41 research outputs found
The beta Pictoris association: Catalog of photometric rotational periods of low-mass members and candidate members
We intended to compile the most complete catalog of bona fide members and
candidate members of the beta Pictoris association, and to measure their
rotation periods and basic properties from our own observations, public
archives, and exploring the literature. We carried out a multi-observatories
campaign to get our own photometric time series and collected all archived
public photometric data time series for the stars in our catalog. Each time
series was analyzed with the Lomb-Scargle and CLEAN periodograms to search for
the stellar rotation periods. We complemented the measured rotational
properties with detailed information on multiplicity, membership, and projected
rotational velocity available in the literature and discussed star by star. We
measured the rotation periods of 112 out of 117 among bona fide members and
candidate members of the beta Pictoris association and, whenever possible, we
also measured the luminosity, radius, and inclination of the stellar rotation
axis. This represents to date the largest catalog of rotation periods of any
young loose stellar association. We provided an extensive catalog of rotation
periods together with other relevant basic properties useful to explore a
number of open issues, such as the causes of spread of rotation periods among
coeval stars, evolution of angular momentum, and lithium-rotation connection.Comment: Forthcoming article, Received: 20 June 2016 / Accepted: 09 September
2016; 40 pages, 2 figures. The online figures A1-A73 are available at CD
The nature of supernovae 2010O and 2010P in Arp 299-I. Near-infrared and optical evolution
We present near-infrared and optical photometry, plus optical spectroscopy of two stripped-envelope supernovae (SNe) 2010O and 2010P that exploded in two different components of an interacting luminous infrared galaxy Arp 299 within only a few days of one another. SN 2010O is found to be photometrically and spectroscopically similar to many normal Type Ib SNe and our multiwavelength observations of SN 2010P suggest it to be a Type IIb SN. No signs of clear hydrogen features or interaction with the circumstellar medium are evident in the optical spectrum of SN 2010P. We derive estimates for the host galaxy line-of-sight extinctions for both SNe, based on both light curve and spectroscopic comparison finding consistent results. These methods are also found to provide much more robust estimates of the SN host galaxy reddening than the commonly used empirical relations between extinction and equivalent width of Na i D absorption features. The SN observations also suggest that different extinction laws are present in different components of Arp 299. For completeness, we study high-resolution pre-explosion images of Arp 299 and find both SNe to be close to, but not coincident with, extended sources that are likely massive clusters. A very simple model applied to the bolometric light curve of SN 2010O implies a rough estimate for the explosion parameters of E-k approximate to 3 x 10(51) erg, M-ej approximate to 2.9 M-circle dot and M-Ni approximate to 0.16 M-circle dot.</p
Centralised and Distributed Optimization for Aggregated Flexibility Services Provision
The recent deployment of distributed battery units in prosumer premises offer
new opportunities for providing aggregated flexibility services to both
distribution system operators and balance responsible parties. The optimization
problem presented in this paper is formulated with an objective of cost
minimization which includes energy and battery degradation cost to provide
flexibility services. A decomposed solution approach with the alternating
direction method of multipliers (ADMM) is used instead of commonly adopted
centralised optimization to reduce the computational burden and time, and then
reduce scalability limitations. In this work we apply a modified version of
ADMM that includes two new features with respect to the original algorithm:
first, the primal variables are updated concurrently, which reduces
significantly the computational cost when we have a large number of involved
prosumers; second, it includes a regularization term named Proximal Jacobian
(PJ) that ensures the stability of the solution. A case study is presented for
optimal battery operation of 100 prosumer sites with real-life data. The
proposed method finds a solution which is equivalent to the centralised
optimization problem and is computed between 5 and 12 times faster. Thus,
aggregators or large-scale energy communities can use this scalable algorithm
to provide flexibility services.Comment: 10 pages, 7 figure
Ephemeris Updates for Seven Selected HATNet Survey Transiting Exoplanets
We refined the ephemeris of seven transiting exoplanets HAT-P-6b, HAT-P-12b,
HAT-P-18b, HAT-P-22b, HAT-P-32b, HAT-P-33b, and HAT-P-52b. We observed 11
transits from eight observatories in different filters for HAT-P-6b and
HAT-P-32b. Also, the Exoplanet Transit Database (ETD) observations for each of
the seven exoplanets were analyzed, and the light curves of five systems were
studied using Transiting light Exoplanet Survey Satellite (TESS) data. We used
Exofast-v1 to simulate these ground- and space-based light curves and estimate
mid-transit times. We obtained a total of 11, 175 and 67 mid-transit times for
these seven exoplanets from our observations, ETD and TESS data, respectively,
along with 155 mid-transit times from the literature. Then, we generated
transit timing variation (TTV) diagrams for each using derived mid-transit
times as well as those found in the literature. The systems' linear ephemeris
was then refined and improved using the Markov Chain Monte Carlo (MCMC) method.
All of the studied exoplanets, with the exception of the HAT-P-12b system,
displayed an increasing trend in the orbital period in the TTV diagrams.Comment: 11 Pages, submitted to the Astrophysics journa
A low energy core-collapse supernova without a hydrogen envelope
The final fate of massive stars depends on many factors, including mass,
rotation rate, magnetic fields and metallicity. Theory suggests that some
massive stars (initially greater than 25-30 solar masses) end up as Wolf-Rayet
stars which are deficient in hydrogen because of mass loss through strong
stellar winds. The most massive of these stars have cores which may form a
black hole and theory predicts that the resulting explosion produces ejecta of
low kinetic energy, a faint optical display and a small mass fraction of
radioactive nickel(1,2,3). An alternative origin for low energy supernovae is
the collapse of the oxygen-neon core of a relatively lowmass star (7-9 solar
masses) through electron capture(4,5). However no weak, hydrogen deficient,
core-collapse supernovae are known. Here we report that such faint, low energy
core-collapse supernovae do exist, and show that SN2008ha is the faintest
hydrogen poor supernova ever observed. We propose that other similar events
have been observed but they have been misclassified as peculiar thermonuclear
supernovae (sometimes labelled SN2002cx-like events(6)). This discovery could
link these faint supernovae to some long duration gamma-ray bursts. Extremely
faint, hydrogen-stripped core-collapse supernovae have been proposed to produce
those long gamma-ray bursts whose afterglows do not show evidence of
association with supernovae (7,8,9).Comment: Submitted 12 January 2009 - Accepted 24 March 200
Homogeneously derived transit timings for 17 exoplanets and reassessed TTV trends for WASP-12 and WASP-4
We homogeneously analyse ∼3.2 × 105 photometric measurements for ∼1100 transit lightcurves belonging to 17 exoplanet hosts. The photometric data cover 16 years 2004–2019 and include amateur and professional observations. Old archival lightcurves were reprocessed using up-to-date exoplanetary parameters and empirically debiased limb-darkening models. We also derive self-consistent transit and radial-velocity fits for 13 targets. We confirm the nonlinear TTV trend in the WASP-12 data at a high significance, and with a consistent magnitude. However, Doppler data reveal hints of a radial acceleration about ( − 7.5 ± 2.2) m/s/yr, indicating the presence of unseen distant companions, and suggesting that roughly 10 per cent of the observed TTV was induced via the light-travel (or Roemer) effect. For WASP-4, a similar TTV trend suspected after the recent TESS observations appears controversial and model-dependent. It is not supported by our homogeneus TTV sample, including 10 ground-based EXPANSION lightcurves obtained in 2018 simultaneously with TESS. Even if the TTV trend itself does exist in WASP-4, its magnitude and tidal nature are uncertain. Doppler data cannot entirely rule out the Roemer effect induced by possible distant companions
Transit timing analysis of the exoplanet TrES-5 b. Possible existence of the exoplanet TrES-5 c
peer reviewedIn this work, we present transit timing variations detected for the exoplanet TrES-5b. To obtain the necessary amount of photometric data for this exoplanet, we have organized an international campaign to search for exoplanets based on the transit-timing variation (TTV) method and as a result of this we collected 30 new light curves, 15 light curves from the Exoplanet Transit Database (ETD) and 8 light curves from the literature for the timing analysis of the exoplanet TrES-5b. We have detected timing variations with a semi-amplitude of A≈ 0.0016 d and a period of P≈ 99 d. We carried out the N-body modelling based on the three-body problem. The detected perturbation of TrES-5b may be caused by a second exoplanet in the TrES-5 system. We have calculated the possible mass and resonance of the object: M ≈ 0.24MJup at a 1:2 Resonance. © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.RSF: 14-50-0004
SN 2009N: linking normal and subluminous Type II-P Sne
We present ultraviolet, optical, near-infrared photometry and spectroscopy of
SN 2009N in NGC 4487. This object is a type II-P supernova with spectra
resembling those of subluminous II-P supernovae, while its bolometric
luminosity is similar to that of the intermediate luminosity SN 2008in. We
created SYNOW models of the plateau phase spectra for line identification and
to measure the expansion velocity. In the near-infrared spectra we find signs
indicating possible weak interaction between the supernova ejecta and the
pre-existing circumstellar material. These signs are also present in the
previously unpublished near-infrared spectra of SN 2008in. The distance to SN
2009N is determined via the expanding photosphere method and the standard
candle method as . The produced nickel-mass
is estimated to be . We infer the
physical properties of the progenitor at the explosion through hydrodynamical
modelling of the observables. We find the values of the total energy as , the ejected mass as , and the initial radius as .Comment: 23 pages, 18 figures, accepted for publication by MNRA
The bright Type IIP SN 2009bw, showing signs of interaction
We present photometry and spectroscopy of the type IIP supernova 2009bw in
UGC 2890 from few days after the outburst to 241 days. The light curve of SN
2009bw during the photospheric phase is similar to that of normal SNe IIP but
with brighter peak and plateau (Mmax R = -17.82 mag, Mplateau R = -17.37 mag).
The luminosity drop from the photospheric to the nebular phase is one of the
fastest ever observed, ~2.2 mag in about 13 days. The radioactive tail of the
bolometric light curve indicates that the amount of ejected 56 Ni is \approx
0.022 M\odot. The photospheric spectra reveal high velocity lines of H{\alpha}
and H{\beta} until about 105 days after the shock breakout, suggesting a
possible early interaction between the SN ejecta and pre-existent circumstellar
material, and the presence of CNO elements. By modeling the bolometric light
curve, ejecta expansion velocity and photospheric temperature, we estimate a
total ejected mass of 8-12M\odot, a kinetic energy of ~0.3 foe and an initial
radius of ~ 3.6 - 7 \times 10^13 cm.Comment: Accepted for publication in MNRAS, 19 pages, 13 figures, 9 table