- ID:
- ivo://CDS.VizieR/J/A+A/633/A146
- Title:
- Radial velocities of stars in NGC 2546
- Short Name:
- J/A+A/633/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of a broader project on the role of binary stars in clusters, we present a spectroscopic study of the open cluster NGC 2546, which is a large cluster lacking previous spectroscopic analysis. We report the finding of two open clusters in the region of NGC 2546. For the two star groups, we determine radial velocity, parallax, proper motion, reddening, distance modulus, and age, using our spectroscopic observations and available photometric and astrometric data, mainly from Gaia Data Release 2 (Gaia DR2). We also determine the orbit of four spectroscopic binaries in these open clusters. From mid-resolution spectroscopic observations for 28 stars in the NGC 2546 region, we determined radial velocities and evaluate velocity variability. To analyze double-lined spectroscopic binaries, we used a spectral separation technique and fit the spectroscopic orbits using a least-squares code. The presence of two stellar groups is suggested by the radial velocity distribution and confirmed by available photometric and astrometric data. We applied a multi-criteria analysis to determine cluster membership, and we obtained kinematic and physical parameters of the clusters. NGC 2546 is actually two clusters, NGC 2546A and NGC 2546B, the are not physically related to each other. NGC 2546A has an age of about 180Myr and a distance of 950pc. It has a half-number radius of 8pc and contains about 480 members brighter than G=18 mag. NGC 2546B is a very young cluster (<10Myr) located at a distance of 1450pc. It is a small cluster with 80 members and a half-number radius of 1.6pc. Stars less massive than 2.5 solar masses in this cluster would be pre- main-sequence objects. We detected four spectroscopic binaries and determined their orbits. The two binaries of NGC 2546A contain chemically peculiar components: HD 68693 is composed of two mercury- manganese stars and HD 68624 has a Bp silicon secondary. Among the most massive objects of NGC 2546B, there are two binary stars: HD 68572, with P=124.2d, and CD -37 4344 with P=10.4d.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/828/47
- Title:
- Radial velocities of the Be star HR 2142
- Short Name:
- J/ApJ/828/47
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a spectroscopic investigation of the Be+sdO binary system HR 2142 that is based upon large sets of ultraviolet observations from the International Ultraviolet Explorer (IUE) and ground-based H{alpha} observations. We measured radial velocities for the Be star component from these spectra and computed a revised orbit. In order to search for the spectral signature of the hot subdwarf, we cross-correlated the short wavelength end of each IUE spectrum with a model hot star spectrum, and then we used the predicted Doppler shifts of the subdwarf to shift-and-add all the cross-correlation functions to the frame of the subdwarf. This merged function shows the weak signal from the spectral lines of the hot star, and a best fit is obtained with a mass ratio M_2_/M_1_=0.07+/-0.02, companion temperature T_eff_>=43+/-5kK, projected rotational velocity Vsini<30km/s, and a monochromatic flux ratio near 1170{AA} of f_2_/f_1_>0.009+/-0.001. This hot subdwarf creates a one-armed spiral, tidal wake in the disk of the Be star, and we present a circumbinary disk model that can explain the occurrence of shell absorption lines by gas enhancements that occur where gas crossing the gap created by the subdwarf strikes the disk boundaries. The faint companion of HR 2142 may be representative of a significant fraction of Be stars with undetected former mass donor companion stars.
- ID:
- ivo://CDS.VizieR/J/AJ/145/139
- Title:
- Radial velocities of TYC 3010-1494-1
- Short Name:
- J/AJ/145/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R{<~}30000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msini~50M_Jup_) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very-low-mass companion: its large eccentricity (e~0.8), its relatively long period (P~238days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight ({omega}~189{deg}). As a result of these properties, for ~95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e~0.3). Only during the ~5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of ~15km/s reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.
- ID:
- ivo://CDS.VizieR/J/A+A/370/974
- Title:
- Radial velocities of UX Ari
- Short Name:
- J/A+A/370/974
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- All radial velocities of the two components of UX Ari (RV_1_ referring to the cooler primary, RV_2_ to the hotter secondary) as measured or taken from the literature together with the errors given in the literature, measured for the new data or estimated for the very old data; additionally the subdivisions of the datasets are indicated.
- ID:
- ivo://CDS.VizieR/J/AJ/129/2294
- Title:
- Radial velocities of weak-lines T Tauri stars
- Short Name:
- J/AJ/129/2294
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To search for thermal emission from substellar companions, we have obtained Z-band images of 15 weak-lined T Tauri stars in the Taurus-Auriga and Ophiuchus star-forming regions using the Planetary Camera 2 on the Hubble Space Telescope. To complement the imaging program, extensive spectroscopic observations were obtained with the Center for Astrophysics Digital Speedometers.
- ID:
- ivo://CDS.VizieR/J/MNRAS/455/1275
- Title:
- Radial velocities of WR21a
- Short Name:
- J/MNRAS/455/1275
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch spectroscopic observations of the massive binary system WR21a, which include the 2011 January periastron passage. Our spectra reveal multiple SB2 lines and facilitate an accurate determination of the orbit and the spectral types of the components. We obtain minimum masses of 64.4+/-4.8M_{sun} and 36.3+/-1.7M_{sun} for the two components of WR21a. Using disentangled spectra of the individual components, we derive spectral types of O3/WN5ha and O3Vz ((f*)) for the primary and secondary, respectively. Using the spectral type of the secondary as an indication for its mass, we estimate an orbital inclination of i=58.8+/-2.5{deg} and absolute masses of 103.6+/-10.2M_{sun} and 58.3+/-3.7M_{sun}_, in agreement with the luminosity of the system. The spectral types of the WR21a components indicate that the stars are very young (1-2Myr), similar to the age of the nearby Westerlund 2 cluster. We use evolutionary tracks to determine the mass-luminosity relation for the total system mass. We find that for a distance of 8kpc and an age of 1.5Myr, the derived absolute masses are in good agreement with those from evolutionary predictions.
- ID:
- ivo://CDS.VizieR/J/A+A/623/A146
- Title:
- Radial Velocity and BIS measurements of Polaris
- Short Name:
- J/A+A/623/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate temporally changing variability amplitudes and the multi- periodicity of the type-I Cepheid Polaris using 162 high-precision radial velocity (RV) and bisector inverse span (BIS) measurements based on optical spectra recorded using Hermes at the 1.2m Flemish Mercator telescope on La Palma, Canary Islands, Spain. Using an empirical template fitting method, we show that Polaris' RV amplitude has been stable to within ~30m/s between September 2011 and November 2018. We apply the template fitting method to publicly accessible, homogeneous RV data sets from the literature and provide an updated solution of Polaris' eccentric 29.3yr orbit. While the inferred pulsation-induced RV amplitudes differ among individual data sets, we find no evidence for time-variable RV amplitudes in any of the separately considered, homogeneous data sets. Additionally, we find that increasing photometric amplitudes determined using SMEI photometry are likely spurious detections due to as yet ill-understood systematic effects of instrumental origin. Given this confusing situation, further analysis of high-quality homogeneous data sets with well-understood systematics is required to confidently establish whether Polaris' variability amplitude is subject to change over time. We confirm periodic bisector variability periods of 3.97d and 40.22d using Hermes BIS measurements and identify a third signal at a period of 60.17d. Although the 60.17d signal dominates the BIS periodogram, we caution that this signal may not be independent of the 40.22d signal. Finally, we show that the 40.22d signal cannot be explained by stellar rotation. Further long-term, high-quality spectroscopic monitoring is required to unravel the complete set of Polaris' periodic signals, which has the potential to provide unprecedented insights into the evolution of Cepheid variables.
- ID:
- ivo://CDS.VizieR/J/A+A/621/A108
- Title:
- Radial velocity compilation for 45 CEMP-no stars
- Short Name:
- J/A+A/621/A108
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Carbon-enhanced metal-poor (CEMP) stars comprise a high percentage of stars at the lowest metallicities. The stars in the CEMP-no subcategory do not show any s-process enhancement and therefore cannot easily be explained by transfer of carbon and s-process elements from a binary AGB companion. We have performed radial velocity monitoring of a sample of 22 CEMP-no stars to further study the role that binarity plays in this type of CEMP star. We find four new binary CEMP-no stars based on their radial velocity variations; this significantly enlarges the population of known binaries to a total of 11. One of the new stars found to be in a binary system is HE 0107-5240, which is one of the most iron-poor stars known. This supports the binary transfer model for the origin of the abundance pattern of this star.We find a difference in binary fraction in our sample that depends on the absolute carbon abundance, with a binary fraction of 47 (+15/-14) % for stars with a higher absolute carbon abundance and 18 (+14/-9) % for stars with a lower absolute carbon abundance. This might imply a relation between a high carbon abundance and the binarity of a metal-poor star. Although binarity does not equate to mass transfer, there is a possibility that a CEMP-no star in a binary system has been polluted, and care has to be taken in the interpretation of their abundance patterns. We furthermore demonstrate the potential of Gaia of discovering additional binary candidates.
- ID:
- ivo://CDS.VizieR/J/AJ/148/114
- Title:
- Radial velocity curve of {delta} Cir
- Short Name:
- J/AJ/148/114
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Delta Cir is known as an O7.5 III eclipsing and spectroscopic binary with an eccentric orbit. Penny et al. discovered the presence of a third component in the IUE spectra. The eclipsing binary and the third body revolve around a common center of gravity with a period of 1644days in an eccentric orbit with a semimajor axis of 10AU. We demonstrate the presence of apsidal-line rotation with a period of {approx}141yr, which is considerably longer than its theoretically predicted value, based on the published radii of the binary components derived from the Hipparchos H_p_ light curve. However, our new solution of the same light curve resulted in smaller radii and better agreement between the observed and predicted period of the apsidal-line advance. There are indications that the third body is a binary. The object was resolved by VLTI using the PIONIER combiner; in 2012 June, the separation was 3.78mas with magnitude difference in the H region 1.75fm. This result means that (assuming a distance of 770pc) the inclination of the long orbit is 87.7{deg}.
- ID:
- ivo://CDS.VizieR/J/A+AS/123/209
- Title:
- Radial velocity curve of Sigma Gem
- Short Name:
- J/A+AS/123/209
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table contains the radial velocities of the RS CVn star sigma Geminorum measured by cross-correlation using Beta Oph as template from the high-resolution SOFIN spectra around 6175A.
