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- ID:
- ivo://CDS.VizieR/J/A+A/556/A133
- Title:
- Astrometric orbit of DENIS-P J082303.1-49120
- Short Name:
- J/A+A/556/A133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Little is known about the existence of extrasolar planets around ultracool dwarfs. Furthermore, binary stars with Sun-like primaries and very low-mass binaries composed of ultracool dwarfs show differences in the distributions of mass ratio and orbital separation that can be indicative of distinct formation mechanisms. Using FORS2/VLT optical imaging for high precision astrometry we are searching for planets and substellar objects around ultracool dwarfs to investigate their multiplicity properties for very low companion masses. Here we report astrometric measurements with an accuracy of one tenth of a milli-arcsecond over two years that reveal orbital motion of the L1.5 dwarf DENIS-P J082303.1-491201 (having 7.5+/-1% of the Sun's mass) caused by a companion with a mass of 28+/-2 Jupiter masses that revolves about its host on an eccentric orbit in 246.4+/-1.4days. This new system is nearby at 20.77+/-0.08pc and has the smallest mass ratio (0.36+/-0.02) of known very low-mass binaries with a characterised orbit. With this discovery we demonstrate 100 micro-arcsecond astrometry over an arc-minute field and over several years that is sufficient to discover sub-Jupiter mass planets around ultracool dwarfs. We also show that the achieved parallax accuracy of <0.4% makes it possible to remove distance as a dominant source of uncertainty in the modelling of ultracool dwarfs.
- ID:
- ivo://CDS.VizieR/J/A+A/442/365
- Title:
- Astrometric orbits of SB9 stars
- Short Name:
- J/A+A/442/365
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Hipparcos Intermediate Astrometric Data (IAD) have been used to derive astrometric orbital elements for spectroscopic binaries from the newly released Ninth Catalogue of Spectroscopic Binary Orbits (S_B^9^_). This endeavour is justified by the fact that (i) the astrometric orbital motion is often difficult to detect without the prior knowledge of the spectroscopic orbital elements, and (ii) such knowledge was not available at the time of the construction of the Hipparcos Catalogue for the spectroscopic binaries which were recently added to the S_B^9^_ catalogue. Among the 1374 binaries from S_B^9^_ which have an HIP entry (excluding binaries with visual companions, or DMSA/C in the Double and Multiple Stars Annex), 282 have detectable orbital astrometric motion (at the 5% significance level). Among those, only 70 have astrometric orbital elements that are reliably determined (according to specific statistical tests), and for the first time for 20 systems. This represents a 8.5% increase of the number of astrometric systems with known orbital elements (The Double and Multiple Systems Annex contains 235 of those DMSA/O systems).
- ID:
- ivo://CDS.VizieR/J/A+A/653/A134
- Title:
- AT 2018bwo light curves
- Short Name:
- J/A+A/653/A134
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Luminous red novae (LRNe) are astrophysical transients associated with the partial ejection of a binary system's common envelope (CE) shortly before its merger. Here we present the results of our photometric and spectroscopic follow-up campaign of AT 2018bwo (DLT 18x), a LRN discovered in NGC 45, and investigate its progenitor system using binary stellar-evolution models. The transient reached a peak magnitude of M_r_=-10.97+/-0.11 and maintained this brightness during its optical plateau of t_p_=41+/-5d ays. During this phase, it showed a rather stable photospheric temperature of ~3300K and a luminosity of ~10^40^erg/s. Although the luminosity and duration of AT 2018bwo is comparable to the LRNe V838 Mon and M31-2015LRN, its photosphere at early times appears larger and cooler, likely due to an extended mass-loss episode before the merger. Toward the end of the plateau, optical spectra showed a reddened continuum with strong molecular absorption bands. The IR spectrum at +103 days after discovery was comparable to that of an M8.5 II type star, analogous to an extended AGB star. The reprocessed emission by the cooling dust was also detected in the mid-infrared bands ~1.5 years after the outburst. Archival Spitzer and Hubble Space Telescope data taken 10-14yrs before the transient event suggest a progenitor star with T_prog_~6500K, R_prog_~100R_{sun}_, and L_prog_=2x10^4^L_{sun}_, and an upper limit for optically thin warm (1000K) dust mass of M_d_<10^-6^M_{sun}_. Using stellar binary-evolution models, we determined the properties of binary systems consistent with the progenitor parameter space. For AT 2018bwo, we infer a primary mass of 12-16M_{sun}_, which is 9-45% larger than the ~11M_{sun}_ obtained using single-star evolution models. The system, consistent with a yellow-supergiant primary, was likely in a stable mass-transfer regime with -2.4 <= log (M_dot/Msun /yr) <= -1.2 a decade before the main instability occurred. During the dynamical merger, the system would have ejected 0.15-0.5M_{sun}_ with a velocity of ~500km/s.
- ID:
- ivo://CDS.VizieR/J/A+A/647/A93
- Title:
- AT 2020hat and AT 2020kog light curves
- Short Name:
- J/A+A/647/A93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our monitoring campaigns of the luminous red novae (LRNe) AT 2020hat in NGC 5068 and AT 2020kog in NGC 6106. The two objects were imaged (and detected) before their discovery by routine survey operations. They show a general trend of slow luminosity rise lasting at least a few months. The subsequent major LRN outbursts were extensively followed in photometry and spectroscopy. The light curves present an initial short-duration peak, followed by a redder plateau phase. AT 2020kog is a moderately luminous event peaking at ~7x10^40^erg/s, while AT 2020hat is almost one order of magnitude fainter than AT 2020kog, although it is still more luminous than V838 Mon. In analogy with other LRNe, the spectra of AT 2020kog change significantly with time. They resemble those of type IIn supernovae at early phases, then they become similar to those of K-type stars during the plateau, and to M-type stars at very late phases. In contrast, AT 2020hat already shows a redder continuum at early epochs, and its spectrum shows the late appearance of molecular bands. A moderate-resolution spectrum of AT 2020hat taken at +37d after maximum shows a forest of narrow P Cygni lines of metals with velocities of 180 km/s, along with an Halpha emission with a full-width at half-maximum velocity of 250km/s. For AT 2020hat, a robust constraint on its quiescent progenitor is provided by archival images of the Hubble Space Telescope. The progenitor is clearly detected as a mid-K type star, with an absolute magnitude of M_F606W=-3.33+/-0.09mag and a colour of F606W-F814W=1.14+/-0.05mag, which are inconsistent with the expectations from a massive star that could later produce a core-collapse supernova. Although quite peculiar, the two objects nicely match the progenitor versus light curve absolute magnitude correlations discussed in the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/563/L10
- Title:
- BD+33 2642 and HD 112313 radial velocities
- Short Name:
- J/A+A/563/L10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the impact of binary interaction processes on the evolution of low- and intermediate-mass stars using long-term monitoring of their radial velocity. Here we report on our results on the central stars of two planetary nebulae (PNe): the well-studied spectrophotometric standard BD+33 2642 (central star of PNG 052.7+50.7) and HD 112313 (central star of PN LoTr5), the optical light of which is dominated by a rapidly rotating G star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/319/215
- Title:
- Binary evolution
- Short Name:
- J/MNRAS/319/215
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using Eggleton's stellar evolution code, we carry out 150 runs of Population I binary evolution calculations with the initial primary mass between 1 and 8 solar masses, the initial mass ratio q=M_1/M_2 between 1.1 and 4, and the onset of Roche lobe overflow (RLOF) at an early, middle or late Hertzsprung-gap stage. We assume that the RLOF is conservative in the calculations. We list characteristics for binaries with different initial parameters at the beginning of RLOF, minimum luminosity during RLOF, the end of the last episode of RLOF and the end of the evolutionary calculations. The characteristics includes the age of the primary, its mass, mass transfer rate, its effective temperature, its luminosity, its radius, its helium core mass, its carbon-oxygen core mass, the hydrogen abundance at its surface, the mass ratio of the binary, and the orbital period.
- ID:
- ivo://CDS.VizieR/J/A+A/586/A158
- Title:
- Binary properties of CH and CEMP stars
- Short Name:
- J/A+A/586/A158
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The HERMES spectrograph installed on the 1.2-m Mercator telescope has been used to monitor the radial velocity of 13 low-metallicity carbon stars, among which seven carbon-enhanced metal-poor (CEMP) stars and six CH stars. All stars but one show clear evidence for binarity. New orbits are obtained for eight systems. The sample covers an extended range in orbital periods, extending from 3.4d (for the dwarf carbon star HE 0024-2523) to about 54yr (for the CH star HD 26, the longest known among barium, CH, and extrinsic S stars). The period - eccentricity diagram for the 40 low-metallicity carbon stars with orbits now available shows no difference between CH and CEMP-s stars (the latter corresponding to those CEMP stars enriched in s-process elements, as are CH stars). We suggest that they must be considered as one and the same family and that their different names only stem from historical reasons. Indeed, these two families have as well very similar mass-function distributions, corresponding to companions with masses in the range 0.5-0.7M_{sun}_, indicative of white-dwarf companions, adopting 0.8-0.9M_{sun}_ for the primary component. This result confirms that CH and CEMP-s stars obey the same mass-transfer scenario as their higher-metallicity analogues, barium stars. The P-e diagrams of barium, CH, and CEMP-s stars are indeed very similar. They reveal two different groups of systems: one with short orbital periods (P<1000d) and mostly circular or almost circular orbits, and another with longer period and eccentric (e>0.1) orbits. These two groups either trace different evolutionary channels during the mass-transfer episode responsible for the chemical peculiarities of the Ba/CH/CEMP-s stars, or result from the operation of tidal circularisation in a more recent past, when the current giant star was ascending the first giant branch.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A32
- Title:
- CARMENES SB2 orbital parameters
- Short Name:
- J/A+A/619/A32
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The CARMENES spectrograph is surveying ~300 M dwarf stars in search for exoplanets. Among the target stars, spectroscopic binary systems have been discovered, which can be used to measure fundamental properties of stars. Using spectroscopic observations we determine the orbital and physical properties of nine new double-line spectroscopic binary systems by analysing their radial velocity curves. We use two-dimensional cross-correlation techniques to derive the radial velocities of the targets, which are then employed to determine the orbital properties. Photometric data from the literature are also analysed to search for possible eclipses and to measure stellar variability, which can yield rotation periods. Out of the 342 stars in the CARMENES sample, only 9 have been found to be SB2s. We provide empirical orbital properties and minimum masses for the sample of spectroscopic binaries, with periods ranging from 1.13 to 8000 days and eccentricities up to ~0.54. Absolute masses are also estimated from mass-luminosity calibrations, ranging between ~0.1M_{sun}_ and ~0.6M_{sun}_. These new binary systems increase the number of double-line M dwarf binary systems with known orbital parameters by 14%, and suggest that low-mass binaries seem to have lower mass ratios than more massive systems.
- ID:
- ivo://CDS.VizieR/J/AcA/64/359
- Title:
- Catalog of binary UV Ceti stars
- Short Name:
- J/AcA/64/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A catalogue of nearby UV Ceti type flare stars in (137) visual binary systems is presented in the form of two separate tables of information. The catalogue has developed from Catalogue and Bibliography of UV Cet stars (Gershberg et al., 1999, Cat. J/A+AS/139/555) and the list of nearby flare stars (Pettersen, 1991MmSAI..62..217P) by including more recent and additional information from catalogues of binary stars (WDS, Mason et al., 2001-2014, Cat. B/wds; ORB6, Hartkopf et al. 2006-2014; DM3, Mason+ 2006-2014) and data from the Catalog of Nearby Stars, Preliminary 3rd Version (Gliese et al., 1991, Cat. V/70), from Hipparcos, the New Reduction (van Leeuwen 2007, Cat. I/311) and from SIMBAD. Some issues relating to the mass, luminosity and spectrum relations of flare stars are also discussed.
