- ID:
- ivo://CDS.VizieR/J/ApJ/672/914
- Title:
- HST photometry in NGC 346
- Short Name:
- J/ApJ/672/914
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the third part of our photometric study of the star-forming region NGC 346/N66 and its surrounding field in the Small Magellanic Cloud (SMC), we focus on the large number of low-mass pre-main-sequence (PMS) stars revealed by the Hubble Space Telescope observations with the Advanced Camera for Surveys. We investigate the origin of the observed broadening of the PMS population in the V-I,V color-magnitude diagram. The most likely explanations are either the presence of differential reddening or an age spread among the young stars.
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- ID:
- ivo://CDS.VizieR/J/ApJ/896/79
- Title:
- HST survey of ONC in H20 1.4um abs. band. I.
- Short Name:
- J/ApJ/896/79
- Date:
- 11 Mar 2022
- Publisher:
- CDS
- Description:
- In order to obtain a complete census of the stellar and substellar population, down to a few M_Jup_ in the ~1Myr old Orion Nebula Cluster, we used the infrared channel of the Wide Field Camera 3 of the Hubble Space Telescope with the F139M and F130N filters. These bandpasses correspond to the 1.4{mu}m H2O absorption feature and an adjacent line-free continuum region. Out of 4504 detected sources, 3352 (about 75%) appear fainter than m130=14 (Vega mag) in the F130N filter, a brightness corresponding to the hydrogen- burning limit mass (M~0.072M_{sun}_) at ~1Myr. Of these, however, only 742 sources have a negative F130M-F139N color index, indicative of the presence of H2O vapor in absorption, and can therefore be classified as bona fide M and L dwarfs, with effective temperatures T<~2850K at an assumed 1Myr cluster age. On our color-magnitude diagram (CMD), this population of sources with H2O absorption appears clearly distinct from the larger background population of highly reddened stars and galaxies with positive F130M-F139N color index and can be traced down to the sensitivity limit of our survey, m130~21.5, corresponding to a 1Myr old ~3M_Jup_ planetary-mass object under about 2mag of visual extinction. Theoretical models of the BT-Settl family predicting substellar isochrones of 1, 2, and 3 Myr down to ~1M_Jup_ fail to reproduce the observed H2O color index at M<~20M_Jup_. We perform a Bayesian analysis to determine extinction, mass, and effective temperature of each substellar member of our sample, together with its membership probability.
- ID:
- ivo://CDS.VizieR/J/ApJ/738/137
- Title:
- HST VI stars in Shapley Constellation III
- Short Name:
- J/ApJ/738/137
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our investigation of pre-main-sequence (PMS) stellar populations in the Large Magellanic Cloud (LMC) from imaging with Hubble Space Telescope Wide-Field Planetary Camera 2. Our targets of interest are four star-forming regions located at the periphery of the super-giant shell LMC 4 (Shapley Constellation III). The PMS stellar content of the regions is revealed through the differential Hess diagrams and the observed color-magnitude diagrams (CMDs). Further statistical analysis of stellar distributions along cross sections of the faint part of the CMDs allowed the quantitative assessment of the PMS stars census, and the isolation of faint PMS stars as the true low-mass stellar members of the regions. These distributions are found to be well represented by a double-Gaussian function, the first component of which represents the main-sequence field stars and the second the native PMS stars of each region. Based on this result, a cluster membership probability was assigned to each PMS star according to its CMD position. The higher extinction in the region LH 88 did not allow the unambiguous identification of its native stellar population. The CMD distributions of the PMS stars with the highest membership probability in the regions LH 60, LH 63, and LH 72 exhibit an extraordinary similarity among the regions, suggesting that these stars share common characteristics, as well as common recent star formation history. Considering that the regions are located at different areas of the edge of LMC 4, this finding suggests that star formation along the super-giant shell may have occurred almost simultaneously.
- ID:
- ivo://CDS.VizieR/J/AJ/116/1801
- Title:
- IC 4996 CCD photometry
- Short Name:
- J/AJ/116/1801
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of a UBV CCD photometric study of the cluster IC 4996 are presented. We obtain new values for the cluster parameters: E(B-V)=0.71+/-0.08, V_0_-M_V_=11.9+/-0.1, and age=(7.5+/-3)x10^6^yr. The combined evidence from the photometric diagrams suggests the presence of a number of premain-sequence (PMS) cluster members with spectral types ~A0 to F5. The interpretation of these objects as PMS candidates is further supported by independent results from CCD uvbyH{beta} observations. If confirmed, these stars would bridge the existing gap in the sample of PMS stars, between the coolest Herbig AeBe stars (HAeBe), and the hottest T Tauri stars. These PMS candidates are located some 0.5 and 1 mag above the main sequence in the V-(B-V) diagram, around the location of spectral types AF. This feature, together with their locations in the (U-B)-(B-V) diagram and the interpretation that they are PMS members, suggest an additional reddening law with a slope {alpha}=E(U-B)/E(B-V)~0.55, probably caused by circumstellar material.
- ID:
- ivo://CDS.VizieR/J/MNRAS/400/317
- Title:
- IC 4665 low-mass members
- Short Name:
- J/MNRAS/400/317
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used fibre spectroscopy to establish cluster membership and examine pre-main-sequence (PMS) lithium depletion for low-mass stars (spectral types F to M) in the sparse young (~30Myr) cluster IC 4665. We present a filtered candidate list of 40 stars that should contain 75 per cent of single cluster members with 11.5<V<18 in the central square degree of the cluster. Whilst F- and G-type stars in IC 4665 have depleted little or no lithium, the K- and early M-type stars have depleted more Li than expected when compared with similar stars in other clusters of known age. An empirical age estimate based on Li depletion among the late-type stars of IC 4665 would suggest that it is older than 100Myr.
- ID:
- ivo://CDS.VizieR/J/MNRAS/358/341
- Title:
- Ic photometry of IC 348
- Short Name:
- J/MNRAS/358/341
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a photometric study of I-band variability in the young cluster IC 348. The main purpose of the study was to identify periodic stars. In all, we find 50 periodic stars, of which 32 were previously unknown. For the first time in IC 348, we discover periods in significant numbers of lower-mass stars (M<0.25M_{sun}_) and classical T Tauri stars.
- ID:
- ivo://CDS.VizieR/J/AJ/161/206
- Title:
- Infrared imaging of new born cluster H72.97-69.39
- Short Name:
- J/AJ/161/206
- Date:
- 20 Jan 2022
- Publisher:
- CDS
- Description:
- Young massive clusters and super star clusters (SSCs) represent an extreme mode of star formation. Far-infrared imaging of the Magellanic Clouds has identified one potential embedded SSC, HSO-BMHERICC-J72.971176-69.391112 (H72.97-69.39 in short), in the southwest outskirts of the Large Magellanic Cloud. We present Gemini Flamingos 2 and GSAOI near-infrared imaging of a 3'x3' region around H72.97-69.39 in order to characterize the stellar content of the cluster. The stellar content is probed down to 1.5M{sun}. We find substantial dust extinction across the cluster region, extending up to A_K_ of 3. Deeply embedded stars are associated with ALMA-detected molecular gas suggesting that star formation is ongoing. The high spatial resolution of the GSAOI data allows identification of the central massive object associated with the ^13^CO ALMA observations and detection of fainter low-mass stars around the H30{alpha} ALMA source. The morphology of the molecular gas and the nebulosity from adjacent star formation suggest they have interacted covering a region of several parsecs. The total stellar content in the cluster is estimated from the intermediate and high-mass stellar content to be at least 10000M{sun}, less than R136 with up to 100000M{sun} within 4.7pc radius, but places it in the regime of an SSC. Based on the extinction determination of individual stars we estimate a molecular gas mass in the vicinity of H72.97-69.39 of 6600M{sun}, suggesting more star formation can be expected.
- ID:
- ivo://CDS.VizieR/J/other/NewA/44.1
- Title:
- Infrared photometric study of Herbig Ae/Be stars
- Short Name:
- J/other/NewA/44.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we collected almost all HAeBe stars known so far (253 sources in total) to photometrically study their infrared properties. The 2MASS, WISE, IRAS and AKARI data are employed to make analyses. It is shown from several two-color diagrams that from 1um to 60um infrared radiations from circumstellar disks with the power law distribution play a very important role for infrared excesses which are much larger than that for ordinary Be stars. In the WISE two-color diagram, (W2-W3) vs. (W1-W2), some sources show thermal emissions probably due to dust surrounded and enhanced PAH features at 3.3 and 11.3um. In the wavelength longer than 60um infrared radiations are not so influenced by the circumstellar disk, but mainly from the ISM surrounded.
- ID:
- ivo://CDS.VizieR/J/AJ/160/268
- Title:
- Infrared photometry of binaries in Orion OB1
- Short Name:
- J/AJ/160/268
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Statistics of low-mass pre-main-sequence binaries in the Orion OB1 association with separations ranging from 0.6" to 20" (220 to 7400au at 370pc) are studied using images from the VISTA Orion mini survey and astrometry from Gaia. The input sample based on the CVSO catalog contains 1137 stars of K and M spectral types (masses between 0.3 and 0.9M{odot}), 1021 of which are considered to be association members. There are 135 physical binary companions to these stars with mass ratios above ~0.13. The average companion fraction is 0.09{+/-}0.01 over 1.2 decades in separation, slightly less than, but still consistent with, the field. We found a difference between the Ori OB1a and OB1b groups, the latter being richer in binaries by a factor of 1.6{+/-}0.3. No overall dependence of the wide- binary frequency on the observed underlying stellar density is found, although in the Ori OB1a off-cloud population, these binaries seem to avoid dense clusters. The multiplicity rates in Ori OB1 and in sparse regions like Taurus differ significantly, hinting that binaries in the field may originate from a mixture of diverse populations.
- ID:
- ivo://CDS.VizieR/J/ApJ/573/366
- Title:
- Infrared photometry of Trapezium cluster
- Short Name:
- J/ApJ/573/366
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the results of a new multiepoch, multiwavelength, near-infrared census of the Trapezium cluster in Orion to construct and analyze the structure of its infrared (K-band) luminosity function. Specifically, we employ an improved set of model luminosity functions to derive this cluster's underlying initial mass function (IMF) across the entire range of mass from OB stars to substellar objects down to near the deuterium-burning limit. The observations were performed at FLWO (Fred Lawrence Whipple Observatory, Smithsonian Astrophysical Observatory), and ESO-NTT (European Southern Observatory, New Technology Telescope), between Dec. 1997 and Marche 2000 (see the "Table 5" section below)
