Lunar occultations of Aldebaran and other late-type stars observed from Devasthal

Further milliarcsecond resolution results on cool giants and binary stars from lunar occultations at Devashtal

“…All events were recorded at Devasthal (India) with two different telescopes and instruments, both operated by the Aryabhatta Research Institute of Observational Sciences (ARIES). A log of the observations is provided in Table 1, which follows the style used in Richichi et al (2018). The first few columns list the date, time, type of event (disappearance or reappearance), source designation, V magnitude and spectrum.…”

“…The data products were FITS cubes, which were converted to photometric light curves using a digital extraction mask hand-tailored in each case to the seeing and image motion of the source. This process was described in Richichi et al (2018) and references therein. Only about 1-2 s of data were analyzed, corresponding to an apparent lunar motion of ≈ 2 ′′ on the sky.…”

“…We have reported on 26 additional LO measurements carried out at Devashtal since our latest paper (Richichi et al 2018). In addition to the EMCCD on the 1.3-m telescope, we have also used for the first time the near-IR camera TIR-CAM2 on the DOT 3.6-m telescope.…”

“…The scope and methods of the lunar occultation (LO) program at Devasthal have been described in detail in our previous papers (Richichi et al 2017a(Richichi et al , 2018) so that we keep the discussion to a minimum in the present work. We use the LO technique mainly for two purposes: to investigate properties of late-type giants such as angular diameter, effective temperature and in the case of very evolved star the possible presence of circumstellar matter; and to study subarcsecond separation binary stars which are either already known but with incomplete data, or discover new systems.…”

Science with an ngVLA: Stellar Activity on Red Giant and Supergiant Stars: Mass Loss and the Evolution of the Stellar Dynamo

“…Spatial resolution breaks the spatial impasse that limits what can be learned from disk integrated flux diagnostics alone (e.g., Harper et al 2013). There are some recent clues that red giants show signs of magnetic cycles (Sennhauser & Berdyugina 2011) and non-uniform optical brightness distributions (Richichi et al 2018), indications that magnetic phenomena might be important Graham M. Harper in creating starspots and active regions. High spatial resolution ngVLA observations would reveal the radio size and uniformity of the chromosphere for the nearest red giant stars.…”