- ID:
- ivo://CDS.VizieR/J/AcA/52/241
- Title:
- QSO candidates in OGLE-II data
- Short Name:
- J/AcA/52/241
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A search for faint slowly variable objects was undertaken in the hope of finding QSO candidates behind the Small and Large Magellanic Clouds (SMC and LMC). This search used the optical variability properties of point sources from the Magellanic Cloud OGLE-II photometric data. Objects bluer than V-I=0.9mag and within 17mag<I<20.5mag were studied. Robust variograms/structure functions have been computed for each time-series and only candidates showing a significantly increasing variability over longer time scales were selected. Several light curves were identified as having probable artifacts and were therefore removed. Stars showing signs of periodicity or small trends in their light curves were also removed and we are left with mostly either Be stars ({gamma} Cas stars) or QSO candidates. We present a list of 25 slowly varying objects for SMC and 155 for LMC, out of 15000 and 53000 variable objects respectively. Of these, about 15 objects for the SMC and 118 objects for the LMC are QSO candidates.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/747/107
- Title:
- QSO Candidates in the MACHO LMC database
- Short Name:
- J/ApJ/747/107
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog the 2566 QSO candidates in the MACHO LMC database. In these catalogs, we complied number of properties of the objects including RA, Dec, crossmatched IDs with several catalogs, magnitudes, photometric redshifts, etc. See Kim et al. (2011ApJ...735...68K) for the SVM (a.k.a. Support Vector Machine, a supervised machine learning algorithm) QSO classification model based on the time variability of lightcurves. We used the model to select the 2566 QSO candidates. In this work, we employed multiple diagnostics such as X-ray flux, mid-IR color and AGN SED fitting in order to select 663 promising QSO candidates among the 2,566 candidates. These candidates are flagged in the catalog. We calibrated the MACHO RA and Dec of the candidates using the UCAC3 catalog and improved the average astrometric accuracy from ~3" to ~0.5".
- ID:
- ivo://CDS.VizieR/J/A+A/549/A29
- Title:
- Quasars behind the Magellanic system
- Short Name:
- J/A+A/549/A29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The number and spatial distribution of confirmed quasi-stellar objects (QSOs) behind the Magellanic system is limited. This undermines their use as astrometric reference objects for different types of studies. We have searched for criteria to identify candidate QSOs using observations from the VISTA survey of the Magellanic Clouds system (VMC) that provides photometry in the YJKs bands and 12 epochs in the Ks band. The (Y-J) versus (J-Ks) diagram has been used to distinguish QSO candidates from Milky Way stars and stars of the Magellanic Clouds. Then, the slope of variation in the Ks band has been used to identify a sample of high confidence candidates. These criteria were developed based on the properties of 117 known QSOs presently observed by the VMC survey.
- ID:
- ivo://CDS.VizieR/J/A+A/415/531
- Title:
- Radial velocities of 10 Galactic Cepheids
- Short Name:
- J/A+A/415/531
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present here the appendix to the paper with the new high precision radial velocities for a sample of Galactic Cepheids. The stars are: SU Cas, EV Sct, del Cep, CV Mon, U Sgr, eta Aql, X Cyg, T Mon, RS Pup, and SV Vul.
- ID:
- ivo://CDS.VizieR/J/A+A/460/459
- Title:
- Radial velocities of LMC RR Lyrae
- Short Name:
- J/A+A/460/459
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- All galaxies that have been adequately examined so far have shown an extended stellar halo. To search for such a halo in the LMC we have obtained low-resolution spectra for 100 LMC RR Lyrae stars, of which 87 are in the field and 13 in the clusters NGC 1835 and NGC 2019. We measured radial velocities for 87 LMC RR Lyrae stars, and metallicities for 78 RR Lyrae stars, nearly tripling the previous sample. These targets are located in 10 fields covering a wide range of distances, out to 2.5 degrees from the center of the LMC.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2514
- Title:
- Radial velocities of red giants in the SMC
- Short Name:
- J/AJ/131/2514
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic survey of 2079 red giant stars, distributed over the central 4kpcx2kpc of the Small Magellanic Cloud (SMC). After fitting and removing a small velocity gradient across the SMC (8.3km/s/{deg} oriented at 23.4{deg} east of north), we measure an rms velocity scatter of 27.5+/-0.5km/s.
- ID:
- ivo://CDS.VizieR/J/MNRAS/386/826
- Title:
- Radial velocities of SMC massive stars
- Short Name:
- J/MNRAS/386/826
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present radial velocities for 2045 stars in the Small Magellanic Cloud (SMC), obtained from the 2dF survey by Evans et al. (2004, Cat. J/MNRAS/353/601). The great majority of these stars are of OBA type, tracing the dynamics of the young stellar population. Dividing the sample into ad hoc `bar' and `wing' samples (north and south, respectively, of the line: delta=-77^{deg}50' + [4{alpha}]', where alpha is in minutes of time) we find that the velocities in the SMC bar show a gradient of 26.3+/-1.6km/s/deg at a position angle of 126+/-4deg. The derived gradient in the bar is robust to the adopted line of demarcation between the two samples. The largest redshifts are found in the SMC wing, in which the velocity distribution appears distinct from that in the bar, most likely a consequence of the interaction between the Magellanic Clouds that is predicted to have occurred 0.2Gyr ago. The mean velocity for all stars in the sample is +172.0+/-0.2km/s (redshifted by ~20km/s when compared to published results for older populations), with a velocity dispersion of 30km/s.
- ID:
- ivo://CDS.VizieR/J/AJ/148/118
- Title:
- Radial velocity curves of LMC ellipsoidal variables
- Short Name:
- J/AJ/148/118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ellipsoidal red giant binaries are close binary systems where an unseen, relatively close companion distorts the red giant, leading to light variations as the red giant moves around its orbit. These binaries are likely to be the immediate evolutionary precursors of close binary planetary nebula and post-asymptotic giant branch and post-red giant branch stars. Due to the MACHO and OGLE photometric monitoring projects, the light variability nature of these ellipsoidal variables has been well studied. However, due to the lack of radial velocity curves, the nature of their masses, separations, and other orbital details has so far remained largely unknown. In order to improve this situation, we have carried out spectral monitoring observations of a large sample of 80 ellipsoidal variables in the Large Magellanic Cloud and we have derived radial velocity curves. At least 12 radial velocity points with good quality were obtained for most of the ellipsoidal variables. The radial velocity data are provided with this paper. Combining the photometric and radial velocity data, we present some statistical results related to the binary properties of these ellipsoidal variables.
- ID:
- ivo://CDS.VizieR/J/ApJ/860/1
- Title:
- Radial velocity measurements of 20 EBs in LMC
- Short Name:
- J/ApJ/860/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a determination of the precise fundamental physical parameters of 20 detached, double-lined, eclipsing binary stars in the Large Magellanic Cloud (LMC) containing G- or early K-type giant stars. Eleven are new systems; the remaining nine are systems already analyzed by our team for which we present updated parameters. The catalog results from our long-term survey of eclipsing binaries in the Magellanic Clouds suitable for high-precision determination of distances (the Araucaria Project). The V-band brightnesses of the systems range from 15.4 to 17.7mag, and their orbital periods range from 49 to 773days. Six systems have favorable geometry showing total eclipses. The absolute dimensions of all eclipsing binary components are calculated with a precision of better than 3%, and all systems are suitable for a precise distance determination. The measured stellar masses are in the range 1.4 to 4.6M_{sun}_, and comparison with the MESA isochrones gives ages between 0.1 and 2.1Gyr. The systems show an age-metallicity relation with no evolution of metallicity for systems older than 0.6Gyr, followed by a rise to a metallicity maximum at age 0.5Gyr and then a slow metallicity decrease until 0.1Gyr. Two systems have components with very different masses: OGLE LMC-ECL-05430 and OGLE LMC-ECL-18365. Neither system can be fitted by a single stellar evolution isochrone, explained by a past mass transfer scenario in the case of ECL-18365 and a gravitational capture or hierarchical binary merger scenario in the case of ECL-05430. The longest-period system, OGLE LMC SC9_230659, shows a surprising apsidal motion that shifts the apparent position of the eclipses. This is a clear sign of a physical companion to the system; however, neither investigation of the spectra nor light-curve analysis indicates a third-light contribution larger than 2%-3%. In one spectrum of OGLE LMC-ECL-12669, we noted a peculiar dimming of one of the components by 65% well outside of the eclipses. We interpret this observation as arising from an extremely rare occultation event, as a foreground Galactic object covers only one component of an extragalactic eclipsing binary.
- ID:
- ivo://CDS.VizieR/J/ApJ/702/940
- Title:
- Radio and UV spectra of HVC toward the MC
- Short Name:
- J/ApJ/702/940
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the spectra of 139 early-type Large Magellanic Cloud (LMC) stars observed with Far Ultraviolet Spectroscopic Explorer and with deep radio Parkes HI 21cm observations along with those stars, we search for and analyze the absorption and emission from high-velocity gas at +90<={nu}_LSR_<=+175km/s. The HI column density of the high-velocity clouds (HVCs) along these sightlines ranges from <1018.4 to 1019.2cm^-2^. The incidence of the HVC metal absorption is 70%, significantly higher than the HI emission occurrence of 32%. We find that the mean metallicity of the HVC is [OI/HI]=-0.51+/-^0.12^_0.16_. This is the first example of a large (>10^6^M_{sun}_) HVC complex that is linked to stellar feedback occurring in a dwarf spiral galaxy.
