- ID:
- ivo://CDS.VizieR/J/other/Nat/563.365
- Title:
- Barnard's star radial velocity curve
- Short Name:
- J/other/Nat/563.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Barnard's star is a red dwarf, and has the largest proper motion (apparent motion across the sky) of all known stars. At a distance of 1.8 parsecs, it is the closest single star to the Sun; only the three stars in the α Centauri system are closer. Barnard's star is also among the least magnetically active red dwarfs known and has an estimated age older than the Solar System. Its properties make it a prime target for planetary searches; various techniques with different sensitivity limits have been used previously, including radial-velocity imaging, astrometry and direct imaging, but all ultimately led to negative or null results. Here we combine numerous measurements from high-precision radial-velocity instruments, revealing the presence of a low-amplitude periodic signal with a period of 233 days. Independent photometric and spectroscopic monitoring, as well as an analysis of instrumental systematic effects, suggest that this signal is best explained as arising from a planetary companion. The candidate planet around Barnard's star is a cold super-Earth, with a minimum mass of 3.2 times that of Earth, orbiting near its snow line (the minimum distance from the star at which volatile compounds could condense). The combination of all radial-velocity datasets spanning 20 years of measurements additionally reveals a long-term modulation that could arise from a stellar magnetic-activity cycle or from a more distant planetary object. Because of its proximity to the Sun, the candidate planet has a maximum angular separation of 220 milliarcseconds from Barnard's star, making it an excellent target for direct imaging and astrometric observations in the future.
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- ID:
- ivo://CDS.VizieR/J/AJ/101/1763
- Title:
- CCD search for Cepheids in Crux and Centaurus
- Short Name:
- II/162
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog contains the results of a photometric survey for variable stars in a 9.4 square degree region along the galactic plane in Crux and Centaurus. A total of 300308 stars were observed at seven epochs over 42 days; 224 524 of these stars were detected at multiple epochs and were tested for possible variations in brightness that exceed observational error. 2422 stars are identified as variable at a formal confidence level of 99%; 270 of the new variables brighter than I=14.0 are classified as long period variables. A list of 242 likely short period variables with RMS amplitudes ≥0.060mag is given. From this list, 37 Cepheid candidates were selected after inspection of their light curves.
- ID:
- ivo://CDS.VizieR/J/other/Ser/199.39
- Title:
- Long-Term Photometry of five PMS stars
- Short Name:
- J/other/Ser/199.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results from long-term optical photometric and spectroscopic observations of five pre-main sequence stars, located in the vicinity of the bright nebula NGC 7129. We obtained UBVRI photometric observations in the field centered on the star V391 Cep, north-west of the bright nebula NGC 7129. Our multicolor CCD observations spanned the period from February 1998 to November 2016. At the time of our photometric monitoring, a total of thirteen medium-resolution optical spectra of the stars were obtained. The results from our photometric study show that all stars exhibit strong variability in all optical passbands. Long-term light curves of the five stars indicate the typical classical T Tauri star variations in brightness with large amplitudes. We did not find any reliable periodicity in the brightness variations of all five stars. The results from spectral observations showed that all studied stars can be classified as classical T Tauri stars with rich emission line spectra and strong variability in profiles and intensity of emission lines.
- ID:
- ivo://CDS.VizieR/J/other/Nat/493.378
- Title:
- LRL 54361 Spitzer light curves
- Short Name:
- J/other/Nat/493.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Periodic increases in luminosity arising from variable accretion rates have been predicted for some pre-main-sequence close binary stars as they grow from circumbinary disks. The phenomenon is known as pulsed accretion and can affect the orbital evolution and mass distribution of young binaries, as well as the potential for planet formation. Accretion variability is a common feature of young stars, with a large range of amplitudes and timescales as measured from multi-epoch observations at optical and infrared wavelengths. Periodic variations consistent with pulsed accretion have been seen in only a few young binaries via optical accretion tracers albeit intermittently with accretion luminosity variations ranging from zero to 50 per cent from orbit to orbit. Here we report that the infrared luminosity of a young protostar (of age about 10<SUP>5</SUP> years) increases by a factor of ten in roughly one week every 25.34 days. We attribute this to pulsed accretion associated with an unseen binary companion. The strength and regularity of this accretion signal is surprising; it may be related to the very young age of the system, which is a factor of ten younger than the other pulsed accretors previously studied.
- ID:
- ivo://CDS.VizieR/J/other/Nat/481.167
- Title:
- 2002-2007 PLANET microlensing events
- Short Name:
- J/other/Nat/481.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most known extrasolar planets (exoplanets) have been discovered using the radial velocity or transit methods. Both are biased towards planets that are relatively close to their parent stars, and studies find that around 17-30% of solar-like stars host a planet. Gravitational microlensing on the other hand, probes planets that are further away from their stars. Recently, a population of planets that are unbound or very far from their stars was discovered by microlensing. These planets are at least as numerous as the stars in the Milky Way. Here we report a statistical analysis of microlensing data (gathered in 2002-07) that reveals the fraction of bound planets 0.5-10AU (Sun-Earth distance) from their stars. We find that of stars host Jupiter-mass planets (0.3-10M<SUB>J</SUB>, where M<SUB>J</SUB>=318M<SUB>{earth}</SUB> and M<SUB>{earth}</SUB> is Earth's mass). Cool Neptunes (10-30M<SUB>{earth}</SUB>) and super-Earths (5-10M<SUB>{earth}</SUB>) are even more common: their respective abundances per star are 52<SUP>+22</SUP><SUB>–29</SUB>% and 62<SUP>+35</SUP><SUB>–37</SUB>%. We conclude that stars are orbited by planets as a rule, rather than the exception.
- ID:
- ivo://CDS.VizieR/J/AJ/110/2288
- Title:
- RR Lyrae Metallicities
- Short Name:
- III/176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog presents metal abundance, distance and radial velocity data on a sample of 302 ab-type RR Lyrae variables within about 2.5 kpc of the Sun. The metal abundance information was obtained from low-medium resolution spectra, using the pseudo-equivalent widths of the Ca II K line and the the H-delta, H-gamma and H-beta lines. The technique employed was similar to Preston's (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1959ApJ...130..507P%201959ApJ...130..507P">1959ApJ...130..507P 1959ApJ...130..507P</A>) Δ-S method, though significant differences exist; see the source reference for details. The data were calibrated to the Zinn & West (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1984ApJS...55...45Z%201984ApJS...55...45Z">1984ApJS...55...45Z 1984ApJS...55...45Z</A>) globular cluster abundance scale. The photometry employed in the distance determinations was primarily taken from the General Catalog of Variable Stars (1985, hereafter GCVS4). Exceptions are noted in column 29; the letters match the footnotes in Table 10 of Layden (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1994AJ....108.1016L%201994AJ....108.1016L">1994AJ....108.1016L 1994AJ....108.1016L</A>). The minimum and maximum light photometry, and rise-time were combined following Barnes & Hawley (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1986ApJ...307L...9B%201986ApJ...307L...9B">1986ApJ...307L...9B 1986ApJ...307L...9B</A>) to give an estimate of the intensity- averaged magnitude, i.e. the magnitude the star would have if it were not variable. When the GCVS4 quoted magnitudes in passbands other than V, the GCVS4 magnitudes were transformed to the V passband using the relations established in Layden (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1994AJ....108.1016L%201994AJ....108.1016L">1994AJ....108.1016L 1994AJ....108.1016L</A>). The interstellar absorption estimates are from Burstein & Heiles (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1982AJ.....87.1165B%201982AJ.....87.1165B">1982AJ.....87.1165B 1982AJ.....87.1165B</A>), modified by a simple dust-distribution model. The distances were computed assuming the Mv(RR)-[Fe/H] relation of Carney, Storm & Jones (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1992ApJ...386..663C%201992ApJ...386..663C">1992ApJ...386..663C 1992ApJ...386..663C</A>). Radial velocities were measured from the spectra via cross-correlation with secondary velocity standards. The velocities from the individual spectra were fit with a standard radial velocity curve in the (phase, velocity) plane, to give an estimate of the systemic (center of mass) velocity of each star. The error in this value was estimated from the scatter about the best-fit velocity curve, and the quality of the spectra employed. Other methods were used to combine the individual velocities when the situation demanded (cm = 2,3 in column 70; see Layden (<A HREF="http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1994AJ....108.1016L%201994AJ....108.1016L">1994AJ....108.1016L 1994AJ....108.1016L</A>) for details). The observed velocities were combined with values from the literature to produce a final, best estimate of the systemic radial velocity of each star, and its error.
- ID:
- ivo://CDS.VizieR/J/other/Nat/485.478
- Title:
- Superflares on solar-type stars
- Short Name:
- J/other/Nat/485.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Solar flares are caused by the sudden release of magnetic energy stored near sunspots. They release 10<SUP>29</SUP> to 10<SUP>32</SUP>ergs of energy on a timescale of hours. Similar flares have been observed on many stars, with larger 'superflares' seen on a variety of stars, some of which are rapidly rotating and some of which are of ordinary solar type. The small number of superflares observed on solar-type stars has hitherto precluded a detailed study of them. Here we report observations of 365 superflares, including some from slowly rotating solar-type stars, from about 83,000 stars observed over 120 days. Quasi-periodic brightness modulations observed in the solar-type stars suggest that they have much larger starspots than does the Sun. The maximum energy of the flare is not correlated with the stellar rotation period, but the data suggest that superflares occur more frequently on rapidly rotating stars. It has been proposed that hot Jupiters may be important in the generation of superflares on solar-type stars, but none have been discovered around the stars that we have studied, indicating that hot Jupiters associated with superflares are rare.
