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LONG-PERIOD VARIATIONS IN THE RADIAL VELOCITY OF SPECTROSCOPIC BINARY M GIANT<i>μ</i>URSAE MAJORIS
Lee, Byeong-Cheol,Han, Inwoo,Park, Myeong-Gu,Mkrtichian, David E.,Hatzes, Artie P.,Jeong, Gwanghui,Kim, Kang-Min American Astronomical Society 2016 The Astronomical journal Vol.151 No.4
<P>We report that the spectroscopic binary mu Ursae Majoris (mu UMa) has secondary RV variations of 471.2 days in addition to those of 230.0 days already known. Keplerian orbit analysis yields stellar mass companions of 1.6. M-circle dot for the 230 day period and 0.14. M-circle dot for the 471 day period. However, the HIPPARCOS photometries show a period similar to the stellar rotational period, which is one-quarter of the RV period. Variations in the bisector velocity curvature show a period of 463.6 days. We also find similar to 473 day variations in the equivalent width (EW) measurements of the H-alpha and H-beta lines, whose origin is probably stellar activity. We note that the nature of 471 day variations is similar to one observed in 'Sequence D' of Asymptotic Giant Branch pulsating stars. We therefore conclude that the RV and the EW variations in the spectroscopic binary M giant mu UMa. A originate from the complex pulsations and the chromospheric activity.</P>
Lee, Byeong-Cheol,Jeong, Gwanghui,Park, Myeong-Gu,Han, Inwoo,Mkrtichian, David E.,Hatzes, Artie P.,Gu, Shenghong,Bai, Jinming,Lee, Sang-Min,Oh, Hyeong-Il,Kim, Kang-Min American Astronomical Society 2017 The Astrophysical journal Vol.844 No.1
<P>We present the detection of long-period RV variations in HD. 36384, HD. 52030, and HD. 208742 by using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) for the precise radial velocity (RV) survey of about 200 northern circumpolar stars. Analyses of RV data, chromospheric activity indicators, and bisector variations spanning about five years suggest that the RV variations are compatible with planet or brown dwarf companions in Keplerian motion. However, HD. 36384 shows photometric variations with a period very close to that of RV variations as well as amplitude variations in the weighted wavelet Z-transform (WWZ) analysis, which argues that the RV variations in HD. 36384 are from the stellar pulsations. Assuming that the companion hypothesis is correct, HD. 52030 hosts a companion with minimum mass 13.3 M-Jup orbiting in 484 days at a distance of 1.2 au. HD. 208742 hosts a companion of 14.0 M-Jup at 1.5 au with a period of 602 days. All stars are located at the asymptotic giant branch (AGB) stage on the H-R diagram after undergoing. the helium flash and leaving. the giant clump. With stellar radii of 53.0 R-circle dot and 57.2 R-circle dot for HD. 52030 and HD. 208742, respectively, these stars may be the largest yet, in terms of stellar radius, found to host substellar companions. However, given possible RV amplitude variations and the fact that these are highly evolved stars, the planet hypothesis is not yet certain.</P>
Kambe, Eiji,Ando, Hiroyasu,Sato, Bun’ei,Izumiura, Hideyuki,Sekii, Takashi,Paulson, Diane B.,Yanagisawa, Kenshi,Masuda, Seiji,Shibahashi, Hiromoto,Hatzes, Artie P.,MARTI´C, Milena,LEBRUN, Jean-Claude,M Astronomical Society of Japan 2008 Publications of the Astronomical Society of Japan Vol.60 No.1
An improvement of the radial-velocity measurement accuracy is crucial for the detection of tiny stellar oscillationsand exoplanets. Through the analysis of week-long extensive observations of solar-type stars (Procyon in 2000, 2002, and 2006/2007 and τ Cet in 2002 and 2006/2007), we have carefully examined, revised, and finelytuned the widely used multiple Gaussian IP fitting method for the spectrograph, HIDES. By determining a necessaryand sufficient number of free parameters in the model as well as introducing an iterative process in the radial-velocityanalysis, we can reach a precision of below 3ms<SUP>-1</SUP>, which is much smaller than the precision of 6ms<SUP>-1</SUP> officially announced so far for HIDES. We also make our technique refined for the 2002 McDonald Procyon data. Even with our revised method, slow radial velocity variations with an amplitude of about 10ms<SUP>-1</SUP> are left in the Procyon data. We emphasize that it is neither due to particular observing instruments nor radial-velocity analysis, and thus could be due to stellar origin. The analysis presented here makes the foundations of our next scientific analysis of the radial-velocity variations of Procyon, which will be presented in our forthcoming papers.
Photosensitized production of singlet oxygen: spatially-resolved optical studies in single cells
Breitenbach, Thomas,Kuimova, Marina K.,Gbur, Peter,Hatz, Sonja,Schack, Nickolass Bitsch,Pedersen, Brian Wett,Lambert, John D.C.,Poulsen, Lars,Ogilby, Peter R. Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.4
Singlet molecular oxygen, $O_2(a^1{\Delta}_g)$, can be created in photosensitized experiments with sub-cellular spatial resolution in a single cell. This cytotoxic species can subsequently be detected by its 1270 nm phosphorescence ($a^1{\Delta}_g\;{\rightarrow}\;X^3{\Sigma}^-_g$). Cellular responses to the creation of singlet oxygen can be monitored using viability assays. Time- and spatially-resolved optical measurements of both singlet oxygen and its precursor, the excited state sensitizer, reflect the complex and dynamic morphology of the cell. These experiments help elucidate photoinduced, oxygen-dependent events that compromise cell function and ultimately lead to cell death. In this perspective, recent work on the photosensitized production and detection of singlet oxygen in single cells is summarized, highlighting the advantages and current limitations of this unique experimental approach to study an old problem.