ﻻ يوجد ملخص باللغة العربية
Focusing on B-emission stars, we investigated a set of H$alpha$ equivalent widths calculated from observed spectra acquired over a period of about 4 years from 2003 to 2007. During this time, changes in equivalent width for our program stars were monitored. We have found a simple statistical method to quantify these changes in our observations. This statistical test, commonly called the F ratio, involves calculating the ratio of the external and internal error. We show that the application of this technique can be used to place bounds on the degree of variability of Be stars. This observational tool provides a quantitative way to find Be stars at particular stages of variability requiring relatively little observational data.
In order to study the growth and evolution of circumstellar disks around classical Be stars, we analyze optical time-series photometry from the KELT survey with simultaneous infrared and visible spectroscopy from the APOGEE survey and BeSS database f
We present a grid of computed non-local thermodynamic equilibrium (NLTE) equivalent widths (EW) and NLTE abundance corrections for four Ba II lines: 4554, 5853, 6141, and 6496 A. The grid can be useful in deriving the NLTE barium abundance in stars h
We investigate the short-term optical variability of two gamma Cas analogs, pi Aqr and BZ Cru, thanks to intensive ground-based spectroscopic and space-borne photometric monitorings. For both stars, low-amplitude (mmag) coherent photometric variabili
We employ 76 type Ia supernovae with optical spectrophotometry within 2.5 days of B-band maximum light obtained by the Nearby Supernova Factory to derive the impact of Si and Ca features on supernovae intrinsic luminosity and determine a dust reddeni
Aims. We attempt to determine if a dependency on spectral subtype or vsini exists for stars undergoing phase-changes between B and Be states, as well as for those stars exhibiting variability in H{alpha} emission. Methods. We analyse the changes in H