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A JEM­X CATALOG OF X­RAY SOURCES
Niels J. Westergaard, Jerome Chenevez, Niels Lund, Carl Budtz­JÜrgensen, and SÜren Brandt Danish National Space Center, Juliane Maries Vej 30, Copenhagen, Denmark

ABSTRACT The JEM­X catalog of X-ray sources presented here is based on detections in individual science windows with a sensitivity limit of about 10 mCrab (5 ­ 15 keV). It contains 127 sources and only those that can be identified from the existing reference catalog. The input data are taken from the, up to now, 300 INTEGRAL orbits with public data. Key words: JEM­X; X-ray source catalog.

seen by JEM­X but not reported in [6] are marked ( ) in table 1.

2.

DATA ANALYSIS

All science windows i.e. individual pointings of typical duration between 1500 s and 2000 s have been analyzed for sources in the four energy intervals: 3 ­ 4, 4 ­ 8, 8 ­ 15, and 15 ­ 25 keV. The analysis software system is OSA­5.1 (Offline Analysis Software) by ISDC (INTEGRAL Science Data Center, Versoix, Switzerland). The revolutions used for JEM­X2 are: 10, 12, 13, 20170, 179, 208, 239, 300, 365. The revolutions used for JEMX­1 are: 10, 12, 13, 24, 25, 39-45, 102, 103, 167, 170-252, 255-276, 278-285, 287-295, 300-303, 308-323, 326, 357-360, 365. The four images produced (one for each energy band) are searched independently for peaks characterized by a detection significance which is the highest peak value divided by the RMS value of the immediate surrounding. A source is accepted if it appears at the same place in at least two of the images with a detection significance larger than 3 or in a single image with a detection significance larger than 10. In total 20,000 source candidates are registrered during the survey of which 1100 are spurious i.e. not identified. 22470 science windows have been searched and source candidates were found in 11071 of those. The catalog was constructed by grouping sources sufficiently close to each other (less than 5 ), deriving the average position by weighting with the individual detection significances. The sources included in the JEM­X source catalog are the ones with a position deviation less than 5 from a source in the reference catalog.

1.

INTRODUCTION

The search for sources has been performed in images from individual pointings (Science Windows). Extracting sources from mosaic images and thereby obtaining better sensitivity for persistent sources is the goal of ongoing activities and has so far led to the discovery of three new X-ray sources [1, 2, 3]. Both JEM­X [4] instruments have been used, through INTEGRAL revolutions 39 ­ 170 and from 170 to 326 (with some exceptions, see large part of the sky is covered as illustrated which is a map of the combined exposure time. JEM­X2 JEM­X1 later). A in Fig. 1

The image reconstruction process includes a backprojection method taking into account a detailed model of the instrument and then an IROS (Iterative Removal Of Sources) algorithm for finding weaker sources. In spite of the effort to exclude spurious sources automatically a number of these will appear in the list of sources. The most efficient way of removing those is to demand that the source should exist in a reference catalog of Xray sources and here we have used version 25 of the INTEGRAL General Reference Catalog [5]. The JEM­X catalog itself is given in table 1 on the last page of this paper and the explanations for the columns are given immediately before the table. The 2nd IBIS/ISGRI soft gamma-ray survey catalog [6] contains about 200 sources. There are more sources because the ISGRI FOV is much larger than the JEM­X FOV and the collecting area is also larger. The sources

3.

SOURCE LOCALIZATION ACCURACY

The error of the source localization has a counting statistics and a systematic component. The analysis of BudtzJÜrgensen et al. [7] demonstrates a weak dependence on temperature of the satellite structure measured at the mask which is not taken into account in the present anal-


Figure 1. Map in galactic coordinates of exposure time in the science windows used for the present catalog. The contour lines are at 10 , 10 , 10 , and 10 s. ysis. Another effect is the not quite accurate detector response modelling used in the IROS process. Fig. 2 shows the deviation between the found source positions and the reference catalog positions as a function of maximal detection significance for the individual source. tioned and they are subject to further investigation. On the other hand 4U 1901+03 is a well established source where the JEM­X position deviates 40 from the reference catalog position that perhaps should be revised. The 2 confidence limit for source localization in single science windows is defined as the radius that contains 95% of the individual detections in each of four off-axis angle intervals as given in Fig. 3.

Figure 2. The source position deviation from the reference catalog plotted against the maximal detection significance. The open circles represent sources with one or two detections, the filled circles have more than 2 detections and those that have an extra circle have been detected more than 150 times. GRS 1915+105 is indicated because it has the highest detection significance and 4U 1901+03 is highlighted because the reference catalog position probably is off by 40 .

Four sources: IGR J18450-0435, 3EG J1639-4702, AX J1637.8-4656, and AX J1911.0+0906 deviate more than 150 from the reference catalog position. Each is only detected once so the identification might be ques-

Figure 3. The 95% confidence limits for the localization accuracy determined as a function of the detection significance. The results from four off-axis angle intervals are shown.


4.

DETECTION SENSITIVITY
22.025

The JEM­X sensitivity has been determined as the lower intensity limit of the identifiable sources. The exposure time was selected to be around 2000 s, which is typical for the INTEGRAL science window durations. Fig. 4 shows the result given in cgs units in the interval where JEM­X is most sensitive (highest effective area).

22.020 22.015

83.645

83.640

83.635

83.630

83.625

83.620

83.615

Figure 5. Chandra image of the Crab Nebula. The double ring indicates the position of the centroid of the count distribution. The square is the position of the j ima iros position (764 observations) and the smaller circle indicates the pulsar ('Crab' position in the reference catalog).

REFERENCES Figure 4. The source detection limit for an observation time of 2000 s. The dashed lines gives the comparison with the Crab flux. [1] [2] [3] [4] [5] [6] Chenevez et al., 2004, ATEL#223. Chenevez et al., 2006, ATEL#756. Kuulkers, J. et al., 2006, A&A in preparation. Lund, N. et al., 2003, A&A, 411, L231. Ebisawa et al.(2003) Astron. & Astrophys. 411, 59. Bird, A.J., Barlow, E.J., Bassani, L., et al., 2006, ApJ, 636, 765. [7] Budtz-JÜrgensen, C., Lund, N., Westergaard, N.J. et al., 2006, Proc. SPIE Vol. 6266.

5.

CRAB NEBULA

The Crab Nebula needs special attention since it is an extended X-ray emitter (see Fig. 5) of diameter of 1 . The position is therefore not so well defined and SIMBAD as well as the ISDC reference catalog quote the Crab Pulsar position (RA: 83.6332 , Dec: 22.0145 , J2000). Since JEM­X is not able to resolve this source the measured position will represent the centroid of the distribution of the emission. As a first approximation to derive that a Chandra image was used (acisf01999N001) as shown in Fig. 5. The centroid of the Chandra observation excluding the pulsar is at 83.6296 , 22.0182 , whereas the JEM­X position found here is 83.6307 , 22.0176 which is between the Chandra centroid and the pulsar. Hence the reference catalog position is not adequate for an instrument that cannot resolve the nebula.

6. 6.1.

THE CATALOG Description of columns

The sources that are not found in the IBIS catalog [6] are marked with a dagger ( ). The dubious sources far from their positions in the reference catalog [5] are marked with an asterisk ( ). R.A. Right Ascension (J2000) in degrees. Dec Declination (J2000) in degrees.

ACKNOWLEDGEMENTS Based on observations with INTEGRAL, an ESA project with instruments and science data centre funded by ESA member states (especially the PI countries: Denmark, France, Germany, Italy, Switzerland, Spain), Czech Republic and Poland, and with the participation of Russia and the USA.

Err Error radius (1 ) in arcmin. N Number of detections in the entire survey.


Table 1. The JEM­X Catalog Source name R.A. Dec
IGR J00291+5934 IGR J00370+6122 gam Cas SMC X-1 3A 0114+650 H 0115+634 RX J0146.9+6121 NGC 1275 EXO 0331+530 LMC X-2 LMC X-4 Crab LMC X-3 LMC X-1 H 0614+091 Vela Pulsar Ginga 0836-429 Vela X-1 H 0918-549 GRO J1008-57 Cen X-3 IGR J11215-5952 HR 4492 IGR J11435-6109 1E 1145.1-6141 H 1145-619 NGC 4151 NGC 4388 GX 301-2 3C 273 3A 1246-588 1H 1254-690 2RXP J130159.5-63580 Cen A 4U 1323-62 IC 4329A NGC 5506 Cir X-1 H 1538-522 4U 1543-624 XTE J1550-564 1H 1556-605 H 1608-522 Sco X-1 H 1624-490 IGR J16318-4848 IGR J16320-4751 4U 1630-47 AX J1637.8-4656 3EG J1639-4702 IGR J16393-4643 H 1636-536 GX 340+0 IGR J16479-4514 GRO J1655-40 OAO 1657-415 GX 339-4 4U 1700-377 GX 349+2 H 1702-429 H 1705-440 XTE J1709-267 7.276 9.323 14.211 19.271 19.523 19.637 26.744 49.946 53.746 80.130 83.219 83.631 84.730 84.935 94.283 128.844 129.347 135.531 140.112 152.450 170.322 170.449 174.862 175.975 176.876 177.020 182.635 186.457 186.661 187.277 192.438 194.404 195.513 201.365 201.662 207.338 213.316 230.171 235.594 236.982 237.744 240.270 243.178 244.979 247.011 247.938 248.020 248.507 249.526 249.638 249.800 250.231 251.451 252.012 253.501 255.201 255.707 255.987 256.437 256.561 257.226 257.368 59.566 61.354 60.711 -73.444 65.283 63.744 61.351 41.514 53.176 -71.955 -66.366 22.017 -64.083 -69.736 9.135 -45.198 -42.892 -40.553 -55.213 -58.301 -60.625 -59.874 -65.394 -61.123 -61.955 -62.213 39.403 12.651 -62.770 2.048 -59.113 -69.290 -63.961 -43.012 -62.141 -30.318 -3.217 -57.166 -52.383 -62.568 -56.471 -60.738 -52.423 -15.640 -49.198 -48.816 -47.878 -47.393 -47.032 -46.937 -46.729 -53.750 -45.612 -45.185 -39.845 -41.653 -48.790 -37.844 -36.424 -43.035 -44.102 -26.652

Err
0.39 1.51 1.20 0.49 0.99 0.33 1.51 0.37 0.26 0.27 0.25 0.18 0.53 0.26 0.72 2.13 0.22 0.24 0.81 0.44 0.24 0.85 1.28 2.13 0.45 0.66 0.28 0.93 0.32 0.55 2.13 0.47 2.13 0.30 0.48 1.00 0.71 0.21 0.27 0.32 0.27 0.45 0.25 0.28 0.20 1.42 0.63 0.22 2.13 2.13 2.13 0.21 0.19 2.13 0.42 0.33 0.24 0.24 0.21 0.30 0.24 1.51

N
46 2 4 25 5 59 2 46 123 119 161 1038 19 127 12 1 251 186 8 34 205 7 3 1 36 13 104 6 90 19 1 29 1 86 28 5 10 353 130 69 119 30 187 109 508 3 14 344 1 1 1 321 652 1 44 74 210 194 366 101 237 2

IGR J17098-3628 Oph Cluster 4U 1708-40 XTE J1716-389 XTE J1720-318 4U 1722-30 3A 1728-169 GX 354-0 GX 1+4 4U 1730-335 SLX 1735-269 4U 1735-444 IGR J17391-3021 SLX 1737-282 XTE J1743-363 1E 1740.7-2942 1A 1742-294 IGR J17464-3213 1A 1743-288 SLX 1744-299 GX 3+1 SLX 1746-331 1H 1746-370 GRS 1747-312 IGR J17544-2619 GX 5-1 GRS 1758-258 GX 9+1 GX 13+1 4U 1812-12 GX 17+2 H 1820-303 AX J1824.7-1253 H 1822-000 3A 1822-371 Ginga 1826-24 Ser X-1 IGR J18410-0535 IGR J18450-0435 Ginga 1843+009 IGR J18483-0311 3A 1850-087 XTE J1855-026 XTE J1858+034 4U 1901+03 H 1907+097 AX J1910.7+0917 4U 1909+07 AX J1911.0+0906 Aql X-1 SS 433 IGR J19140+0951 GRS 1915+105 4U 1916-053 KS 1947+300 3A 1954+319 Cyg X-1 4U 1957+115 EXO 2030+375 Cyg X-3 SAX J2103.5+4545 SS Cyg Cyg X-2 3A 2206+543 Cas A

257.421 258.081 258.094 258.964 259.995 261.889 262.935 262.989 263.011 263.355 264.575 264.742 264.794 265.171 265.796 265.989 266.528 266.565 266.761 266.858 266.986 267.452 267.553 267.690 268.608 270.286 270.300 270.384 273.630 273.756 274.005 275.918 276.194 276.340 276.446 277.367 279.988 280.259 281.241 281.384 282.057 283.261 283.873 284.678 285.913 287.400 287.676 287.698 287.737 287.816 287.946 288.512 288.798 289.696 297.400 298.919 299.586 299.853 308.063 308.106 315.892 325.693 326.168 331.979 350.860

-36.447 -23.356 -40.841 -38.856 -31.751 -30.804 -16.962 -33.834 -24.747 -33.390 -26.997 -44.450 -30.337 -28.298 -36.370 -29.753 -29.519 -32.233 -28.883 -30.017 -26.564 -33.202 -37.051 -31.276 -26.344 -25.077 -25.742 -20.530 -17.158 -12.098 -14.036 -30.359 -12.900 -0.011 -37.104 -23.796 5.036 -5.601 -4.546 0.868 -3.164 -8.696 -2.606 3.436 3.204 9.833 9.279 7.593 9.053 0.584 4.986 9.881 10.946 -5.234 30.206 32.088 35.202 11.713 37.638 40.957 45.753 43.590 38.320 54.519 58.818

2.13 2.13 0.52 1.51 0.43 0.23 0.25 0.19 0.24 0.26 0.66 0.24 1.24 2.13 2.13 0.25 0.21 0.19 0.26 0.31 0.18 0.28 0.25 0.46 1.56 0.18 0.62 0.21 0.22 1.25 0.21 0.21 2.13 0.29 0.29 0.27 0.21 1.54 1.68 0.82 1.57 1.25 0.62 0.33 0.22 0.33 2.13 0.53 1.51 0.26 0.30 0.82 0.18 0.27 0.98 1.04 0.21 1.58 0.29 0.19 0.33 1.35 0.28 1.21 0.20

1 1 22 2 33 228 173 762 205 145 23 191 5 1 1 156 332 781 138 72 1646 132 175 30 2 1233 15 471 317 3 343 358 1 94 93 128 366 2 2 8 2 3 14 78 247 77 1 20 2 169 86 9 853 113 7 6 345 2 122 696 67 3 124 4 364