- ID:
- ivo://CDS.VizieR/J/A+A/440/1061
- Title:
- Southern red high proper motion objects
- Short Name:
- J/A+A/440/1061
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of spectroscopic follow-up observations for a sample of 71 red objects with high proper motions in the range 0.08-1.14 arcsec/yr as detected using APM and SuperCOSMOS Sky Surveys (SSS) measurements of multi-epoch photographic Schmidt plates. Red objects were selected by combining the photographic BjRI magnitudes with 2MASS near-infrared JHKs magnitudes. Some 50 of the 71 spectroscopically classified objects turn out to be late-type (>M6) dwarfs and in more detail, the sample includes 35 ultracool dwarfs with spectral types between M8 and L2, some previously reported, as well as five M-type subdwarfs, including a cool esdM6 object, SSSPM J0500-5406. Distance estimates based on the spectral types and 2MASS J magnitudes place almost all of the late-type (>M6) dwarfs within 50pc, with 25 objects located inside the 25pc limit of the catalogue of nearby stars. Most of the early-type M dwarfs are located at larger distances of 100-200pc, suggesting halo kinematics for some of them. All objects with Halpha equivalent widths larger than 10 Angstroms have relatively small tangential velocities (<50km/s). Finally, some late-type but blue objects are candidate binaries.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/402/575
- Title:
- Southern ultracool dwarfs in young moving groups
- Short Name:
- J/MNRAS/402/575
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We associate 132 low-mass ultracool dwarfs in the southern hemisphere as candidate members of five moving groups (MGs) using photometric and astrometric selection techniques. Of these objects, we present high-resolution spectroscopy for seven candidates and combine these with previous measurements from the literature to determine spectral types and radial velocities. We thus constrain distance and space motion spectroscopically, allowing the kinematic membership of the MGs to be assessed. Possible membership of MGs has allowed ages and metallicities to be constrained for these objects and evolutionary models have been used to estimate their mass. We estimate that up to ~75 of our candidate MG members should be genuine, and discuss future work that will confirm and exploit this major new sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/821/56
- Title:
- Space telescope RM project. III. NGC 5548 LCs
- Short Name:
- J/ApJ/821/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present ground-based optical photometric monitoring data for NGC5548, part of an extended multiwavelength reverberation mapping campaign. The light curves have nearly daily cadence from 2014 January to July in nine filters (BVRI and ugriz). Combined with ultraviolet data from the Hubble Space Telescope and Swift, we confirm significant time delays between the continuum bands as a function of wavelength, extending the wavelength coverage from 1158{AA} to the z band (~9160{AA}). We find that the lags at wavelengths longer than the V band are equal to or greater than the lags of high-ionization-state emission lines (such as HeII{lambda}1640 and {lambda}4686), suggesting that the continuum-emitting source is of a physical size comparable to the inner broad-line region (BLR). The trend of lag with wavelength is broadly consistent with the prediction for continuum reprocessing by an accretion disk with {tau}{propto}{lambda}^4/3^. However, the lags also imply a disk radius that is 3 times larger than the prediction from standard thin-disk theory, assuming that the bolometric luminosity is 10% of the Eddington luminosity (L=0.1L_Edd_). Using optical spectra from the Large Binocular Telescope, we estimate the bias of the interband continuum lags due to BLR emission observed in the filters. We find that the bias for filters with high levels of BLR contamination (~20%) can be important for the shortest continuum lags and likely has a significant impact on the u and U bands owing to Balmer continuum emission.
- ID:
- ivo://CDS.VizieR/J/ApJ/829/5
- Title:
- S-PASS & NVSS bright extragalactic radio sources
- Short Name:
- J/ApJ/829/5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a polarization catalog of 533 extragalactic radio sources that have a 2.3GHz total intensity above 420mJy from the S-band Polarization All Sky Survey, S-PASS, with corresponding 1.4GHz polarization information from the NRAO VLA Sky Survey, NVSS. We studied the selection effects and found that fractional polarization, {pi}, of radio objects at both wavelengths depends on the spectral index, the source magnetic field disorder, the source size, and depolarization. The relationship between depolarization, spectrum, and size shows that depolarization occurs primarily in the source vicinity. The median {pi}_2.3_ of resolved objects in NVSS is approximately two times larger than that of unresolved sources. Sources with little depolarization are ~2 times more polarized than both highly depolarized and re-polarized sources. This indicates that intrinsic magnetic field disorder is the dominant mechanism responsible for the observed low fractional polarization of radio sources at high frequencies. We predict that number counts from polarization surveys will be similar at 1.4GHz and at 2.3GHz, for fixed sensitivity, although ~10% of all sources may currently be missing because of strong depolarization. Objects with {pi}_1.4_~{pi}_2.3_>=4% typically have simple Faraday structures, so they are most useful for background samples. Almost half of flat-spectrum ({alpha}>=-0.5) and ~25% of steep-spectrum objects are re-polarized. Steep-spectrum, depolarized sources show a weak negative correlation of depolarization with redshift in the range 0<z<2.3. Previous non-detections of redshift evolution are likely due the inclusion of re-polarized sources as well.
- ID:
- ivo://CDS.VizieR/J/ApJ/645/676
- Title:
- Spatial distribution of brown dwarfs in Taurus
- Short Name:
- J/ApJ/645/676
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- By combining photometry from the 2MASS Point Source Catalog and the USNO-B1.0 catalog with optical and infrared spectroscopy, I have performed a search for young brown dwarfs in an area of 225deg^2^ encompassing all of the Taurus star-forming region (tau~1Myr). From this work, I have discovered 22 new members of Taurus, 5 of which were independently found by Guieu and coworkers (2006, Cat. <J/A+A/446/485>). Sixteen of these new members have spectral types later than M6 and thus are likely to be brown dwarfs according to the theoretical evolutionary models of Chabrier and Baraffe (2000ApJ...542..464C). After adding these new members to the previously known members of Taurus, I have compared the spatial distributions of stars and brown dwarfs across the entire region. I find no statistically significant difference between these two distributions. Taurus does not contain the large, extended population of brown dwarfs that has been predicted by some embryo ejection models for the formation of brown dwarfs. However, these results are consistent with other ejection models, as well as models in which stars and brown dwarfs share a common formation mechanism.
- ID:
- ivo://CDS.VizieR/J/AJ/160/9
- Title:
- Speckle holography of binary systems with OAN-SPM
- Short Name:
- J/AJ/160/9
- Date:
- 08 Dec 2021
- Publisher:
- CDS
- Description:
- We present our first results of multiband Speckle Holography of components of visual double stars. The observations were performed during 2019-April at the 2.1m telescope at the Observatorio Astronomico Nacional at Sierra de San Pedro Martir (Mexico). We have observed 190 double stars with separation between 3" and 5". The position angle, separation and magnitude difference in three broadband optical filters (VRI) for these systems are provided. For 15 systems we found different interesting features, we have identified a close component for 9 of those systems; 5 of them are newly discovered. In the remaining 6 systems, although unresolved, we found elongations that we have been able to derive astrometric parameters if proven to be a (newly discovered) close component. This corresponds to about 8% of the sample presenting a certain feature in one of the components and about 5% of the sample having a confirmed close component.
- ID:
- ivo://CDS.VizieR/J/AJ/158/48
- Title:
- Speckle interferometry at SOAR in 2018
- Short Name:
- J/AJ/158/48
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope (SOAR) in 2018 are given, totaling 3097 measurements of 2427 resolved pairs with separations from 11 mas to 5.9" (median 0.15", magnitude difference up to 7 mag) and nonresolutions of 624 targets. This work continues our long-term speckle program. Its main goal is to monitor orbital motion of close binaries, including members of high-order hierarchies and Hipparcos pairs in the solar neighborhood. Also, pre-main-sequence stars in the Orion OB1 association were surveyed, resolving 26 out of 118 targets. In addition, we report the discovery of 35 new companions among field visual multiples (some of which are likely optical) and first-time resolutions of another 31 pairs. By combining the measurements given here with the published ones, we computed 76 orbits for the first time and updated orbital elements of 34 visual binaries. Their periods range from 0.65 to 1100 yr, and their quality varies from first tentative solutions of grade 5 to accurate elements of grades 1 and 2. Finally, a list of 53 spurious pairs discovered by various techniques and unresolved at SOAR is given.
- ID:
- ivo://CDS.VizieR/J/AJ/155/235
- Title:
- Speckle interferometry at SOAR in 2016 and 2017
- Short Name:
- J/AJ/155/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The results of speckle interferometric observations at the 4.1 m Southern Astrophysical Research Telescope in 2016 and 2017 are given, totaling 2483 measurements of 1570 resolved pairs and 609 non-resolutions. We describe briefly recent changes in the instrument and observing method and quantify the accuracy of the pixel scale and position angle calibration. Comments are given on 44 pairs resolved here for the first time. The orbital motion of the newly resolved subsystem BU 83 Aa,Ab roughly agrees with its 36-year astrometric orbit proposed by J. Dommanget. Most Tycho binaries examined here turned out to be spurious.
- ID:
- ivo://CDS.VizieR/J/AJ/161/253
- Title:
- Speckle interferometry at the OAN-SPM Mexico
- Short Name:
- J/AJ/161/253
- Date:
- 09 Mar 2022
- Publisher:
- CDS
- Description:
- In this paper we present multiband speckle interferometric measurements of double stars performed at the 2.1m telescope of the Observatorio Astronomico Nacional, San Pedro Martir, Mexico. We focused our efforts on objects from the Washington Double Star Catalog that were observed during five runs allocated in 2018 and 2019. We report here 2101 astrometric and 2027 photometric measurements of 631 pairs, with angular separations ranging from 0.05" to 6.09", including 1622 measurements with separations smaller than 1", and a magnitude difference up to 5.99mag through the V filter, 5.46mag for the R filter, and 5.85mag for the I filter. We estimated a mean error in separation of 12mas, 1.1{deg} in position angle, and 0.14mag for the magnitude difference. We confirmed 58 double stars discovered by Hipparcos. For the first time we are presenting astrometric measurements for 7 systems listed at the Washington Double Star Catalog as being suspected binaries, which did not have a secondary confirmation, and 15 stars with only one published measurement. We identified a new close companion with a mean angular separation of 0.10", detected in a previously known pair. Finally, we present a correction to two previously published orbital solutions of two visual binaries.
- ID:
- ivo://CDS.VizieR/J/AJ/150/16
- Title:
- Speckle-interferometry in Melotte 111
- Short Name:
- J/AJ/150/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-angular resolution survey for the search of binary and multiple stars in the Galactic open cluster Melotte 111. Combining our own speckle-interferometric observations with data taken from the literature, we found a ratio of the number of single to multiple stars to be 29:8:0:0:0:1 for the most probable members, indicating a multiplicity fraction for this cluster of 25.6%+/-2%. We also observed field stars in the vicinity of the cluster and estimated a ratio of multiplicities of 286:17:1:0:0:0:1 (between one and seven companions), equivalent to a multiplicity fraction of 5.9%+/-3%. We showed that the cumulative distribution of separations for our sample stars is in agreement with Opik's law.
