- ID:
- ivo://CDS.VizieR/J/ApJ/710/597
- Title:
- Accretion in disks in Cep OB2
- Short Name:
- J/ApJ/710/597
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accretion rates for a large number of solar-type stars in the Cep OB2 region, based on U-band observations. Our study comprises 95 members of the ~4Myr old cluster Tr 37 (including 20 "transition" objects (TOs)), as well as the only classical T Tauri star (CTTS) in the ~12Myr old cluster NGC 7160. The stars show different disk morphologies, with the majority of them having evolved and flattened disks. The typical accretion rates are about 1 order of magnitude lower than in regions aged 1-2Myr, and we find no strong correlation between disk morphology and accretion rates. Although half of the TOs are not accreting, the median accretion rates of normal CTTS and accreting "transition" disks are similar (~3x10^-9^ and 2x10^-9^M_{sun}_/yr, respectively). Comparison with other regions suggests that the TOs observed at different ages do not necessarily represent the same type of objects, which is consistent with the fact that the different processes that can lead to reduced IR excess/inner disk clearing (e.g., binarity, dust coagulation/settling, photoevaporation, giant planet formation) do not operate on the same timescales.
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- ID:
- ivo://CDS.VizieR/J/MNRAS/435/429
- Title:
- Berkeley 94 and Berkeley 96 UBVRcIcJHKs
- Short Name:
- J/MNRAS/435/429
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed multiband UBVRcIcJHKs photometry of two young clusters located at large Galactocentric distances in the direction of the Perseus spiral arm. The obtained distances and colour excesses amount to 3.9+/-0.11kpc, E(B-V)=0.62+/-0.05 for Berkeley 94, and 4.3+/-0.15kpc, E(B-V)=0.58+/-0.06 for Berkeley 96. The respective ages, as measured from the comparison of the upper colour-magnitude diagrams to model isochrones, amount to log10Age(yr)=7.5+/-0.07 and 7.0+/-0.07, respectively. A sequence of optical pre-main-sequence (PMS) members is proposed in both clusters. In addition, samples of objects showing (H-Ks) excess are found. Part of these are suggested to be PMS cluster members of lower mass than the optical candidates. The spatial distribution of these sources, the comparison to Galactic models and to the expected number of contaminating distant red galaxies, and the spectral energy distribution in particular cases support this suggestion. The spatial distributions shown by members in different mass ranges can be interpreted in terms of the results from numerical simulations. According to these, different initial conditions and evolutionary dynamical paths are suggested for the clusters. Berkeley 94 would have formed under supervirial conditions, and followed the so-called warm collapse model in its evolution, whereas Berkeley 96 would have formed with a subvirial structure, and would have evolved following a cold collapse path. Both processes would be able to reproduce the suggested degree of mass segregation and their spatial distribution by mass range. Finally, the mass distributions of the clusters, from the most massive stars down to PMS stars around 1.3M_{sun}_, are calculated. An acceptable general agreement with the Salpeter initial mass function slope is found.
- ID:
- ivo://CDS.VizieR/J/MNRAS/415/1202
- Title:
- BVI photometry in W5E HII region
- Short Name:
- J/MNRAS/415/1202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this paper is to present the results of photometric investigations of the central cluster of the W5 E HII region as well as a follow-up study of the triggered star formation in and around bright-rimmed clouds (BRCs). We have carried out wide-field UBVIc and deep VIc photometry of the W5 E HII region. A distance of ~2.1kpc and a mean age of ~1.3Myr have been obtained for the central cluster. The young stellar objects (YSOs) associated with the region are identified on the basis of near-infrared and mid-infrared observations.
- ID:
- ivo://CDS.VizieR/J/MNRAS/375/1220
- Title:
- BVI photometry of young stars in 10 clusters
- Short Name:
- J/MNRAS/375/1220
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have selected pre-main-sequence (PMS) stars in 12 groups of notional ages ranging from 1 to 35Myr, using heterogeneous membership criteria. Using these members we have constructed empirical isochrones in V, V-I colour-magnitude diagrams. This allows us to identify clearly the gap between the radiative main sequence and the convective PMS (the RC gap). We follow the evolution of this gap with age and show that it can be a useful age indicator for groups less than =15 Myr old. We also observe a reduction in absolute spreads about the sequences with age. Finally, the empirical isochrones allow us to place the groups in order of age, independently of theory. The youngest groups can be collated into three sets of similar ages. The youngest set is the ONC, NGC 6530 and IC 5146 (nominally 1Myr); next Cep OB3b, NGC 2362, Ori and NGC 2264 (nominally 3Myr); and finally Ori and IC 348 (nominally 45Myr). This suggests Cep OB3b is younger than previously thought, and IC 348 older. For IC 348 the stellar rotation rate distribution and fraction of stars with discs imply a younger age than we derive. We suggest this is because of the absence of O-stars in this cluster, whose winds and/or ionizing radiation may be an important factor in the removal of discs in other clusters.
- ID:
- ivo://CDS.VizieR/J/AJ/123/304
- Title:
- BV(RI)_C_JHK H{alpha} photometry in IC 5146
- Short Name:
- J/AJ/123/304
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The B0V star BD+46 3474 lies near the front surface of a dense molecular cloud and illuminates the emission/reflection nebula IC 5146. The HAeBe variable BD +46 3471 is embedded in the same cloud, about 10' (3.5pc) away. CCD photometry in BV(RI)_C_ (to V=22) and in JHK (to about K=16.5) has been obtained for the young clusters surrounding each of these two bright stars. Some 100 emission-H{alpha} stars brighter than R=20.5 have been found in the area, most of them in IC 5146. (Among these are two that have spectra resembling a high-excitation Herbig-Haro [HH] object plus a stellar continuum).
- ID:
- ivo://CDS.VizieR/J/AJ/128/2316
- Title:
- BVRIJHKs photometry in sigma Ori cluster
- Short Name:
- J/AJ/128/2316
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report an optical photometric survey of 0.89deg^2^ of the Orion OB1b association centered on sigma Ori. This region includes most of the sigma Ori cluster, the highest-density region within Orion OB1b. We have developed a statistical procedure to identify the young, low-mass, pre-main-sequence population of the association. We estimate that the cluster has 160 members in the mass range (0.2M_{sun}_<=M<=1.0M_{sun}_). The cluster has a radius of 35pc and an estimated age of 2.5+/-0.3Myr. We estimate that the total mass of the cluster is 225+/-30M_{sun}_. This mass is similar to the estimated mass of the ~5x10^5^yr old cluster NGC 2024. NGC 2024 and sigma Ori appear to be a well-matched pair of clusters, except for the ~2Myr difference in their ages.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A60
- Title:
- BVRI observations of the FUor star V582 Aur
- Short Name:
- J/A+A/556/A60
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from optical photometric and spectroscopic observations of the eruptive pre-main sequence star V582 Aur. Variability of the star was reported a few years ago when it was suspected as a possible FU Orionis object. Due to the small number of currently known FUors, a new object of this type is ideal target for follow-up photometric and spectroscopic observations. We carried out BVRI CCD photometric observations in the field of V582 Aur from 2009 August to 2013 April. We acquired high-, medium-, and low-resolution spectroscopy of V582 Aur during this period. To study the pre-outburst variability of the target and construct its historical light curve, we searched for archival observations in photographic plate collections. The pre-outburst photographic observations of V582 Aur show low-amplitude light variations typical of T Tauri stars. Archival photographic observations indicate that the increase in brightness began in late 1984 or early 1985 and the star reached the maximum level of brightness at 1986 January. Our BVRI photometric observations show large amplitude variations ({Delta}V~2.8mag.) during the 3.5 year period of observations. Most of the time, however, the star remains in a state close to the maximum brightness. The deepest drop in brightness was observed in the spring of 2012, when the brightness of the star fell to a level close to the pre-outburst. The multicolor photometric data show a color reversal during the minimum in brightness, which is typical of UX Ori variables.
- ID:
- ivo://CDS.VizieR/J/A+A/345/521
- Title:
- BVRI photometry of NGC 2264
- Short Name:
- J/A+A/345/521
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The pre-main-sequence (PMS) population in the mass range between =~0.2 and =~3M_{sun}_ in southern part of the star-forming region NGC 2264 has been studied, determining both the Initial Mass Function in the region as well as the star-formation rates for different mass ranges. The sample is a composite one, derived through the union of samples obtained through different techniques and each suffering from different biases: previously known PMS stars in the region from the literature, photometrically-selected T Tauri candidates (from our own photometric data, discussed in detail in the present paper) and X-ray selected PMS candidates (discussed in detail in a companion paper) have been joined to form a sample which we show to be statistically complete (i.e. free from the biases which affect each of the parent samples) down to =~0.6M_{sun}_ (while being incomplete at lower masses). Individual masses and ages have been derived by placing the individual stars on evolutionary tracks, allowing us to derive both the IMF and the star formation rate. The Initial Mass Function thus derived for NGC 2264 shows evidence for a bimodal distribution of masses, with a break in the IMF at around 1M_{sun}_.
- ID:
- ivo://CDS.VizieR/J/other/BAJ/24.62
- Title:
- BVRI Photometry of 14 PMS stars
- Short Name:
- J/other/BAJ/24.6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New photometric data from CCD multicolour BVRI observations of 14 pre-main sequence stars during the period from 2013 April to 2015 September are presented. The studied objects are located in the field of 'Gulf of Mexico' in the NGC 7000/IC 5070 star-forming complex. The stars from our study exhibit different types of photometric variability in all optical passbands. Using our long-term observations and data published by other authors, we tried to define the reasons for the observed brightness variations. On the basis of our new data previously unknown periodicity in the light curve of the star LkHa 189 (2.45-days) was registered.
- ID:
- ivo://CDS.VizieR/J/other/BAJ/22.3
- Title:
- BVRI photometry of 5 PMS stars
- Short Name:
- J/other/BAJ/22.3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new data from BVRI photometric observations of five PMS stars during the period from April 2013 to July 2014. The stars are located in the field of NGC 7000/IC 5070 ("Gulf of Mexico") - a region with active star formation. The presented paper is a continuation of our long-term photometric investigations of the young stellar objects in this region. The long-term multicolor photometric observations of PMS stars are very important for their exact classification. Our results show that the studied stars exhibit different types of photometric variability in all bands. We tried to classify them using our data from the long-term photometry and data published by other authors.
