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 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 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:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
4u.dat 154 339 4th Uhuru catalogue
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See also:
IX/6 : Positions of X-Ray Sources, 2nd ed. (Dolan 1983)
Byte-by-byte Description of file: 4u.dat
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Bytes Format Units Label Explanations
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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/cm2/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)
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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.
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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