- ID:
- ivo://CDS.VizieR/J/AJ/162/153
- Title:
- X-ray properties of A,B-types, T-Tauri stars & YSOs
- Short Name:
- J/AJ/162/153
- Date:
- 15 Mar 2022
- Publisher:
- CDS
- Description:
- We use X-ray and infrared observations to study the properties of three classes of young stars in the Carina Nebula: intermediate-mass (2-5M{sun}) pre-main-sequence stars (IMPS; i.e., intermediate-mass T Tauri stars), late-B and A stars on the zero-age main sequence (AB), and lower-mass T Tauri stars (TTS). We divide our sources among these three subclassifications and further identify disk-bearing young stellar objects versus diskless sources with no detectable infrared (IR) excess emission using IR (1-8{mu}m) spectral energy distribution modeling. We then perform X-ray spectral fitting to determine the hydrogen-absorbing column density (N_H_), absorption-corrected X-ray luminosity (L_X_), and coronal plasma temperature (kT) for each source. We find that the X-ray spectra of both IMPS and TTS are characterized by similar kT and N_H_, and on average L_X_/L_bol_~4x10^-4^. IMPS are systematically more luminous in X-rays (by ~0.3dex) than all other subclassifications, with median L_X_=2.5x10^31^erg/s, while AB stars of similar masses have X-ray emission consistent with TTS companions. These lines of evidence converge on a magnetocoronal flaring source for IMPS X-ray emission, a scaled-up version of the TTS emission mechanism. IMPS therefore provide powerful probes of isochronal ages for the first ~10Myr in the evolution of a massive stellar population, because their intrinsic, coronal X-ray emission decays rapidly after they commence evolving along radiative tracks. We suggest that the most luminous (in both X-rays and IR) IMPS could be used to place empirical constraints on the location of the intermediate-mass stellar birth line.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/477/593
- Title:
- X-ray properties of Carina OB1 association
- Short Name:
- J/A+A/477/593
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- X-ray properties of the stellar population in the Carina OB1 association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding the nature of X-ray formation mechanisms in the winds of single and binary early-type stars. A timing and spectral analysis of five observations with XMM-Newton is performed using various statistical tests and thermal spectral models. 235 point sources have been detected within the field of view. Several of these sources are probably pre-main sequence stars with characteristic short-term variability. Seven sources are possible background AGNs. Spectral analysis of twenty three sources of type OB and WR 25 was performed. We derived spectral parameters of the sources and their fluxes in three energy bands. Estimating the interstellar absorption for every source and the distance to the nebula, we derived X-ray luminosities of these stars and compared them to their bolometric luminosities. We discuss possible reasons for the fact that, on average, the observed X-ray properties of binary and single early type stars are not very different, and give several possible explanations.
- ID:
- ivo://CDS.VizieR/J/A+A/475/959
- Title:
- X-ray properties of young stellar objects
- Short Name:
- J/A+A/475/959
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To study the X-ray properties of young stellar objects (YSOs), we analyze an exceptionally sensitive Chandra dataset of the Coronet cluster in the CrA star-forming region, achieving a limiting luminosity of L_X,min_~5x10^26^erg/s for lightly absorbed sources. This dataset represents one of the most sensitive X-ray observations ever obtained of a star-forming region. The X-ray data are used to investigate the membership status of tentative members of the region, to derive plasma temperatures and X-ray luminosities of the YSOs, and to investigate variability on the timescale of several years. 46 of the 92 X-ray sources in the merged Chandra image can be identified with optical or near/mid-infrared counterparts. X-ray emission is detected from all of the previously known optically visible late-type (spectral types G to M) stellar cluster members, from five of the eight brown dwarf candidates, and from nine embedded objects ("protostars") with class 0, class I, or flat-spectrum spectral-energy distributions (SEDs) in the field of view. While the Herbig Ae/Be stars TY CrA and R CrA, a close companion of the B9e star HD 176386, and the F0e star T CrA are detected, no X-ray emission is found from any of the Herbig-Haro (HH) objects or the protostellar cores without infrared source. We find indications for diffuse X-ray emission near R CrA/IRS 7.
- ID:
- ivo://CDS.VizieR/J/ApJ/562/446
- Title:
- X-rays and protostars in Trifid nebula
- Short Name:
- J/ApJ/562/446
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Trifid Nebula is a young HII region, recently rediscovered as a "pre-Orion" star-forming region, containing protostars undergoing violent mass ejections visible in optical jets as seen in images from the Infrared Space Observatory and the Hubble Space Telescope. We report the first X-ray observations of the Trifid Nebula using ROSAT and ASCA. The ROSAT image shows a dozen X-ray sources, with the brightest X-ray source being the O7 star, HD 164492, which provides most of the ionization in the nebula. We also identify 85 T Tauri star and young, massive star candidates from near-infrared colors using the JHKs color-color diagram from the Two-Micron All-Sky Survey (2MASS). Ten X-ray sources have counterpart near-infrared sources. The 2MASS stars and X-ray sources suggest there are potentially numerous protostars in the young HII region of the Trifid. ASCA moderate-resolution spectroscopy of the brightest source shows hard emission up to 10keV with a clearly detected FeK line.
- ID:
- ivo://CDS.VizieR/J/ApJ/605/259
- Title:
- X-rays from HH 80/81 complex
- Short Name:
- J/ApJ/605/259
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report detections of X-rays from HH 80 and HH 81 with the ACIS instrument on the Chandra X-Ray Observatory. These are among the most luminous Herbig-Haro (HH) sources in the optical, and they are now the most luminous known in X-rays. These X-rays arise from the strong shocks that occur when the southern extension of this bipolar outflow slams into the ambient material. We imaged the central region of the bipolar flow revealing a complex of X-ray sources, including one near but not coincident with the putative power source in the radio and infrared.
- ID:
- ivo://CDS.VizieR/J/ApJ/584/911
- Title:
- X-rays in the Orion nebula cluster
- Short Name:
- J/ApJ/584/911
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A recent observation of the Orion Nebula Cluster with the ACIS instrument on board the Chandra X-Ray Observatory detected 1075 sources, 525 of which are pre-main-sequence (PMS) stars with measured bulk properties such as bolometric luminosities, masses, ages, and disk indicators. Nearly half of these stars have photometrically measured rotational periods. This provides a uniquely large and well-defined sample to study the dependence of magnetic activity on bulk properties for stars descending the Hayashi tracks.
- ID:
- ivo://CDS.VizieR/J/ApJS/168/100
- Title:
- X-ray study of star-forming region NGC 6357
- Short Name:
- J/ApJS/168/100
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first high spatial resolution X-ray study of the massive star-forming region NGC 6357, obtained in a 38ks Chandra/ACIS observation. Inside the brightest constituent of this large HII region complex is the massive open cluster Pismis 24. It contains two of the brightest and bluest stars known, yet remains poorly studied; only a handful of optically bright stellar members have been identified. We investigate the cluster extent and initial mass function and detect ~800 X-ray sources with a limiting sensitivity of ~10^30^ergs/s; this provides the first reliable probe of the rich intermediate-mass and low-mass population of this massive cluster, increasing the number of known members from optical study by a factor of ~50.
- ID:
- ivo://CDS.VizieR/J/A+A/596/A82
- Title:
- X-ray study of the young cluster NGC6231
- Short Name:
- J/A+A/596/A82
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6231 is a massive young star cluster, near the center of the Sco OB1 association. While its OB members are well studied, its low-mass population has received little attention. We present high-spatial resolution Chandra ACIS-I X-ray data, where we detect 1613 point X-ray sources. Our main aim is to clarify global properties of NGC 6231 down to low masses through a detailed membership assessment, and to study the cluster stars' spatial distribution, the origin of their X-ray emission, the cluster age and formation history, and initial mass function. We use X-ray data, complemented by optical and IR data, to establish cluster membership. The spatial distribution of different stellar subgroups also provides highly significant constraints on cluster membership, as does the distribution of X-ray hardness. We perform spectral modelling of group-stacked X-ray source spectra.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A115
- Title:
- X-ray survey of NGC7000/IC5070
- Short Name:
- J/A+A/602/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first extensive X-ray study of the North-America and Pelican star-forming region (NGC7000/IC5070), 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. We 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 us to identify young stars in different stages of formation. Less than 30% of X-ray sources are identified with a previously known young star. We 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 X-ray properties such as spectrum 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 1-10Myrs. 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. We 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, we also determine the local optical-IR reddening law, and compute an updated reddening map of the entire region.
580. X-ray view of IC348
- ID:
- ivo://CDS.VizieR/J/A+A/537/A135
- Title:
- X-ray view of IC348
- Short Name:
- J/A+A/537/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- IC348 is a nearby (~310pc), young (~2-3Myr) open cluster with >300 members identified from optical and infrared observations. We study the properties of the coronae of the young low-mass stars in IC348 combining X-ray and optical/infrared data. The four existing Chandra observations of IC348 are merged, thus providing a deeper and spatially more complete X-ray view than previous X-ray studies of the cluster. We have compiled a comprehensive catalog of IC348 members taking into account recent updates to the cluster census. Our data collection comprises fundamental stellar parameters, infrared excess indicating the presence of disks, Halpha emission as a tracer of chromospheric emission or accretion and mass accretion rates. We have detected 290 X-ray sources in four merged Chandra exposures, of which 187 are associated with known cluster members corresponding to a detection rate of ~60% for the cluster members of IC348 identified in optical/infrared studies. According to the most recent spectral classification of IC348 members only four of the X-ray sources are brown dwarfs (spectral type M6 and later). The detection rate is highest for diskless Class III stars and increases with stellar mass. This may be explained with higher X-ray luminosities for higher mass and later evolutionary stage that is evident in the X-ray luminosity functions. In particular, we find that for the lowest examined masses (0.1-0.25 Msun) there is a difference between the X-ray luminosity functions of accreting and non-accreting stars (classified on the basis of their Halpha emission strength) as well as those of disk-bearing and diskless stars (classified on the basis of the slope of the spectral energy distribution). These differences disappear for higher masses. This is related to our finding that the Lx/Lbol ratio is non-constant across the mass/luminosity sequence of IC348 with a decrease towards lower luminosity stars. Our analysis of an analogous stellar sample in the Orion Nebula Cluster suggests that the decline of Lx/Lbol for young stars at the low-mass end of the stellar sequence is likely universal.
