- ID:
- ivo://CDS.VizieR/J/ApJ/567/423
- Title:
- CHANDRA obs. of YSOs in Monoceros R2
- Short Name:
- J/ApJ/567/423
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observed the Monoceros R2 molecular cloud with the ACIS-I array on board the Chandra X-Ray Observatory. From the central 3.2'x3.2' region, we detect 154 sources above the detection limit of ~5x10^-16^erg/s/cm^2^ with a 100ks exposure. About 85% of the X-ray sources are identified with an infrared counterpart, including four high-mass stars in the zero-age main-sequence (ZAMS) and/or premain-sequence (PMS) phase. The X-ray spectra of the high-mass ZAMS and PMS stars are represented by a thin thermal plasma model of a temperature above ~2keV. The X-rays are time variable and exhibit rapid flares. This high-temperature plasma and flaring activity is similar to that seen in low-mass PMS stars and is contrary to the behavior observed in high-mass main-sequence stars.The X-ray luminosity increases as the intrinsic K-band flux increases. However, the X-ray luminosity saturates at a level of ~10^31^erg/s. We conclude that high-mass ZAMS and PMS stars emit X-rays, possibly because of magnetic activity such as that of low-mass stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/566/974
- Title:
- CHANDRA obs. of YSOs in OMC-2 and OMC-3
- Short Name:
- J/ApJ/566/974
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report X-ray results of the Chandra observation of OMC-2 and OMC-3. A deep exposure of ~100ks detects ~400 X-ray sources in the field of view of the ACIS array, providing one of the largest X-ray catalogs in a star-forming region. Coherent studies of the source detection, time variability, and energy spectra are performed. We classify the X-ray sources into Class I, Class II, and Class III+MS based on the J-, H-, and K-band colors of their near-infrared counterparts and discuss the X-ray properties (temperature, absorption, and time variability) along these evolutionary phases.
- ID:
- ivo://CDS.VizieR/J/AJ/128/787
- Title:
- Chandra Orion flanking fields data
- Short Name:
- J/AJ/128/787
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of Chandra observations of two flanking fields (FFs) in Orion, outside the Orion Nebula Cluster (ONC). We present a catalog of 417 sources, which includes X-ray luminosity, optical and infrared photometry, and X-ray variability information.
- ID:
- ivo://CDS.VizieR/J/ApJS/239/13
- Title:
- Chandra PHAT X-ray catalog of the M31 disk
- Short Name:
- J/ApJS/239/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The X-ray source populations within galaxies are typically difficult to identify and classify with X-ray data alone. We are able to break through this barrier by combining deep new Chandra ACIS-I observations with extensive Hubble Space Telescope (HST) imaging from the Panchromatic Hubble Andromeda Treasury of the M31 disk. We detect 373 X-ray sources down to 0.35-8.0keV flux of 10^-15^erg/cm^-2^/s over 0.4deg^2^, 170 of which are reported for the first time. We identify optical counterpart candidates for 188 of the 373 sources, after using the HST data to correct the absolute astrometry of our Chandra imaging to 0.1". While 58 of these 188 are associated with point sources potentially in M31, over half (107) of the counterpart candidates are extended background galaxies, 5 are star clusters, 12 are foreground stars, and 6 are supernova remnants. Sources with no clear counterpart candidate are most likely to be undetected background galaxies and low-mass X-ray binaries in M31. The hardest sources in the 1-8keV band tend to be matched to background galaxies. The 58 point sources that are not consistent with foreground stars are bright enough that they could be high-mass stars in M31; however, all but 8 have optical colors inconsistent with single stars, suggesting that many could be background galaxies or binary counterparts. For point-like counterparts, we examine the star formation history of the surrounding stellar populations to look for a young component that could be associated with a high-mass X-ray binary. About one-third of the point sources are not physically associated with a young population, and are therefore more likely to be background galaxies. For the 40 point-like counterpart candidates associated with young populations, we find that their age distribution has two peaks at 15-20Myr and 40-50Myr. If we only consider the 8 counterpart candidates with typical high-mass main-sequence optical star colors, their age distribution peaks mimic those of the sample of 40. Finally, we find that intrinsic faintness, and not extinction, is the main limitation for finding further counterpart candidates.
- ID:
- ivo://CDS.VizieR/J/A+A/462/449
- Title:
- Chandra point-source counts in galaxy cluster
- Short Name:
- J/A+A/462/449
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- With the superb angular resolution of the Chandra Observatory, it is now possible to detect X-ray point sources, either embedded in galaxy clusters or along the cluster line of sight, which could not be resolved by previous instruments. This now allows studies of source counts in distant cluster fields. We want to analyze the inner region of clusters of galaxies to check for the presence of any over-density of X-ray point sources embedded in the gas diffuse emission. These point sources are possible AGN belonging to the clusters and could contaminate the cluster emission. We used a sample of 18 distant (0.25<z<1.01) galaxy clusters from the Chandra archive to construct the logN-logS, in both the soft and hard energy bands, for the X-ray point sources detected in the central cluster region to be compared with the counts of point sources detected in similarly deep fields without clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/383/330
- Title:
- Chandra Small Magellanic Cloud Wing Survey
- Short Name:
- J/MNRAS/383/330
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have detected 523 sources in a survey of the Small Magellanic Cloud (SMC) Wing with Chandra. By cross-correlating the X-ray data with optical and near-infrared catalogues, we have found 300 matches. Using a technique that combines X-ray colours and X-ray to optical flux ratios, we have been able to assign preliminary classifications to 265 of the objects. Our identifications include four pulsars, one high-mass X-ray binary (HMXB) candidate, 34 stars and 185 active galactic nuclei (AGN). In addition, we have classified 32 sources as hard AGN which are likely absorbed by local gas and dust, and nine soft AGN whose nature is still unclear. Considering the abundance of HMXBs discovered so far in the Bar of the SMC the number that we have detected in the Wing is low.
- ID:
- ivo://CDS.VizieR/J/ApJ/716/1217
- Title:
- Chandra SMC deep field sources
- Short Name:
- J/ApJ/716/1217
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a pair of 100ks Chandra observations in the Small Magellanic Cloud (SMC) to survey high-mass X-ray binaries (HMXBs), stars, and low-mass X-ray binaries (LMXBs)/cataclysmic variables down to L_x_=4.3x10^32^erg/s. The two SMC Deep Fields (DFs) are located in the most active star-forming region of the bar, with Deep Field-1 positioned at the most pulsar-rich location identified from previous surveys. Two new pulsars were discovered in the outburst: CXOU J004929.7-731058 (P=892s), CXOU J005252.2-721715 (P=326s), and three new HMXB candidates were identified. Of the 15 Be-pulsars now known in the field, 13 were detected, with pulsations seen in 9 of them. Bright optical counterparts exist for 40 of the X-ray sources, of which 33 are consistent with early-type stars (M_V_<-2, B-V<0.2), and are the subject of a companion paper. The results point to an underlying HMXB population density up to double that of active systems. The full catalog of 394 point sources is presented along with detailed analyses of timing and spectral properties.
- ID:
- ivo://CDS.VizieR/J/ApJS/166/211
- Title:
- Chandra sources in Antennae galaxies, NGC 4038/39
- Short Name:
- J/ApJS/166/211
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the properties of the discrete X-ray sources detected in our monitoring survey of the Antennae galaxies with Chandra ACIS-S. We detect ~70 sources down to a typical luminosity of 7x10^37^ergs/s in each of the six monitoring observations. In the co-added observation (which has a total exposure of 411ks) we detect a total of 120 sources down to a luminosity of (2-5)x10^37^ergs/s, depending on the local background. Fifteen sources have a strong extended component. Fourteen of the pointlike sources have luminosities above 10^39^ergs/s, at least in one exposure, which qualifies them as ultraluminous X-ray sources (ULXs). Ten of the ULXs show long-term variability, while one is observed only once, suggesting that it is a transient source. We find that 25 sources exhibit long-term variability clearly associating them with accreting compact objects. Twenty-one sources also show spectral variability. However, their variability patterns are diverse, indicating that they belong to different source classes. Finally, we find a weak excess of hard sources at the low luminosities that we tentatively associate with pulsar X-ray binaries.
- ID:
- ivo://CDS.VizieR/J/ApJ/614/267
- Title:
- Chandra sources in Cha I North
- Short Name:
- J/ApJ/614/267
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Sensitive X-ray imaging surveys provide a new and effective tool to establish the census of pre-main-sequence (PMS) stars in nearby young stellar clusters. We report here a deep Chandra X-Ray Observatory observation of PMS stars in the Chamaeleon I North cloud, achieving a limiting luminosity of log L_t_~27ergs/s (0.5-8keV band) in a 0.8x0.8pc^2^ region. Of the 107 X-ray sources, 37 are associated with Galactic stars of which 27 are previously recognized cloud members.
- ID:
- ivo://CDS.VizieR/J/ApJS/165/173
- Title:
- Chandra sources in Galaxy central 150pc
- Short Name:
- J/ApJS/165/173
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the catalog of X-ray sources detected in a shallow Chandra survey of the inner 2{deg}x0.8{deg} of the Galaxy and in two deeper observations of the Radio Arches and Sgr B2. The catalog contains 1352 objects that are highly absorbed (NH>~4x10^22^cm^-2^) and are therefore likely to lie near the Galactic center (D~8kpc), and 549 less absorbed sources that lie within 6kpc of Earth.
