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Confirmation of 177 objects in the NSV Catalogue as red long period variables
Colours are derived from online surveys for suspected variables in theNSV having good positions and a red subset of the resultant data isassessed against the ASAS3 online time series database
| A photometric pilot study on Sonneberg archival patrol plates. How many ``constant'' stars are in fact long-term variables?
The light curves of 216 arbitrarly chosen field stars and of 23 knownvariables in the Aur/Tau/Ori region were derived (7.8 m ≤ B ≤12.2 m) from scanned, blue-sensitive archival patrol plates, covering atotal of 34 years (1961-1995). We achieved a photometric accuracy of0.07 ... 0.12 mag in spite of rather unfavourable locations of moststars near the plate borders. 17 field stars turned out to be variables,most of them with time scales of 1000-8000 days in the form of slowwaves with amplitudes between 0.1 and 0.3 mag, i.e. below the thresholdof traditional variable searches on photographic plates. About 50% ofthese new long-term variables exhibit drifts indicating periodic orerratic variability at much longer time scales than covered here. Forthe 23 known variables we achieved improvements in their periods andamplitudes and detected long-term variations (drifts, waves) in about50% of them. The above fraction of low-amplitude long-term variablesamong field stars implies that a total of about 45 000 new variablesshould be detectable in the Sonneberg patrol plate archive. They willrepresent a new, hitherto not investigated population of variable starswith a possibly significant impact on our understanding of the stellarinterior and evolution.Tables 2 and 3 are only available in electronic form athttp://www.edpsciences.org
| Photometric variations of Orion population stars. II Ae-irregular variables and T Tauri stars
UBVRI and H-alpha photometry of five T Tauri stars and threeAe-irregular variables obtained during the 1982/83 observing season atVVO and KPNO is presented. RY Tau shows very little change in color withbrightness, except in (V-R) where it actually becomes bluer as it fades.The 'turnaround' in (U-B) suggested in last year's data on CO Ori hasbeen confirmed when faint, the star ceases becoming redder as it dimsand begins to get bluer. The turnaround is also now clearly seen in B -V. Similar turnarounds are found in two of the Ae stars, BF Ori and UXOri, the latter confirming Zajtseva's (1973) result. These 'blueing'trends make interpretations of the variability based on dust obscurationimplausible. The Ae stars monitored were nearly indistinguishable intheir photometric behavior from the G-type weak emission line T Tauristars SU Aur and CO Ori, suggesting a common mechanism for theirvariability. A general scheme for integrating the diverse properties ofthese variables is proposed, which involves photospheric andchromospheric responses to strong surface magnetic fields.
| Optical monitoring of Orion population stars. I - Results for some T Tauri and Herbig Ae/Be stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982AJ.....87.1710H&db_key=AST
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