Leonita Beatriz Girardi

A substellar companion around the intermediate-mass giant star HD 11977

We report the discovery of a substellar companion to the intermediate-mass star HD 11977 (G5 III). Radial velocities of this star have been monitored for five years with FEROS at the 1.52-m ESO and later at the 2.2-m MPG/ESO telescope in of K 1 = Chile. Based on the collected data we calculated an orbital solution with a period of P = 711 days, a semi-amplitude of K 1 = 105 ms -1 , and an eccentricity of e = 0.4. The period of the radial-velocity variation is longer than that of the estimated stellar rotation, rendering it unlikely that rotational modulation is the source of the variation in the radial velocity. This hypothesis is supported by the absence of a correlation between stellar activity indicators and radial-velocity variation. By determining a primary stellar mass of M * = 1.91 M ○. , the best-fit minimum mass of the companion and semi-major axis of the orbit are m 2 sin i = 6.54 M Jup and a 2 = 1.93 AU, respectively. An upper limit for the mass of the companion of m 2 ? 65.5 M Jup has been calculated from HIPPARCOS astrometric measurements. Although the possibility of a brown-dwarf companion cannot be excluded, HD 11977 B is one of the few planet candidates detected around an intermediate-mass star. The progenitor main-sequence star of HD 11977 is probably an A-type star. This discovery gives an indirect evidence for planetary companions around early type main-sequence stars.

Precise radial velocity measurements of G and K giants Multiple systems and variability trend along the Red Giant Branch

We present the results of our radial velocity (RV) measurements of G and K giants, concentrating on the presence of multiple systems in our sample. Eighty-three giants have been observed for 2.5 years with the fiber-fed echelle spectrograph FEROS at the 1.52 m ESO telescope in La Silla, Chile. Seventy-seven stars (93%) of the targets have been analyzed for RV variability using simultaneous Th-Ar calibration and a cross-correlation technique. We estimate the long-term precision of our measurement as better than 25 m s −1 . Projected rotational velocities have been measured for most stars of the sample. Within our time-base only 21 stars (or 27%) show variability below 2σ, while the others show RV variability with amplitudes up to several km s −1 . The large amplitude (several km s −1 ) and shape (high eccentricity) of the RV variations for 11 of the program stars are consistent with stellar companions, and possibly brown dwarf companions for two of the program stars. In those systems for which a full orbit could be derived, the companions have minimum masses from ∼0.6 Mdown to 0.1 M� .T o these multiple systems we add the two candidates of giant planets already discovered in the sample. This analysis shows that multiple systems contribute substantially to the long-term RV variability of giant stars, with about 20% of the sample being composed of multiple systems despite screening our sample for known binary stars. After removing binaries, the range of RV variability in the whole sample clearly decreases, but the remaining stars retain a statistical trend of RV variability with luminosity: luminous cool giants with B − V ≥ 1.2 show RV variations with σRV > 60 m s −1 , while giants with B − V < 1.2 including those in the clump region exhibit less variability or they are constant within our accuracy. The same trend is observed with respect to absolute visual magnitudes: brighter stars show a larger degree of variability and, when plotted in the RV variability vs. magnitude diagram a trend of increasing RV scatter with luminosity is seen. The amplitude of RV variability does not increase dramatically, as predicted, for instance, by simple scaling laws. At least two luminous and cooler stars of the sample show a correlation between RV and chromospheric activity and bisector asymmetry, indicating that in these two objects RV variability is likely induced by the presence of (chromospheric) surface structures.

Qualidade de sementes e mudas de Schizolobium parahyba procedentes do Rio Grande do Sul, Santa Catarina e Paraná

Neste trabalho, objetivou-se estudar o vigor por diferentes testes e a sanidade de sementes de guapuruvu (Schizolobium parahyba) procedentes dos estados do Rio Grande do Sul (RS), Santa Catarina (SC) e Parana (PR) e avaliar a qualidade das mudas produzidas por estas sementes. As avaliacoes em sementes foram: teor de agua, germinacao, diferentes testes de vigor e sanidade e as de mudas em viveiro foram: sementes duras e mortas, emergencia, altura de plântula e comprimento de raiz, diâmetro do colo, peso fresco e peso seco. Para as sementes, as amostras procedentes de SC e PR tiveram melhor desempenho nas avaliacoes de primeira contagem de germinacao, massa seca e envelhecimento acelerado, as quais foram eficientes para estratificar as procedencias de sementes em diferentes niveis de vigor. Os fungos encontrados nas sementes foram Aspergillus sp., Alternaria sp., Penicillium sp. e Trichoderma sp. Com relacao as mudas, as sementes de PR apresentaram os melhores resultados nos testes em que as diferencas foram significativas (emergencia, comprimento de raiz e peso de materia seca de plântulas). Algumas variaveis de laboratorio tiveram correlacao com as de viveiro, indicando estreita relacao entre os testes.