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NGC1291CXO - NGC 1291 Chandra X-ray Point Source Catalog

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Overview

This table contains some of the results from a study of the X-ray binary (XRB) populations in the bulge and ring regions of the ring galaxy NGC 1291. Utilizing the four available Chandra observations totaling an effective exposure of 179 ks, the authors detect 169 X-ray point sources in the galaxy in the full band (0.3 - 8.0 keV) with a false-positive probability threshold of 10-6 (implying approximately 2 false detections given the size of the image). Of these sources, 75 are in the bulge and 71 are in the ring. The authors report photometric properties of these sources in a point-source catalog. There are ~ 40% of the bulge sources and ~ 25% of the ring sources showing > 3-sigma long-term variability in their X-ray count rate. The X-ray colors suggest that a significant fraction of the bulge (~ 75%) and ring (~ 65%) sources are likely low-mass X-ray binaries (LMXBs). The spectra of the nuclear source indicate that it is a low-luminosity active galactic nucleus (AGN) with moderate obscuration; spectral variability is observed between individual observations. The authors construct 0.3-8.0 keV X-ray luminosity functions (XLFs) for the bulge and ring XRB populations, taking into account the detection incompleteness and background AGN contamination. They reach 90% completeness limits of ~ 1.5 x 1037 and ~ 2.2 x 1037 erg s-1 for the bulge and ring populations, respectively. Both XLFs can be fit with a broken power-law model, and the shapes are consistent with those expected for populations dominated by LMXBs. In the paper, the authors perform detailed population synthesis modeling of the XRB populations in NGC 1291, which suggests that the observed combined XLF is dominated by an old LMXB population. They compare the bulge and ring XRB populations, and argue that the ring XRBs are associated with a younger stellar population than the bulge sources, based on the relative overdensity of X-ray sources in the ring, the generally harder X-ray color of the ring sources, the overabundance of luminous sources in the combined XLF, and the flatter shape of the ring XLF.

Catalog Bibcode

2012ApJ...749..130L

References

Probing the X-Ray Binary Populations of the Ring Galaxy NGC 1291
     Luo B., Fabbiano G., Fragos T., Kim D.-W., Belczynski K.,
     Brassington N.J., Pellegrini S., Tzanavaris P., Junfeng Wang, Zezas A.
    <Astrophysical Journal, 749, 130 (2012)>
    =2012ApJ...749..130L

Provenance

This table was created by the HEASARC in May 2012 based on an electronic version of Table 2 from the reference paper obtained from the ApJ website.

Parameters

Source_Number
A running number for the X-ray source in order of increasing J2000.0 Right Ascension.

Alt_Name
An alternative source designation created by the HEASARC using the style recommended by the Dictionary of Nomenclature of celestial Objects, viz., '[LFF2012] NNN', where NNN is the source number and the prefix identifies the reference paper of Luo, Fabbiano, Fragos et al. (2012).

Name
The source designation created by the HEASARC using the style recommended by the Dictionary of Nomenclature of celestial Objects for Chandra-detected X-ray sources, viz., 'CXOU JHHMMSS.s_DDMMSS', where the numerical string is the J2000.0 position and the prefix stands for Chandra X-ray Observatory, unregistered.

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.01 seconds of time in the original table.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.1 arcseconds in the original table.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Off_Axis
The angular distance of the X-ray source from the Chandra aim point of RA, Dec (J2000.0) = 3 17 09.31, -41 06 25.1 (exposure-weighted average of the 4 ACIS-S3 observations), in arcminutes.

Radial_Distance
The radial angular distance of the X-ray source from the nucleus of NGC 1291 (RA, Dec (J2000.0) = 3 17 18.6, -41 06 29), in arcminutes.

FB_Counts
The aperture-corrected net (background-subtracted) source counts in the full (0.3 - 8.0 keV) band.

FB_Counts_Neg_Err
The lower 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

FB_Counts_Pos_Err
The upper 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

SB_Counts_Limit
This flag parameter is set to '<' if the corresponding band counts is an upper limit rather than a significant detection.

SB_Counts
The aperture-corrected net (background-subtracted) source counts in the soft (0.3-2.0 keV) band.

SB_Counts_Neg_Err
The lower 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

SB_Counts_Pos_Err
The upper 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

CSB_Counts_Limit
This flag parameter is set to '<' if the corresponding band counts is an upper limit rather than a significant detection.

CSB_Counts
The aperture-corrected net (background-subtracted) source counts in the conventional soft (0.5-2.0 keV) band.

CSB_Counts_Neg_Err
The lower 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

CSB_Counts_Pos_Err
The upper 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

HB_Counts_Limit
This flag parameter is set to '<' if the corresponding band counts is an upper limit rather than a significant detection.

HB_Counts
The aperture-corrected net (background-subtracted) source counts in the hard (2.0-8.0 keV) band.

HB_Counts_Neg_Err
The lower 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

HB_Counts_Pos_Err
The upper 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

SB1_Counts_Limit
This flag parameter is set to '<' if the corresponding band counts is an upper limit rather than a significant detection.

SB1_Counts
The aperture-corrected net (background-subtracted) source counts in the soft (0.3-1.0 keV) sub-band 1.

SB1_Counts_Neg_Err
The lower 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

SB1_Counts_Pos_Err
The upper 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

SB2_Counts_Limit
This flag parameter is set to '<' if the corresponding band counts is an upper limit rather than a significant detection.

SB2_Counts
The aperture-corrected net (background-subtracted) source counts in the soft (1.0-2.0 keV) sub-band 2.

SB2_Counts_Neg_Err
The lower 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

SB2_Counts_Pos_Err
The upper 1-sigma error in the corresponding band source counts using the Gehrels (1986, ApJ, 303, 336) formulation and propagating the errors of the extracted source counts and the background counts following the numerical method of Lyons (1991, Data Analysis for Physical Science Students, Section 1.7.3).

Exposure
The full-band effective exposure time, in seconds, determined from the exposure map, which has been corrcted for vignetting and quantum-efficiency degradation.

Soft_Color
The soft X-ray color SC of the source, where SC = (M-S)/T, where S, M, H and T are the count rates in the 0.3-1.0 keV, 1.0-2.0 keV, 2.0-8.0 keV and 0.3-8.0 keV bands, respectively. A Bayesian approach was used to calculate the colors and their associated errore following the method developed by Park et al. (2006, ApJ, 652, 610).

Soft_Color_Neg_Err
The lower 1-sigma statistical error in the soft color of the source.

Soft_Color_Pos_Err
The upper 1-sigma statistical error in the soft color of the source.

Hard_Color
The hard X-ray color HC of the source, where HC = (H-M)/T, where S, M, H and T are the count rates in the 0.3-1.0 keV, 1.0-2.0 keV, 2.0-8.0 keV and 0.3-8.0 keV bands, respectively. A Bayesian approach was used to calculate the colors and their associated errore following the method developed by Park et al. (2006, ApJ, 652, 610).

Hard_Color_Neg_Err
The lower 1-sigma statistical error in the hard color of the source.

Hard_Color_Pos_Err
The upper 1-sigma statistical error in the hard color of the source.

Photon_Index
The X-ray power-law photon index Gamma of the source, derived from spectral fitting using an absorbed power-law model TBABS * POW or set to 1.7 if the number of full-band counts is less than 30.

Lx
The observed full-band X-ray luminosity of the source, in erg/s. A distance of 8.9 Mpc for NGC 1291 and a Galactic column density along the line of site to this galaxy of 2.1 x 1020 cm-2 (Dickey and Lockman 1990, 28, 215) resulting in a small correction factor of 1.05 were used to estimate these 'observed' luminosities.

Var_Significance
The statistical significance sigmavar of the full-band flux variability of the source. This is calculated for sources that were dectected in at least one individual observation and were covered by at least two observations. A source is considered to be variable if its sigmavar value is greater than 3, i.e., there is a 3-sigma variation. For further details, see Section 4.3 of the reference paper.

Region_Flag
This parameter contains information on the region of the galaxy in which the source is located: 'Bulge' if the source is located in the Galactic bulge, 'Ring' if the source is located in the galaxy's ring and 'Other' if the source is located neither in the bulge nor the ring.

Contact Person

Questions regarding the NGC1291CXO database table can be addressed to the HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Thursday, 24-May-2012 11:24:28 EDT