- ID:
- ivo://CDS.VizieR/J/ApJ/578/114
- Title:
- Chandra HRC source in M31
- Short Name:
- J/ApJ/578/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from a 47ks observation of the Andromeda galaxy, M31, using the High Resolution Camera of the Chandra X-Ray Observatory. We detect 142 point sources spanning 3 orders of magnitude in luminosity, from L_X_=2x10^35^ to 2x10^38^erg/s in the 0.1-10keV band. The X-ray source location accuracy is better than 1" in the central regions of the galaxy. One source lies within 1.3" of SN 1885 but does not coincide with the UV absorption feature identified as the supernova remnant.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/656/A117
- Title:
- Chandra J1030 Redshift identification
- Short Name:
- J/A+A/656/A117
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- We publicly release the spectroscopic and photometric redshift catalog of the sources detected with Chandra in the field of the z=6.3 quasar SDSS J1030+0525. This is currently the fifth deepest X-ray field, and reaches a 0.5-2keV flux limit f_0.5-2_=6x10^-17^erg/s/cm^2^. By using two independent methods, we measure a photometric redshift for 243 objects, while 123 (51%) sources also have a spectroscopic redshift, 110 of which coming from an INAF-Large Binocular Telescope (LBT) Strategic Program. We use the spectroscopic redshifts to determine the quality of the photometric ones, and find it in agreement with that of other X-ray surveys which used a similar number of photometric data-points. In particular, we measure a sample normalized median absolute deviation sigma_NMAD_=1.48xmedia(||z_phot_-z_spec_||/(1+z_spec_)=0.065. We use these new spectroscopic and photometric redshifts to study the properties of the Chandra J1030 field. We observe several peaks in our spectroscopic redshift distribution between z=0.15 and z=1.5, and find that the sources in each peak are often distributed across the whole Chandra field of view. This evidence confirms that X-ray selected AGN can efficiently track large-scale structures over physical scales of several Mpc. Finally, we computed the Chandra J1030 z>3 number counts: while the spectroscopic completeness at high-redshift of our sample is limited, our results point towards a potential source excess at z>=4, which we plan to either confirm or reject in the near future with dedicated spectroscopic campaigns.
- ID:
- ivo://CDS.VizieR/J/ApJS/197/24
- Title:
- Chandra large-scale extragalactic jets. I.
- Short Name:
- J/ApJS/197/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we report the first stages of an investigation into the X-ray properties of extragalactic jets (XJET project). Our approach is to subject all sources for which X-ray emission has been detected by Chandra to uniform reduction procedures. Using Chandra archival data for 106 such sources, we measure X-ray fluxes in three bands and compare these to radio fluxes. We discuss the sample, the reduction methods, and present first results for the ratio of X-ray to radio flux for jet knots and hotspots. In particular, we apply statistical tests to various distributions of key observational parameters to evaluate differences between the different classes of sources.
2364. Chandra LMXB in NGC 1332
- ID:
- ivo://CDS.VizieR/J/ApJ/612/848
- Title:
- Chandra LMXB in NGC 1332
- Short Name:
- J/ApJ/612/848
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chandra ACIS-S3 (Advanced CCD Imaging Spectrometer) observations of the nearby S0 galaxy NGC 1332 resolve much of the X-ray emission into 73 point sources, of which 37 lie within the D_25_ isophote.
2365. Chandra LMXB in NGC 4649
- ID:
- ivo://CDS.VizieR/J/ApJ/600/729
- Title:
- Chandra LMXB in NGC 4649
- Short Name:
- J/ApJ/600/729
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a Chandra X-ray observation of the X-ray bright E2 elliptical galaxy NGC 4649. In addition to bright diffuse emission, we resolve 165 discrete sources, most of which are presumably low-mass X-ray binaries. As found in previous studies, the luminosity function of the resolved sources is well-fitted by a broken power law. In NGC 4697 and NGC 1553, the break luminosity was comparable to the Eddington luminosity of a 1.4M_{sun}_ neutron star.
- ID:
- ivo://CDS.VizieR/J/ApJ/599/218
- Title:
- Chandra LMXB in NGC 4365 and NGC 4382
- Short Name:
- J/ApJ/599/218
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the Chandra X-Ray Observatory ACIS-S3 to image the X-ray-faint elliptical galaxy NGC 4365 and lenticular galaxy NGC 4382. The observations resolve much of the X-ray emission into 99 and 58 sources, respectively, most of which are low-mass X-ray binaries (LMXBs) associated with each of the galaxies. Within one effective radius of NGC 4365, about 45% of the counts are resolved into sources, 30% are attributed to unresolved LMXBs, and 25% are attributed to diffuse gas. Within two effective radii of NGC 4382, about 22% of the counts are resolved into sources, 33% are attributed to unresolved LMXBs, and 45% are attributed to diffuse gas. We identify 18 out of the 37 X-ray sources in a central field in NGC 4365 with globular clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/150/94
- Title:
- Chandra Local Volume Survey. I.
- Short Name:
- J/AJ/150/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present comprehensive X-ray point source catalogs of NGC55, NGC2403, and NGC4214 as part of the Chandra Local Volume Survey. The combined archival observations have effective exposure times of 56.5ks, 190ks, and 79ks for NGC55, NGC2403, and NGC4214, respectively. When combined with our published catalogs for NGC300 and NGC404, our survey contains 629 X-ray sources total down to a limiting unabsorbed luminosity of ~5x10^35^erg/s in the 0.35-8keV band in each of the five galaxies. We present X-ray hardness ratios, spectral analysis, radial source distributions, and an analysis of the temporal variability for the X-ray sources detected at high significance. To constrain the nature of each X-ray source, we carried out cross-correlations with multi-wavelength data sets. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections to provide preliminary classifications for each X-ray source as a likely X-ray binary, background active galactic nucleus, supernova remnant, or foreground star.
- ID:
- ivo://CDS.VizieR/J/ApJ/763/128
- Title:
- Chandra Local Volume Survey: NGC 404 sources
- Short Name:
- J/ApJ/763/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive X-ray point-source catalog of NGC 404 obtained as part of the Chandra Local Volume Survey. A new 97ks Chandra ACIS-S observation of NGC 404 was combined with archival observations for a total exposure of ~123ks. Our survey yields 74 highly significant X-ray point sources and is sensitive to a limiting unabsorbed luminosity of ~6x10^35^erg/s in the 0.35-8keV band. To constrain the nature of each X-ray source, cross-correlations with multi-wavelength data were generated. We searched overlapping Hubble Space Telescope observations for optical counterparts to our X-ray detections, but find only two X-ray sources with candidate optical counterparts. We find 21 likely low-mass X-ray binaries (LMXBs), although this number is a lower limit due to the difficulties in separating LMXBs from background active galactic nuclei. The X-ray luminosity functions (XLFs) in both the soft and hard energy bands are presented. The XLFs in the soft band (0.5-2keV) and the hard band (2-8keV) have a limiting luminosity at the 90% completeness limit of 10^35^erg/s and 10^36^erg/s, respectively, significantly lower than previous X-ray studies of NGC 404. We find the XLFs to be consistent with those of other X-ray populations dominated by LMXBs. However, the number of luminous (>10^37^erg/s) X-ray sources per unit stellar mass in NGC 404 is lower than is observed for other galaxies. The relative lack of luminous XRBs may be due to a population of LMXBs with main-sequence companions formed during an epoch of elevated star formation ~0.5Gyr ago.
- ID:
- ivo://CDS.VizieR/J/ApJ/643/238
- Title:
- Chandra/2MASS sources in Cygnus OB2
- Short Name:
- J/ApJ/643/238
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A 50ks Chandra observation of the unidentified TeV source in Cygnus reported by the HEGRA collaboration reveals no obvious diffuse X-ray counterpart. However, 240 point-like X-ray sources are detected within or nearby the extended TeV J2032+4130 source region, of which at least 36 are massive stars and two may be radio emitters. That the HEGRA source is a composite, having as a counterpart the multiple point-like X-ray sources we observe, cannot be ruled out. Indeed, the distribution of point-like X-ray sources appears nonuniform and concentrated broadly within the extent of the TeV source region. We offer a hypothesis for the origin of the very high energy gamma-ray emission in Cyg OB2 based on the local acceleration of TeV-range cosmic rays and the differential distribution of OB versus less massive stars in this association.
- ID:
- ivo://CDS.VizieR/J/ApJ/879/112
- Title:
- Chandra multi-epoch study of the spiral gal. NGC7331
- Short Name:
- J/ApJ/879/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray point sources in galaxies are dominated by X-ray binaries (XRBs) that are variables or transients, and whether their variability would alter the X-ray luminosity functions (XLFs) is still in debate. Here we report on NGC 7331 as an example to test this with seven Chandra observations. Their detection limit is 7x10^37^erg/s in the energy range 0.3-8.0keV by assuming a power-law (PL) spectral model with a photon index of 1.7. We detected 55 X-ray sources. Thirteen of them are variables, of which three are transients, and some of the sources possess a bimodal feature in their luminosity-hardness ratio, which is often observed among XRBs. Nine more ultraluminous X-ray sources are found in comparison with previous studies and eight are likely to be low-mass or high-mass XRBs. Twenty-one optical counterpart candidates are found based on the Hubble Space Telescope images, but we cannot rule out the possibility of positional coincidence. The spectral analysis of SN 2014C shows a trend of increasing soft photons and decreasing hydrogen column densities as its outer shell expands. We fit the seven incompleteness-corrected XLFs to both a PL and a PL with an exponential cut-off (PLC) model using the Bayesian method, which is used for the first time in XLF fitting. The hierarchical PLC model can describe the XLF of NGC 7331 best with a slope of ~0.5 and a luminosity cut-off around 8x10^38^erg/s. This study proves that multi-epoch observations decrease the deviation due to the variable luminous sources in XLFs.
