- ID:
- ivo://CDS.VizieR/J/AJ/130/2212
- Title:
- X-ray and NIR studies of L1448
- Short Name:
- J/AJ/130/2212
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of X-ray and near-infrared (NIR) observations of L1448, a star-forming region in the Perseus cloud complex using the Chandra X-Ray Observatory and the 4m telescope at the Kitt Peak National Observatory. We detect 72 X-ray sources in a ~17'x17' region with a 68 ks ACIS exposure down to the X-ray flux limit of ~10^-15^ergs/s/cm2 (0.5-8keV), for which we conduct follow-up NIR imaging observations in a concentric ~11'x11' region with FLAMINGOS down to mi_Ks_~17mag. Twelve X-ray sources have NIR or optical counterparts.
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- ID:
- ivo://CDS.VizieR/J/A+A/539/A64
- Title:
- X-ray data for IC 348 young stars
- Short Name:
- J/A+A/539/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The physical origin of the strong magnetic activity in T Tauri stars and its relation to stellar rotation is not yet well-understood. We investigate the relation between the X-ray activity, rotation, and Rossby number for a sample of young stars in the ~3Myr old cluster IC 348. We use the data of four Chandra observations of IC 348 to derive the X-ray luminosities of the young stars. Basic stellar parameters and rotation rates are collected from the literature. This results in a sample of 82 X-ray detected stars with known rotation periods. We determine the Rossby numbers (i.e. the ratio of rotation period to convective turnover time) of 76 of these stars from stellar structure- and evolution-models for pre-main sequence stars.
- ID:
- ivo://CDS.VizieR/J/A+A/625/A66
- Title:
- X-ray data for 56 protoplanetary disk sources
- Short Name:
- J/A+A/625/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Consistent modeling of protoplanetary disks requires the simultaneous solution of both continuum and line radiative transfer, heating and cooling balance between dust and gas and, of course, chemistry. Such models depend on panchromatic observations that can provide a complete description of the physical and chemical properties and energy balance of protoplanetary systems. Along these lines we present a homogeneous, panchromatic collection of data on a sample of 85 T Tauri and Herbig Ae objects for which data cover a range from X-rays to centimeter wavelengths. Datasets consist of photometric measurements, spectra, along with results from the data analysis such as line fluxes from atomic and molecular transitions. Additional properties resulting from modeling of the sources such as disc mass and shape parameters, dust size and PAH properties are also provided for completeness. The purpose of this data collection is to provide a solid base that can enable consistent modeling of the properties of protoplan- etary disks. To this end, we performed an unbiased collection of publicly available data that were combined to homogeneous datasets adopting consistent criteria. Targets were selected based on both their properties but also on the availability of data. Data from more than 50 different telescopes and facilities were retrieved and combined in homogeneous datasets directly from public data archives or after being extracted from more than 100 published articles. X-ray data for a subset of 56 sources represent an exception as they were reduced from scratch and are presented here for the first time. Compiled datasets along with a subset of continuum and emission-line models are stored in a dedicated database and distributed through a publicly accessible online system. All datasets contain metadata descriptors that allow to backtrack them to their original resources. The graphical user interface of the online system allows the user to visually inspect individual objects but also compare between datasets and models. It also offers to the user the possibility to download any of the stored data and metadata for further processing.
- ID:
- ivo://CDS.VizieR/J/ApJS/160/450
- Title:
- X-ray emission in Orion Nebula young stars
- Short Name:
- J/ApJS/160/450
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the spatial distribution of X-ray-emitting plasma in a sample of young Orion Nebula Cluster stars by modulation of their X-ray light curves due to stellar rotation. The study, part of the Chandra Orion Ultradeep Project (COUP, Cat. <J/ApJS/160/319>), is made possible by the exceptional length of the observation: 10 days of ACIS integration during a time span of 13 days, yielding a total of 1616 detected sources in the 17'x17' field of view. We here focus on a subsample of 233 X-ray-bright stars with known rotational periods. We search for X-ray modulation using the Lomb Normalized Periodogram method.
- ID:
- ivo://CDS.VizieR/J/A+A/454/595
- Title:
- X-ray emission of T Tau stars in Lupus 3
- Short Name:
- J/A+A/454/595
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- I present analysis results of an XMM-Newton observation of the Lupus 3 region that contains a high proportion of young low mass T Tauri stars in the Lupus star-forming complex. The detection of X-ray sources in 0.5 to 4.5-keV images of the Lupus 3 core was performed using the standard source detection method of the XMM-Newton Science Analysis Software. One hundred and two candidate X-ray sources were detected in the 30-arcmin diameter field-of-view of the EPIC cameras, of which 25 have visible or near-IR counterparts that are known as pre-main sequence stars.
- ID:
- ivo://CDS.VizieR/J/A+A/474/495
- Title:
- X-ray flares from Cygnus OB2 young stars
- Short Name:
- J/A+A/474/495
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We characterize individual and ensemble properties of X-ray flares from stars in the Cygnus OB2 and ONC star-forming regions. We analyzed X-ray light-curves of 1003 Cygnus OB2 sources observed with Chandra for 100ks and of 1616 ONC sources detected in the "Chandra Orion Ultra-deep Project" 850ks observation. We employed a binning-free maximum likelihood method to segment the light-curves into intervals of constants signal and identified flares on the basis of both the amplitude and the time-derivative of the source luminosity. We then derived and compared the flare frequency and energy distribution of Cygnus OB2 and ONC sources. The effect of the length of the observation on these results was investigated by repeating the statistical analysis on five 100ks-long segments extracted from the ONC data.
- ID:
- ivo://CDS.VizieR/J/ApJ/688/418
- Title:
- X-ray flares in Orion young stars. I.
- Short Name:
- J/ApJ/688/418
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Pre-main-sequence (PMS) stars are known to produce powerful X-ray flares, which resemble magnetic reconnection solar flares scaled by factors up to 104. However, there are numerous puzzles, including the structure of X-ray-emitting coronae and magnetospheres, the effects of protoplanetary disks, and the effects of stellar rotation. To investigate these issues in detail, we examine 216 of the brightest flares from 161 PMS stars observed in the Chandra Orion Ultradeep Project (COUP, Getman et al. Cat. J/ApJS/160/319). The current study (Paper I) examines the flare morphologies, and provides a general comparison of COUP flare characteristics with those of other active X-ray stars and the Sun.
- 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.
- 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.
