J/A+A/299/39 Orion Trapezium area ROSAT PSPC obs. I. (Geier+, 1995)
ROSAT PSPC observations of the Orion Trapezium area.
I. Pre-main sequence and O stars.
Geier S., Wendker H.J., Wisotzki L.
<Astron. Astrophys. 299, 39 (1995)>
=1995A&A...299...39G 1995A&A...299...39G
ADC_Keywords: Clusters, open ; X-ray sources ; Stars, pre-main sequence
Mission_Name: ROSAT
Keywords: early-type stars - pre-main sequence stars - ISM: bubbles -
associations: Orion Trapezium - X-rays: stars
Abstract:
A deep ROSAT PSPC image centred on the Orion Trapezium has revealed
that most of the X-ray emission originates from discrete sources, in
contrast to previous EINSTEIN data which suggested a diffuse emission
component. We present a list of 171 X-ray sources all situated in the
so-called inner ring of the field of view (20' radius). The field is
crowded with sources. A special procedure had to be developed to cope
with the severe blending of sources. The present list is not complete
for LX<3.5*1029erg/s due to this reason and many more sources can
still be expected by a next step in the reduction. Nearly all of the
sources could be identified with pre-main sequence stars of the Ori OB
1 association in its subgroups Ic and Id. The statistics of this
ensemble are discussed. It seems that members of the above subgroups
can be distinguished on the basis of an additional amount of X-ray
extinction seen in their spectra or hardness ratios. The O stars in
the area ({teta}1 Ori C, {teta}2 Ori A and ι Ori) are briefly
discussed. Six B stars are identified with X-ray sources.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 73 171 Positions and identifications of X-ray sources
table2.dat 38 171 X-ray properties of the sample
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See also:
IX/30 : Second ROSAT PSPC Catalog (ROSAT, 2000)
IX/31 : The WGACAT version of ROSAT sources (White+ 2000)
J/AN/321/81 : Orion Trapezium area ROSAT PSPC obs. II. (Lohmann+, 2000)
J/ApJ/540/1016 : K-band & NICMOS phot. of Trapezium Cluster (Luhman+, 2000)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ROS-ORI [1/171]+ Sequential number
5- 6 I2 h RAh Right ascension (J2000.0)
8- 9 I2 min RAm Right ascension (J2000.0)
11- 14 F4.1 s RAs Right ascension (J2000.0)
16 A1 --- DE- Declination sign (J2000.0)
17- 18 I2 deg DEd Declination (J2000.0)
20- 21 I2 arcmin DEm Declination (J2000.0)
23- 24 I2 arcsec DEs Declination (J2000.0)
26- 30 F5.2 arcmin phi Off-axis angle
32- 35 I4 --- P ? Parenago (1954TrSht..25....1P 1954TrSht..25....1P) number
37- 40 I4 --- JW ? Jones & Walker (1988AJ.....95.1755J 1988AJ.....95.1755J) number
42- 51 A10 --- Var Variable name
53- 82 A30 --- Names Other names
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- ROS-ORI [1/171]+ Sequential number
5- 9 I5 ct NPhot Net X-ray photon count
11- 17 F7.2 ct/ks CountRate Count rate
19- 23 F5.2 --- HR1 Hardness ratio HR1
25- 29 F5.2 --- HR2 Hardness ratio HR2
31- 33 F3.1 MK Tx ? Temperature of corona plasma
35- 38 F4.1 10+21cm-2 N(HI) ? HI column density
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History:
Prepared via OCR at CDS.
(End) James Marcout, Patricia Bauer [CDS] 05-Oct-2000