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IX/4                Fourth UHURU Catalogue  (4U)             (Forman+ 1978)

Fourth UHURU Catalogue Forman W., Jones C., Cominsky L., Julien P., Murray S., Peters G., Tananbaum H., Giacconni R. <Astrophys. J. Suppl. Ser. 38, 357 (1978)> =1978ApJS...38..357F
ADC_Keywords: X-ray sources Mission_Name: SAS-1 Keywords: X-rays: sources Abstract: The Fourth Uhuru (4U) Catalog lists 339 X-ray sources that were observed with the Uhuru (SAS A) X-ray observatory. It contains positional information in the form of 90% confidence level error boxes, 2-6keV intensities, possible optical and radio counterparts, and alternative names for sources observed in earlier compilations. The major classes of identified objects include binary stellar systems, supernova remnants, Seyfert galaxies, clusters of galaxies, and possibly the new class of superclusters of galaxies. The Uhuru satellite was a scanning X-ray instrument with a narrow (1 by 10 degree FWFM) and a wide (10 by 10 degree FWFM) collimator (cf. Giacconi et al. 1971ApJ...165L..27G). Typically, the scan rate was 0.5degree/second, with the spin axis in one position for roughly one day. During the interval for which the spin axis was fixed, repeated scans were made of the same 10 by 360 degrees band of the sky. For this catalog, the individual scans were superposed using aspect data from an orthogonally mounted triad of magnetometers and a Sun sensor onboard the spacecraft, supplemented by observations of well-located X-ray sources. The observations employed in producing this catalog were obtained over a total of 429 days between 1970 December 12 and 1973 March 18, apart from a gap between 1972 July and December when the spacecraft's transmitter was operating improperly. Description: Positions and intensities are presented for 339 X-ray sources observed by the Uhuru (SAS-1) X-ray satellite observatory. Correspondances with the sources in the 3U and 2A catalogs are given. Optical and radio counterparts are suggested based on positional coincidence This online catalog was created by the HEASARC in March 2003 based on a table obtained originally from the ADC website (ftp://legacy.gsfc.nasa.gov/heasarc/dbase/misc_files/uhuru4/4u.dat), which was modified by the HEASARC to include some parameters that were in the published catalog (Table 1 in the reference) but were not in the ADC table. The HEASARC made a small number of other changes and corrections to the table which are listed in the HEASARC_Implementation section of this help. Notice that the ADC table itself differs in a number of respects from the published Table 1, e.g., the comments are sometimes abbreviated and/or different, some of the names are slightly different (usually by one digit in the RA minutes part), and three of the entries have differing names and positions. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file 4u.dat 154 339 4th Uhuru catalogue
See also: IX/6 : Positions of X-Ray Sources, 2nd ed. (Dolan 1983) Byte-by-byte Description of file: 4u.dat
Bytes Format Units Label Explanations
1- 2 A2 --- --- [4U] 3- 9 A7 --- 4U 4U name (HHMM+DD) 11- 12 I2 h RAh Right ascension (B1950) (1) 14- 15 I2 min RAm Right ascension (B1950) (1) 17- 20 F4.1 s RAs Right ascension (B1950) (1) 22 A1 --- DE- Declination sign (B1950) (1) 23- 24 I2 deg DEd Declination (B1950) (1) 26- 27 I2 arcmin DEm Declination (B1950) (1) 29- 30 I2 arcsec DEs Declination (B1950) (1) 32- 39 F8.4 deg GLON Galactic longitude (1) 41- 48 F8.4 deg GLAT Galactic latitude (1) 50- 56 F7.4 deg+2 a90 Area of the 90% confidence level error box 58- 65 F8.2 ct/s CR Count rate (2) 67- 70 F4.1 ct/s e_CR ? rms uncertainty on CR (3) 72 A1 --- l_var Limit flag on var 73- 77 F5.1 --- var ? Ratio of the maximum to minimum observed count rate, maxtomin_ratio (4) 79- 86 E8.3 mW/m2 Flux X-ray flux in the 2-6keV band (erg/cm^2^/s) (5) 88- 94 E7.2 mW/m2 e_Flux ? rms uncertainty on Flux 96-103 F8.2 mCrab FluxC X-ray flux in the 2-6keV band, in milliCrabs (6) 105-109 F5.2 mCrab e_FluxC ? rms uncertainty on FluxC 111-154 A44 --- Com Comments (7)
Note (1): Position of the source maximum probability density. Note (2): The average intensity of the lines of position used in the source position determination (for sources that were constant in intensity within the statistics of the measurement), or the maximum intensity (for sources that were observed to be variable), in Uhuru counts per second. In the latter cases, the maxtomin_ratio parameter contains the ratio of the maximum to minimum observed values. The intensities reported were derived only from positive source detections, and days on which a source was not detected are not included in the calculation of the average intensity; thus, the quoted values can substantially overestimate the true average intensities, particularly for weak sources. Note (3): The uncertainty in the average intensity of the lines of position used in the source position determination, in Uhuru counts per second. This is quoted only for sources that were constant in intensity within the statistics of the measurement. Note (4): This is quoted only for sources that were observed to be variable. Note (5): This was calculated by the HEASARC using the conversion formula given in the published paper: 1.7x10-11erg/cm2/s (17fW/m2) = 1 Uhuru count/s. These values were computed for a Crab-like spectrum, but vary by only 10-20% for all but the most extreme source spectra. The intensities reported were derived only from positive source detections, and days on which a source was not detected are not included in the calculation of the average intensity; thus, the quoted values can substantially overestimate the true average intensities, particularly for weak sources. Note (6): This was calculated by the HEASARC using the conversion formula: 1.0559milliCrab=1 Uhuru count/s. The conversion factor was chosen so that the flux of the source 4U0531+21 associated with the Crab was 1000milliCrabs. Note (7): This parameter contains the then-available information on possible source identifications, including optical, radio, and previous X-ray identifications. Information on the source type and (usually X-ray) periods is also sometimes given.
History: * The original 4U catalog on magnetic tape (4u_ori.txt) was prepared at Goddard Space Flight Center (GSFC) in April 1978; is was originally assigned the number VII/18 in the CDS collection. * The file "4u.dat" is the version prepared at Heasarc (http://heasarc.gsfc.nasa.gov/W3Browse/uhuru/uhuru4.html)
(End) Patricia Vannier [CDS] 10-Jul-2012
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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