61 research outputs found
FS CMa type binaries
FS CMa type stars is a group of ~70 objects formerly known as unclassified
stars with the B[e] phenomenon. Their very strong emission-line spectra in
combination with a nearly main-sequence luminosity suggest the binary nature
for them. They possess strong IR excesses due to radiation of circumstellar
dust that implies a compact distribution probably in a circumbinary disk. Our
long-term spectroscopic monitoring revealed neutral metal lines, which always
include that of Li I 6708 \AA, in the spectra of some FS CMa objects indicating
the presence of a cool star. We present a summary of our results with a first
overview of FS CMa type binaries and review possible implications for the
nature and evolutionary status of the entire group.Comment: 4 pages, 1 figure, to appear in EAS Publication Series, in
proceedings of the "Physics Of Evolved Star 2015" conferenc
The Vela and Geminga pulsars in the mid-infrared
The Vela and Geminga pulsars are rotation powered neutron stars, which have
been identified in various spectral domains, from the near-infrared to hard
-rays. In the near-infrared they exhibit tentative emission excesses,
as compared to the optical range. To check whether these features are real, we
analysed archival mid-infrared broadband images obtained with the Spitzer Space
Telescope in the 3.6--160 m range and compared them with the data in other
spectral domains. In the 3.6 and 5.8 m bands we detected at
(4--5) significance level a point-like object, that is likely to be the
counterpart of the Vela pulsar. Its position coincides with the pulsar at < 0.4
arcsec 1-accuracy level. Combining the measured fluxes with the
available multiwavelength spectrum of the pulsar shows a steep flux increase
towards the infrared, confirming the reality of the near-infrared excess
reported early, and, hence, the reality of the suggested mid-infrared pulsar
identification. Geminga is also identified, but only at a marginal 2
detection level in one 3.6 m band. This needs a farther confirmation by
deeper observations, while the estimated flux is also compatible with the
near-infrared Geminga excess. The detection of the infrared excess is in
contrast to the Crab pulsar, where it is absent, but is similar to the two
magnetars, 4U 0142+61 and 1E 2259+586, showing similar features. We discuss
X-ray irradiated fall-back discs around the pulsars, unresolved pulsar nebula
structures, and pulsar magnetospheres as possible origins of the excesses. We
note also possible infrared signatures of an extended tail behind Geminga and
of the Vela plerion radio lobes.Comment: 16 pages, 9 figures, 2 table
The PSR J1124-5916 wind nebula in the near-infrared
The young radio pulsar J1124-5916 is associated with a Cas A like supernova
remnant G292.0+1.8. It powers a compact torus-like pulsar wind nebula with a
jet first detected in X-rays and then identified in the optical and
mid-infrared. We carried out deep near-infrared observations of the pulsar
field to identify the pulsar and its nebula in this range. The direct imaging
mode of the NACO adaptive optics instrument at the ESO VLT in the H and Ks
bands was used. In both bands we detected a faint, H=21.30(10) and
Ks=20.45(10), extended elliptical object, whose center position is consistent
with the X-ray position of the pulsar. The morphology of the object and the
orientation of its major axis are in a good agreement with those observed for
the pulsar torus-like nebula in the mid-infrared, optical, and X-rays. This
suggests that it is the near-infrared counterpart of the nebula. The measured
fluxes compiled with the data in other ranges show a complicated unabsorbed
power law spectrum of the torus-like nebula with several steep breaks between
the near-infrared and mid-infrared, the optical and X-rays, and possibly in the
mid-infrared. This implies a multiple relativistic particle population
responsible for the synchrotron emission of the nebula in different spectral
ranges. We have not resolved the pulsar counterpart from its nebula and place
only upper limits on its brightness, H >= 23.9$ and Ks >= 22.7. Based on that,
its contribution to the total near-infrared flux of the pulsar+nebula system is
<= 10%, which is comparable with the expected contribution in the optical.Comment: 7 pages, 6 figures, 3 tables, Accepted for publication in A&
The B[e] phenomenon in the Milky Way and Magellanic Clouds
Discovered over 30 years ago, the B[e] phenomenon has not yet revealed all
its puzzles. New objects that exhibit it are being discovered in the Milky Way,
and properties of known objects are being constrained. We review recent
findings about objects of this class and their subgroups as well as discuss new
results from studies of the objects with yet unknown nature. In the Magellanic
Clouds, the population of such objects has been restricted to supergiants. We
present new candidates with apparently lower luminosities found in the LMC.Comment: 5 pages, 2 figures, IAU Symposium 272, Active OB stars: structure,
evolution, mass loss and critical limit
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