- 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.
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- 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/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/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.
