921 research outputs found
Diagnostics Of Disks Around Hot Stars
We discuss three different observational diagnostics related to disks around hot stars: absorption line determinations of rotational velocities of Be stars; polarization diagnostics of circumstellar disks; and X-ray line diagnostics of one specific magnetized hot star, theta(1) Ori C. Some common themes that emerge from these studies include (a) the benefits of having a specific physical model as a framework for interpreting diagnostic data; (b) the importance of combining several different types of observational diagnostics of the same objects; and (c) that while there is often the need to reinterpret traditional diagnostics in light of new theoretical advances, there are many new and powerful diagnostics that are, or will soon be, available for the study of disks around hot stars
Toward Mapping the Detailed Density Structure of Classical Be Circumstellar Disks
We present the preliminary results of near contemporaneous optical and infrared spectroscopic observations of select classical Be stars. We find strong evidence of oppositely oriented V/R hydrogen line profiles in the optical versus infrared spectra of zeta Tau, and briefly discuss how sustained contemporaneous optical and infrared spectroscopic observations might enable us to trace the detailed density structure of classical Be circumstellar disks
Properties of galactic B[e] supergiants: II. HDE 327083
The emission-line object HDE 327083 has long been considered to be one of the most luminous stars in the Milky Way. Nevertheless, no reliable physical parameters have been published for it. Our high-resolution optical spectroscopy revealed the presence of photospheric lines of a cool luminous companion. We detected significant antiphased radial velocity variations of the emission and absorption lines. The data obtained are still insufficient to derive a reliable orbital solution; however, the orbital period is most likely of the order of 6 months. We conclude that HDE 327083 is a binary system consisting of an early B-type primary and early F-type secondary, with luminosities log L/L⊙ = 5.0 ± 0.4 and 4.2 ± 0.4, respectively, and whose orbital plane is viewed nearly edge-on. We also obtained new multicolour optical and infrared photometry of HDE 327083. From both the photometric and spectroscopic data, we found that the system is located at a distance of 1.5 ± 0.5 kpc. Most of the circumstellar gas seems to be orbiting the primary and is distributed in a mildly flattened envelope with a height scale and velocity decreasing outward from the star. We suggest that HDE 327083 represents an advanced evolutionary stage of a β Lyrae type binary.Fil: Miroshnichenko, A. S.. Russian Academy of Sciences at Pulkovo; Rusia. University of Toledo; Estados UnidosFil: Levato, Orlando Hugo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; ArgentinaFil: Bjorkman, K. S.. University of Toledo; Estados UnidosFil: Grosso, Monica Gladys. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - San Juan. Complejo Astronómico "El Leoncito". Universidad Nacional de Córdoba. Complejo Astronómico "El Leoncito". Universidad Nacional de la Plata. Complejo Astronómico "El Leoncito". Universidad Nacional de San Juan. Complejo Astronómico "El Leoncito"; Argentin
The continued optical to mid-IR evolution of V838 Monocerotis
The eruptive variable V838 Monocerotis gained notoriety in 2002 when it
brightened nine magnitudes in a series of three outbursts and then rapidly
evolved into an extremely cool supergiant. We present optical, near-IR, and
mid-IR spectroscopic and photometric observations of V838 Monocerotis obtained
between 2008 and 2012 at the Apache Point Observatory 3.5m, NASA IRTF 3m, and
Gemini South 8m telescopes. We contemporaneously analyze the optical & IR
spectroscopic properties of V838 Monocerotis to arrive at a revised spectral
type L3 supergiant and effective temperature Teff~2000--2200 K. Because there
are no existing optical observational data for L supergiants in the optical, we
speculate that V838 Monocerotis may represent the prototype for L supergiants
in this wavelength regime. We find a low level of Halpha emission present in
the system, consistent with interaction between V838 Monocerotis and its B3V
binary; however, we cannot rule out a stellar collision as the genesis event,
which could result in the observed Halpha activity. Based upon a two-component
blackbody fit to all wavelengths of our data, we conclude that, as of 2009, a
shell of ejecta surrounded V838 Monocerotis at a radius of R=263+/-10 AU with a
temperature of T=285+/-2 K. This result is consistent with IR interferometric
observations from the same era and predictions from the Lynch et al. model of
the expanding system, which provides a simple framework for understanding this
complicated system.Comment: 6 pages, 2 tables, 6 figures; accepted to A
Validity and Reliability of Electronic Devices to Measure Muscular Power during Linear Weight Lifting Movements
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Properties of galactic B[e] supergiants. IV. Hen3-298 and Hen3-303
We present the results of optical and near-IR spectroscopic and near-IR
photometric observations of the emission-line stars Hen3-298 and Hen3-303.
Strong emission in the H-alpha line is found in both objects. The presence of
Fe II and [O I] emission lines in the spectrum of Hen3-298 indicates that it is
a B[e] star. The double-peaked CO line profiles, found in the infrared spectrum
of Hen3-298, along with the optical line profiles suggest that the star is
surrounded by a rotating circumstellar disk. Both objects also show infrared
excesses, similar to those of B[e] stars. The radial velocities of the
absorption and emission lines as well as a high reddening level suggest that
the objects are located in the Norma spiral arm at a distance of 3-4.5 kpc. We
estimated a luminosity of log (L/L_sun) ~ 5.1 and a spectral type of no earlier
than B3 for Hen3-298. Hen3-303 seems to be a less luminous B-type object (log
(L/L_sun) ~ 4.3), located in the same spiral arm.Comment: 8 pages, 5 figures, accepted by Astronomy and Astrophysic
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