88 research outputs found
The GTC exoplanet transit spectroscopy survey. VII. An optical transmission spectrum of WASP-48b
We obtained long-slit optical spectroscopy of one transit of WASP-48b with
the Optical System for Imaging and low-Intermediate-Resolution Integrated
Spectroscopy (OSIRIS) spectrograph at the 10.4 m Gran Telescopio Canarias
(GTC). We integrated the spectrum of WASP-48 and one reference star in several
channels with different wavelength ranges, creating numerous color light curves
of the transit. We fit analytic transit curves to the data taking into account
the systematic effects present in the time series in an effort to measure the
change of the planet-to-star radius ratio () across wavelength. After
removing the transit model and systematic trends to the curves we reached
precisions between 261 ppm and 455-755 ppm for the white and spectroscopic
light curves, respectively. We obtained uncertainty values between
and for all the curves analyzed in
this work. The measured transit depth for the curves made by integrating the
wavelength range between 530 nm and 905 nm is in agreement with previous
studies. We report a relatively flat transmission spectrum for WASP-48b with no
statistical significant detection of atmospheric species, although the
theoretical models that fit the data more closely include of TiO and VO.Comment: 8 pages, 8 figures. Accepted for publication in Astronomy and
Astrophysic
The long Galactic bar as seen by UKIDSS Galactic Plane Survey
Over the last decade there have been a series of results supporting the
hypothesis of the existence of a long thin bar in the Milky Way with a
half-length of 4.5 kpc and a position angle of around 45 deg. This is
apparently a very different structure from the triaxial bulge of the Galaxy,
which is thicker and shorter and dominates the star counts at |l|<10 deg. In
this paper, we analyse the stellar distribution in the inner Galaxy to see if
there is clear evidence for two triaxial or bar-like structures in the Milky
Way.
By using the red-clump population as a tracer of Galactic structure, we
determine the apparent morphology of the inner Galaxy. Deeper and higher
spatial resolution NIR photometry from the UKIDSS Galactic Plane Survey allows
us to use in-plane data even at the innermost Galactic longitudes, a region
where the source confusion is a dominant effect that makes it impossible to use
other NIR databases such as 2MASS or TCS-CAIN. We show that results previously
obtained with using the red-clump giants are confirmed with the in-plane data
from UKIDSS GPS. There are two different structures coexisting in the inner
Galactic plane: one with a position angle of 23.60+-2.19 deg that can be traced
from the Galactic Centre up to l=10 deg (the Galactic bulge), and other with a
larger position angle of 42.44+-2.14 deg, that ends around l=28 deg (the long
Galactic bar).Comment: (8 pages, 14 figures, accepted for publication in A&A
Water-ice driven activity on Main-Belt Comet P/2010 A2 (LINEAR) ?
The dust ejecta of Main-Belt Comet P/2010 A2 (LINEAR) have been observed with
several telescopes at the at the Observatorio del Roque de los Muchachos on La
Palma, Spain. Application of an inverse dust tail Monte Carlo method to the
images of the dust ejecta from the object indicates that a sustained, likely
water-ice driven, activity over some eight months is the mechanism responsible
for the formation of the observed tail. The total amount of dust released is
estimated to be 5E7 kg, which represents about 0.3% of the nucleus mass. While
the event could have been triggered by a collision, this cannot be decided from
the currently available data.Comment: Accepted for ApJ Letter
Visible and near-infrared observations of asteroid 2012 DA14 during its closest approach of February 15, 2013
Near-Earth asteroid 2012 DA14 made its closest approach on February 15, 2013,
when it passed at a distance of 27,700 km from the Earth's surface. It was the
first time an asteroid of moderate size was predicted to approach that close to
the Earth, becoming bright enough to permit a detailed study from ground-based
telescopes. Asteroid 2012 DA14 was poorly characterized before its closest
approach. We acquired data using several telescopes on four Spanish
observatories: the 10.4m Gran Telescopio Canarias (GTC) and the 3.6m Telescopio
Nazionale Galileo (TNG), both in the El Roque de los Muchachos Observatory
(ORM, La Palma); the 2.2m CAHA telescope, in the Calar Alto Observatory
(Almeria); the f/3 0.77m telescope in the La Hita Observatory (Toledo); and the
f/8 1.5m telescope in the Sierra Nevada Observatory (OSN, Granada). We obtained
visible and near-infrared color photometry, visible spectra and time-series
photometry. Visible spectra together with color photometry of 2012 DA14 show
that it can be classified as an L-type asteroid, a rare spectral type with a
composition similar to that of carbonaceous chondrites. The time-series
photometry provides a rotational period of 8.95 +- 0.08 hours after the closest
approach, and there are indications that the object suffered a spin-up during
this event. The large amplitude of the light curve suggests that the object is
very elongated and irregular, with an equivalent diameter of around 18m. We
obtain an absolute magnitude of H_R = 24.5 +- 0.2, corresponding to H_V = 25.0
+- 0.2. The GTC photometry also gives H_V = 25.29 +- 0.14. Both values agree
with the value listed at the Minor Planet Center shortly after discovery. From
the absolute photometry, together with some constraints on size and shape, we
compute a geometric albedo of p_V = 0.44 +- 0.20, which is slightly above the
range of albedos known for L-type asteroids (0.082 - 0.405).Comment: 7 pages, 4 figures, 1 table. Accepted in A&A (June 17 2013
Peculiar emission line spectra of core extremely red BOSS quasars at z ~ 2-3: orientation and/or evolution?
Context. Core extremely red quasars (core ERQ) have been proposed to represent an intermediate evolutionary phase in which a heavily obscured quasar blows out the circumnuclear interstellar medium with very energetic outflows before it becomes an optical quasar.
Aims. We investigate whether the properties of core ERQ fit the AGN orientation-based unification scenario.
Methods. We revised the general UV and optical emission line properties of core ERQ in the context of the orientation-based scenario. We used diagnostic diagrams based on UV emission line ratios and UV-to-optical line kinematic information to compare the physical and kinematic gas properties of core ERQ with those of other luminous narrow- and broad-line AGN. In particular, we provide a revised comparison of the [OIII] kinematics in 21 core ERQ (20 from Perrotta et al. 2019, MNRAS, 488, 4126 and SDSS J171420.38+414815.7, based on GTC EMIR near-infrared spectroscopy) with other samples of quasars with matching luminosity with the aim of evaluating whether core ERQ host the most extreme [OIII] outflows.
Results. The UV line ratios suggest that the physical properties (e.g., density and metallicity) of the ionised gas in core ERQ are similar to those observed in the broad-line region of blue nitrogen-loud quasars. The [OIII] outflow velocities of core ERQ are on average consistent with those of very luminous blue type 1 quasars, although extreme outflows are much more frequent in core ERQ. These similarities can be explained in the context of the AGN unification model under the assumption that core ERQ are viewed with an intermediate orientation between type 2 (edge-on) and type 1 (face-on) quasars. Conclusions. We propose that core ERQ are very luminous but otherwise normal quasars viewed at an intermediate orientation. This orientation allows a direct view of the outer part of the large broad-line region from which core ERQ UV line emission originates; the extreme [OIII] outflow velocities are instead a consequence of the very high luminosity of core ERQ
Tracing the long bar with red-clump giants
Over the last decade a series of results have lent support to the hypothesis
of the existence of a long thin bar in the Milky Way with a half-length of 4.5
kpc and a position angle of around 45 deg. This is apparently a very different
structure from the triaxial bulge of the Galaxy.
In this paper, we analyse the stellar distribution in the inner 4 kpc of the
Galaxy to see if there is clear evidence for two triaxial or barlike
structures, or whether there is only one. By using the red-clump population as
a tracer of the structure of the inner Galaxy we determine the apparent
morphology of the inner Galaxy. Star counts from 2MASS are used to provide
additional support for this analysis.
We show that there are two very different large-scale triaxial structures
coexisting in the inner Galaxy: a long thin stellar bar constrained to the
Galactic plane (|b|<2 deg) with a position angle of 43.1 +- 1.8 deg, and a
distinct triaxial bulge that extends to at least |b|<7.5 deg with a position
angle of 12.6 +- 3.2 deg. The scale height of the bar source distribution is
around 100 pc, whereas for the bulge the value of this parameter is five times
larger.Comment: 16 pages, 35 figures, accepted for publication in A&
Limited impact of jet induced feedback in the multi-phase nuclear interstellar medium of 4C12.50
Although the ultraluminous infrared radio galaxy 4C12.50 at z=0.12 is a
promising candidate to reveal how radio induced feedback may regulate star
formation in galaxies, we find no solid evidence for current or past impact of
this mechanism on the evolution of this system, neither by clearing out the
dusty central cocoon efficiently, nor by suppressing star formation. We study
in detail for the first time the hot (>~1500 K) molecular gas in this object.
The potential impact of the radio jet on this gas phase, as well as on the star
formation activity, are investigated. 4C12.50 hosts (2.1+/-0.4)x1e4 Msun of hot
molecular gas. An unusually high rotational temperature T =3020+/-160 K is
inferred. The molecular gas mass obeys a power law temperature distribution
d(M(H2))/dT ~ T^-5 from T~300 K and up to ~3000 K. Both results support that
shocks (probably induced by the radio jet) contribute to the heating and
excitation of the hot molecular gas. A molecular outflow is not detected. The
coupling of the outflowing ionized and neutral outflows with the hot molecular
gas is poor. We find no evidence for star formation supression. NIR and MIR
integral field spectroscopy at very high spatial resolution (for instance, with
the JWST) would be of key value to further investigate these issues.Comment: Accepted for publication in A&A,18 pages, 13 figure
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