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J/ApJ/643/238       Chandra/2MASS sources in Cygnus OB2      (Butt+, 2006)

Deeper Chandra follow-up of Cygnus TeV source perpetuates mystery. Butt Y.M., Drake J., Benaglia P., Combi J.A., Dame T., Miniati F., Romero G.E. <Astrophys. J., 643, 238-244 (2006)> =2006ApJ...643..238B
ADC_Keywords: Clusters, open ; X-ray sources ; Infrared sources Keywords: acceleration of particles - cosmic rays - gamma rays: observations - ISM: bubbles - open clusters and associations: individual (Cygnus OB2) Abstract: A 50ks Chandra observation of the unidentified TeV source in Cygnus reported by the HEGRA collaboration reveals no obvious diffuse X-ray counterpart. However, 240 point-like X-ray sources are detected within or nearby the extended TeV J2032+4130 source region, of which at least 36 are massive stars and two may be radio emitters. That the HEGRA source is a composite, having as a counterpart the multiple point-like X-ray sources we observe, cannot be ruled out. Indeed, the distribution of point-like X-ray sources appears nonuniform and concentrated broadly within the extent of the TeV source region. We offer a hypothesis for the origin of the very high energy gamma-ray emission in Cyg OB2 based on the local acceleration of TeV-range cosmic rays and the differential distribution of OB versus less massive stars in this association. Description: TeV J2032+4130 was observed by Chandra on 2004 July 12 at UT 02:04:33 for a total effective exposure time of 48728s using the Advanced CCD Imaging Spectrometer-Imager (ACIS-I) detector in its standard Timed Exposure Very Faint mode. All four imaging chips were active, in addition to spectroscopy chips S3 and S4. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 72 240 Detected sources in Cyg OB2
See also: B/chandra : The Chandra Archive Log (CXC, 1999-) II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 3 I3 --- [BDB2006] Running X-ray identification number 5- 6 I2 h RAh Chandra Hour of Right Ascension (J2000) 8- 9 I2 min RAm Chandra Minute of Right Ascension (J2000) 11- 16 F6.3 s RAs Chandra Second of Right Ascension (J2000) 17 A1 --- DE- Chandra Sign of Declination (J2000) 18- 19 I2 deg DEd Chandra Degree of Declination (J2000) 21- 22 I2 arcmin DEm Chandra Arcminute of Declination (J2000) 24- 28 F5.2 arcsec DEs Chandra Arcsecond of Declination (J2000) 30- 35 F6.3 --- SNR Signal-to-noise of source 37- 42 F6.3 --- HR Hardness ratio (1) 44- 48 F5.1 ct Ct Source counts from ACIS-I 50- 51 I2 h RA2h ? 2MASS Hour of Right Ascension (J2000) 53- 54 I2 min RA2m ? 2MASS Minute of Right Ascension (J2000) 56- 60 F5.2 s RA2s ? 2MASS Second of Right Ascension (J2000) 61 A1 --- DE2- 2MASS Sign of Declination (J2000) 62- 63 I2 deg DE2d ? 2MASS Degree of Declination (J2000) 65- 66 I2 arcmin DE2m ? 2MASS Arcminute of Declination (J2000) 68- 72 F5.2 arcsec DE2s ? 2MASS Arcsecond of Declination (J2000)
Note (1): Defined as (2-10keV)/(0.5-2keV). For reasons of computational expediency, we employed a binning by 4 pixels in both image dimensions for these calculations. This process was carried out for images made from event lists filtered in the energy ranges 0.5-2 and 2-10keV. These particular energy ranges were chosen so as to contain approximately one half of the X-ray photon events in each. The resulting images were then binned by a further factor of 32 in order to accumulate sufficient counts in each bin to estimate a meaningful hardness ratio.
History: From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Vannier [CDS] 26-Sep-2008
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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