L-band data of RCW 57 at 3.5 micron taken with SPIREX (South Pole Infrared Explorer) is presented. The photometry was combined with 2MASS JHK data at 1.25 -2.2 micron. Colour-colour and colour-magnitude diagrams are constructed and used to determine the sources with infrared excess. These are interpreted as circumstellar disks, and enable the fraction of sources with disks (the cluster disk fraction or CDF) to be determined. We find that more than 50% of the sources detected at L-band in RCW 57 have an IR-excess.
We present the results of a near-infrared monitoring programme of a selected sample of stars, initially suspected to be Mira variables and OH/IR stars, covering more than a decade of observations. The objects monitored cover the typical range of IRAS colours shown by O-rich stars on the asymptotic giant branch and show a surprisingly large diversity of variability properties. Sixteen objects are confirmed as large-amplitude variables.
J, H, K, and L photometry for the stars in the central ~2' (~5pc) of the Galaxy are presented. Using the observed J-H, H-K, and K-L colors and assumed intrinsic colors, we determine the interstellar extinction at 2.2mm (A_K_) for approximately 1100 individual stars. The mean A_K_ (=3.3mag) is similar to previous results, but we find that the reddening is highly variable, and some stars are likely to be seen through A_K_>6mag. The dereddened K-band luminosity function points to a significantly brighter component to the stellar population (>1.5mag at K) than found in the stellar population in Baade's window, confirming previous work done at lower spatial resolution. The observed flux of all Galactic center stars with estimated K0 (dereddened magnitude) =<7.0mag is ~25% of the total in the 2'x2' field. The data were obtained in July 11-13 on the 4m telescope at the Cerro Tololo Observatory (CTIO) using the Ohio State Infrared Imager qnd Spectrometer (OSIRIS). Our observations confirm the recent finding that several bright M stars in the Galactic center are variable. Our photometry also establishes the near-infrared variability of the M1-2 supergiant, IRS 7.
We present results of a high angular resolution survey of massive OB stars in the Cygnus OB2 association that we conducted with the Near-Infrared Imager camera and ALTAIR adaptive optics system of the Gemini North telescope. We observed 74 O- and early-B-type stars in Cyg OB2 in the JHK infrared bands in order to detect binary and multiple companions. The observations are sensitive to equal-brightness pairs at separations as small as 0.08", and progressively fainter companions are detectable out to {Delta}K=9mag at a separation of 2". This faint contrast limit due to read noise continues out to 10" near the edge of the detector. We assigned a simple probability of chance alignment to each companion based upon its separation and magnitude difference from the central target star and upon areal star counts for the general star field of Cyg OB2. Companion stars with a field membership probability of less than 1% are assumed to be physical companions. This assessment indicates that 47% of the targets have at least one resolved companion that is probably gravitationally bound. Including known spectroscopic binaries, our sample includes 27 binary, 12 triple, and 9 systems with 4 or more components. These results confirm studies of high-mass stars in other environments that find that massive stars are born with a high-multiplicity fraction. The results are important for the placement of the stars in the Hertzsprung-Russell diagram, the interpretation of their spectroscopic analyses, and for future mass determinations through measurement of orbital motion.
JHK photometry and spectroscopy for L and T dwarfs
Short Name:
J/AJ/127/3553
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new JHK photometry on the MKO-NIR (Mauna Kea Observatories Near-Infrared) system and JHK spectroscopy for a large sample of L and T dwarfs. Photometry has been obtained for 71 dwarfs, and spectroscopy for 56. The sample comprises newly identified very red objects from the Sloan Digital Sky Survey (SDSS, http://www.sdss.org/) and known dwarfs from the SDSS and the Two Micron All Sky Survey (2MASS, Cat. <II/246>). Spectral classification has been carried out using four previously defined indices from Geballe et al. (2002ApJ...564..466G) that measure the strengths of the near infrared water and methane bands.
We present the results of a near-infrared survey of the young stellar cluster associated with IRAS 09149-4743, a member of the Vela Molecular Ridge. The main purpose of this survey is to study the cluster members and find the ionizing sources of the associated HII region.
RAFGL7009S is a deeply embedded massive young stellar objet (YSO) showing strong ice and saturated silicate absorption features in the mid infrared. It is associated with the ultracompact H II region G25.65+1.05, which may be excited by a B1V star. We have obtained JHK images of a 1' field centred on this YSO. In K we detect a non-resolved object coinciding with the radio continuum emission peak. Considering the high extinction towards this source (A_V_>=100mag), the observed K emission is more than 7~mag in excess of that expected for a B1V star. We suggest that this emission is mainly due to scattering of the central zone emission, as recently found for a sample of embedded massive YSOs associated with 3.1{mu}m H_2_O ice absorption (Ishii et al., 2002AJ....124..430I). We estimate the YSO's age to be 2x10^4^ years. The outflow, the methanol maser emission and the strong ice absorption features suggest the presence of a dense medium very close to the star, possibly a disk. The observations were obtained with the Montreal Near-IR Camera (MONICA, Nadeau et al., 1994PASP..106..909N) mounted at the F/8 Cassegrain focus of the 3.6-m Canada-France-Hawaii Telescope on 1996 July 1 UT. Frames were obtained through the J, H and K broad-band filters with total integration times of 840s, 160s and 100s Details about the instrumentation, the calibration and the data analysis can be found in Deharveng et al. (1999, Cat. <J/A+A/344/943>).
These Tables give the J2000 coordinates and JHK photometry of the stars in a 3.5'x3.5' field centred on Sh 219 (table3.dat) and a 3.1'x3.2' field centred on Sh 217 (table4.dat).
Observed properties of sources in the region S233IR in a field of 3.1 arcmin by 3.1 arcmin, which contains two young stellar clusters located to the northeast (NE) and southwest (SW) of the field center (RA = 05 35 49.79, DE = +35 44 01.9). Source positions, JHK photometry, extinction and estimated stellar mass are provided.
