- ID:
- ivo://nasa.heasarc/ngc2547xmm
- Title:
- NGC 2547 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC2547XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains a list of point sources detected by XMM-Newton EPIC in a pointing towards the young open cluster NGC 2547, made in order to allow the authors to characterize coronal activity in solar-type stars, and stars of lower mass, at an age of 30 Myr. X-ray emission was seen from stars at all spectral types, peaking among G stars at luminosities (0.3 - 3 keV) of L<sub>x</sub> ~= 10<sup>30.5</sup> erg/s and declining to L<sub>x</sub> <= 10<sup>29</sup> erg/s among M stars with masses >=0.2 solar masses. Coronal spectra show evidence for multi-temperature differential emission measures and low coronal metal abundances of Z~= 0.3. Most of the solar-type stars in NGC 2547 exhibit saturated or even supersaturated X-ray activity levels. The median levels of L<sub>x</sub> and L<sub>x</sub>/L<sub>bol</sub> in the solar-type stars of NGC 2547 are very similar to those in T-Tauri stars of the Orion Nebula cluster (ONC), but an order of magnitude higher than in the older Pleiades. The spread in X-ray activity levels among solar-type stars in NGC 2547 is much smaller than in older or younger clusters. This table contains the properties of those X-ray sources which are correlated with optical cluster members (see Section 2.2 of the reference paper for details on the correlation procedure that was adopted), as well as the properties of those X-ray sources which are uncorrelated with any optical cluster members. The table lists the cross-identifications with optical catalogs for the candidate cluster sources along with their X-ray luminosities and X-ray to bolometric flux ratios, as well as the correlations between cluster members which were detected by XMM-Newton and those detected 7 years earlier by the ROSAT HRI instrument, along with the X-ray luminosities and flux ratios as determined by the HRI. This table was created by the HEASARC in February 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/MNRAS/367/781">CDS Catalog J/MNRAS/367/781</a> files table1.dat, table2.dat, table3.dat and table7.dat. This is a service provided by NASA HEASARC .
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- ID:
- ivo://nasa.heasarc/ngc2808xmm
- Title:
- NGC 2808 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC2808XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- Galactic globular clusters harbor binary systems that are detected as faint X-ray sources. These close binaries are thought to play an important role in the stability of the clusters by liberating energy and delaying the inevitable core collapse of globular clusters. The inventory of close binaries and their identification is therefore essential. This table contains some of the results, namely an X-ray source catalog, from XMM-Newton observations of the Galactic globular cluster NGC 2808. The authors use X-ray spectral and variability analysis combined with ultraviolet observations made with the XMM-Newton optical monitor and published data from the Hubble Space Telescope to identify sources associated with the clusters. They compare the results of their observations with estimates from population synthesis models. Five sources out of 96 X-ray sources detected above 4-sigma significance are likely to be related to NGC 2808. The authors find one quiescent neutron star low-mass X-ray binary candidate in the core of NGC 2808, and propose that the majority of the central sources in NGC 2808 are cataclysmic variables. An estimation leads to 20 +/- 10 cataclysmic variables with luminosity above 4.25 x 10<sup>31</sup> erg s<sup>-1</sup>. Millisecond pulsars could also be present in the core of NGC 2808, and some sources outside the half-mass radius could possibly be linked to the cluster. NGC 2808 was observed on February 1st 2005, for 41.8 kiloseconds (ks) with the three European Photon Imaging Cameras (EPIC MOS1, MOS2 and pn) on board the XMM-Newton observatory, in imaging mode, using a full frame window and a medium filter. This table was created by the HEASARC in February 2009 based on the electronic version of Table 2 from the paper which was obtained from the CDS (their catalog J/A+A/480/397 file table2.dat). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc2264xmm
- Title:
- NGC 2264 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC2264XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains (some of) the results from an X-ray imaging survey of the young cluster NGC 2264, carried out with the European Photon Imaging Cameras (EPIC) on board the XMM-Newton spacecraft. XMM-Newton EPIC observations were made separately of the northern and southern portions of NGC 2264 on 2001 March 20 and 2002 March 17 - 18, respectively. Details concerning the two pointings are summarized in Table 1 of the reference paper. The nominal integration time was 42 ks for both observations. The three EPIC cameras were operated in full window mode. To prevent contamination of the X-ray images by the XUV and EUV emission of the optically and UV-bright sources in the field of view, the thick filter was used, which imposes a strong cut-off in the response at the lower energies. The X-ray data are merged with extant optical and near-infrared photometry, spectral classifications, H-alpha emission strengths, and rotation periods to examine the interrelationships between coronal and chromospheric activity, rotation, stellar mass, and internal structure for a statistically significant sample of pre-main-sequence stars. Out of the 316 distinct point-like sources that were detected at >= 3-sigma levels in one or more of six EPIC images, a total of 300 distinct X-ray sources can be identified with optical or near-infrared counterparts. The sources are concentrated within three regions of the cluster: in the vicinity of S Mon, within the large emission/reflection nebulosity southwest of S Mon, and along the broad ridge of molecular gas that extends from the Cone Nebula to the NGC 2264 IRS 2 field. From the extinction-corrected color-magnitude diagram of the cluster, ages and masses for the optically identified X-ray sources are derived. A median age of ~ 2.5 Myr and an apparent age dispersion of ~ 5 Myr are suggested by pre-main-sequence evolutionary models. The X-ray luminosity of the detected sources appears well-correlated with bolometric luminosity, although there is considerable scatter in the relationship. Stellar mass contributes significantly to this dispersion, while isochronal age and rotation do not. X-ray luminosity and mass are well correlated such that L<sub>X</sub> ~ (M/M<sub>solar</sub>)<sup>1.5</sup>, which is similar to the relationship found within the younger Orion Nebula Cluster. No strong evidence is found for a correlation between E(H-K), the near-infrared color excess, and the fractional X-ray luminosity, which suggests that optically thick dust disks have little direct influence on the observed X-ray activity levels. Among the X-ray-detected weak-line T Tauri stars, the fractional X-ray luminosity, L<sub>X</sub>/L<sub>bol</sub>, is moderately well correlated with the fractional H-alpha luminosity, L<sub>H(alpha)</sub>/L<sub>bol</sub>, but only at the 2-sigma level of significance. The cumulative distribution functions for the X-ray luminosities of the X-ray-detected classical and weak-line T Tauri stars within the cluster are comparable, assuming the demarcation between the two classes is at an H-alpha equivalent width of 10 Angstroms. However, if the non-detections in X-rays for the entire sample of H-alpha emitters known within the cluster are taken into account, then the cumulative distribution functions of these two groups are clearly different, such that classical T Tauri stars are underdetected by at least a factor of 2 relative to the weak-line T Tauri stars. Examining a small subsample of X-ray-detected stars that are probable accretors based on the presence of strong H-alpha emission and near-infrared excess, the authors conclude that definitive non-accretors are ~ 1.6 times more X-ray luminous than their accreting counterparts. In agreement with earlier published findings for the Orion Nebula Cluster, the authors find a slight positive correlation (valid at the 2-sigma confidence level) between L<sub>X</sub>/L<sub>bol</sub> and the rotation period in NGC 2264 stars. The lack of a strong anti-correlation between X-ray activity and rotation period in the stellar population of NGC 2264 suggests that either the deeply convective T Tauri stars are rotationally saturated or that the physical mechanism responsible for generating magnetic fields in pre-main-sequence stars is distinct from the one that operates in evolved main-sequence stars. This table was created by the HEASARC in September 2007 based on the electronic version of Table 2 from the reference paper which was obtained from the electronic AJ site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6530xmm
- Title:
- NGC 6530 XMM-Newton X-Ray Point Source Catalog
- Short Name:
- NGC6530XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of a 20 ks XMM-Newton observation of the Lagoon Nebula (M 8). The EPIC images of this region reveal a cluster of point sources, most of which have optical counterparts inside the very young open cluster NGC 6530. The bulk of these X-ray sources are probably associated with low and intermediate mass pre-main sequence stars. One of the sources experienced a flare-like increase of its X-ray flux making it the second brightest source in M 8 after the O4 star 9 Sgr. The X-ray spectra of most of the brightest sources can be fitted with thermal plasma models with temperatures of kT ~ a few keV. Only a few of the X-ray selected PMS candidates are known to display H-alpha emission and were previously classified as classical T Tauri stars. This suggests that most of the X-ray emitting PMS stars in NGC 6530 are weak-line T Tauri stars. In addition to 9 Sgr, the EPIC field of view contains also a few early-type stars. This table contains information on 117 of the 119 X-ray sources (2 sources, a point source associated with 9 Sgr and an extended source associated with the Hourglass Nebula were excluded from this table by the authors) that were detected using the SAS source detection algorithms in the soft band (0.5 - 1.2 keV) of an EPIC observation of 9 Sgr which have either a combined likelihood >= 20 and are detected in the individual images from all 3 EPIC instruments with -ln p_i >= 3.0 or (in two cases) where clearly detected in 2 of the 3 instruments but fell outside of the FOV of the third. The faintest sources in this category have about 10-3 cts s<sup>-1</sup> over the 0.5 - 1.2 keV band of the MOS instruments. Assuming a 1 keV thermal spectrum with a neutral hydrogen column density of 0.17 x 10<sup>22</sup> cm<sup>-2</sup>, the faintest sources correspond to an observed flux of about 8.9 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup> and an unabsorbed flux of 13.1 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup> in the 0.5 - 5.0 keV energy range. Note that the corresponding observed flux in the 0.5 - 1.2 keV soft band would be 5.2 x 10<sup>-15</sup> erg cm<sup>-2</sup> s<sup>-1</sup>. 72 X-ray sources have a single optical counterpart from the Sung et al (2000, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/AJ/120/333">CDS Cat. <J/AJ/120/333></a>) catalog or in the SIMBAD database within a radius of less than 9 arcsec. The average angular separation between the X-ray source and the optical counterpart is 4.1 +/- 2.1 arcseconds. 17 X-ray sources have two or more optical stars falling within the 9 arcsec radius. Seven of these sources have at least one known H-alpha emission star inside their error box. 28 sources do not have an optical counterpart in the catalogue of Sung et al. The authors have cross-correlated these sources with the Guide Star Catalog and, in most cases, they find one or several GSC objects inside the 9 arcsec radius. These optical counterparts are usually very faint (V or R >=17) except for sources 91, 92 and 94 that have counterparts with R magnitudes 15.0, 14.6 and 13.3 respectively (note that these sources fall outside the area investigated by Sung et al.). Sources 93, 96, 98, 99, 100, 101, 102 and 112 have no GSC counterpart. Most of the objects in Table 3 are therefore X-ray sources with high X-ray to visual luminosity ratios. Given the galactic coordinates of NGC 6530 (l_II = 6.14, b_II = -1.38), the total galactic column density along this line of sight must be extremely large and the number of extragalactic sources in the soft detection energy band should be extremely low. This table was created by the HEASARC in March 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/395/499">CDS catalog J/A+A/395/499</a> files table1.dat, table2.dat and table3.dat. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ngc6231xmm
- Title:
- NGC 6231 XMM-Newton X-Ray Source Catalog
- Short Name:
- NGC6231XMM
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the results of an X-ray campaign towards the young open cluster NGC 6231. The XMM-Newton observations, of a total duration of ~ 180 ks, reveal that NGC 6231 is very rich in the X-ray domain too. Indeed, 610 X-ray sources were detected in the present field of view, centered on the colliding wind binary HD 152248 in the cluster core (RA, Dec J2000.0 of 16 54 10.06, -41 49 30.1). The limiting sensitivity of this survey is approximately 6 x 10^-15<sup>erg/s/cm</sup>2 but clearly depends on the location in the field of view and on the source spectrum. Using different existing catalogs, over 85% of the X-ray sources could be associated with at least one optical and/or infrared counterpart within a limited cross-correlation radius of 2.5 or 3-arcsec according to the optical/IR catalog used. The surface density distribution of the X-ray sources presents a slight N-S elongation. Once corrected for the spatial sensitivity variation of the EPIC instruments, the radial profile of the source surface density is well described by a King profile with a central density of about 8 sources per arcmin<sup>2</sup> and a core radius close to 3.1 arcminutes. The distribution of the X-ray sources seems closely related to the optical source distribution. The expected number of foreground and background sources should represent about 9% of the detected sources, thus strongly suggesting that most of the observed X-ray emitters are physically belonging to NGC 6231. Finally, beside a few bright but soft objects -- corresponding to the early-type stars of the cluster -- most of the sources are relatively faint (~5 x 10<sup>-15</sup> erg/s/cm<sup>2</sup>) with an energy distribution peaked around 1.0 - 2.0 keV. The catalog of the 610 X-ray sources detected in the 30'-diameter field of view of XMM-Newton is presented here, including the equatorial coordinates, logarithmic likelihoods and count rates for the three EPIC instruments and for various energy ranges, as well as the cross-identification of the X-ray sources with various optical/infrared catalogs (2MASS, GSC2.2, USNO B1.0, SSB06) and their most commonly used names (HD/HDE, CD, CPD, Segg., SBL98, Braes), with only the closest identifications being reported here. This table was created by the HEASARC in March 2007 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/454/1047">CDS catalog J/A+A/454/1047</a> files table3.dat and table6.dat. This is a service provided by NASA HEASARC .
616. NICER Master Catalog
- ID:
- ivo://nasa.heasarc/nicermastr
- Title:
- NICER Master Catalog
- Short Name:
- NICERMASTR
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table records high-level information for the observations obtained with NICER (Neutron star Interior Composition ExploreR) and provides access to the NICER data archive. NICER is a NASA Explorer program Mission of Opportunity dedicated to the study of the neutron stars, exploring the exotic states of matter where density and pressure are higher than in atomic nuclei. NICER instrument is a payload aboard the International Space Station (ISS). It was launched on 3 June 2017 on a SpaceX Falcon 9 rocket and placed on the ISS. Normal operation started on 17 July 2017 after a commission phase to test the system and perform initial calibration. NICER's X-ray Timing Instrument (XTI) consists of an aligned collection of 56 X-ray "concentrator" optics (XRC) and silicon drift detector (SDD) pairs working in the energy range of 0.2-12 keV. Each XRC collects X-rays over a large geometric area from a roughly 30 arcmin<sup>2</sup> region of the sky and focuses them onto a small SDD. The SDD detects individual photons, recording both energies (with a 3% energy resolution at 6 keV) and high precision times (with 100 nanoseconds RMS relative to Universal Time). During one day of operation, NICER monitors several sources. For each observed source the data are divided into intervals of one day and labeled with a sequence number. This database table contains one record for each sequence number and includes parameters related to the observation. This contents of this database table are generated at the NICER Science and Mission Operations Center (SMOC) and updated regularly with new observations. Note that some fields have been added and are populated by the HEASARC. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/nltt
- Title:
- NLTTCatalog&FirstSupplement
- Short Name:
- NLTT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This catalog (Luyten 1979, 1980) is a collection of stars on more than 800 Palomar Proper Motion Survey plates found to have relative annual proper motions exceeding 0.18 arcsec. The motions have been determined by Luyten and his coworkers by either hand blinking and measuring or with the automated- computerized scanner and measuring machine built by Control Data Corporation and located at the University of Minnesota. The new catalog replaces the LTT Catalogues (Luyten 1957, 1961, 1962), wherein stars in the Bruce Proper Motion Survey discovered to have motions exceeding 0.2 arcsec had been compiled. For further information on the NLTT Catalogue itself, including discussions of positional errors, estimation of magnitudes, star designations used in the catalog, completeness, and accuracy of the measured motions, the introduction to the published NLTT (see Volume I) should be consulted. The First Supplement to the NLTT Catalogue (Luyten and Hughes 1980) is the result of continued plate analysis and measurements during printing of the NLTT. The Supplement contains data for 398 stars having motions larger than 0.179 arcsec annually. Duplicate entries were removed from the HEASARC implementation of this catalog in June 2019. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/narcscat
- Title:
- NormaArmRegionChandraSurveyPoint&ExtendedSourceCatalog
- Short Name:
- NARCSCAT
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the catalog of 1,415 X-ray sources identified in the Norma Arm Region Chandra Survey (NARCS), which covers a 2 degree x 0.8 degree region in the direction of the Norma spiral arm to a depth of ~ 20 ks. Of these sources, 1,130 are point-like sources detected with >= 3-sigma confidence in at least one of three energy bands (0.5 - 10, 0.5 - 2, and 2 - 10 keV), five have extended emission, and the remainder are detected at low significance. Since most sources have too few counts to permit individual classification, they are divided into five spectral groups defined by their quantile properties. The authors analyze stacked spectra of X-ray sources within each group, in conjunction with their fluxes, variability, and infrared counterparts, to identify the dominant populations in this survey. They find that ~ 50% of their sources are foreground sources located within 1 - 2 kpc, which is consistent with expectations from previous surveys. Approximately 20% of sources are likely located in the proximity of the Scutum-Crux and near Norma arm, while 30% are more distant, in the proximity of the far Norma arm or beyond. The authors argue that a mixture of magnetic and non-magnetic cataclysmic variables dominates the Scutum-Crux and near Norma arms, while intermediate polars and high-mass stars (isolated or in binaries) dominate the far Norma arm. In the paper, they also present the cumulative number count distribution for sources in this survey that are detected in the hard energy band. A population of very hard sources in the vicinity of the far Norma arm and active galactic nuclei dominate the hard X-ray emission down to f<sub>X</sub> ~ 10<sup>-14</sup> erg cm<sup>-2</sup> s<sup>-1</sup>, but the distribution curve flattens at fainter fluxes. The authors find good agreement between the observed distribution and predictions based on other surveys. Chandra ACIS-I observations were performed in faint mode of a 2 degree by 0.8 degree region of the Norma spiral arm in 2011 June. This field was subdivided into 27 pointings; Table 1 in the reference paper reports their coordinates and exposure times and Figure 1 (op. cit.) is a mosaic image of the survey. The observing strategy was to cover a wide area with relatively uniform flux sensitivity and good spatial resolution; therefore, the authors chose field centers spaced by 12 arcminutes, which provided roughly 70 arcminute<sup>2</sup> of overlap on the outskirts of adjacent observations such that the additional exposure time in these overlapping regions partly made up for the worsening point-spread function (PSF) at large off-axis angles. This table was created by the HEASARC in March 2015 based on electronic versions of Tables 3, 4 and 5 from the reference paper which were obtained from the ApJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/napexmmcxo
- Title:
- NorthAmerica(NGC7000)&Pelican(IC5070)NebulaeX-RaySourceCatalog
- Short Name:
- NAPEXMMCXO
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from the first extensive X-ray study of the North-America and Pelican star-forming region (NGC 7000/IC 5070), with the aim of finding and characterizing the young population of this cloud. X-ray data from Chandra (four pointings) and XMM-Newton (seven pointings) were reduced and source detection algorithm applied to each image. The authors complement the X-ray data with optical and near-IR data from the IPHAS, UKIDSS, and 2MASS catalogs, and with other published optical and Spitzer IR data. More than 700 X-ray sources are detected, the majority of which have an optical or NIR counterpart. This allowed the authors to identify young stars in different stages of formation. Less than 30% of the X-ray sources are identified with a previously known young star. the authors argue that most X-ray sources with an optical or NIR counterpart, except perhaps for a few tens at near-zero reddening, are likely candidate members of the star-forming region, on the basis of both their optical and NIR magnitudes and colors, and of their X-ray properties such as spectral hardness or flux variations. They are characterized by a wide range of extinction, and sometimes near-IR excesses, both of which prevent derivation of accurate stellar parameters. The optical color-magnitude diagram suggests ages between 1-10 Myr. The X-ray members have a very complex spatial distribution with some degree of subclustering, qualitatively similar to that of previously known members. The detailed distribution of X-ray sources relative to the objects with IR excesses identified with Spitzer is sometimes suggestive of sequential star formation, especially near the 'Gulf of Mexico' region, probably triggered by the O5 star which illuminates the whole region. The authors confirm that around the O5 star no enhancement in the young star density is found, in agreement with previous results. Thanks to the precision and depth of the IPHAS and UKIDSS data used, the authors also determine the local optical-IR reddening law, and compute an updated reddening map of the entire region. This table contains the catalog of X-ray sources, with their optical and near-IR identifications, in the NGC 7000/IC 5070 (North America/Pelican) star formation complex. The final X-ray source list comprises 721 objects, of which there are 378 ACIS detections (of which 34 have an XMM-Newton counterpart), and 343 XMM-Newton-only detection. The chosen detection threshold, corresponding to approximately one spurious detection per field, ensures that no more than approximately ten of the 721 detections are spurious. The 11 XMM-Newton and Chandra fields analyzed in this study are listed in Tables 1 and 2, respectively, of the reference paper. This table was created by the HEASARC in July 2017 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/602/A115">CDS Catalog J/A+A/602/A115</a> file table3.dat, the list of detected X-ray sources in the North America (NGC 7000) & Pelican Nebulae (IC 5070), and file table4.dat, the list of optical and near-IR photometric information for the counterparts of these X-ray sources. It does not contain table5.dat, the list of X-ray undetected stars that have IR or H-alpha excesses. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/ncp21cma
- Title:
- North Celestial Pole Region Radio Sources Detected by the 21cm Array
- Short Name:
- NCP21CMA
- Date:
- 07 Mar 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains the catalog of 624 radio sources detected around the North Celestial Pole (NCP) with the 21 Centimeter Array (21CMA), a radio interferometer dedicated to the statistical measurement of the epoch of reionization (EoR). The data are taken from a 12-hr observation made on 2013 April 13, with a frequency coverage from 75 to 175 MHz and an angular resolution of ~4 arcminutes. The catalog includes flux densities at eight sub-bands across the 21CMA bandwidth and provides the in-band spectral indices for the detected sources. To reduce the complexity of interferometric imaging from the so-called "w" term and ionospheric effects, the present analysis is restricted to the east-west baselines within 1500 m only. 624 radio sources are found within 5 degrees around the NCP down to ~0.1 Jy (100 mJy). These source counts are compared, and also exhibit a good agreement, with deep low-frequency observations made recently with the GMRT and MWA. In particular, for fainter radio sources below ~1 Jy, the authors find a flattening trend of source counts toward lower frequencies. While the thermal noise (~0.4 mJy) is well controlled to below the confusion limit, the dynamical range (~10<sup>4</sup>) and sensitivity of current 21CMA imaging are largely limited by calibration and deconvolution errors, especially the grating lobes of very bright sources, such as 3C061.1, in the NCP field, which result from the regular spacings of the 21CMA. The authors note that particular attention should be paid to the extended sources, and their modeling and removal may constitute a large technical challenge for current EoR experiments. Their analysis may serve as a useful guide to the design of next generation low-frequency interferometers like the Square Kilometre Array (SKA). The 21CMA is a ground-based radio interferometer dedicated to the detection of the EoR. The array, sited in the Ulastai valley of western China, consists of 81 pods or stations, and a total of 10,287 log-periodic antennas are deployed in two perpendicular arms along the east-west (6.1 km) (see Figure 1 in the reference paper) and north-south (4 km) directions, respectively. The spacing of these 81 pods is chosen such that a sufficiently large number of redundant baselines and a good uniform UV coverage can both be guaranteed. Each antenna element has 16 pairs of dipoles with lengths varying from 0.242 to 0.829 m, optimized to cover a frequency range of 50-200 MHz, which gives rise to an angular resolution of 3 arcminutes at 200 MHz. All of the antennas are fixed on the ground and point at the NCP for the sake of simplicity and economy. In the current work, the radio point sources observed with the 40 pods of the 21 Centimeter Array (21CMA) E-W baselines in an integration of 12 hours made on 2013 April 13 centered on the North Celestial Pole (NCP) are presented. An extra deep sample with a higher sensitivity from a longer integration time of up to years will be published later. The authors have detected a total of 624 radio sources over the central field within 3 degrees in a frequency range of 75-175 MHz band and in the outer annulus from 3-5 degrees in the 75-125 MHz band. By performing a Monte-Carlo simulation, the authors estimate a completeness of 50% at a flux density of ~0.2 Jy. This table was created by the HEASARC in May 2017 based upon the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/ApJ/832/190">CDS Catalog J/ApJ/832/190</a> file table3.dat. Some of the values for the name parameter in the HEASARC's implementation of this table were corrected in April 2018. This is a service provided by NASA HEASARC .
