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IRAS observations and IR excesses of RS CVn-type binaries
No full textThe authors present a complete list of IRAS observations of RS CVn-type
binaries, according to the revised version of the IRAS Point Source
Catalog. Selected samples of the data are compared to the colour
sequences for normal stars compiled by Cohen et al. (1987) and to the
flux ratios expected from black bodies. In both cases, some (but not
all) of the sources show evidence of an IR excess, pointing out that RS
CVn variables do not behave in a unique way at IR wavelengths. Since the
excess, when present, is not correlated with the activity level nor with
the evolutionary status, it is concluded that its origin still calls for
a clear explanation, perhaps in terms of mass-loss phenomena near the
Main Sequence
CCD images of nebular sources in star forming regions
No full textCCD images are presented in V, R and I broad-band filters of the two
young stellar objects PP1 and PP9, selected from the Parsamian and
Petrosian (1979) list, for which integrated photometry with standard
stars was obtained. The results of this analysis are discussed, together
with near-IR and IRAS photometric data, on the basis of the energy
distribution diagrams and morphological considerations
IRAS sources associated with nebulosities resembling Herbig-Haro objects
No full textThe IRAS Survey has been used to search 22 nebulosities resembling
Herbig-Haro objects for evidence of newly forming stars. Half the
peculiar nebulae are found to have associated IRAS sources. From a study
of the energy distributions, obtained from JHKL photometry and IRAS flux
densities, the physical characteristics of the sources have been
derived. The IRAS sources 04073 + 3800(GY 10), 05173-0555(GY 14), and
05439 + 3035(GY 18) have been identified as possible low-mass
protostars, while the sources 03134 + 5958(GY 5) and 21004 + 7811(GY 21)
are T Tauri stars with nebular disks and surrounding dust envelopes of
residual infall. Finally, the IRAS source 04591-0856, associated with
the nebula GY 13, could be in an evolutionary stage intermediate between
a protostar in the pure infall phase and that of an obscured T Tauri
IRAS and near infrared observations of peculiar nebulosities
No full textThe authors used the IRAS survey to search for IR emission from 95
peculiar nebulosities with CO emission. Fifty-two IRAS sources are
associated with them. The authors discuss the nature of the sources on
the basis of their IRAS color-color diagram and of near-IR observations
Evidence from Infrared Observations of Circumstellar Matter around Chromospherically Active Binaries
No full textWe analyse a sample of 12 RS CVn-type systems for which accurate photometry exists, extending from optical to near-infrared and even to IRAS bandpasses in some cases. We reconstruct the energy distribution
expected from the binaries, taking into account the radii and spectral
types of the components, and we compare them with the observed fluxes.
In five cases, an infrared excess (in the range 0.4-1.2 mag) is clearly
present. Assuming that this is due to an absorbing shell, we estimate
the required mass of dust, which turns out to be in the range
10-11-10-14 Msun, corresponding to
total shell masses (including gas) in the range
10-9-10-12 Msun. We suggest that the
circumstellar envelopes are built by mass loss in the form of stellar winds driven by magnetic activity
A search for young stellar objects in southern dark clouds
No full textThe IRAS Point Source Catalog has been used to search 482 southern dark
clouds for evidence of young stellar objects. Only 6 percent of the
selected dark clouds have associated IRAS sources with IRAS colors
typical of pre-main-sequence stars. A study of the energy distributions
obtained from JHKLM photometry and IRAS flux densities give an
identification of these IRAS sources. Thirteen sources have been
classified as new low-mass protostellar objects and T Tauri-type stars
with nebular surrounding material disks, while four IRAS sources have no
evidence of near-IR excesses and appear to be similar to post T Tauri
stars in which the nebular disks are probably absent or optically thin
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