119 research outputs found
The Properties of Jovian Trojan Asteroids Listed in SDSS Moving Object Catalog 3
We analyze 1187 observations of about 860 unique candidate Jovian Trojan
asteroids listed in the 3rd release of Sloan Digital Sky Survey (SDSS) Moving
Object Catalog. The sample is complete at the faint end to r=21.2 mag (apparent
brightness) and H=13.8 (absolute brightness, approximately corresponding to 10
km diameter). A subset of 297 detections of previously known Trojans were used
to design and optimize a selection method based on observed angular velocity
that resulted in the remaining objects. Using a sample of objects with known
orbits, we estimate that the candidate sample contamination is about 3%. The
well-controlled selection effects, the sample size, depth and accurate
five-band UV-IR photometry enabled several new findings and the placement of
older results on a firmer statistical footing. We find that there are
significantly more asteroids in the leading swarm (L4) than in the trailing
swarm (L5): N(L4)/N(L5)=1.60.1, independently of limiting object's size.
The overall counts normalization suggests that there are about as many Jovians
Trojans as there are main-belt asteroids down to the same size limit, in
agreement with earlier estimates. We find that Trojan asteroids have a
remarkably narrow color distribution (root-mean-scatter of only 0.05 mag)
that is significantly different from the color distribution of the main-belt
asteroids. The color of Trojan asteroids is correlated with their orbital
inclination, in a similar way for both swarms, but appears uncorrelated with
the object's size. We extrapolate the results presented here and estimate that
Large Synoptic Survey Telescope will determine orbits, accurate colors and
measure light curves in six photometric bandpasses for about 100,000 Jovian
Trojan asteroids.Comment: 17 pages, 19 figures (49 figure panels), 1 table, accepted by MNRA
Photometry of SN 2002bo with template image subtraction
VRI photometry of the type Ia supernova 2002bo is presented. This SN exploded
in a dusty region of the host galaxy NGC 3190, thus, subtraction of a template
frame was necessary to obtain reliable photometry. We used a template frame of
NGC 3190 taken during the course of our galaxy imaging project, fortunately,
just a few days before SN 2002bo was discovered. The aim of this project is to
collect template frames of nearby galaxies that are potential hosts of bright
SNe. Subtraction of pre-SN images helped us to exclude the background light
contamination of the host galaxy. The maximum occurred at JD 2452346, with
maximal V brightness of 13.58. MLCS analysis led to T0(B)=JD 2452346.1 pm 0.8
(fiducial B-maximum), E(B-V)=0.24 pm 0.02, mu0=32.46 pm 0.06, Delta=-0.14 pm
0.04. E(B-V)=0.24(2) indicates a significant extinction in the host galaxy as
the galactic reddening is negligible toward NGC 3190. The accepted value of
Delta indicates that SN 2002bo was a slightly overluminous SN by about 0.14
relative to fiducial SN Type Ia. The distance turned out to be 31.0 pm 3 Mpc.
In addition, the heavily obscured SN 2002cv was also detected on the I frame
taken on JD 2452434 (June 8, 2002), and a variable star is found in the field,
very close to the host galaxy.Comment: accepted by Astronomy and Astrophysic
Activity of 50 Long-Period Comets Beyond 5.2 AU
Remote investigations of the ancient solar system matter has been
traditionally carried out through the observations of long-period (LP) comets
that are less affected by solar irradiation than the short-period counterparts
orbiting much closer to the Sun. Here we summarize the results of our
decade-long survey of the distant activity of LP comets. We found that the most
important separation in the dataset is based on the dynamical nature of the
objects. Dynamically new comets are characterized by a higher level of activity
on average: the most active new comets in our sample can be characterized by
afrho values >3--4 higher than that of our most active returning comets. New
comets develop more symmetric comae, suggesting a generally isotropic outflow.
Contrary to this, the coma of recurrent comets can be less symmetrical,
ocassionally exhibiting negative slope parameters, suggesting sudden variations
in matter production. The morphological appearance of the observed comets is
rather diverse. A surprisingly large fraction of the comets have long, teniouos
tails, but the presence of impressive tails does not show a clear correlation
with the brightness of the comets.Comment: 21 pages, 4 figures, accepted for publication in A
A new sdO+dM binary with extreme eclipses and reflection effect
We report the discovery of a new totally-eclipsing binary (RA=06:40:29.11;
Dec=+38:56:52.2; J=2000.0; Rmax=17.2 mag) with an sdO primary and a strongly
irradiated red dwarf companion. It has an orbital period of
Porb=0.187284394(11) d and an optical eclipse depth in excess of 5 magnitudes.
We obtained two low-resolution classification spectra with GTC/OSIRIS and ten
medium-resolution spectra with WHT/ISIS to constrain the properties of the
binary members. The spectra are dominated by H Balmer and He II absorption
lines from the sdO star, and phase-dependent emission lines from the irradiated
companion. A combined spectroscopic and light curve analysis implies a hot
subdwarf temperature of Teff(spec) = 55 000 +/- 3000K, surface gravity of log
g(phot) = 6.2 +/- 0.04 (cgs) and a He abundance of log(nHe/nH) = -2.24 +/-
0.40. The hot sdO star irradiates the red-dwarf companion, heating its
substellar point to about 22 500K. Surface parameters for the companion are
difficult to constrain from the currently available data: the most remarkable
features are the strong H Balmer and C II-III lines in emission. Radial
velocity estimates are consistent with the sdO+dM classification. The
photometric data do not show any indication of sdO pulsations with amplitudes
greater than 7mmag, and Halpha-filter images do not provide evidence of the
presence of a planetary nebula associated with the sdO star.Comment: 13 pages, 5 figures; accepted for publication in Ap
The Young, Massive, Star Cluster Sandage-96 After the Explosion of SN 2004dj in NGC 2403
The bright Type II-plateau supernova (SN) 2004dj occurred within the young,
massive stellar cluster Sandage-96 in a spiral arm of NGC 2403. New
multi-wavelength observations obtained with several ground-based and
space-based telescopes are combined to study the radiation from Sandage-96
after SN 2004dj faded away. Sandage-96 started to dominate the flux in the
optical bands starting September 2006 (~800 d after explosion). The optical
fluxes are equal to the pre-explosion ones within the observational
uncertainties. An optical Keck spectrum obtained ~900 d after explosion shows
the dominant blue continuum from the cluster stars shortward of 6000 \AA as
well as strong SN nebular emission lines redward. The integrated spectral
energy distribution (SED) of the cluster has been extended into the ultraviolet
region by archival XMM-Newton and new Swift observations, and compared with
theoretical models. The outer parts of the cluster have been resolved by the
Hubble Space Telescope, allowing the construction of a color-magnitude diagram.
The fitting of the cluster SED with theoretical isochrones results in cluster
ages between 10--40 Myr, depending on metallicity and the model family. The
isochrone fitting indicates that the resolved part of the cluster has a bimodal
age distribution: a younger population at ~10--16 Myr, and an older one at
~32--100 Myr which is similar to the age distribution of the nearby field
stars. These stars may have been captured from the field during the cluster
formation. The young age of Sandage-96 suggest 12 < M_prog < 20 M_\odot as the
most probable mass range for the progenitor of SN 2004dj. This is consistent
with, but perhaps slightly higher than, most of the other Type II-plateau SN
progenitor masses determined so far.Comment: accepted in Ap
HD 181068: A Red Giant in a Triply-Eclipsing Compact Hierarchical Triple System
Hierarchical triple systems comprise a close binary and a more distant
component. They are important for testing theories of star formation and of
stellar evolution in the presence of nearby companions. We obtained 218 days of
Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by groundbased
spectroscopy and interferometry, which show it to be a hierarchical triple with
two types of mutual eclipses. The primary is a red giant that is in a 45-day
orbit with a pair of red dwarfs in a close 0.9-day orbit. The red giant shows
evidence for tidally-induced oscillations that are driven by the orbital motion
of the close pair. HD 181068 is an ideal target for studies of dynamical
evolution and testing tidal friction theories in hierarchical triple systems.Comment: 22 pages, including supporting on-line material. This is the author's
version of the work. It is posted here by permission of the AAAS for personal
use, not for redistribution. The definitive version was published in Science
Vol. 332 no. 6026 pp. 216-218 (8 April 2011), doi:10.1126/science.1201762.
http://www.sciencemag.org/content/332/6026/216.ful
A Resolved Debris Disk Around the Candidate Planet-hosting Star HD 95086
Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD 95086. The strong infrared excess of the system indicates that, similar to HR8799, Beta Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD 95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared, and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of approx. 6.0 5.4 (540 490 AU) and disk inclination of approx 25 deg. Assuming the same inclination for the planet candidate's orbit, its reprojected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD 95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modeling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks coexist
Multi-site campaign for transit timing variations of WASP-12 b: possible detection of a long-period signal of planetary origin
The transiting planet WASP-12 b was identified as a potential target for
transit timing studies because a departure from a linear ephemeris was reported
in the literature. Such deviations could be caused by an additional planet in
the system. We attempt to confirm the existence of claimed variations in
transit timing and interpret its origin. We organised a multi-site campaign to
observe transits by WASP-12 b in three observing seasons, using 0.5-2.6-metre
telescopes. We obtained 61 transit light curves, many of them with
sub-millimagnitude precision. The simultaneous analysis of the best-quality
datasets allowed us to obtain refined system parameters, which agree with
values reported in previous studies. The residuals versus a linear ephemeris
reveal a possible periodic signal that may be approximated by a sinusoid with
an amplitude of 0.00068+/-0.00013 d and period of 500+/-20 orbital periods of
WASP-12 b. The joint analysis of timing data and published radial velocity
measurements results in a two-planet model which better explains observations
than single-planet scenarios. We hypothesize that WASP-12 b might be not the
only planet in the system and there might be the additional 0.1 M_Jup body on a
3.6-d eccentric orbit. A dynamical analysis indicates that the proposed
two-planet system is stable over long timescales.Comment: Accepted for publication in A&
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