ABSTRACT
A new survey is presented, which explores the second data release of the ESA-Gaia mission, in order to search for stellar companions of exoplanet host stars, located at distances closer than ...about 500 pc around the Sun. In total, 176 binaries, 27 hierarchical triples, and one hierarchical quadruple system are detected among more than 1300 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of the exoplanet host stars of at least about 15 per cent. The detected companions and the exoplanet host stars are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.078 and 1.4 M⊙ with a peak in their mass distribution between 0.15 and $0.3\, \mathrm{M}_{\odot }$. The companions are separated from the exoplanet host stars by about 20 up to 9100 au, but are found most frequently within a projected separation of 1000 au. While most of the detected companions are early M dwarfs, eight white dwarf companions of exoplanet host stars are also identified in this survey, whose true nature is revealed with their photometric properties. Hence, these degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post-main-sequence evolution of their former primary star.
Aims. Analyzing exoplanets detected by radial velocity (RV) or transit observations, we determine the multiplicity of exoplanet host stars in order to study the influence of a stellar companion on ...the properties of planet candidates. Methods. Matching the host stars of exoplanet candidates detected by radial velocity or transit observations with online multiplicity catalogs in addition to a literature search, 57 exoplanet host stars are identified having a stellar companion. Results. The resulting multiplicity rate of at least 12% for exoplanet host stars is about four times smaller than the multiplicity of solar like stars in general. The mass and the number of planets in stellar multiple systems depend on the separation between their host star and its nearest stellar companion, e.g. the planetary mass decreases with an increasing stellar separation. We present an updated overview of exoplanet candidates in stellar multiple systems, including 15 new systems (compared to the latest summary from 2009).
We present the results of our high-contrast imaging survey of close stellar and substellar companions of exoplanet host stars, carried out with the adaptive optics imager NACO at the ESO Paranal ...observatory, in Chile. In total, 33 exoplanet host stars were observed with NACO in the K...-band. New comoving companions could be identified close to the stars HD 9578, HD 96167, and HD 142245. The newly detected companions exhibit masses between 0.21 and 0.56 M... and are located at projected separations from their primaries between about 190 and 510 au. In the case of HD 142245, we found evidence that the detected companion is actually a close binary itself with a projected separation of only about 4 au, i.e. HD 142245 might be a hierarchical triple stellar system, which hosts an exoplanet, a new member in the short list of such systems, presently known. In our imaging campaign, a limiting magnitude of K... = 18.5 mag is reached in average in the background noise limited region around our targets at projected separations beyond about 100 au, which allows the detection of substellar companions with masses down to about 60 M... With our NACO observations we can rule out additional stellar companions at projected separations between about 30 and 370 au around the observed exoplanet host stars. (ProQuest: ... denotes formulae/symbols omitted.)
We report the detection of a new low-mass stellar companion to the white dwarf HIP 3678 A, the central star of the planetary nebula NGC 246. The newly found companion is located about 1 arcsec (at ...projected separation of about 500 au) north-east of HIP 3678 A, and shares a common proper motion with the white dwarf and its known comoving companion HIP 3678 B. The hypothesis that the newly detected companion is a non-moving background object can be rejected on a significance level of more than 8σ, by combining astrometric measurements from the literature with follow-up astrometry, obtained with Wide Field Planetary Camera 2/Hubble Space Telescope and NACO/Very Large Telescope. From our deep NACO imaging data, we can rule out additional stellar companions of the white dwarf with projected separations between 130 up to 5500 au. In the deepest high-contrast NACO observation, we achieve a detection limit in the Ks band of about 20 mag, which allows the detection of brown dwarf companions with masses down to 36 M
jup at an assumed age of the system of 260 Myr. To approximate the masses of the companions HIP 3678 B and C, we use the evolutionary Baraffe et al. models and obtain about 0.85 M⊙ for HIP 3678 B and about 0.1 M⊙ for HIP 3678 C. According to the derived absolute photometry, HIP 3678 B should be a early to mid-K dwarf (K2–K5), while HIP 3678 C should be a mid M dwarf with a spectral type in the range between M5 and M6.
Discovery of an OB runaway star inside SNR S147 Dinçel, B; Neuhäuser, R; Yerli, S. K ...
Monthly notices of the Royal Astronomical Society,
04/2015, Letnik:
448, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We present first results of a long-term study: Searching for OB-type runaway stars inside supernova remnants (SNRs). We identified spectral types and measured radial velocities by optical ...spectroscopic observations and we found an early type runaway star inside SNR S147. HD 37424 is a B0.5V-type star with a peculiar velocity of 74 ± 8 km s−1. Tracing back the past trajectories via Monte Carlo simulations, we found that HD 37424 was located at the same position as the central compact object, PSR J0538+2817, 30 ± 4 kyr ago. This position is only ∼4 arcmin away from the geometrical centre of the SNR. So, we suggest that HD 37424 was the pre-supernova binary companion to the progenitor of the pulsar and the SNR. We found a distance of 1333
${^{+103}_{-112}}$
pc to the SNR. The zero-age main sequence progenitor mass should be greater than 13 M⊙. The age is 30 ± 4 kyr and the total visual absorption towards the centre is 1.28 ± 0.06 mag. For different progenitor masses, we calculated the pre-supernova binary parameters. The Roche lobe radii suggest that it was an interacting binary in the late stages of the progenitor.
We present seven new widely separated companions of exoplanet host stars, detected via common proper motion, whose companionship could be confirmed with photometry, and in two cases also with ...follow-up spectroscopy. We derive the masses and projected separations of all detected companions, among them HD 107148 B, a further wide white dwarf companion of an exoplanet host star. The current multiplicity rate of the exoplanet host stars is found to be about 13 per cent.
Results from regular monitoring of relativistic compact binaries like PSR 1913+16 are consistent with the dominant (quadrupole) order emission of gravitational waves (GWs). We show that observations ...associated with the binary black hole (BBH) central engine of blazar OJ 287 demand the inclusion of gravitational radiation reaction effects beyond the quadrupolar order. It turns out that even the effects of certain hereditary contributions to GW emission are required to predict impact flare timings of OJ 287. We develop an approach that incorporates this effect into the BBH model for OJ 287. This allows us to demonstrate an excellent agreement between the observed impact flare timings and those predicted from ten orbital cycles of the BBH central engine model. The deduced rate of orbital period decay is nine orders of magnitude higher than the observed rate in PSR 1913+16, demonstrating again the relativistic nature of OJ 287's central engine. Finally, we argue that precise timing of the predicted 2019 impact flare should allow a test of the celebrated black hole "no-hair theorem" at the 10% level.
ABSTRACT
After core hydrogen burning, massive stars evolve from blue-white dwarfs to red supergiants by expanding, brightening, and cooling within few millennia. We discuss a previously neglected ...constraint on mass, age, and evolutionary state of Betelgeuse and Antares, namely their observed colour evolution over historical times: We place all 236 stars bright enough for their colour to be discerned by the unaided eye (V ≤ 3.3 mag) on the colour-magnitude-diagram (CMD), and focus on those in the Hertzsprung gap. We study pre-telescopic records on star colour with historically critical methods to find stars that have evolved noticeably in colour within the last millennia. Our main result is that Betelgeuse was recorded with a colour significantly different (non-red) than today (red, B − V = 1.78 ± 0.05 mag). Hyginus (Rome) and Sima Qian (China) independently report it two millennia ago as appearing like Saturn (B − V = 1.09 ± 0.16 mag) in colour and ‘yellow’ (quantifiable as B − V = 0.95 ± 0.35 mag), respectively (together, 5.1σ different from today). The colour change of Betelgeuse is a new, tight constraint for single-star theoretical evolutionary models (or merger models). It is most likely located less than one millennium past the bottom of the red giant branch, before which rapid colour evolution is expected. Evolutionary tracks from MIST consistent with both its colour evolution and its location on the CMD suggest a mass of ∼14 M⊙ at ∼14 Myr. The (roughly) constant colour of Antares for the last three millennia also constrains its mass and age. Wezen was reported white historically, but is now yellow.
ABSTRACT We searched for OB-runaway stars inside supernova remnants (SNRs) as a pre-supernova binary companion. As the majority of massive stars are found in close binary systems, a runaway star ...ejected by the orbital energy after the supernova (SN) is expected to be found. Considering a binary mass fraction, q = 0.25−1.0, the runaway star is likely to have an OB spectral type. We selected 12 SNRs at Galactic longitudes 109°−189°. Using Gaia astrometry, we selected stars having consistent distances with those of the SNRs and showing a peculiar proper motion directed away from the central region of the SNRs. We also determined the radial distribution of the extinction towards the SNRs and estimated the spectral types of the OB-runaway candidates through Gaia and Two Micron All Sky Survey photometry. We found two candidates among 12 SNRs. By spectroscopic observations, Gaia DR3 195632152560621440 inside SNR G166.0 + 4.3 was found to be an evolved A3 type star that cannot be the pre-SN binary companion to the progenitor. Gaia DR3 513927750767375872 inside SNR HB 3 is the only OB-runaway candidate (2D space velocity of 33.3 ± 3.3 km s−1). Based on photometric study, the star can be an early B-type main-sequence star with a slightly higher extinction relative to the SNR; however, it might instead be an evolved A-type star at the same distance. The other 11 SNRs do not host an OB-runaway star within their central regions. Although the runaway search was performed in a large interval of distance and extinction, we also estimated distances to the SNRs.
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