- ID:
- ivo://CDS.VizieR/J/ApJ/837/130
- Title:
- Collinder 261 Chandra sources & optical counterparts
- Short Name:
- J/ApJ/837/130
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first X-ray study of Collinder 261 (Cr261), which at an age of 7Gyr is one of the oldest open clusters known in the Galaxy. Our observation with the Chandra X-Ray Observatory is aimed at uncovering the close interacting binaries in Cr261, and reaches a limiting X-ray luminosity of L_X_~4x10^29^erg/s (0.3-7keV) for stars in the cluster. We detect 107 sources within the cluster half-mass radius r_h_, and we estimate that among the sources with L_X_>~10^30^erg/s, ~26 are associated with the cluster. We identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of Cr261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, we estimate that Cr261 has an approximate mass of 6500M_{sun}_, roughly the same as the old open cluster NGC6791. The X-ray emissivity of Cr261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity.
Number of results to display per page
Search Results
- ID:
- ivo://nasa.heasarc/cr261cxo
- Title:
- Collinder 261 Chandra X-Ray Point Source Catalog
- Short Name:
- CR261CXO
- Date:
- 09 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from the first X-ray study of Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open clusters known in the Galaxy. This observation with the Chandra X-Ray Observatory was aimed at uncovering the close interacting binaries in Cr 261, and reached a limiting X-ray luminosity of L<sub>X</sub> ~ 4 x 10<sup>29</sup> erg s<sup>-1</sup> (0.3-7 keV) for stars in the cluster. The authors detected 107 sources within the cluster half-mass radius r<sub>h</sub>, and they estimate that among the sources with L<sub>X</sub> >~ 10<sup>30</sup> erg s<sup>-1</sup>, about 26 are associated with the cluster. They identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of CR 261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, the authors estimate that Cr 261 has an approximate mass of 6500 M<sub>sun</sub>, roughly the same as the old open cluster NGC 6791. The X-ray emissivity of Cr 261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity. Cr 261 was observed with the Advanced CCD Imaging Spectrometer (ACIS) on board Chandra starting 2009 November 9 14:50 UTC, for a total exposure time of 53.8 ks (ObsID 11308). The observation was made in Very Faint, Timed exposure mode, with a single frame exposure time of 3.2 s. Kharchenko et al. (2013, A&A, 558, A53) estimate that the radius of Cr 261 is ~ 14.1 arcminutes. This is considerably larger than a single ACIS chip (8 4 x 8 4 arcminute<sup>2</sup>) and therefore the authors placed the center of the cluster (J2000.0 RA = 12<sup>h</sup> 38<sup>m</sup> 06.0<sup>s</sup>, Dec = -68<sup>o</sup> 22' 01" according to Kharchenko et al. 2013) close to the I3 aimpoint so that a larger contiguous part of the cluster could be imaged (see Figure 1 in the reference paper). The CCDs used were I0, I1, I2, and I3 from the ACIS-I array, and S2 and S3 from the ACIS-S array. The authors limited the X-ray analysis to the data from chips I0, I1, I2, and I3. The S2 and S3 chips lie far from the I3 aimpoint, giving rise to large positional errors on any sources detected on them. Such large errors make it hard to identify optical counterparts, and thus to classify the sources. Source detection was done in soft (0.3-2.0 keV), hard (2-7 keV) and broad (0.3-7 keV) energy bands. The CIAO source detection routine wavdetect was run for eight wavelet scales ranging from 1.0 to 11.3 pixels. The wavdetect detection threshold (sigthresh) was set at 10<sup>-7</sup>. The corresponding expected number of spurious detections per wavelet scale is 0.42 for all four ACIS chips combined, or 3.35 in total for all wavelet scales. The authors ran wavdetect for the three different energy bands and then cross-correlated the resulting source lists to obtain a master X-ray source list. They detected 113 distinct X-ray sources. To check if any real sources were missed, they ran wavdetect again with a detection threshold of 10<sup>-6</sup>, which increased the expected total number of spurious detections to 33.5, and found a total of 151 distinct X-ray sources with more than two counts (0.3-7 keV) in this case. The positions of 7 of the extra 38 sources were found to match those of short-period binaries discovered by Mazur et al. (1995, MNRAS, 273, 59; see Section 3.4). Close, interacting binaries are plausible real X-ray sources, and indeed the expected number of chance alignments between the Chandra detections and the binaries in the Mazur catalog is very low, as discussed in Section 3.5 of the reference paper. It is therefore likely that at least these seven additional sources are real, but given the ~ 34 spurious detections that are expected, the authors do not believe that there are many more real sources among the extra detections. They flagged the sources that are only found for sigthresh = 10<sup>-6</sup>, but kept them in the master source list. This HEASARC table contains the list of 151 X-ray sources found by wavdetect using a detection threshold of 10<sup>-6</sup> from Table 1 of the reference paper. Information about the 135 optical counterparts to these X-ray sources is available in the HEASARC table CR261OID (based on Table 2 of the reference paper) to which this current table has links. This table was created by the HEASARC in June 2017 based upon the machine-readable version of Table 1 from the reference paper, the catalog of Chandra sources in Cr 261, that was obtained from the ApJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/cr261oid
- Title:
- Collinder 261 Chandra X-Ray Source Optical Counterparts Catalog
- Short Name:
- CR261OID
- Date:
- 09 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from the first X-ray study of Collinder 261 (Cr 261), which at an age of 7 Gyr is one of the oldest open clusters known in the Galaxy. This observation with the Chandra X-Ray Observatory was aimed at uncovering the close interacting binaries in Cr 261, and reached a limiting X-ray luminosity of L<sub>X</sub> ~ 4 x 10<sup>29</sup> erg s<sup>-1</sup> (0.3-7 keV) for stars in the cluster. The authors detected 107 sources within the cluster half-mass radius r<sub>h</sub>, and they estimate that among the sources with L<sub>X</sub> >~ 10<sup>30</sup> erg s<sup>-1</sup>, about 26 are associated with the cluster. They identify a mix of active binaries and candidate active binaries, candidate cataclysmic variables, and stars that have "straggled" from the main locus of CR 261 in the color-magnitude diagram. Based on a deep optical source catalog of the field, the authors estimate that Cr 261 has an approximate mass of 6500 M<sub>sun</sub>, roughly the same as the old open cluster NGC 6791. The X-ray emissivity of Cr 261 is similar to that of other old open clusters, supporting the trend that they are more luminous in X-rays per unit mass than old populations of higher (globular clusters) and lower (the local neighborhood) stellar density. This implies that the dynamical destruction of binaries in the densest environments is not solely responsible for the observed differences in X-ray emissivity. Cr 261 was observed with the Advanced CCD Imaging Spectrometer (ACIS) on board Chandra starting 2009 November 9 14:50 UTC, for a total exposure time of 53.8 ks (ObsID 11308). The observation was made in Very Faint, Timed exposure mode, with a single frame exposure time of 3.2 s. Kharchenko et al. (2013, A&A, 558, A53) estimate that the radius of Cr 261 is ~ 14.1 arcminutes. This is considerably larger than a single ACIS chip (8 4 x 8 4 arcminute<sup>2</sup>) and therefore the authors placed the center of the cluster (J2000.0 RA = 12<sup>h</sup> 38<sup>m</sup> 06.0<sup>s</sup>, Dec = -68<sup>o</sup> 22' 01" according to Kharchenko et al. 2013) close to the I3 aimpoint so that a larger contiguous part of the cluster could be imaged (see Figure 1 in the reference paper). The CCDs used were I0, I1, I2, and I3 from the ACIS-I array, and S2 and S3 from the ACIS-S array. The authors limited the X-ray analysis to the data from chips I0, I1, I2, and I3. The S2 and S3 chips lie far from the I3 aimpoint, giving rise to large positional errors on any sources detected on them. Such large errors make it hard to identify optical counterparts, and thus to classify the sources. The authors retrieved optical images of Cr 261 in the B and V bands from the ESO public archive. These data were taken as part of the ESO Imaging Survey (EIS; program ID 164.O-0561). The observations of Cr 261 were made using the Wide Field Imager (WFI), mounted on the 2.2 m MPG/ESO telescope at La Silla, Chile. After correcting the X-ray source positions for the (almost negligible) boresight correction (0.06 =/- 0.07 arcseconds in RA and 0.09 +/- 0.08 arcseconds in Dec), the authors matched their X-ray source list with the entire optical source list, using 95% match radii. For 89 unique X-ray sources, they found 124 optical matches; of the latter, 104 are present in both the V and B images, while for 20 there is only a V or B detection. The authors also inspected the area around each X-ray source in the WFI images by eye, and discovered that five more X-ray sources have candidate optical counterparts that are saturated and therefore missing from their optical catalog. Finally, they added to the list of candidate counterparts six optical sources that lay just outside the 95% match radius, but inside the 3-sigma radius. In total, 98 of the 151 unique X-ray sources were thus matched to one or more optical sources. This HEASARC table contains the list of the 135 optical counterparts to 98 of the 151 X-ray sources from Table 2 of the reference paper. Information about the 151 X-ray sources is available in the HEASARC table CR261CXO (based on Table 1 of the reference paper) to which this current table has links. This table was created by the HEASARC in June 2017 primarily based upon the machine-readable version of Table 2 from the reference paper, the catalog of optical counterparts to Chandra sources in Cr 261, that was obtained from the ApJ web site. The information on the X-ray source positions was taken from the machine-readable version of Table 1 from the reference paper that was also obtained from the ApJ web site. This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/coll69oid
- Title:
- Collinder 69 Cluster Optical/IR Counterparts to XMM-Newton X-Ray Point Sources
- Short Name:
- COLL69OID
- Date:
- 09 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from the first paper of a series devoted to the Lambda Orionis star-forming region, Orion's Head, from the X-ray perspective. The final aim of this research is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. The authors aim to uncover the population of the central, young star cluster Collinder 69, and in particular to find those diskless Class III pre-main sequence objects which have not been identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association. The authors have combined two exposures taken with the XMM-Newton satellite with an exhaustive data set of optical, near- and mid-infrared photometry to assess the membership of the X-ray sources based on different color-color and color-magnitude diagrams, as well as other properties, such as effective temperatures, masses and bolometric luminosities derived from spectral energy distribution fitting and comparison with theoretical isochrones. The presence of circumstellar disks is discussed using mid-infrared photometry from the Spitzer Space Telescope. The authors searched for optical and IR counterparts for their X-ray detections, using a radius of 5.1 arcseconds. This search radius is motivated by the astrometry of XMM-Newton (~ 1-2 arcsec) and the statistical errors of the X-ray sources (<= 4 arcsecs). Multiple counterparts were found for several X-ray sources within their search radius. The visual inspection of all optical and IR images indicated that in a few cases there were additional possible counterparts even slightly beyond this search radius. In order to be as comprehensive as possible, the authors have also retained them. They compiled a master catalog with all sources that were present in at least one of the mappings (optical, near-IR or mid-IR) and extracted the photometry from these surveys. The photometry of all possible counterparts to X-ray sources is listed in this table. The reference sources for the optical and infrared magnitudes are discussed in Section 3 of the reference paper. In this table, they are coded as follows: <pre> Code Reference Source 1 = 2MASS Catalog, <a href="https://cdsarc.cds.unistra.fr/ftp/cats/II/246">CDS Cat. II/246</a> 2 = XMM-Newton Optical Monitor (XMM OM) 3 = Spitzer 4 = Omega 2000 Camera photometry in 2005 5 = CFHT1999 Survey 6 = Barrado y Navascues et al. (2004 ApJ, 610, 1064; 2007 ApJ, 664, 481) 7 = Dolan & Mathieu (1999 AJ, 118, 2409; 2001 AJ, 121, 2124) 8 = Dolan & Mathieu (2002 AJ, 123, 387) 9 = Omega 2000 Camera photometry in 2007 </pre> Thus, this table contains optical and infrared data, as well as membership information, on 205 possible counterparts to the 164 XMM-Newton X-ray sources detected in EPIC observations of the Collinder 69, East and West Fields (C69E and C69W), respectively, with maximum likelihood (ML) values > 15.0. A companion HEASARC Browse table COLL69XMM contains the X-ray data for these X-ray sources. This table was created by the HEASARC in July 2011 based on the electronic versions of Tables 5, 6, 8 and 9 from the reference paper which were obtained from the CDS (their catalog J/A+A/526/A21 files table5.dat, table6.dat, table8.dat and table9.dat). This is a service provided by NASA HEASARC .
- ID:
- ivo://nasa.heasarc/coll69xmm
- Title:
- Collinder 69 Cluster XMM-Newton X-Ray Point Source Catalog
- Short Name:
- COLL69XMM
- Date:
- 09 May 2025
- Publisher:
- NASA/GSFC HEASARC
- Description:
- This table contains some of the results from the first paper of a series devoted to the Lambda Orionis star-forming region, Orion's Head, from the X-ray perspective. The final aim of this research is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. The authors aim to uncover the population of the central, young star cluster Collinder 69, and in particular to find those diskless Class III pre-main sequence objects which have not been identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association. The authors have combined two exposures taken with the XMM-Newton satellite with an exhaustive data set of optical, near- and mid-infrared photometry to assess the membership of the X-ray sources based on different color-color and color-magnitude diagrams, as well as other properties, such as effective temperatures, masses and bolometric luminosities derived from spectral energy distribution fitting and comparison with theoretical isochrones. The presence of circumstellar disks is discussed using mid-infrared photometry from the Spitzer Space Telescope. This table contains the XMM-Newton X-ray point source catalog for all sources detected in the EPIC observations of the Collinder 69, East and West Fields (C69E and C69W), respectively, with maximum likelihood (ML) values > 15.0. A companion HEASARC Browse table COLL69OID contains optical and infrared data as well as membership information on counterparts to these X-ray sources. This table was created by the HEASARC in July 2011 based on the electronic versions of Tables 3 and 4 from the reference paper which were obtained from the CDS (their catalog J/A+A/526/A21 files table3.dat and table4.dat). This is a service provided by NASA HEASARC .
- ID:
- ivo://CDS.VizieR/J/A+A/418/525
- Title:
- Collinder 232 & Trumpler 14/16 UBVRI photometry
- Short Name:
- J/A+A/418/525
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present and analyze new CCD UBVRI photometry down to V~21 in the region of the young open cluster Collinder 232, located in the Carina spiral arm, and discuss its relationship to Trumpler 14 and Trumpler 16, the two most prominent young open clusters located in the core of NGC 3372 (the Carina Nebula).
- ID:
- ivo://CDS.VizieR/J/A+A/536/A63
- Title:
- Collinder 69 very low mass stars and brown dwarfs
- Short Name:
- J/A+A/536/A63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have studied age dependent features in optical and near-infrared spectra of candidate members to the cluster (such as alkali lines and accretion associated indicators). In addition, we have complemented that study with the analysis of other youth indicators like X-ray emission or mid-infrared excess. We have confirmed the membership to Collinder 69 of ~90 photometric candidate members. As a byproduct we have determined a temperature scale for young M, very low-mass stars and brown dwarfs. We have assembled one of the most complete Initial Mass Functions from 0.016 to 20M_{sun}_. And, finally, we have studied the implications of the spatial distribution of the confirmed members on the proposed mechanisms of brown dwarfs formation.
- ID:
- ivo://CDS.VizieR/J/A+A/526/A21
- Title:
- Collinder 69 X-ray sources
- Short Name:
- J/A+A/526/A21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This is the first paper of a series devoted to the {lambda} Orionis star-forming region, Orion's Head, from the X-ray perspective. Our final aim is to provide a comprehensive view of this complex region, which includes several distinct associations and dark clouds. We aim to uncover the population of the central, young star cluster Collinder 69, and in particular those diskless Class III objects not identified by previous surveys based on near- and mid-infrared searches, and to establish the X-ray luminosity function for the association.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A121
- Title:
- Collisional effects in blue wing of Balmer-alpha
- Short Name:
- J/A+A/657/A121
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In order to investigate the near wing of the Lyman-{alpha} line, accurate line profile calculations and molecular data are both required due to the existence of a close line satellite responsible for its asymmetrical shape. Lyman-{alpha} lines observed with the Cosmic Origin Spectograph (COS) on the Hubble Space Telescope (HST) show this peculiarity in the spectra of DBA and DA white dwarf stars. A similar asymmetrical shape in the blue wing can be predicted in the Balmer-{alpha} line of H perturbed by He and H atoms. In continuation with a very recent work on the Lyman-{alpha} line, where the n = 2 potential energies and transition dipole moments from the ground state were determined, we present new accurate H-He potential energies and electronic transition dipole moments involving the molecular states correlated with H(n=3)+He and their transition dipole moments with the states correlated with H(n=2)+He. Those new data and existing molecular data for H(n=2,3)-H are used to provide a theoretical investigation of the collisional effects in the blue wing of the Balmer-{alpha} line of H perturbed by He and H atoms. We note the consequences for the Balmer-{alpha} line shape in the physical conditions found in the cool atmosphere of DZA white dwarfs where helium densities may be as high as 10^21^cm^-3^. This study is undertaken with a unified theory of spectral line broadening valid at very high helium densities.
- ID:
- ivo://CDS.VizieR/J/A+A/531/A103
- Title:
- Collisional excitation of sulfur dioxide
- Short Name:
- J/A+A/531/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present collisional rate coefficients for SO_2_ with ortho and para molecular hydrogen for the physical conditions prevailing in dark molecular clouds. Rate coefficients for the first 31 rotational levels of this species (energies up to 55K) and for temperatures between 5 and 30K are provided. We have found that these rate coefficients are about ten times more than those previously computed for SO_2_ with helium. We calculated the expected emission of the centimeter wavelength lines of SO_2_. We find that the transition connecting the metastable 2_02_ level with the 111 one is in absorption against the cosmic background for a wide range of densities. The 4_04_-3_13_ line is found to be inverted for densities below a few 10^4^cm^-3^. We observed the 1_11_-2_02_ transition with the 100m Green Bank Telescope towards some dark clouds. The line is observed, as expected, in absorption and provides an abundance of SO_2_ in these objects of a few 10^-10^. The potential use of millimeter lines of SO_2_ as tracers of the physical conditions of dark clouds is discussed.
