- ID:
- ivo://CDS.VizieR/J/ApJ/575/354
- Title:
- Young stellar objects in the NGC 1333
- Short Name:
- J/ApJ/575/354
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 1333, a highly active star formation region within the Perseus molecular cloud complex, has been observed with the ACIS-I detector on board the Chandra X-Ray Observatory. In our image with a sensitivity limit of ~19^28^erg/s, we detect 127 X-ray sources, most with subarcsecond positional accuracy. While 32 of these sources appear to be foreground stars and extragalactic background, 95 X-ray sources are Identified with known cluster members.
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- ID:
- ivo://CDS.VizieR/J/ApJ/878/7
- Title:
- 2yr obs. of JHK variability of stars in Tr37
- Short Name:
- J/ApJ/878/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have monitored nearly a square degree in IC 1396A/Tr 37 over 21 epochs extending over 2014-2016 for sources variable in the JHK bands. In our data, 65%+/-8% of previously identified cluster members show variations, compared with <=0.3% of field stars. We identify 119 members of Tr 37 on the basis of variability, forming an unbiased sample down to the brown dwarf regime. The K-band luminosity function in Tr 37 is similar to that of IC 348 but shifted to somewhat brighter values, implying that the K- and M-type members of Tr 37 are younger than those in IC 348. We introduce methods to classify the causes of variability, based on behavior in the color-color and color-magnitude diagrams. Accretion hot spots cause larger variations at J than at K with substantial scatter in the diagrams; there are at least a dozen, with the most active resembling EXors. Eleven sources are probably dominated by intervention of dust clumps in their circumstellar disks, with color behavior indicating the presence of grains larger than for interstellar dust, presumably due to grain growth in their disks. Thirteen sources have larger variations at K than at J or H. For 11 of them, the temperature fitted to the variable component is very close to 2000K, suggesting that the changes in output are caused by turbulence at the inner rim of the circumstellar disk exposing previously protected populations of grains.
- ID:
- ivo://CDS.VizieR/J/PASP/132/J4401
- Title:
- YSOs detection with W filter
- Short Name:
- J/PASP/132/J4401
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the design and implementation of a medium-band near-IR filter tailored for detecting low-mass stars and brown dwarfs from the summit of Maunakea. The W-band filter is centered at 1.45{mu}m with a bandpass width of 6%, designed to measure the depth of the H_2_O water absorption prominent in objects with spectral types of M6 and later. When combined with standard J and H photometry, the W-band filter is designed to determine spectral types to ~=1.4 subtypes for late-M and L dwarfs, largely independent of surface gravity and reddening. This filter's primary application is completing the census of young substellar objects in star-forming regions, using W-band selection to greatly reduce contamination by reddened background stars that impede broad-band imaging surveys. We deployed the filter on the UH 88 inch telescope to survey ~3 degree^2^ of the NGC 1333, IC 348, and {rho} Ophiuchus star-forming regions. Our spectroscopic followup of W-band selected candidates resulted in the confirmation of 48 ultracool dwarfs with a success rate of 89%, demonstrating the efficacy of this new filter and selection method.
1404. YSOs in Camelopardalis
- ID:
- ivo://CDS.VizieR/J/BaltA/19/1
- Title:
- YSOs in Camelopardalis
- Short Name:
- J/BaltA/19/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using photometric data of infrared surveys, young stellar object (YSO) status is verified for 141 objects selected in our previous papers in the Cassiopeia and Camelopardalis segment of the Milky Way bounded by Galactic Using photometric data of infrared surveys, young stellar object (YSO) status is verified for 141 objects selected in our previous papers in the Cassiopeia and Camelopardalis segment of the Milky Way bounded by Galactic (l, b) = 132-158{deg}, +/-12{deg}). The area includes the known starforming regions in the emission nebulae W3, W4 and W5 and the massive YSOAFGL 490. Spectral energy distribution (SED) curves between 700 nm and 160um, constructed from the GSC 2, 2MASS, IRAS, MSX, Spitzer and AKARI data, are used to estimate the evolutionary stages of these stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/98
- Title:
- YSOs search in Stock 8 with opt. to IR photom.
- Short Name:
- J/ApJ/836/98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The evolution of H II regions/supershells can trigger a new generation of stars/clusters at their peripheries, with environmental conditions that may affect the initial mass function, disk evolution, and star formation efficiency. In this paper we study the stellar content and star formation processes in the young cluster Stock 8, which itself is thought to be formed during the expansion of a supershell. We present deep optical photometry along with JHK and 3.6 and 4.5{mu}m photometry from UKIDSS and Spitzer-IRAC. We use multicolor criteria to identify the candidate young stellar objects in the region. Using evolutionary models, we obtain a median log(age) of ~6.5 (~3.0Myr) with an observed age spread of ~0.25dex for the cluster. Monte Carlo simulations of the population of Stock 8, based on estimates for the photometric uncertainty, differential reddening, binarity, and variability, indicate that these uncertainties introduce an age spread of ~0.15dex. The intrinsic age spread in the cluster is ~0.2dex. The fraction of young stellar objects surrounded by disks is ~35%. The K-band luminosity function of Stock 8 is similar to that of the Trapezium cluster. The initial mass function (IMF) of Stock 8 has a Salpeter-like slope at >0.5M_{Sun}_ and flattens and peaks at ~0.4M_{Sun}_, below which it declines into the substellar regime. Although Stock 8 is surrounded by several massive stars, there seems to be no severe environmental effect in the form of the IMF due to the proximity of massive stars around the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/145/107
- Title:
- Zr, Ba, La, and Eu abundances in 19 open clusters
- Short Name:
- J/AJ/145/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an analysis of the s-process elements Zr, Ba, and La and the r-process element Eu in a sample of 50 stars in 19 open clusters. Stellar abundances of each element are based on measures of a minimum of two lines per species via both equivalent width and spectrum synthesis techniques. We investigate cluster mean neutron-capture abundance trends as a function of cluster age and location in the Milky Way disk and compare them to results found in other studies in the literature. We find a statistically significant trend of increasing cluster [Ba/Fe] as a function of decreasing cluster age, in agreement with recent findings for other open cluster samples, supporting the increased importance of low-mass asymptotic giant branch stars to the generation of s-process elements. However, the other s-process elements, [La/Fe] and [Zr/Fe], do not show similar dependences, in contrast to theoretical expectations and the limited observational data from other studies. Conversely, cluster [Eu/Fe] ratios show a slight increase with increasing cluster age, although with marginal statistical significance. Ratios of [s/r]-process abundances, [Ba/Eu] and [La/Eu], however, show more clearly the increasing efficiency of s-process relative to r-process enrichment in open cluster chemical evolution, with significant increases among younger clusters. Last, cluster neutron-capture element abundances appear to be independent of Galactocentric distance. We conclude that a homogeneous analysis of a larger sample of open clusters is needed to resolve the apparent discrepant conclusions between different studies regarding s-process element abundance trends with age to better inform models of galactic chemical evolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/380/712
- Title:
- ZYJHK photometry in Pleiades
- Short Name:
- J/MNRAS/380/712
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a deep wide-field near-infrared survey of 12deg^2^ of the Pleiades conducted as part of the United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey (GCS). We have extracted over 340 high-probability proper motion (PM) members down to 0.03M_{sun}_ using a combination of UKIDSS photometry and PM measurements obtained by cross-correlating the GCS with data from the Two Micron All Sky Survey, the Isaac Newton Telescope and the Canada-France-Hawaii Telescope. Additionally, we have unearthed 73 new candidate brown dwarf (BD) members on the basis of five-band UKIDSS photometry alone. We have identified 23 substellar multiple system candidates out of 63 candidate BDs from the (Y-K, Y) and (J-K, J) colour-magnitude diagrams, yielding a binary frequency of 2844 per cent in the 0.075-0.030M_{sun}_ mass range.
- ID:
- ivo://CDS.VizieR/J/MNRAS/374/372
- Title:
- ZYJHK photometry in Upper Sco
- Short Name:
- J/MNRAS/374/372
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present first results from a deep (J=18.7), wide-field (6.5deg^2^) infrared (ZY JHK) survey in the Upper Sco association conducted within the science verification phase of the United Kingdom Infrared Telescope Infrared Deep Sky Survey Galactic Cluster Survey (GCS). Cluster members define a sequence well separated from field stars in the (Z-J, Z) colour-magnitude diagram. We have selected a total of 164 candidates with J =10.5-8.7mag from the (Z-J, Z) and (Y-J, Y) diagrams. We further investigated the location of those candidates in the other colour-magnitude and colour-colour diagrams to weed out contaminants. The cross-correlation of the GCS catalogue with the Two-Micron All-Sky Survey data base confirms the membership of 116 photometric candidates down to 20 Jupiter masses as they lie within a 2 circle centred on the association mean motion. The final list of cluster members contains 129 sources with masses between 0.3 and 0.007M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/MNRAS/373/95
- Title:
- ZYJHK survey of Upper Sco association
- Short Name:
- J/MNRAS/373/95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a 9.3-deg^2^ infrared (ZYJHK) survey in the Upper Scorpius association extracted from the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Cluster Survey Early Data Release (Dye et al., 2006MNRAS.372.1227D). We have selected a total of 112 candidates from the (Z-J, Z) colour-magnitude diagram over the Z=12.5-20.5 magnitude range, corresponding to M=0.25-0.01M_{sun}_ at an age of 5Myr and a distance of 145pc. Additional photometry in J and K filters revealed most of them as reddened stars, leaving 32 possible members. Among them, 15 have proper motion consistent with higher-mass members from Hipparcos and optical spectra with strong H{alpha} in emission and weak gravity features. We have also extracted two lower-mass candidate members for which no optical spectra are in hand. Three members exhibit strong H{alpha} equivalent widths (>20{AA}), suggesting that they could still undergo accretion, whereas two other dwarfs show signs of chromospheric activity. The likelihood of the binarity of a couple of new stellar and substellar members is discussed as well.
