- ID:
- ivo://CDS.VizieR/J/AJ/121/2124
- Title:
- {lambda} Ori pre-main-sequence stars photometry
- Short Name:
- J/AJ/121/2124
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The {lambda} Ori star-forming region presents a snapshot of a moderate-mass giant molecular cloud 1-2Myr after cloud disruption by OB stars, with the OB stars, the low-mass stellar population, remnant molecular clouds, and the dispersed gas all still present. We have used optical photometry and multiobject spectroscopy for lithium absorption to identify 266 pre-main-sequence stars in 8deg^2^ of the region. We also present new Stroemgren photometry for the massive stars, from which we derive a distance of 450pc and a turnoff age of 6-7Myr. Using these parameters and pre-main-sequence evolutionary models, we map the star formation history of the low-mass stars. We find that low-mass star formation started throughout the region at about the same time as the birth of the massive stars, and thereafter the birth rate accelerated. Within the last 1-2Myr star formation ceased in the center of the star-forming region, near the concentration of OB stars, while it continues in dark clouds 20pc away. We suggest that a supernova 1-2Myr ago destroyed the molecular cloud core from which the OB stars formed, but it did not terminate star formation in more distant reaches of the giant molecular cloud. We find no secure evidence for triggered or sequential star formation in the outer molecular clouds. The global star formation of the {lambda} Ori region has generated the field initial mass function, but local star formation in subregions shows large deviations from the expected ratio of high- to low-mass stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/366/645
- Title:
- LARCS. 11 X-ray luminous clusters
- Short Name:
- J/MNRAS/366/645
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the analysis of the spectroscopic and photometric catalogues of 11 X-ray luminous clusters at 0.07<z<0.16 from the Las Campanas/Anglo-Australian Telescope Rich Cluster Survey. Our spectroscopic data set consists of over 1600 galaxy cluster members, of which two-thirds are outside r_200_. These spectra allow us to assign cluster membership using a detailed mass model and expand on our previous work on the cluster colourmagnitude relation (CMR) where membership was inferred statistically.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A118
- Title:
- Lensed QSOs light curves & spectral monitoring
- Short Name:
- J/A+A/616/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the framework of the Gravitational LENses and DArk MAtter (GLENDAMA) project, we present a database of nine gravitationally lensed quasars (GLQs) that have two or four images brighter than r=20mag and are located in the northern hemisphere. This new database consists of a rich variety of follow-up observations included in the GLENDAMA global archive, which is publicly available online and contains 6557 processed astronomical frames of the nine lens systems over the period 1999-2016. In addition to the GLQs, our archive also incorporates binary quasars, accretion-dominated radio-loud quasars, and other objects, where about 50% of the non-GLQs were observed as part of a campaign to identify GLQ candidates. Most observations of GLQs correspond to an ongoing long-term macro-programme with 2-10m telescopes at the Roque de los Muchachos Observatory, and these data provide information on the distribution of dark matter at all scales. We outline some previous results from the database, and we additionally obtain new results for several GLQs that update the potential of the tool for astrophysical studies.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A103
- Title:
- Light curves for variables in 5 clusters
- Short Name:
- J/A+A/573/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we present the analysis of time-series observations from 2013 and 2014 of five metal rich ([Fe/H]>-1) globular clusters: NGC6388, NGC6441, NGC6528, NGC6638, and NGC6652. The data have been used to perform a census of the variable stars in the central parts of these clusters. The observations were made with the electron multiplying CCD (EMCCD) camera at the Danish 1.54m Telescope at La Silla, Chile, and they were analysed using difference image analysis (DIA) to obtain high-precision light curves of the variable stars. It was possible to identify and classify all of the previously known or suspected variable stars in the central regions of the five clusters. Furthermore, we were able to identify, and in most cases classify 48, 49, 7, 8, and 2 previously unknown variables in NGC 6388, NGC 6441, NGC 6528, NGC 6638, and NGC 6652, respectively. Especially interesting is the case of NGC 6441, for which the variable star population of about 150 stars has been thoroughly examined by previous studies, including a Hubble Space Telescope study. In this paper we are able to present 49 new variable stars for this cluster, of which one (possibly two) are RR Lyrae stars, two are W Virginis stars, and the rest are long period semi-regular or irregular variables on the red giant branch. We have also detected the first double mode RR Lyrae in the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/148/126
- Title:
- Light curves of four overcontact binaries
- Short Name:
- J/AJ/148/126
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze new, high quality multicolor light curves of four overcontact binaries: AK Her, HI Dra, V1128 Tau, and V2612 Oph, and determine their orbital and physical parameters using the modeling program of G. Djurasevic and recently published results of radial velocity studies. The achieved precision in absolute masses is between 10% and 20%, and the precision in absolute radii is between 5% and 10%. All four systems are W UMa-type binaries with bright or dark spots indicative of mass and energy transfer or surface activity. We estimate the distances and the ages of the systems using the luminosities computed through our analysis, and perform an O-C study for V1128 Tau, which reveals a complex period variation that can be interpreted in terms of mass loss/exchange and either the presence of the third body, or the magnetic activity on one of the components. We conclude that further observations of these systems are needed to deepen our understanding of their nature and variability.
- ID:
- ivo://CDS.VizieR/J/A+A/632/A95
- Title:
- Light curves of NGC 6910 pulsating stars
- Short Name:
- J/A+A/632/A95
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The aim of this study is to obtain the age of the open cluster NGC 6910 by means of ensemble asteroseismology of the early-type pulsating members, to derive their stellar parameters, and to classify the excited modes. We used time-series analysis, performed photometric and spectroscopic mode identification, and calculated grids of evolutionary and seismic models to apply the procedure of ensemble asteroseismology for nine pulsating members of NGC 6910. With two iterations of the procedure of ensemble asteroseismology we derived an age of 10.6^+0.9^_-0.8_Myr for NGC 6910. We also identified the degree l for 8 of 37 modes detected in these stars and classified all modes in terms of p, g, and mixed-mode pulsations. Of the nine pulsating stars examined in the paper, eight are {beta} Cep stars, including three that are hybrid {beta} Cep and slowly pulsating B-type (SPB) pulsators, and one is an SPB star. Interestingly, the least massive {beta} Cep star, NGC 6910-38, has a mass of about 5.6 solar masses. The present theory does not predict unstable p modes in B-type stars with such a low mass. The g modes with relatively high frequencies (>3.5d^-1^), observed in three members of the cluster, are also stable according to seismic modelling. Both findings pose a challenge for theoretical calculations and prompt a revision of the opacities. The procedure of ensemble asteroseismology was found to be successful for NGC 6910 and {chi} Per on the basis of pulsating B-type stars and can therefore be applied to other young open clusters that are rich in such stars.
- ID:
- ivo://CDS.VizieR/J/A+A/404/621
- Title:
- Light curves of ROTSE-I delta Scuti type stars
- Short Name:
- J/A+A/404/621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-passband CCD photometry of 20 ROTSE-I {delta} Scuti type pulsating stars and 1 RR Lyrae star to re-classify their variable types using the comparison of amplitudes between V and I passbands. For the re-classification, we used a criterion that pulsating stars have larger amplitude differences between passbands than eclipsing binaries because brightness changes of pulsating stars are mainly due to the temperature variations. As a result, only six stars were re-confirmed as {delta} Scuti variables and thirteen stars turned out to be W UMa type eclipsing binaries. The other two stars were identified as one cataclysmic variable and one non-variable, respectively. Our results suggest that a number of ROTSE-I {delta} Scuti type stars, which do not show typical pulsating light curves of high amplitude {delta} Scuti stars, are W UMa type eclipsing binaries.
- ID:
- ivo://CDS.VizieR/J/MNRAS/357/645
- Title:
- LMC far-UV HST observations
- Short Name:
- J/MNRAS/357/645
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new analysis of the deepest pure-ultraviolet (UV) observations with the highest angular resolution ever performed. A set of 12 exposures with the Hubble Space Telescope (HST) WFPC2 and F160BW filter obtained in parallel observing mode, which cover ~12arcmin^2^ in the Large Magellanic Cloud (LMC), north of the bar and in the 'general field' region of the LMC, contain stars with far-UV monochromatic magnitudes as faint as 22mag. The 198 detected UV sources represent an accumulated exposure of 2x10^4^s and reveal stars as faint as m_UV_=~20mag. We combine these observations with deep UBVI charge-coupled device (CCD) imaging of the same region reaching as faint as V=~26mag, and reselect probable optical counterparts for the UV sources. After a two-stage search-and-analysis process, we detect robust counterparts for 129 stars. These are mostly upper main-sequence stars, from early B to early A spectral classes, with several F stars. We point out the lack of blue supergiants, which could have been easily detected in our survey. We measure a foreground extinction E(B-V)=~0.08mag by Galactic dust and a surface density of star formation rate twice the average Galactic value. These observations indicate that relatively recent star formation took place even off the bar of the LMC.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A185
- Title:
- Long-term optical monitoring of TeV Blazars
- Short Name:
- J/A+A/620/A185
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ten years of R-band monitoring data of 31 northern blazars which were either detected at very high-energy (VHE) gamma rays or listed as potential VHE gamma-ray emitters. The data comprise 11820 photometric data points in the R-band obtained in 2002-2012. We analyzed the light curves by determining their power spectral density (PSD) slopes assuming a power-law dependence with a single slope beta and a Gaussian probability density function (PDF). We used the multiple fragments variance function (MFVF) combined with a forward-casting approach and likelihood analysis to determine the slopes and perform extensive simulations to estimate the uncertainties of the derived slopes. We also looked for periodic variations via Fourier analysis and quantified the false alarm probability through a large number of simulations. Comparing the obtained PSD slopes to values in the literature, we find the slopes in the radio band to be steeper than those in the optical and gamma rays. Our periodicity search yielded one target, Mrk 421, with a significant (p<5%) period. Finding one significant period among 31 targets is consistent with the expected false alarm rate, but the period found in Mrk 421 is very strong and deserves further consideration.
- ID:
- ivo://CDS.VizieR/J/ApJS/134/103
- Title:
- Low-mass members of IC 2391
- Short Name:
- J/ApJS/134/103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have identified a large sample of probable low-mass members of the young open cluster IC 2391 based on optical (VRIZ) and infrared (JHKs) photometry. Our sample includes 50 probable members and 82 possible members, both very low-mass stars and brown dwarfs. We also provide accurate positions for these stars and brown dwarf candidates derived from red UK Schmidt plates measured using the microdensitometer SuperCOSMOS. Assuming an age of 53Myr, we estimate that we have reached a mass of 0.025M_{sun}_, if the identified objects are indeed members of IC 2391.
