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Projected Rotational Velocity (projected + rotational_velocity)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Rotational velocities of the giants in symbiotic stars , III.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
Evidence of fast rotation in S-type symbiotics
ABSTRACT We have measured the projected rotational velocities (v sin i) in a number of symbiotic stars and M giants using high-resolution spectroscopic observations. On the basis of our measurements and data from the literature, we compare the rotation of mass donors in symbiotics with v sin i of field giants and find that: (i) the K giants in S-type symbiotics rotate at v sin i > 4.5 km s,1, which is 2,4 times faster than the field K giants; (ii) the M giants in S-type symbiotics rotate on average 1.5 times faster than the field M giants. Statistical tests show that these differences are highly significant , p-value <10,3 in the spectral-type bins K2III-K5III, M0III-M6III and M2III-M5III and (iii) our new observations of D'-type symbiotics also confirm that they are fast rotators. As a result of the rapid rotation, the cool giants in symbiotics should have 3,30 times larger mass-loss rates. Our results suggest also that bipolar ejections in symbiotics seem to happen in objects where the mass donors rotate faster than the orbital period. All spectra used in our series of papers can be obtained upon request from the authors. [source]

H, long-term monitoring of the Be star , Cephei Aa

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008
G. Catanzaro
ABSTRACT Papers published in recent years have contributed to resolve the enigma of the hypothetical Be nature of the hot pulsating star , Cephei. This star shows variable emission in the H, line, typical for Be stars, but its projected rotational velocity is very much lower than the critical limit, contrary to what is expected for a typical Be star. The emission has been attributed to the secondary component of the , Cephei spectroscopic binary system. In this paper, using both our and archived spectra, we attempt to recover the H, profile of the secondary component and to analyse its behaviour with time for a long period. To accomplish this task, we first derive the atmospheric parameters of the primary, Teff= 24 000 ± 250 K and log g= 3.91 ± 0.10, and then we use these values to compute its synthetic H, profile, and finally we reconstruct the secondary's profile disentangling the observed one. The secondary's H, profile shows the typical two-peak emission of a Be star with a strong variability. We also analysed the behaviour versus time of some linewidth parameters: equivalent width, ratio of blue to red peak intensities, full width at half-maximum, peak separation and radial velocity of the central depression. The projected rotational velocity (v sin i) of the secondary and the dimension of the equatorial surrounding disc have also been estimated. [source]

The stellar mass ratio of GK Persei

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2002
L. Morales-Rueda
We study the absorption lines present in the spectra of the long-period cataclysmic variable GK Per during its quiescent state, which are associated with the secondary star. By comparing quiescent data with outburst spectra we infer that the donor star appears identical during the two states and the inner face of the secondary star is not noticeably irradiated by flux from the accreting regions. We obtain new values for the radial velocity semi-amplitude of the secondary star, , a projected rotational velocity, and consequently a measurement of the stellar mass ratio of GK Per, . The inferred white dwarf radial velocities are greater than those measured traditionally using the wings of Doppler-broadened emission lines suspected to originate in an accretion disc, highlighting the unsuitability of emission lines for mass determinations in cataclysmic variables. We determine mass limits for both components in the binary, and . [source]

Orbital eccentricity of the symbiotic star MWC 560,

ASTRONOMISCHE NACHRICHTEN, Issue 3 2010
R.K. Zamanov
Abstract We present projected rotational velocity measurements of the red giant in the symbiotic star MWC 560, using the high-resolution spectroscopic observations with the FEROS spectrograph. We find that the projected rotational velocity of the red giant is v sin i = 8.2 ± 1.5 km s,1, and estimate its rotational period tobe Prot = 144,306 days. Using the theoretical predictions of tidal interaction and pseudosynchronization, we estimate the orbital eccentricity e = 0.68,0.82. We briefly discuss the connection of our results with the photometric variability of the object (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]