- ID:
- ivo://CDS.VizieR/J/A+A/590/A45
- Title:
- GU Mon BV light curves
- Short Name:
- J/A+A/590/A45
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a comprehensive analysis, including B and V light curves and 11 high-resolution spectra, to verify the orbital period and determine parameters. The spectroscopic and photometric analyses agree on a period of 0.896640+/-0.000007d. We determine a mass of 9.0+/-0.6M_{sun}_ for each component and temperatures of 28000+/-2000K. Both values are consistent with the spectral type B1V. The two stars are overfilling their respective Roche lobes, sharing a common envelope, and therefore the orbit is synchronised and circularised. Thetwo stars are in a very advanced stage of interaction, with their extreme physical similarity likely due to the common envelope. The expected evolution of such a system will very probably lead to a merger while still on the main sequence.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/110/2739
- Title:
- H-alpha emitting regions in M33
- Short Name:
- J/AJ/110/2739
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report finding charts and accurate positions for 432 compact H{alpha} emitting regions in the Local Group Galaxy M33 (NGC 598), in an effort to isolate candidates for an SS433-like stellar system. The objects were extracted from narrowband images, centered in the rest frame H{alpha} ({lambda}6563A) and in the red continuum at 6100A. The atlas is complete down to V=~20, and includes 279 compact H II regions and 153 line emitting point-like sources. The point-like sources undoubtedly include a variety of objects: very small H II regions, early type stars with intense stellar winds, and Wolf-Rayet stars, but should also contain objects with the characteristics of SS433. This extensive survey of compact H{alpha} regions in M33 is a first step towards the identification of peculiar stellar systems like SS433 in external galaxies.
- ID:
- ivo://CDS.VizieR/J/A+A/633/A44
- Title:
- HARPS Young Nearby Stars - YNS
- Short Name:
- J/A+A/633/A44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Young nearby stars are good candidates in the search for planets with both radial velocity (RV) and direct imaging techniques. This, in turn, allows for the computation of the giant planet occurrence rates at all separations. The RV search around young stars is a challenge as they are generally faster rotators than older stars of similar spectral types and they exhibit signatures of magnetic activity (spots) or pulsation in their RV time series. Specific analyses are necessary to characterize, and possibly correct for, this activity. Our aim is to search for planets around young nearby stars and to estimate the giant planet (GP) occurrence rates for periods up to 1000 days. We used the HARPS spectrograph on the 3.6m telescope at La Silla Observatory to observe 89 A-M young (<600Myr) stars. We used our SAFIR (Spectroscopic data via Analysis of the Fourier Interspectrum Radial velocities) software to compute the RV and other spectroscopic observables. Then, we computed the companion occurrence rates on this sample. We confirm the binary nature of HD 177171, HD 181321 and HD 186704. We report the detection of a close low mass stellar companion for HIP 36985. No planetary companion was detected. We obtain upper limits on the GP (<13M_Jup_) and BD ({in}[13;80]M_Jup_) occurrence rates based on 83 young stars for periods less than 1000 days, which are set, 2_-2_^+3^ and 1_-1_^+3^%.
- ID:
- ivo://CDS.VizieR/J/AJ/148/64
- Title:
- HAZMAT. I. FUV and NUV emission in early M stars
- Short Name:
- J/AJ/148/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectral energy distribution, variability, and evolution of the high-energy radiation from an M dwarf planet host is crucial in understanding the planet's atmospheric evolution and habitability and in interpreting the planet's spectrum. The star's extreme-UV (EUV), far-UV (FUV), and near-UV (NUV) emission can chemically modify, ionize, and erode the atmosphere over time. This makes determining the lifetime exposure of such planets to stellar UV radiation critical for both the evolution of a planet's atmosphere and our potential to characterize it. Using the early M star members of nearby young moving groups, which sample critical ages in planet formation and evolution, we measure the evolution of the GALEX NUV and FUV flux as a function of age. The median UV flux remains at a "saturated" level for a few hundred million years, analogous to that observed for X-ray emission. By the age of the Hyades Cluster (650Myr), we measure a drop in UV flux by a factor of 2-3 followed by a steep drop from old (several Gyrs) field stars. This decline in activity beyond 300Myr follows roughly t^-1^. Despite this clear evolution, there remains a wide range, of 1-2 orders of magnitude, in observed emission levels at every age. These UV data supply the much-needed constraints to M dwarf upper-atmosphere models, which will provide empirically motivated EUV predictions and more accurate age-dependent UV spectra as inputs to planetary photochemical models.
- ID:
- ivo://CDS.VizieR/J/ApJ/632/L131
- Title:
- HD13189 equivalent widths and abundances
- Short Name:
- J/ApJ/632/L131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the abundances of 13 elements in the planetary host HD 13189, a massive giant star.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A96
- Title:
- HD 166734 ESPRESSO spectra
- Short Name:
- J/A+A/607/A96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- HD 166734 is an eccentric eclipsing binary system composed of two supergiant O-type stars, orbiting with a 34.5-day period. In this rare configuration for such stars, the two objects mainly evolve independently, following single-star evolution so far. This system provides a chance to study the individual parameters of two supergiant massive stars and to derive their real masses. An intensive monitoring was dedicated to HD 166734. We analyzed mid- and high-resolution optical spectra to constrain the orbital parameters of this system. We also studied its light curve for the first time, obtained in the VRI filters. Finally, we disentangled the spectra of the two stars and modeled them with the CMFGEN atmosphere code in order to determine the individual physical parameters. HD 166734 is a O7.5If+O9I(f) binary. We confirm its orbital period but we revise the other orbital parameters. In comparison to what we found in the literature, the system is more eccentric and, now, the hottest and the most luminous component is also the most massive one. The light curve exhibits only one eclipse and its analysis indicates an inclination of 63.0+/-2.7{deg}. The photometric analysis provides us with a good estimation of the luminosities of the stars, and therefore their exact positions in the Hertzsprung-Russell diagram. The evolutionary and the spectroscopic masses show good agreement with the dynamical masses of 39.5M_{sun}_ for the primary and 33.5M_{sun}_ for the secondary, within the uncertainties. The two components are both enriched in helium and in nitrogen and depleted in carbon. In addition, the primary also shows a depletion in oxygen. Their surface abundances are however not different from those derived from single supergiant stars, yielding, for both components, an evolution similar to that
- ID:
- ivo://CDS.VizieR/J/A+A/503/945
- Title:
- HD 145788, 21 Peg and pi Cet chemical analysis
- Short Name:
- J/A+A/503/945
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Modern spectroscopy of early-type stars often aims at studying complex physical phenomena such as stellar pulsation, the peculiarity of the composition of the photosphere, chemical stratification, the presence of a magnetic field, and its interplay with the stellar atmosphere and the circumstellar environment. Comparatively less attention is paid to identifying and studying the "normal" A- and B-type stars and testing how the basic atomic parameters and standard spectral analysis allow one to fit the observations. By contrast, this kind of study is paramount for eventually allowing one to correctly quantify the impact of the various physical processes that occur inside the atmospheres of A- and B-type stars. We wish to establish whether the chemical composition of the solar photosphere can be regarded as a reference for early A- and late B-type stars.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A76
- Title:
- Herschel-HIFI water spectra of W43-MM1
- Short Name:
- J/A+A/542/A76
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Herschel/HIFI observations of 14 water lines in W43-MM1, a massive protostellar object in the luminous star-cluster-forming region W43. We place our study in the more general context of high-mass star formation. The dynamics of these regions may be represented by either the monolithic collapse of a turbulent core, or competitive accretion. Water turns out to be a particularly good tracer of the structure and kinematics of the inner regions, allowing an improved description of the physical structure of the massive protostar W43-MM1 and an estimation of the amount of water around it. We analyze the gas dynamics from the line profiles using Herschel-HIFI observations acquired as part of the Water In Star-forming regions with Herschel project of 14 far-IR water lines (H_2_^16^O, H_2_^17^O, H_2_^18^O), CS(11-10), and C^18^O(9-8) lines, using our modeling of the continuum spectral energy distribution. The spectral modeling tools allow us to estimate outflow, infall, and turbulent velocities and molecular abundances. We compare our results to previous studies of low-, intermediate-, and other high-mass objects. As for lower-mass protostellar objects, the molecular line profiles are a mix of emission and absorption, and can be decomposed into 'medium' (full width at half maximum FWHM~=5-10km/s), and 'broad' velocity components (FWHM~=20-35km/s). The broad component is the outflow associated with protostars of all masses. Our modeling shows that the remainder of the water profiles can be well-fitted by an infalling and passively heated envelope, with highly supersonic turbulence varying from 2.2km/s in the inner region to 3.5km/s in the outer envelope. In addition, W43-MM1 has a high accretion rate of between 4.0x10^-4^ and 4.0x10^-2^M_{sun}_/yr, as derived from the fast (0.4-2.9km/s) infall observed. We estimate a lower mass limit for gaseous water of 0.11M_{sun}_ and total water luminosity of 1.5L_{sun}_ (in the 14 lines presented here). The central hot core is detected with a water abundance of 1.4x10^-4^, while the water abundance for the outer envelope is 8x10^-8^. The latter value is higher than in other sources, and most likely related to the high turbulence and the micro-shocks created by its dissipation. Examining the water lines of various energies, we find that the turbulent velocity increases with the distance from the center. While not in clear disagreement with the competitive accretion scenario, this behavior is predicted by the turbulent core model. Moreover, the estimated accretion rate is high enough to overcome the expected radiation pressure.
- ID:
- ivo://CDS.VizieR/J/MNRAS/411/2596
- Title:
- High Galactic latitude runaway stars
- Short Name:
- J/MNRAS/411/2596
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We estimate the distribution of ejection velocities for the known population of high Galactic latitude runaway stars. The initial sample is a collection of 174 early-type stars selected from the literature. The stars are first classified according to their evolutionary status in order to obtain a homogeneous sample of 96 genuine main-sequence stars. Their present velocities and flight times are then estimated using proper motion data from various astrometric catalogues (including Tycho-2, UCAC2 and USNO-B) and the ejection velocities are computed by tracing their orbits back in time, based on a Galactic potential. The potential used is constructed from a mass density model chosen to fit the most recent observational constraints.
- ID:
- ivo://CDS.VizieR/J/A+AS/132/93
- Title:
- Hipparcos photometry of CP stars
- Short Name:
- J/A+AS/132/93
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Hipparcos photometry of the chemically peculiar main-sequence B, A and F stars are examined for variability. Some non-magnetic CP stars, Mercury-Manganese and metallic-line stars, which according to canonical wisdom should not be variable, may be variable and are identified for further study. Some potentially important magnetic CP stars are noted.
