during the first GPS observation (26th INTEGRAL revolution).
1997, A&AS, 125,557 4. Ubertini, P., Lebrun, F., Di Cocco, G. et al., 2003, A&A special issue devoted to INTEGRAL 5. Winkler C., 2001, ESA SP-459, 471 September 2001, Proceeding of the 4th INTEGRAL 6. Winkler C., Courvoisier, TJ.L., Di Cocco, G. et al, 2003, A&A special issue devoted to INTEGRAL
From BeppoSAX to INTEGRAL: Wide Field Camera results on the Galactic Plane and INTEGRAL prospective F. Capitanioa , A. Bazzanoa, M. Cocchia , L. Nataluccia , P. Ubertinia , J.J.M. in ’t Zandbc and J. Heisebc a
Istituto di Astrofisica Spaziale e Fisica Cosmica, CNR, Via del Fosso del Cavaliere 100, 00133 Roma, Italy b c
Astronomical Institute, Utrecht University, P.O. Box 80000, NL-3508 TA Utrecht, The Nethelands,
SRON National Institute for Space Research, Sorbonnelaan 2,NL -3584 CA Utrecht, The Nethelands
During 6 years of the BeppoSAX operational life, the Wide Field Camera observations covered almost the full sky providing a coverage of the Galactic Plane at different epochs. We analysed the longest Wide Field Camera pointing in the Galactic Plane in different energy bands in order to predict sources detection with INTEGRAL instruments. In fact, about 30 % of INTEGRAL Core Programme (CP) observing time is dedicated to a survey of the Galactic Plane with the aim to detect new sources, trigger TOO observations for CP and General Observer programme and to map the diffuse emission. Here we focus on producing a map containing all sources detected by BeppoSAX along the Galactic Plane for comparison with the same IBIS/INTEGRAL exposed sky region.
1. INTRODUCTION Ffor the first AO, the 35% of the INTEGRAL satellite Observing Time is devoted to a regular survey of the Galactic plane and to periodic Galactic centre deep exposures. Moreover, during the operational life of BeppoSAX [1], the Wide Field Camera (WFCs) secondary mode observations covered all the Galactic Plane. We choose a sample of these observations to generate a WFC map of the Galactic plane. The aim of this work is to predict persistent, though variable, source detection along the Core Programme INTEGRAL observations with IBIS, the coded mask imager on board INTEGRAL. 2. WFC GALACTIC PLANE OBSERVATIONS The two identical Wide Field Camera (WFCs) [3] on board BeppoSAX mapped the sky in the energy range 1.8 - 28 keV during 1996-2002. The instrument design is based on the coded mask principle using multi-wire proportional counters. The two WFCs were mounted in opposite directions and perpendicular to the pointing direction 0920-5632/$ – see front matter © 2004 Published by Elsevier B.V. doi:10.1016/j.nuclphysbps.2004.04.128
of the Narrow Field Instruments (NFI), looking at different sky zones during any NFI pointing. They each had a 40 × 40 degrees field of view, a 5’ angular resolution and about 20 % spectral resolution (FWHM) at 6 keV. In this way, during the 6 years of the BeppoSAX operational life, the WFCs secondary mode observations covered most of the sky. Moreover, two times a year (autumn and spring), the WFCs observed, as primary BeppoSAX instrument, the Galactic Centre region with an average of one day per week [2]. The time in this program correspond to 8 % of the total devoted observing time. Twelve campaigns were carried out amounting to a total net exposure up to 6 Msec. The large field of view coupled with the good angular resolution resulted in an unprecedented simultaneous observation of a large fraction (almost 50 %) of the low-mass X-ray binaries population in our Galaxy. 3. THE INTEGRAL GRAMME
CORE
PRO-
INTEGRAL [6] is a ESA medium-sized scientific mission devoted to γ-rays that was launched
F. Capitanio et al. / Nuclear Physics B (Proc. Suppl.) 132 (2004) 580–583
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Table 1 List of X-ray Galactic Sources detected by WFC (18 - 28 keV) Source name GRO J1744-28 SAX J1747.0-2853 SAX J1750.8-2900 KS 1731-260 GX 1+4 GX 3+1 4U 1820-303 GRS 1758-25 GX 5-1 GX 9+9 GX 9+1 RX J1829.4-2347 GX 13+1 GX 17+2 4U 1823-00 4U 1916-05 Aql X-1 Ser X-1 X1908+075 EXO 1908+092 GRS 1915+105 4U 1957+115 KS 1947+300 4U 1954+31 Cyg X-1 Cyg X-3 Cyg X-2 SS Cyg Cas-A A0114+650 Crab 4U 0614+091 Vela X-1 Cen X-3 1E 1145.1-6141 GX 301-2 4U 1254-690 4U 1323-619 Cen X-2 4U 1416-62 4U 1543-62 4U 1626-67 Cir X-1 4U 1556-60 XTE J1550-564 Nor X-2 4U 1608-522 4U 1636-536 4U 1624-49 Nor X-1 GX 339-4 GX 340+0 4U 1705-44 OAO 1657-419 GRO J1655-40 4U 1735-44 4U 1700-37 GX 349+2 GX 354-0 GRS 1724-308 GRS 1737-31 1E 1740.7-2943 SLX 1744-299 SLX 1744-300 A 1742-294
l (deg)
b (deg)
0.04 0.20 0.45 1.06 1.94 2.29 2.79 4.52 5.07 8.51 9.07 9.27 13.52 16.44 29.93 31.34 35.73 36.13 41.91 43.77 45.39 51.31 66.10 68.40 71.33 79.83 87.32 90.54 111.74 125.71 184.55 200.88 263.06 292.11 295.51 300.11 303.46 307.03 309.98 313.04 321.74 321.78 322.11 324.14 325.93 327.40 330.91 332.90 334.92 336.91 338.96 339.59 343.33 344.39 345.00 346.06 347.77 349.10 354.32 356.28 357.57 359.11 359.27 359.28 359.56
0.31 -0.23 -0.96 3.66 4.81 0.80 -7.92 -1.36 -1.02 9.05 1.15 -6.09 0.11 1.28 5.80 -8.47 -4.14 4.85 -0.81 0.49 -0.22 -9.31 2.08 1.92 3.06 0.69 -11.31 -7.11 -2.16 2.56 -5.80 -3.35 3.93 0.34 -0.01 -0.03 -6.42 0.43 -2.77 -1.60 -6.33 -13.12 0.05 -5.97 -1.81 2.19 -0.84 -4.81 -0.26 0.25 -4.33 -0.07 -2.32 0.33 2.46 -6.99 2.15 2.75 -0.14 2.33 -0.10 -0.12 -0.91 -0.90 -0.39
Obs. flux (10−3 cts s−1 cm−2 ) 91 ±1 19±1 7±2 34 ±2 11 ±2 81 ±2 85 ±3 18 ±2 247 ±3 55 ±4 159 ±4 19 ±3 79 ±5 1311 ±5 60 ±3 19 ±2 716 ±5 385 ±4 21 ±2 30 ±3 1288 ±7 65 ±6 27 ±1 38 ±2 579 ±4 510 ±7 166±2 7±1 6±1 5±1 397±2 5±2 142 ±2 23 ±2 6±2 40 ±2 15±1 7±1 13 ±1 13±1 9±1 8±1 239±2 7±1 26±2 17 ±1 18±2 46±1 17±2 10 ±1 22±3 119±8 19±4 21±3 451 ±9 64±5 92±6 211±4 49±2 19±2 9±2 9±2 9±2 8±1 11±1
Figure 1. Schematic view of two consecutive INTEGRAL GPS scans.
on 2002, October 17th . It consists of two main γ-rays instruments: a Spectrometer (SPI) and an Imager (IBIS) covering the 15 keV - 10 MeV band complemented by two monitor instruments in the X-ray domain (JEM-X, 3-35 keV) and optical range (OMC, 550-850 nm). INTEGRAL has been designed to complement our knowledge following the results of the Compton γ-ray Observatory (CGRO) and Granat-SIGMA mission. The INTEGRAL Core Programme observing time consists in part of guaranteed time observations for the INTEGRAL Science Working Team [5]. The Core Programme is characterised by three elements: - the scanning of the Galactic Plane (GPS): it is done to provide frequent monitoring of the plane in order to detect transient sources. In fact, the γ-ray sky in the INTEGRAL energy range is dominated by the extreme variability of many sources. Another reason is to build up time-resolved maps of the Galactic Plane in continuum and diffuse line emission; - deep survey of the Galactic centre, called the Galactic Centre Deep Exposure (GCDE), which is driven by the following objectives: mapping line emission from nucleosynthesis radioisotopes (e.g. 26 Al, 44 Ti, 511 keV), mapping continuum emission of the Galactic ridge, and performing deep imaging and spectroscopic studies of the central region of the Galaxy; - pointed observations of a few selected sources: part of the Core Programme observing time is reserved to perform target of opportunity
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F. Capitanio et al. / Nuclear Physics B (Proc. Suppl.) 132 (2004) 580–583
Figure 2. Wide Field Camera Galactic Plane Map (18 - 28 keV). For sources location in the GC region see Fig. 3
Galactic Plane (Fig. 1). Each subsequent scan is shifted by 27.5 degrees in galactic longitude. On the contrary, the galactic centre region is observed using a set of four rectangular pointing grids each with a pitch of 2.4 degrees [5]. 4. GALACTIC PLANE MAP
Figure 3. Zoom on the Galactic Center region (18 - 28 keV). For sources location see table 1.
(”TOOs”) observations for transient events which have either been detected during the INTEGRAL’s GPS and GCDE or triggered by other instruments at different wavelengths. The scans during the GPS are performed every three orbits by performing a ”slew and stare” maneuver of spacecraft along the visible part of the Galactic Plane with latitude extent ±10 degrees. The angular distance between subsequent exposures (2200 seconds each) along the scan part is 6 degrees. The scan is performed as a sawtooth with inclination of 21 degrees respect to the
The INTEGRAL Galactic Centre Deep Exposure of the Core Programme is thus comparable to the BeppoSAX Core Programme investigations, both in coverage and exposure time. The secondary WFC observations covered all the Galactic Plane with an exposure depending on different sky positions. From all the longest WFC Observing Periods (OP) (100 ks), we selected those with low galactic longitude (-10 < l < +10), covering all the Galactic Plane with at least one WFC observation. For the (GCDE) region we used also a sample of 100 ks primary WFC OP. We analysed all the selected OP with the SAX WFC Data Analysis System, extracting the images for the whole energy range and for the highest band (18 - 28 keV). This band was selected for direct comparison between WFC and IBIS [4], the coded mask γ-rays telescope on board INTEGRAL satellite. We generated a list of the X-ray galactic sources in two different energy ranges. In Tab. 1 we report the source list of the highest en-
583
10
.00
0
15
.00
0
F. Capitanio et al. / Nuclear Physics B (Proc. Suppl.) 132 (2004) 580–583
CygX-3 .00
0
5.0
CygX-1
00
80
75
.00
0
KS 1947+300 70
.00
0
-5 . 00 0
65
Figure 4. The Cygnus zone from the Galactic Plane map of the WFC data (18 - 28 keV)
ergy range (18 - 28 keV). The Galactic Plane map between 18- 28 keV is shown in 2: we plotted (in galactic coordinates) all the detected sources as a filled circle with the radius representing (logarithmic scale) the average flux corresponding to different detections in all the OP sampled. Besides predicting persistent, though variable, source detection with IBIS along the Core Programme INTEGRAL observations, the same set of data is currently used to perform archival searches of new sources discovered by INTEGRAL. As an example we show in Fig.4 the image of the Cygnus region extracted from the WFC Galactic Plane map that has been used for the first GPS of INTEGRAL satellite. For comparison we show in Fig. 5 the equivalent image from IBIS. REFERENCES 1. Boella, G., Butler R.C., Perola, C. et al., 1997, A&AS, 122,299 2. In ’t Zand, J.M., 2001, ESA SP-459, 463, September 2001, Proceeding of the 4th INTEGRAL workshop 3. Jager, R., Mels, W.A., Brinkman, A.C. et al.,
.00
0
Figure 5. IBIS (ISGRI) image of the Cygnus zone between 20-40 keV. The image has been produced during the first GPS observation (26th INTEGRAL revolution).
1997, A&AS, 125,557 4. Ubertini, P., Lebrun, F., Di Cocco, G. et al., 2003, A&A special issue devoted to INTEGRAL 5. Winkler C., 2001, ESA SP-459, 471 September 2001, Proceeding of the 4th INTEGRAL 6. Winkler C., Courvoisier, TJ.L., Di Cocco, G. et al, 2003, A&A special issue devoted to INTEGRAL