- ID:
- ivo://CDS.VizieR/J/A+A/658/A69
- Title:
- RVs of B stars in NGC 6231
- Short Name:
- J/A+A/658/A69
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- It is well known that massive O stars are frequently (if not always) found in binary or higher-order multiple systems, but this fact has been less robustly investigated for the lower mass range of the massive stars, represented by B-type stars. Obtaining the binary fraction and orbital parameter distributions of B-type stars is crucial to understand the impact of multiplicity on the archetypal progenitor of core-collapse supernovae as well as to properly investigate formation channels for gravitational wave progenitors. This work aims to characterise the multiplicity of the B star population of the young open cluster NGC 6231 through multi-epoch optical spectroscopy of 80 B-type stars. We analyse 31 FLAMES/GIRAFFE observations of 80 B-type stars, monitoring their radial velocities (RVs) and performing a least-squares spectral analysis (Lomb-Scargle) to search for periodicity in those stars with statistically significant variability in their RVs. We constrained an observed spectroscopic binary fraction of 33+/-5% for the B-type stars of NGC 6231, with a first order bias correction giving a true spectroscopic binary fraction of 52+/-8%. Out of 27 B-type binary candidates, we obtained orbital solutions for 20 systems: 15 single-lined (SB1) and five double-lined spectroscopic binaries (SB2s). We present these orbital solutions and the orbital parameter distributions associated with them. Our results indicate that Galactic B-type stars are less frequently found in binary systems than their more massive O-type counterparts, but their orbital properties generally resemble those of B- and O-type stars in both the Galaxy and Large Magellanic Cloud.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/160/151
- Title:
- RVs of 5 cataclysmic variable candidates
- Short Name:
- J/AJ/160/151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report follow-up observations of five cataclysmic variable candidates from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) published by Hou et al. LAMOSTJ024048.51+195226.9 is the most unusual of the five; an early-M type secondary star contributes strongly to its spectrum, and its spectral and photometric behavior are strikingly reminiscent of the hitherto-unique propeller system AE Aqr. We confirm that a 7.34hr period discovered in the Catalina survey data is orbital. Another object, LAMOSTJ204305.95+341340.6, appears to be a near twin of the novalike variable V795Her, with an orbital period in the so-called 2-3hr "gap." LAMOSTJ035913.61+405035.0 is evidently an eclipsing, weakly outbursting dwarf nova with a 5.48hr period. Our spectrum of LAMOSTJ090150.09+375444.3 is dominated by a late-type secondary and shows weak, narrow Balmer emission moving in phase with the absorption lines, but at lower amplitude; we do not see the HeII {lambda}4686 emission evident in the published discovery spectrum. We again confirm that a period from the Catalina data, in this case 6.80hr, is orbital. LAMOSTJ033940.98+414805.7 yields a radial-velocity period of 3.54hr, and its spectrum appears to be typical of novalike variables in this period range. The spectroscopically selected sample from LAMOST evidently includes some interesting cataclysmic variables that have been unrecognized until now, apparently because of the relatively modest range of their photometric variations.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A4
- Title:
- RVs of 18 Galactic luminous blue variable stars
- Short Name:
- J/A+A/657/A4
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Luminous blue variables (LBVs) are characterised by strong photometric and spectroscopic variability. They are thought to be in a transitory phase between O-type stars on the main sequence and the Wolf-Rayet stage. Recent studies also evoked the possibility that they might be formed through binary interaction. Only a few are known in binary systems so far, but their multiplicity fraction is still uncertain. We derive the binary fraction of the Galactic LBV population. We combine multi-epoch spectroscopy and long-baseline interferometry to probe separations from 0.1 to 120mas around confirmed and candidate LBVs. We used a cross-correlation technique to measure the radial velocities of these objects. We identified spectroscopic binaries through significant radial velocity variability with an amplitude larger than 35km/s. We also investigated the observational biases to take them into account when we established the intrinsic binary fraction. We used candid to detect interferometric companions, derive their flux fractions, and their positions on the sky. From the multi-epoch spectroscopy, we derive an observed spectroscopic binary fraction of 26-10+16%. Considering period and mass ratio ranges from log(Porb)=0-3 (i.e. from 1 to 1000days), q=0.1-1.0, and a representative set of orbital parameter distributions, we find a bias-corrected binary fraction of 62_-24_^+38^%. Based on data of the interferometric campaign, we detect a binary fraction of 70+/-9% at projected separations between 1 and 120mas. Based on the derived primary diameters and considering the distances of these objects, we measure for the first time the exact radii of Galactic LBVs to be between 100 and 650R_{sun}_. This means that it is unlikely that short-period systems are included among LBV-like stars. This analysis shows for the first time that the binary fraction in the Galactic LBV population is large. If they form through single-star evolution, their orbit must be large initially. If they form through a binary channel, the implication is that either massive stars in short binary systems must undergo a phase of fully non-conservative mass transfer to be able to sufficiently widen the orbit to form an LBV, or that LBVs form through merging in initially binary or triple systems. Interferometric follow-up would provide the distributions of orbital parameters at more advanced stages and would serve to quantitatively test the binary evolution in massive stars.
- ID:
- ivo://CDS.VizieR/J/AJ/157/136
- Title:
- RVs of RGs with suspected massive companions
- Short Name:
- J/AJ/157/136
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Motivated by the existence of binary systems where a stellar-mass black hole is bound to a normal star, we selected four red giants with large radial velocity (RV) variation from the survey of Space Interferometry Mission (SIM) grid stars and monitored their RVs for several months. None turned out to contain a massive companion above 2.5 solar masses. The red giant TYC 9299-1080-1 with a large RV and a large proper motion is a single-lined spectroscopic binary with a period of 81 days. It is an extreme halo object moving at 350 km/s almost directly toward the Galactic center. HD 206092 is a double-lined binary with a short period of 4.37 days. It belongs to the rare class of active RS CVn-type binaries with evolved primary components, apparently undergoing mass transfer. The X-ray luminosity of HD 206092 is about twice as high as the most luminous coronal X-ray emitters observed by ROSAT, including II Peg and the prototype star RS CVn. HD 318347 has a variable double-peaked emission-line spectrum (not a giant), while HD 324668 has a constant RV. Despite the overall good quality of the SIM survey data confirmed by a comparison with Gaia Data Release 2 (DR2, Cat. I/345) mean RVs, the few large RV variations are explained, mostly, by erroneous data. We discuss the significance of the non-detection of massive companions in the SIM grid sample and the associated work.
- ID:
- ivo://CDS.VizieR/J/AJ/159/290
- Title:
- RVs of 12 spectroscopic binaries M-dwarfs
- Short Name:
- J/AJ/159/290
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectroscopic orbits of 11 nearby, mid-to-late M dwarf binary systems in a variety of configurations: 2 single-lined binaries (SB1s), 7 double-lined binaries (SB2s), 1 double-lined triple (ST2), and 1 triple-lined triple (ST3). Eight of these orbits are the first published for these systems, while five are newly identified multiples. We obtained multi-epoch, high-resolution spectra with the TRES instrument on the 1.5m Tillinghast Reflector at the Fred Lawrence Whipple Observatory located on Mt. Hopkins in AZ. Using the TiO molecular bands at 7065-7165{AA}, we calculated radial velocities for these systems, from which we derived their orbits. We find LHS 1817 to have in a 7hr period a companion that is likely a white dwarf, due to the ellipsoidal modulation we see in our MEarth-North light-curve data. We find G123-45 and LTT11586 to host companions with minimum masses of 41MJup and 44MJup with orbital periods of 35 and 15days, respectively. We find 2MA0930+0227 to have a rapidly rotating stellar companion in a 917 day orbital period. GJ268, GJ1029, LP734-34, GJ1182, G258-17, and LTT7077are SB2s with stellar companions with orbital periods of 10, 96, 34, 154, 5, and 84days; LP655-43 is an ST3 with one companion in an 18day orbital period and an outer component in a longer undetermined period. In addition, we present radial velocities for both components of L870-44AB and for the outer components of LTT11586 and LP655-43.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/2068
- Title:
- RV survey of the Carina Nebula's O stars
- Short Name:
- J/MNRAS/477/2068
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained multi-epoch observations of 31 O-type stars in the Carina Nebula using the CHIRON spectrograph on the CTIO/SMARTS 1.5-m telescope. We measure their radial velocities to 1-2 km/s precision and present new or updated orbital solutions for the binary systems HD 92607, HD 93576, HDE 303312, and HDE 305536. We also compile radial velocities from the literature for 32 additional O-type and evolved massive stars in the region. The combined data set shows a mean heliocentric radial velocity of 0.6km/s. We calculate a velocity dispersion of <=9.1km/s, consistent with an unbound, substructured OB association. The Tr 14 cluster shows a marginally significant 5km/s radial velocity offset from its neighbour Tr 16, but there are otherwise no correlations between stellar position and velocity. The O-type stars in Cr 228 and the South Pillars region have a lower velocity dispersion than the region as a whole, supporting a model of distributed massive star formation rather than migration from the central clusters. We compare our stellar velocities to the Carina Nebula's molecular gas and find that Tr 14 shows a close kinematic association with the Northern Cloud. In contrast, Tr 16 has accelerated the Southern Cloud by 10-15km/s, possibly triggering further massive star formation. The expansion of the surrounding H II region is not symmetric about the O-type stars in radial velocity space, indicating that the ionized gas is constrained by denser material on the far side.
- ID:
- ivo://CDS.VizieR/J/ApJ/811/85
- Title:
- RVs & V-band LCs of probable members of Cyg OB2
- Short Name:
- J/ApJ/811/85
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Cygnus OB2 Association is one of the nearest and largest collections of massive stars in the Galaxy. Situated at the heart of the "Cygnus X" complex of star-forming regions and molecular clouds, its distance has proven elusive owing to the ambiguous nature of kinematic distances along this l~=80{deg} sightline and the heavy, patchy extinction. In an effort to refine the three-dimensional geometry of key Cygnus X constituents, we have measured distances to four eclipsing double-lined OB-type spectroscopic binaries that are probable members of Cyg OB2. We find distances of 1.33+/-0.17, 1.32+/-0.07, 1.44+/-0.18, and 1.32+/-0.13kpc toward MT91 372, MT91 696, CPR2002 A36, and Schulte 3, respectively. We adopt a weighted average distance of 1.33+/-0.06kpc. This agrees well with spectrophotometric estimates for the Association as a whole and with parallax measurements of protostellar masers in the surrounding interstellar clouds, thereby linking the ongoing star formation in these clouds with Cyg OB2. We also identify Schulte 3C (O9.5V), a 4" visual companion to the 4.75 day binary Schulte 3(A+B), as a previously unrecognized Association member.
- ID:
- ivo://CDS.VizieR/J/MNRAS/475/1609
- Title:
- RV variability in NGC 2516 and NGC 2422
- Short Name:
- J/MNRAS/475/1609
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multi-epoch, high-dispersion, optical spectra obtained with the Michigan/Magellan Fiber System of 126 and 125 Sun-like stars in the young clusters NGC 2516 (141Myr) and NGC 2422 (73Myr). We determine stellar properties including radial velocity (RV), Teff, [Fe/H], [{alpha}/Fe], and the line-of-sight rotation rate, v_r_sin(i), from these spectra. Our median RV precision of 80m/s on individual epochs that span a temporal baseline of 1.1yr enables us to investigate membership, stellar binarity, and search for sub-stellar companions. We determine membership probabilities and RV variability probabilities for our sample along with candidate companion orbital periods for a select subset of stars. We identify 81 RV members in NGC 2516, 27 spectroscopic binaries (17 previously identified as photometric binaries), and 16 other stars that show significant RV variability after accounting for average stellar jitter found to be at the 74m/s level. In NGC 2422 we identify 57 members, 11 spectroscopic binaries, and 3 other stars that show significant RV variability after accounting for an average jitter of 138m/s. We use Monte Carlo simulations to verify our stellar jitter measurements, determine the proportion of exoplanets and stellar companions to which we are sensitive, and estimate companion mass limits for our targets. We also report mean cluster metallicity, velocity, and velocity dispersion based on our member targets and identify 58 non-member stars as RV variables - 24 of which have RV amplitudes that imply stellar or brown-dwarf mass companions. Finally, we note the discovery of a separate RV clustering of stars in our NGC 2422 sample.
- ID:
- ivo://CDS.VizieR/J/ApJ/877/44
- Title:
- RV variability in SDSS dwarf carbon stars
- Short Name:
- J/ApJ/877/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dwarf carbon (dC) stars (main-sequence stars showing carbon molecular bands) were initially thought to be an oxymoron because only asymptotic giant branch (AGB) stars dredge carbon into their atmospheres. Mass transfer from a former AGB companion that has since faded to a white dwarf seems the most likely explanation. Indeed, a few types of giants known to show anomalous abundances- notably, the CH, Ba and CEMP-s stars-are known to have a high binary frequency. The dC stars may be the enhanced-abundance progenitors of most, if not all of these systems, but this requires demonstrating a high binary frequency for dCs. Here, for a sample of 240 dC stars targeted for repeat spectroscopy by the SDSS-IV's Time Domain Spectroscopic Survey, we analyze radial velocity (RV) variability to constrain the binary frequency and orbital properties. A handful of dC systems show large velocity variability (>100km/s). We compare the dCs to a control sample with a similar distribution of magnitude, color, proper motion, and parallax. Using Markov chain Monte Carlo methods, we use the measured {Delta}RV distribution to estimate the binary fraction and the separation distribution assuming both a unimodal and bimodal distribution. We find the dC stars have an enhanced binary fraction of 95%, consistent with them being products of mass transfer. These models result in mean separations of less than 1 au corresponding to periods on the order of 1 yr. Our results support the conclusion that dC stars form from close binary systems via mass transfer.
- ID:
- ivo://CDS.VizieR/J/A+A/568/A26
- Title:
- SACY. V. Multiple systems
- Short Name:
- J/A+A/568/A26
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Dynamically undisrupted, young populations of stars are crucial in studying the role of multiplicity in relation to star formation. Loose nearby associations provide us with a great sample of close (<150pc) pre-main sequence (PMS) stars across the very important age range (~5-70Myr) to conduct such research. We characterize the short period multiplicity fraction of the search for associations containing young stars (SACY) sample, accounting for any identifiable bias in our techniques and present the role of multiplicity fractions of the SACY sample in the context of star formation. Using the cross-correlation technique we identified double-lined and triple-lined spectroscopic systems (SB2/SB3s), in addition to this we computed radial velocity (RV) values for our subsample of SACY targets using several epochs of fiber-fed extended range optical spectrograph (FEROS) and ultraviolet and visual echelle spectrograph (UVES) data. These values were used to revise the membership of each association that was then combined with archival data to determine significant RV variations across different data epochs characteristic of multiplicity; single-lined multiple systems (SB1). Results: We identified seven new multiple systems (SB1s: 5, SB2s: 2). We find no significant difference between the short period multiplicity fraction (F_m_) of the SACY sample and that of close star-forming regions (~-2Myr) and the field (F_m_<=10%). These are seen both as a function of age and as a function of primary mass, M_1_, in the ranges P [1:200day] and M_2_ [0.08M_{sun}_-M_1_], respectively. Our results are consistent with the picture of universal star formation, when compared to the field and close star-forming regions (SFRs). We comment on the implications of the relationship between increasing multiplicity fraction with the primary mass within the close companion range in relation to star formation.