Normalized to: R..
[1]
oai:arXiv.org:1503.03447 [pdf] - 950211
On the Nature of Rapidly Rotating Single Evolved Stars
Submitted: 2015-03-11
We present an analysis of the nature of the rapidly rotating, apparently
single giant based on rotational and radial velocity measurements carried out
by the CORAVEL spectrometers. From the analyzed sample, composed of 2010
spectroscopic, apparently single, evolved stars of luminosity classes IV, III,
II, and Ib with spectral types G and K, we classified 30 stars that presented
unusual, moderate to rapid rotation. This work reports, for the first time, the
presence of these abnormal rotators among subgiant, bright giant, and Ib
supergiant stars. To date, this class of stars was reported only among giant
stars of luminosity class III. Most of these abnormal rotators present an IRAS
infrared excess, which, in principle, can be related to dust around these
stars.
[2]
oai:arXiv.org:1410.0842 [pdf] - 908602
The Gaia-ESO Survey: Extracting diffuse interstellar bands from cool
star spectra, DIB-based interstellar medium line-of-sight structures at the
kpc scale
Puspitarini, L.;
Lallement, R.;
Babusiaux, C.;
Chen, H-C.;
Bonifacio, P.;
Sbordone, L.;
Caffau, E.;
Duffau, S.;
Hill, V.;
Monreal-Ibero, A.;
Royer, F.;
Arenou, F.;
R.;
Peralta, A.;
Drew, J. E.;
Bonito, R.;
Lopez-Santiago, J.;
Alfaro, E.;
Bensby, T.;
Bragaglia, A.;
Flaccomio, E.;
Lanzafame, A.;
Pancino, E.;
Recio-Blanco, A.;
Smiljanic, R.;
Costado, M. T.;
Lardo, C.;
de Laverny, P.;
Zwitter, T.
Submitted: 2014-10-03
We study how diffuse interstellar bands (DIBs) measured toward
distance-distributed target stars can be used to locate dense interstellar (IS)
clouds in the Galaxy and probe a line-of-sight (LOS) kinematical structure, a
potential useful tool when gaseous absorption lines are saturated or not
available in the spectral range. Cool target stars are numerous enough for this
purpose. We have devised automated DIB fitting methods appropriate to cool star
spectra and multiple IS components. The data is fitted with a combination of a
synthetic stellar spectrum, a synthetic telluric transmission, and empirical
DIB profiles. In parallel, stellar distances and extinctions are estimated
self-consistently by means of a 2D Bayesian method, from
spectroscopically-derived stellar parameters and photometric data. We have
analyzed Gaia-ESO Survey (GES) and previously recorded spectra that probe
between $\sim$ 2 and 10 kpc long LOS in five different regions of the Milky
Way. Depending on the observed spectral intervals, we extracted one or more of
the following DIBs: $\lambda\lambda$ 6283.8, 6613.6 and 8620.4. For each field,
we compared the DIB strengths with the Bayesian distances and extinctions, and
the DIB Doppler velocities with the HI emission spectra. For all fields, the
DIB strength and the target extinction are well correlated. In case of targets
widely distributed in distance, marked steps in DIBs and extinction radial
distance profiles match with each other and broadly correspond to the expected
locations of spiral arms. For all fields, the DIB velocity structure agrees
with HI emission spectra and all detected DIBs correspond to strong NaI lines.
This illustrates how DIBs can be used to locate the Galactic interstellar gas
and to study its kinematics at the kpc scale.
[3]
oai:arXiv.org:1203.0026 [pdf] - 493624
Ultra Long Period Cepheids: a primary standard candle out to the Hubble
flow
Submitted: 2012-02-29
The cosmological distance ladder crucially depends on classical Cepheids
(with P=3-80 days), which are primary distance indicators up to 33 Mpc. Within
this volume, very few SNe Ia have been calibrated through classical Cepheids,
with uncertainty related to the non-linearity and the metallicity dependence of
their period-luminosity (PL) relation. Although a general consensus on these
effects is still not achieved, classical Cepheids remain the most used primary
distance indicators. A possible extension of these standard candles to further
distances would be important. In this context, a very promising new tool is
represented by the ultra-long period (ULP) Cepheids (P \geq 80 days), recently
identified in star-forming galaxies. Only a small number of ULP Cepheids have
been discovered so far. Here we present and analyse the properties of an
updated sample of 37 ULP Cepheids observed in galaxies within a very large
metallicity range of 12+log(O/H) from ~7.2 to 9.2 dex. We find that their
location in the colour(V-I)-magnitude diagram as well as their Wesenheit (V-I)
index-period (WP) relation suggests that they are the counterparts at high
luminosity of the shorter-period (P \leq 80 days) classical Cepheids. However,
a complete pulsation and evolutionary theoretical scenario is needed to
properly interpret the true nature of these objects. We do not confirm the
flattening in the studied WP relation suggested by Bird et al. (2009). Using
the whole sample, we find that ULP Cepheids lie around a relation similar to
that of the LMC, although with a large spread (~0.4 mag).
[4]
oai:arXiv.org:1012.0782 [pdf] - 1042365
UWISH2 -- The UKIRT Widefield Infrared Survey for H2
D.;
Froebrich;
J., C.;
Davis;
G.;
Ioannidis;
M., T.;
Gledhill;
M.;
Takami;
A.;
Chrysostomou;
J.;
Drew;
J.;
EislУЖffel;
A.;
Gosling;
R.;
Gredel;
J.;
Hatchell;
W., K.;
Hodapp;
N., M. S.;
Kumar;
W., P.;
Lucas;
H.;
Matthews;
G., M.;
Rawlings;
D., M.;
Smith;
B.;
Stecklum;
P., W.;
Varricatt;
T., H.;
Lee;
S., P.;
Teixeira;
A., C.;
Aspin;
T.;
Khanzadyan;
J.;
Karr;
-J., H.;
Kim;
-C., B.;
Koo;
J., J.;
Lee;
-H., Y.;
Lee;
Y., T.;
Magakian;
A., T.;
Movsessian;
H., E.;
Nikogossian;
S., T.;
Pyo;
T.;
Stanke
Submitted: 2010-12-03
We present the goals and preliminary results of an unbiased, near-infrared,
narrow-band imaging survey of the First Galactic Quadrant (10deg<l<65deg ;
-1.3deg<b<+1.3deg). This area includes most of the Giant Molecular Clouds and
massive star forming regions in the northern hemisphere. The survey is centred
on the 1-0S(1) ro-vibrational line of H2, a proven tracer of hot, dense
molecular gas in star-forming regions, around evolved stars, and in supernova
remnants. The observations complement existing and upcoming photometric surveys
(Spitzer-GLIMPSE, UKIDSS-GPS, JCMT-JPS, AKARI, Herschel Hi-GAL, etc.), though
we probe a dynamically active component of star formation not covered by these
broad-band surveys. Our narrow-band survey is currently more than 60% complete.
The median seeing in our images is 0.73arcsec. The images have a 5sigma
detection limit of point sources of K=18mag and the surface brightness limit is
10^-19Wm^-2arcsec^-2 when averaged over our typical seeing. Jets and outflows
from both low and high mass Young Stellar Objects are revealed, as are new
Planetary Nebulae and - via a comparison with earlier K-band observations
acquired as part of the UKIDSS GPS - numerous variable stars. With their
superior spatial resolution, the UWISH2 data also have the potential to reveal
the true nature of many of the Extended Green Objects found in the GLIMPSE
survey.
[5]
oai:arXiv.org:0710.0190 [pdf] - 5513
The potential for intensity interferometry with gamma-ray telescope
arrays
Submitted: 2007-09-30
Intensity interferometry exploits a quantum optical effect in order to
measure objects with extremely small angular scales. The first experiment to
use this technique was the Narrabri intensity interferometer, which was
successfully used in the 1970s to measure 32 stellar diameters at optical
wavelengths; some as small as 0.4 milli-arcseconds. The advantage of this
technique, in comparison with Michelson interferometers, is that it requires
only relatively crude, but large, light collectors equipped with fast
(nanosecond) photon detectors. Ground-based gamma-ray telescope arrays have
similar specifications, and a number of these observatories are now operating
worldwide, with more extensive installations planned for the future. These
future instruments (CTA, AGIS, completion 2015) with 30-90 telescopes will
provide 400-4000 different baselines that range in length between 50m and a
kilometre. Intensity interferometry with such arrays of telescopes attains $50
\mu$-arcsecond resolution for a limiting visual magnitude ~8.5. Phase
information can be extracted from the interferometric measurement with phase
closure, allowing image reconstruction. This technique opens the possibility of
a wide range of studies amongst others, probing the stellar surface activity
and the dynamic AU scale circumstellar environment of stars in various crucial
evolutionary stages. Here we focuse on the astrophysical potential of an
intensity interferometer utilising planned new gamma-ray instrumentation.