82 research outputs found
Proper Motions and CCD-photometry of Stars in the Region of the Open Cluster Trumpler 2
The results of the complex study of galactic open cluster Trumpler 2 are
presented. In order to obtain the proper motions the positions of 2600 stars up
to the limit magnitude B ~ 16.25 mag in the area 80x80 arcmin around the
cluster were measured on 6 plates with the maximal epoch difference of 63
years. The root-mean error of the relative proper motions is 4.2 mas/yr. The
catalogue of BV magnitudes of all the stars in the investigated area was
compiled. Astrometric selection of the cluster members within the region of
R<16 arcmin from the center of the cluster was made by means of the W.Sanders
method. In that field 192 stars were found to have the individual membership
probability greater then 85%, 148 of them are situated within the
+/-3sigma_(B-V) band around the main sequence of the cluster. They are
considered to be cluster members by two criteria. The U-B ~ B-V diagram plotted
for the astrometrical cluster members by the data taken from the Washington
catalogue of the UBV photometry in the galactic cluster fields (Hoag et
al.1961) made it possible to redefine the value of the color excess E(B-V)=0.40
mag. The superposition of the MS of the cluster with the ZAMS Schmidt-Kaler
leads to the coincidence at the value of the apparent distance module
(V-Mv)=10.50 which corresponds to the distance r=725 pc. The luminosity and
mass functions of the Trumpler 2 were constructed and the value of the slope
Gamma=-1.90+/-0.22 was determined. The cluster age of 8.913x10^7 yr was
determined. It is shown that the red giant on the late stage of the evolution
(st N.1095) belongs to cluster and indicates the brightness variability. The
possibility that the number of both known and recently discovered variables are
cluster members was considered. Tables 2,3,3A,5 will be only available in the
electronic form.Comment: 14 pages, 7 figure
Proper Motions and CCD-photometry of Stars in the Region of the Open Cluster NGC 1513
The results of astrometric and photometric investigations of the poorly
studied open cluster NGC 1513 are presented. The proper motions of 353 stars
with the root-mean-square error of 1.9 mas/yr were obtained by means of the
automated measuring complex "Fantasy" scanning of 8 astrometric plates covering
the time interval of 101 years. A total of 141 astrometric cluster members have
been identified. BV CCD-photometry was made for the stars in a square size 17
arcmin x 17 arcmin centered on cluster. 33 stars with the high reliability were
considered to be cluster members by two criteria. The estimation of NGC 1513
age is 2.54 E+08 years. Tables 2 and 3 are only available in electronic form at
the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via
http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/.Comment: 11 pages, 5 figure
The infrared JHK light curves of RR Lyr
We present infrared JHK time series photometry of the variable star RR Lyr,
that allow us to construct the first complete and accurate infrared light
curves for this star. The derived mean magnitudes are =6.74 +/- 0.02,
=6.60 +/- 0.03 and =6.50 +/- 0.02. The magnitude is used to estimate
the reddening, the mass, the mean luminosity and temperature of this variable
star. The use of these RR Lyr data provide a more accurate absolute calibration
of the P-L_K-[Fe/H] relation, and a distance modulus (m-M)_0=18.48 +/- 0.11 to
the globular cluster Reticulum in the LMC.Comment: 6 pages, 2 figures, accepted for publication by MNRA
Fractional quantum Hall state at \nu=1/4 in a wide quantum well
We investigate, with the help of Monte-Carlo and exact-diagonalization
calculations in the spherical geometry, several compressible and incompressible
candidate wave functions for the recently observed quantum Hall state at the
filling factor in a wide quantum well. The quantum well is modeled as
a two-component system by retaining its two lowest subbands. We make a direct
connection with the phenomenological effective-bilayer model, which is commonly
used in the description of a wide quantum well, and we compare our findings
with the established results at in the lowest Landau level. At
, the overlap calculations for the Halperin (5,5,3) and (7,7,1)
states, the generalized Haldane-Rezayi state and the Moore-Read Pfaffian,
suggest that the incompressible state is likely to be realized in the interplay
between the Halperin (5,5,3) state and the Moore-Read Pfaffian. Our numerics
shows the latter to be very susceptible to changes in the interaction
coefficients, thus indicating that the observed state is of multicomponent
nature.Comment: 14 pages, 8 figures; minor changes, accepted for publication in Phys.
Rev.
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
Astrometric observations performed by the Gaia Follow-Up Network for Solar
System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects
first detected by ESA's Gaia mission remain recoverable after their discovery.
An observation campaign on the potentially hazardous asteroid (99 942) Apophis
was conducted during the asteroid's latest period of visibility, from
12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall
performance of the Gaia-FUN-SSO . The 2732 high quality astrometric
observations acquired during the Gaia-FUN-SSO campaign were reduced with the
Platform for Reduction of Astronomical Images Automatically (PRAIA), using the
USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric
reduction process and the precision of the newly obtained measurements are
discussed. We compare the residuals of astrometric observations that we
obtained using this reduction process to data sets that were individually
reduced by observers and accepted by the Minor Planet Center. We obtained 2103
previously unpublished astrometric positions and provide these to the
scientific community. Using these data we show that our reduction of this
astrometric campaign with a reliable stellar catalog substantially improves the
quality of the astrometric results. We present evidence that the new data will
help to reduce the orbit uncertainty of Apophis during its close approach in
2029. We show that uncertainties due to geolocations of observing stations, as
well as rounding of astrometric data can introduce an unnecessary degradation
in the quality of the resulting astrometric positions. Finally, we discuss the
impact of our campaign reduction on the recovery process of newly discovered
asteroids.Comment: Accepted for publication in A&
SN 2008S: an electron capture SN from a super-AGB progenitor?
We present comprehensive photometric and spectroscopic observations of the
faint transient SN 2008S discovered in NGC 6946. SN 2008S exhibited slow
photometric evolution and almost no spectral variability during the first nine
months, implying a high density CS medium. The light curve is similar in shape
to that of SN 1998S and SN 1979C, although significantly fainter at maximum
light. Our quasi-bolometric lightcurve extends to 300 days and shows a tail
phase decay rate consistent with that of ^{56}Co. We propose that this is
evidence for an explosion and formation of ^{56}Ni (0.0015 +/- 0.0004 M_Sun).
The large MIR flux detected shortly after explosion can be explained by a light
echo from pre-exisiting dust. The late NIR flux excess is plausibly due to a
combination of warm newly-formed ejecta dust together with shock-heated dust in
the CS environment. We reassess the progenitor object detected previously in
Spitzer archive images, supplementing this discussion with a model of the MIR
spectral energy distribution. This supports the idea of a dusty, optically
thick shell around SN 2008S with an inner radius of nearly 90AU and outer
radius of 450AU, and an inferred heating source of 3000 K and luminosity of L ~
10^{4.6} L_Sun. The combination of our monitoring data and the evidence from
the progenitor analysis leads us to support the scenario of a weak electron
capture supernova explosion in a super-AGB progenitor star (of initial mass 6-8
M_sun) embedded within a thick CS gaseous envelope. We suggest that all of main
properties of the electron capture SN phenomenon are observed in SN 2008S and
future observations may allow a definitive answer.Comment: accepted for publication in MNRAS (2009 May 7
SN 2008S: an electron-capture SN from a super-AGB progenitor?
We present comprehensive photometric and spectroscopic observations of the faint transient SN 2008S discovered in the nearby galaxy NGC 6946. SN 2008S exhibited slow photometric evolution and almost no spectral variability during the first nine months, implying a long photon diffusion time and a high-density circumstellar medium. Its bolometric luminosity (≃1041 erg s−1 at peak) is low with respect to most core-collapse supernovae but is comparable to the faintest Type II-P events. Our quasi-bolometric light curve extends to 300 d and shows a tail phase decay rate consistent with that of 56Co. We propose that this is evidence for an explosion and formation of 56Ni (0.0014 ± 0.0003 M⊙). Spectra of SN 2008S show intense emission lines of Hα, [Ca ii] doublet and Ca ii near-infrared (NIR) triplet, all without obvious P-Cygni absorption troughs. The large mid-infrared (MIR) flux detected shortly after explosion can be explained by a light echo from pre-existing dust. The late NIR flux excess is plausibly due to a combination of warm newly formed ejecta dust together with shock-heated dust in the circumstellar environment. We reassess the progenitor object detected previously in Spitzer archive images, supplementing this discussion with a model of the MIR spectral energy distribution. This supports the idea of a dusty, optically thick shell around SN 2008S with an inner radius of nearly 90 au and outer radius of 450 au, and an inferred heating source of 3000 K. The luminosity of the central star is L≃ 104.6 L⊙. All the nearby progenitor dust was likely evaporated in the explosion leaving only the much older dust lying further out in the circumstellar environment. The combination of our long-term multiwavelength monitoring data and the evidence from the progenitor analysis leads us to support the scenario of a weak electron-capture supernova explosion in a super-asymptotic giant branch progenitor star (of initial mass 6-8 M⊙) embedded within a thick circumstellar gaseous envelope. We suggest that all of main properties of the electron-capture SN phenomenon are observed in SN 2008S and future observations may allow a definitive answe
ExoClock Project. III. 450 New Exoplanet Ephemerides from Ground and Space Observations
The ExoClock project has been created to increase the efficiency of the Ariel mission. It will achieve this by continuously monitoring and updating the ephemerides of Ariel candidates, in order to produce a consistent catalog of reliable and precise ephemerides. This work presents a homogenous catalog of updated ephemerides for 450 planets, generated by the integration of ∼18,000 data points from multiple sources. These sources include observations from ground-based telescopes (the ExoClock network and the Exoplanet Transit Database), midtime values from the literature, and light curves from space telescopes (Kepler, K2, and TESS). With all the above, we manage to collect observations for half of the postdiscovery years (median), with data that have a median uncertainty less than 1 minute. In comparison with the literature, the ephemerides generated by the project are more precise and less biased. More than 40% of the initial literature ephemerides had to be updated to reach the goals of the project, as they were either of low precision or drifting. Moreover, the integrated approach of the project enables both the monitoring of the majority of the Ariel candidates (95%), and also the identification of missing data. These results highlight the need for continuous monitoring to increase the observing coverage of the candidate planets. Finally, the extended observing coverage of planets allows us to detect trends (transit-timing variations) for a sample of 19 planets. All the products, data, and codes used in this work are open and accessible to the wider scientific community
ExoClock Project III: 450 new exoplanet ephemerides from ground and space observations
The ExoClock project has been created with the aim of increasing the
efficiency of the Ariel mission. It will achieve this by continuously
monitoring and updating the ephemerides of Ariel candidates over an extended
period, in order to produce a consistent catalogue of reliable and precise
ephemerides. This work presents a homogenous catalogue of updated ephemerides
for 450 planets, generated by the integration of 18000 data points from
multiple sources. These sources include observations from ground-based
telescopes (ExoClock network and ETD), mid-time values from the literature and
light-curves from space telescopes (Kepler/K2 and TESS). With all the above, we
manage to collect observations for half of the post-discovery years (median),
with data that have a median uncertainty less than one minute. In comparison
with literature, the ephemerides generated by the project are more precise and
less biased. More than 40\% of the initial literature ephemerides had to be
updated to reach the goals of the project, as they were either of low precision
or drifting. Moreover, the integrated approach of the project enables both the
monitoring of the majority of the Ariel candidates (95\%), and also the
identification of missing data. The dedicated ExoClock network effectively
supports this task by contributing additional observations when a gap in the
data is identified. These results highlight the need for continuous monitoring
to increase the observing coverage of the candidate planets. Finally, the
extended observing coverage of planets allows us to detect trends (TTVs -
Transit Timing Variations) for a sample of 19 planets. All products, data, and
codes used in this work are open and accessible to the wider scientific
community.Comment: Recommended for publication to ApJS (reviewer's comments
implemented). Main body: 13 pages, total: 77 pages, 7 figures, 7 tables. Data
available at http://doi.org/10.17605/OSF.IO/P298
- …