- ID:
- ivo://CDS.VizieR/J/PASP/118/659
- Title:
- RI photometry of 2MASS late M and L dwarfs
- Short Name:
- J/PASP/118/659
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report R and I band observations for 201 late M and L dwarfs selected on the basis of Two Micron All Sky Survey (Cat. II/246) JHKs and photographic red colors, made with a telescope of modest aperture. It is shown that deep surveys covering these red bands can provide data sets that complement JHKs, permitting a fairly good photometric classification system for L dwarfs. Due primarily to the disappearance of strong TiO opacities, R-I reaches a maximum at late M type and turns blueward for subtypes M9 to about L3. Apart from a small plateau at L0-L2, the I-Ks color remains as a monotonic measure of spectral type or temperature over this range, and likewise for M dwarfs. For late L types, both colors probably get redder again, although the accuracy of our data and number of objects do not give us robust conclusions by L6-L8. It is also interesting to look at the dispersions of the IJKs bands at a given spectral type. It is widely believed that this dispersion is caused by object-to-object variations in the amount, location, or other properties of dust or clouds. We find a moderately larger spread for the J-Ks color than for I-J.
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- ID:
- ivo://CDS.VizieR/J/A+A/417/479
- Title:
- RI photometry of NGC 185 carbon stars
- Short Name:
- J/A+A/417/479
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used the CFH12K wide field camera to survey the carbon star population of NGC 185 using the CN-TiO technique. 145 C stars are identified with a mean <I>=19.99+/-0.05, corresponding to <M_I_>=-4.41+/-0.05, a mean luminosity similar to what was recently found for the C star population of NGC 147. The stellar surface density profile of NGC 185 follows a power law with an exponential scale length of 2.53+/-0.07'. The surface density of C stars follows also a power law but with a smaller scale length, 1.56+/-0.06, demonstrating that the intermediate-age population of NGC 185 is more concentrated than its old population. A tidal radius, r_t_=22.5+/-2.2' is determined from red giant star counts. The C/M ratio of NGC 185 is 0.17+/-0.02 with no apparent sign of a radial gradient. We compare the carbon star populations of NGC 185 and NGC 147 to conclude that it is unlikely that they form a close pair.
- ID:
- ivo://CDS.VizieR/J/AJ/125/3037
- Title:
- RI photometry of NGC 205 carbon stars
- Short Name:
- J/AJ/125/3037
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a CFH12K survey of the carbon stars in NGC 205 and its surrounding field. We find that the number of C stars in NGC 205 is low (~500) for its luminosity and that very few C stars are seen outside of the 10 isophote, suggesting tidal stripping by M31. Their <M_I_>=-4.54, a magnitude nearly identical to what has been found in other galaxies with numerous C stars. Stars with accurate (R-I) photometry, to I~22.5, are used to determine the outer profile of NGC 205.
- ID:
- ivo://CDS.VizieR/J/ApJS/202/19
- Title:
- riz photometry in Cyg OB2
- Short Name:
- J/ApJS/202/19
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to fully understand the gravitational collapse of molecular clouds, the star formation process, and the evolution of circumstellar disks, these phenomena must be studied in different Galactic environments with a range of stellar contents and positions in the Galaxy. The young massive association Cygnus OB2, in the Cygnus-X region, is a unique target to study how star formation and the evolution of circumstellar disks proceed in the presence of a large number of massive stars. We present a catalog obtained with recent optical observations in the r, i, z filters with OSIRIS, mounted on the 10.4m Gran Telescopio CANARIAS telescope, which is the deepest optical catalog of CygOB2 to date. The catalog consists of 64,157 sources down to M=0.15M_{sun}_ at the adopted distance and age of Cyg OB2. A total of 38,300 sources have good photometry in all three bands. We combined the optical catalog with existing X-ray data of this region, in order to define the cluster locus in the optical diagrams. The cluster locus in the r-i versus i-z diagram is compatible with an extinction of the optically selected cluster members in the 2.64m<A_V_<5.57m range. We derive an extinction map of the region, finding a median value of A_V_=4.33m in the center of the association, decreasing toward the northwest. In the color-magnitude diagrams, the shape of the distribution of main-sequence stars is compatible with the presence of an obscuring cloud in the foreground ~850+/-25pc from the Sun.
- ID:
- ivo://CDS.VizieR/J/A+A/419/249
- Title:
- RJHKs photometry of sigma Ori low-mass stars
- Short Name:
- J/A+A/419/249
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Coordinates and photometry of probable cluster members in the sigma Ori cluster. Time series observations of this cluster were carried out using the CCD cameras at the 2m Schmidt telescope of the Thuringer Landessternwarte Tautenburg (TLS) and the 1.23m telescope on Calar Alto (CA). From these images, we derived coordinates (columns 2 and 3) as well as photometry in the R- and I-band (columns 5 and 6). Additional near- infrared photometry in J, H, K comes from the 2MASS database (columns 7-9). The cluster member selection is based on (I,I-J) colour magnitude diagrams. The R-I and J-H colours were used to reject contaminating field stars. The column 4 indicates whether the object was identified with the CA photometry (c), the TLS photometry (t), or both. The masses given in column 10 were estimated by comparing the near-infrared photometry with the evolutionary tracks of Baraffe et al. (1998A&A...337..403B). These tracks cover the mass range from 0.02 to 1.4 solar masses, for some objects with lower or higher masses we give upper or lower mass limits. The last two columns contain information about the results of the time series analysis. Column 10 gives the RMS of the CA lightcurve for targets No 1-52 and the RMS of the TLS lightcurve for all others. The last column indicates whether the target is classified as variable (v) and/or periodically variable (p). For a few objects, time series analysis was not possible, because they are either too faint or too bright in most of the images.
- ID:
- ivo://CDS.VizieR/J/A+A/602/A56
- Title:
- R136 JKs photometry from VLT/SPHERE EAO
- Short Name:
- J/A+A/602/A56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the sharpest near-IR images of the massive cluster R 136 to date, based on the extreme adaptive optics of the SPHERE focal instrument implemented on the ESO Very Large Telescope and operated in its IRDIS imaging mode. The crowded stellar population in the core of the R 136 starburst compact cluster remains still to be characterized in terms of individual luminosities, age, mass and multiplicity. SPHERE/VLT and its high contrast imaging possibilities open new windows to make progress on these questions. Stacking-up a few hundreds of short exposures in J and Ks spectral bands over a Field of View (FoV) of 10.9"x12.3" centered on the R136a1 stellar component, enabled us to carry a refined photometric analysis of the core of R136. We detected 1110 and 1059 sources in J and Ks images respectively with 818 common sources. Thanks to better angular resolution and dynamic range for 818 common sources being detected, we found that more than 62.6% (16.5%) of the stars, detected both in J and Ks data, have neighbours closer than 0.2" (0.1"). The closest stars are resolved down to the full width at half maximum (FWHM) of the point spread function (PSF) measured by Starfinder. Among newly resolved and/or detected sources R136a1 and R136c are found to have optical companions and R136a3 is resolved as two stars (PSF fitting) separated by 59+/-2mas. This new companion of R136a3 presents a correlation coefficient of 86% in J and 75% in Ks. The new set of detected sources were used to re-assess the age and extinction of R 136 based on 54 spectroscopically stars that have been recently studied with HST slit-spectroscopy (Crowther et al., 2016MNRAS.458..624C) of the core of this cluster. Over 90% of these 54 sources identified visual companions (closer than 0.2"). We found the most probable age and extinction for these sources are 1.8+1.2-0.8Myr, A_J_=(0.45+/-0.5)mag and A_K_=(0.2+/-0.5) mag within the photometric and spectroscopic error-bars. Additionally, using PARSEC evolutionary isochrones and tracks, we estimated the stellar mass range for each detected source (common in J and K data) and plotted the generalized histogram of mass (MF with error-bars). Using SPHERE data, we have gone one step further and partially resolved and studied the IMF covering mass range of (3-300)M_{sun}_ at the age of 1 and 1.5Myr. The density in the core of R 136 (0.1-1.4pc) is estimated and extrapolated in 3D and larger radii (up to 6pc). We show that the stars in the core are still unresolved due to crowding, and the results we obtained are upper limits. Higher angular resolution is mandatory to overcome these difficulties.
- ID:
- ivo://CDS.VizieR/J/AJ/143/80
- Title:
- R Low-mass stars of beta Pic and AB Dor groups
- Short Name:
- J/AJ/143/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our continuing effort to identify new, low-mass members of nearby, young moving groups (NYMGs), we present a list of young, low-mass candidates in the northern hemisphere. We used our proven proper-motion selection procedure and ROSAT X-ray and GALEX-UV activity indicators to identify 204 young stars as candidate members of the {beta} Pictoris and AB Doradus NYMGs. Definitive membership assignment of a given candidate will require a measurement of its radial velocity and distance. We present a simple system of indices to characterize the young candidates and help prioritize follow-up observations. New group members identified in this candidate list will be high priority targets for (1) exoplanet direct imaging searches, (2) the study of post-T-Tauri astrophysics, (3) understanding recent local star formation, and (4) the study of local galactic kinematics. Information available now allows us to identify eight likely new members in the list. Two of these, a late-K and an early-M dwarf, we find to be likely members of the {beta} Pic group. The other six stars are likely members of the AB Dor moving group. These include an M dwarf triple system, and three very cool objects that may be young brown dwarfs, making them the lowest-mass, isolated objects proposed in the AB Dor moving group to date.
- ID:
- ivo://CDS.VizieR/J/MNRAS/430/1125
- Title:
- RMS survey: NIR spectroscopy of massive YSOs
- Short Name:
- J/MNRAS/430/1125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Near-infrared H- and K-band spectra are presented for 247 objects, selected from the Red MSX Source (RMS) survey as potential young stellar objects (YSOs). 195 (~80%) of the targets are YSOs, of which 131 are massive YSOs (L_BOL_>5x10^3^L_{sun}_, M>8M_{sun}_). This is the largest spectroscopic study of massive YSOs to date, providing a valuable resource for the study of massive star formation. In this paper, we present our exploratory analysis of the data. The YSOs observed have a wide range of embeddedness (2.7<A_V_<114), demonstrating that this study covers minimally obscured objects right through to very red, dusty sources. Almost all YSOs show some evidence for emission lines, though there is a wide variety of observed properties. The most commonly detected lines are Br{gamma}, H_2_, fluorescent FeII, CO bandhead, [FeII] and HeI 2-1 1S-1P, in order of frequency of occurrence. In total, ~40% of the YSOs display either fluorescent FeII 1.6878{mu}m or CO bandhead emission (or both), indicative of a circumstellar disc; however, no correlation of the strength of these lines with bolometric luminosity was found. We also find that ~60% of the sources exhibit [FeII] or H_2_ emission, indicating the presence of an outflow. Three quarters of all sources have Br{gamma} in emission. A good correlation with bolometric luminosity was observed for both the Br{gamma} and H_2_ emission line strengths, covering 1<L_BOL_<3.5x10^5^L_{sun}_. This suggests that the emission mechanism for these lines is the same for low-, intermediate- and high-mass YSOs, i.e. high-mass YSOs appear to resemble scaled-up versions of low-mass YSOs.
- ID:
- ivo://CDS.VizieR/J/A+A/476/1019
- Title:
- RMS survey of southern candidate massive YSOs
- Short Name:
- J/A+A/476/1019
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Red MSX Source (RMS) survey is an ongoing effort to return a large, well-selected sample of massive young stellar objects (MYSOs) within our Galaxy. 2000 candidates have been colour-selected from the Mid-course Space Experiment (MSX) point source catalogue (PSC). A series of ground-based follow-up observations are being undertaken in order to remove contaminant objects (ultra-compact HII (UCHII) regions, planetary nebulae (PN), evolved stars), and to begin characterising these MYSOs. As a part of these follow-up observations, high resolution (~1") mid-IR imaging aids the identification of contaminant objects which are resolved (UCHII regions, PN) as opposed to those which are unresolved (YSOs, evolved stars) as well as identifying YSOs near UCHII regions and other multiple sources. We present 10.4{mu}m imaging observations for 346 candidate MYSOs in the RMS survey in the Southern Hemisphere, primarily outside the region covered by the GLIMPSE Spitzer Legacy Survey. These were obtained using TIMMI2 on the ESO 3.6m telescope in La Silla, Chile. Our photometric accuracy is of order 0.05Jy, and our astrometric accuracy is 0.8", which is an improvement over the nominal 2" accuracy of the MSX PSC.
- ID:
- ivo://CDS.VizieR/J/AJ/155/51
- Title:
- Robo-AO binary star systems in 3 open clusters
- Short Name:
- J/AJ/155/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify and roughly characterize 66 candidate binary star systems in the Pleiades, Praesepe, and NGC 2264 star clusters, based on robotic adaptive optics imaging data obtained using Robo-AO at the Palomar 60" telescope. Only ~10% of our imaged pairs were previously known. We detect companions at red optical wavelengths, with physical separations ranging from a few tens to a few thousands of au. A three-sigma contrast curve generated for each final image provides upper limits to the brightness ratios for any undetected putative companions. The observations are sensitive to companions with a maximum contrast of ~6^m^ at larger separations. At smaller separations, the mean (best) raw contrast at 2" is 3.8^m^ (6^m^), at 1" is 3.0^m^ (4.5^m^), and at 0.5" is 1.9^m^ (3^m^). Point-spread function subtraction can recover nearly the full contrast in the closer separations. For detected candidate binary pairs, we report separations, position angles, and relative magnitudes. Theoretical isochrones appropriate to the Pleiades and Praesepe clusters are then used to determine the corresponding binary mass ratios, which range from 0.2 to 0.9 in q=m_2_/m_1_. For our sample of roughly solar-mass (FGK type) stars in NGC 2264 and sub-solar-mass (K and early M-type) primaries in the Pleiades and Praesepe, the overall binary frequency is measured at ~15.5%+/-2%. However, this value should be considered a lower limit to the true binary fraction within the specified separation and mass ratio ranges in these clusters, given that complex and uncertain corrections for sensitivity and completeness have not been applied.
