- ID:
- ivo://CDS.VizieR/J/ApJ/722/1226
- Title:
- IR photometry in {lambda} Orionis cluster
- Short Name:
- J/ApJ/722/1226
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present IRAC/MIPS Spitzer Space Telescope observations of the solar-type and the low-mass stellar population of the young (~5Myr) {lambda} Orionis cluster. Combining optical and Two Micron All Sky Survey photometry, we identify 436 stars as probable members of the cluster. Given the distance (450pc) and the age of the cluster, our sample ranges in mass from 2M_{sun}_ to objects below the substellar limit. With the addition of the Spitzer mid-infrared data, we have identified 49 stars bearing disks in the stellar cluster. Using spectral energy distribution slopes, we place objects in several classes: non-excess stars (diskless), stars with optically thick disks, stars with "evolved disks" (with smaller excesses than optically thick disk systems), and "transitional disk" candidates (in which the inner disk is partially or fully cleared). The disk fraction depends on the stellar mass, ranging from ~6% for K-type stars (R_C_-J<2) to ~27% for stars with spectral-type M5 or later (R_C_-J>4). We confirm the dependence of disk fraction on stellar mass in this age range found in other studies. Regarding clustering levels, the overall fraction of disks in the {lambda} Orionis cluster is similar to those reported in other stellar groups with ages normally quoted as ~5Myr.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/686/1195
- Title:
- IR photometry in the {gamma} Vel cluster
- Short Name:
- J/ApJ/686/1195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new Spitzer Space Telescope observations of stars in the young (~5Myr) {gamma} Velorum stellar cluster. Combining optical and 2MASS photometry, we have selected 579 stars as candidate members of the cluster. With the addition of the Spitzer mid-infrared data, we have identified five debris disks around A-type stars and five to six debris disks around solar-type stars, indicating that the strong radiation field in the cluster does not completely suppress the production of planetesimals in the disks of cluster members. However, we find some evidence that the frequency of circumstellar primordial disks is lower, and the infrared flux excesses are smaller than for disks around stellar populations with similar ages.
- ID:
- ivo://CDS.VizieR/J/A+A/436/853
- Title:
- IR photometry of Alpha Per low-mass members
- Short Name:
- J/A+A/436/853
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a near-infrared (K'-band) survey of 0.7 square degree area in the {alpha} Persei open cluster (age=90Myr, distance=182pc) carried out with the Omega-Prime camera on the Calar Alto 3.5-m telescope. Combining optical data (Rc and Ic) obtained with the KPNO/MOSA detector and presented in Stauffer et al. (1999ApJ...527..219S; S99) with the K' observations, a sample of new candidate members has been extracted from the optical-infrared colour-magnitude diagram. The location of these candidates in the colour-colour diagram suggests that two-thirds of them are actually reddened background giants. About 20 new candidate members with masses between 0.3 and 0.04M_{sun}_ are added to the ~400 known Alpha Per cluster members. If they are indeed Alpha Per members, four of the new candidates would be brown dwarfs. We discuss the advantages and drawbacks of the near-infrared survey as compared to the optical selection method. We also describe the outcome of optical spectroscopy obtained with the Twin spectrograph on the Calar Alto 3.5-m telescope for about 30 candidates, including selected members from the optical sample presented in Barrado y Navascues et al. (2002, Cat. <J/A+A/395/813>) and from our joint optical/infrared catalogue. These results argue in favour of the optical selection method for this particular cluster.
- ID:
- ivo://CDS.VizieR/J/ApJ/642/972
- Title:
- IR photometry of a star-forming core in NGC 2264
- Short Name:
- J/ApJ/642/972
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze Spitzer and Magellan observations of a star-forming core near IRS 2 in the young cluster NGC 2264. The submillimeter source IRAS 12 S1, previously believed to be an intermediate-mass Class 0 object is shown to be a dense collection of embedded, low-mass stars. We argue that this group of stars represents the fragmenting collapse of a dense, turbulent core, using a number of indicators of extreme youth. With reasonable estimates for the velocity dispersion in the group, we estimate a dynamical lifetime of only a few times 10^4^yr. Spectral energy distributions of stars in the core are consistent with Class I or Class 0 assignments. We present observations of an extensive system of molecular hydrogen emission knots. The luminosity of the objects in the core region are consistent with roughly solar mass protostars.
- ID:
- ivo://CDS.VizieR/J/ApJ/597/555
- Title:
- IR photometry of IC 348 young brown dwarfs
- Short Name:
- J/ApJ/597/555
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a population of young brown dwarf candidates in the open star cluster IC 348 and the development of a new spectroscopic classification technique using narrowband photometry. Observations were made using FLITECAM, the First Light Camera for SOFIA, at the 3m Shane telescope at Lick Observatory. FLITECAM is a new 1-5{mu}m camera with an 8' field of view. Custom narrowband filters were developed to detect absorption features of water vapor (at 1.495{mu}) and methane (at 1.66{mu}m) characteristic of brown dwarfs. These filters enable spectral classification of stars and brown dwarfs without spectroscopy.
- ID:
- ivo://CDS.VizieR/J/MNRAS/442/273
- Title:
- IR photometry of NGC 1893 variables
- Short Name:
- J/MNRAS/442/273
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present time series photometry of 104 variable stars in the cluster region NGC 1893. The association of the present variable candidates to the cluster NGC 1893 has been determined by using (U-B)/(B-V) and (J-H)/(H-K) two colour diagrams, and V/(V-I) colour-magnitude diagram. 45 stars are found to be main-sequence variables and these could be B-type variable stars associated with the cluster. We classified these objects as {beta} Cep, slowly pulsating B stars and new class variables as discussed by Mowlavi et al. (2013, Cat. J/A+A/554/A108). These variable candidates show ~0.005 to ~0.02mag brightness variations with periods of <1.0d. 17 new class variables are located in the H-R diagram between the slowly pulsating B stars and {delta} Scuti variables. Pulsation could be one of the causes for periodic brightness variations in these stars. The X-ray emission of present main-sequence variables associated with the cluster lies in the saturated region of X-ray luminosity versus period diagram and follows the general trend by Pizzolato et al. (2003, Cat. J/A+A/397/147).
- ID:
- ivo://CDS.VizieR/J/AJ/155/99
- Title:
- IR variability among YSOs in the Serpens South cluster
- Short Name:
- J/AJ/155/99
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a time-variability study of young stellar objects (YSOs) in the Serpens South cluster performed at 3.6 and 4.5 {mu}m with the Spitzer Space Telescope; this study is part of the Young Stellar Object VARiability project. We have collected light curves for more than 1500 sources, including 85 cluster members, over 38 days. This includes 44 class I sources, 19 sources with flat spectral energy distributions (SEDs), 17 class II sources, and five diskless YSO candidates. We find a high variability fraction among embedded cluster members of ~70%, whereas young stars without a detectable disk display no variability. We detect periodic variability for 32 sources with periods primarily in the range of 0.2-14 days and a subset of fast rotators thought to be field binaries. The timescale for brightness changes are shortest for stars with the most photospheric SEDs and longest for those with flat or rising SEDs. While most variable YSOs become redder when fainter, as would be expected from variable extinction, about 10% get bluer as they get fainter. One source, SSTYSV J183006.13-020108.0, exhibits "cyclical" color changes.
- ID:
- ivo://CDS.VizieR/J/AcA/58/41
- Title:
- ISM polarization towards NGC 1502
- Short Name:
- J/AcA/58/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The polarimetry was obtained with the University of Wisconsin spectropolarimeter known as HPOL (descriptions in Wolff et al. 1996AJ....111..856W and Nordsieck and Harris 1996, ASP Conf. Ser. 97, 100; website address: http://www.sal.wisc.edu/HPOL/), on the 0.9m telescope at Pine Bluff Observatory or on the WIYN telescope at Kitt Peak.
- ID:
- ivo://CDS.VizieR/II/197
- Title:
- ISM towards IC 348 and Per OB2
- Short Name:
- II/197
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relationship between interstellar extinction and distance in the direction of dark clouds in the areas around the open cluster IC 348 and the association Per OB2 is determined using the results of photoelectric photometry of 189 stars in the Vilnius photometric system.
- ID:
- ivo://CDS.VizieR/J/MNRAS/392/1034
- Title:
- IZJHKL' photometry of NGC 6611
- Short Name:
- J/MNRAS/392/1034
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC 6611 is the massive young cluster (2-3Myr) that ionizes the Eagle Nebula. We present very deep photometric observations of the central region of NGC 6611 obtained with the Hubble Space Telescope and the following filters: ACS/WFC F775W and F850LP and NIC2 F110W and F160W, loosely equivalent to ground-based IZJH filters. This survey reaches down to I~26mag. We construct the initial mass function (IMF) from ~1.5M_{sun}_ well into the brown dwarf regime (down to ~0.02M_{sun}_). We have detected 30-35 brown dwarf candidates in this sample. The low-mass IMF is combined with a higher-mass IMF constructed from the ground-based catalogue from Oliveira et al. We compare the final IMF with those of well-studied star-forming regions: we find that the IMF of NGC 6611 more closely resembles that of the low-mass star-forming region in Taurus than that of the more massive Orion Nebula Cluster. We conclude that there seems to be no severe environmental effect in the IMF due to the proximity of the massive stars in NGC 6611.