345 research outputs found
A PSF-based approach to Kepler/K2 data. I. Variability within the K2 Campaign 0 star clusters M 35 and NGC 2158
Kepler and K2 data analysis reported in the literature is mostly based on
aperture photometry. Because of Kepler's large, undersampled pixels and the
presence of nearby sources, aperture photometry is not always the ideal way to
obtain high-precision photometry and, because of this, the data set has not
been fully exploited so far. We present a new method that builds on our
experience with undersampled HST images. The method involves a point-spread
function (PSF) neighbour-subtraction and was specifically developed to exploit
the huge potential offered by the K2 "super-stamps" covering the core of dense
star clusters. Our test-bed targets were the NGC 2158 and M 35 regions observed
during the K2 Campaign 0. We present our PSF modeling and demonstrate that, by
using a high-angular-resolution input star list from the Asiago Schmidt
telescope as the basis for PSF neighbour subtraction, we are able to reach
magnitudes as faint as Kp~24 with a photometric precision of 10% over 6.5
hours, even in the densest regions. At the bright end, our photometric
precision reaches ~30 parts-per-million. Our method leads to a considerable
level of improvement at the faint magnitudes (Kp>15.5) with respect to the
classical aperture photometry. This improvement is more significant in crowded
regions. We also extracted raw light curves of ~60,000 stars and detrended them
for systematic effects induced by spacecraft motion and other artifacts that
harms K2 photometric precision. We present a list of 2133 variables.Comment: 27 pages (included appendix), 2 tables, 25 figures (5 in low
resolution). Accepted for publication in MNRAS on November 05, 2015. Online
materials will be available on the Journal website soo
Photometry and astrometry with JWST -- II. NIRCam distortion correction
In preparation to make the most of our own planned James Webb Space Telescope
investigations, we take advantage of publicly available calibration and
early-science observations to independently derive and test a
geometric-distortion solution for NIRCam detectors. Our solution is able to
correct the distortion to better than ~0.2 mas. Current data indicate that the
solution is stable and constant over the investigated filters, temporal
coverage, and even over the available filter combinations. We successfully
tested our geometric-distortion solution in three cases: (i) field-object
decontamination of M 92 field; (ii) estimate of internal proper motions of M
92; and (iii) measurement of the internal proper motions of the Large
Magellanic Cloud system. To our knowledge, the here-derived
geometric-distortion solution for NIRCam is the best available and we publicly
release it, as many other investigations could potentially benefit from it.
Along with our geometric-distortion solution, we also release a Python tool to
convert the raw-pixels coordinates of each detector into distortion-free
positions, and also to put all the ten detectors of NIRCam into a common
reference system.Comment: 13 pages, 12 figures (6 in low resolution), 3 tables. Accepted for
publication on February 21st, 2023, by Astronomische Nachrichten
(Astronomical Notes). Distortion correction software available at
https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/JWST/Paper_02/Python
Variable stars in one open cluster within the Kepler/K2-Campaign-5 field: M 67 (NGC 2682)
In this paper we continue the release of high-level data products from the
multiyear photometric survey collected at the 67/92 cm Schmidt Telescope in
Asiago. The primary goal of the survey is to discover and to characterise
variable objects and exoplanetary transits in four fields containing five
nearby open clusters spanning a broad range of ages. This second paper releases
a photometric catalogue, in five photometric bands, of the Solar-age,
Solar-metallicity open cluster M 67 (NGC 2682). Proper motions are derived
comparing the positions observed in 2013 at the Asiago's Schmidt Telescope with
those extracted from [email protected] MPG/ESO images in 2000. We also analyse the
variable sources within M 67. We detected 68 variables, 43 of which are new
detection. Variable periods and proper-motion memberships of a large majority
of sources in our catalogue are improved with respect to previous releases. The
entire catalogue will be available in electronic format. Besides the general
interest on an improved catalogue, this work will be particularly useful
because of: (1) the imminent release of Kepler/K2 Campaign-5 data of this
cluster, for which our catalogue will provide an excellent, high spatial
resolution input list, and (2) characterisation of the M 67 stars which are
targets of intense HARPS and HARPS-N radial-velocity surveys for planet search.Comment: 8 pages, 6 figures (2 at low resolution), 2 tables. Accepted for
publication in MNRAS on October 17, 2015. Electronic materials available at
the url http://groups.dfa.unipd.it/ESPG/M67.html , and later on the Journal
and at the CD
Photometry and astrometry with JWST -- III. A NIRCam-Gaia DR3 analysis of the open cluster NGC 2506
In the third paper of this series aimed at developing the tools for analysing
resolved stellar populations using the cameras on board of the James Webb Space
Telescope (JWST), we present a detailed multi-band study of the 2 Gyr Galactic
open cluster NGC 2506. We employ public calibration data-sets collected in
multiple filters to: (i) derive improved effective Point Spread Functions
(ePSFs) for ten NIRCam filters; (ii) extract high-precision photometry and
astrometry for stars in the cluster, approaching the main-sequence (MS) lower
mass of ~0.1 Msun; and (iii) take advantage of the synergy between JWST and
Gaia DR3 to perform a comprehensive analysis of the cluster's global and local
properties. We derived a MS binary fraction of ~57.5 %, extending the Gaia
limit (~0.8 Msun) to lower masses (~0.4 Msun) with JWST. We conducted a study
on the mass functions (MFs) of NGC 2506, mapping the mass segregation with Gaia
data, and extending MFs to lower masses with the JWST field. We also combined
information on the derived MFs to infer an estimate of the cluster present-day
total mass. Lastly, we investigated the presence of white dwarfs (WDs) and
identified a strong candidate. However, to firmly establish its cluster
membership, as well as that of four other WD candidates and of the majority of
faint low-mass MS stars, further JWST equally deep observations will be
required. We make publicly available catalogues, atlases, and the improved
ePSFs.Comment: 20 pages, 17 figures (5 in low resolution), 4 tables. Accepted for
publication in MNRAS on August 5, 2023. PSF models, catalogs and stacked
images are publicly available at
https://web.oapd.inaf.it/bedin/files/PAPERs_eMATERIALs/JWST/Paper_03
Photometry and spectroscopy of multiple populations along the AGB of NGC2808 and NGC6121 (M4)
We present a photometric and spectroscopic study of multiple populations
along the asymptotic-giant branch (AGB) of the intermediate-metallicity
globular clusters (GCs) NGC2808 and NGC6121 (M4). Chemical abundances of O, Na,
Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Zn, Y, and Ce in AGB stars from
high-resolution FLAMES+UVES@VLT spectra are reported for both clusters. Our
spectroscopic results have been combined with multi-wavelength photometry from
the HST UV survey of Galactic GCs and ground-based photometry, plus proper
motions derived by combining stellar positions from ground-based images and
Gaia DR1. Our analysis reveals that the AGBs of both clusters host multiple
populations with different chemical composition.
In M4 we have identified two main populations of stars with different Na/O
content, lying on distinct AGBs in the mF438W vs. C_F275W,F336W,F438W and the V
vs.C_U,B,I pseudo-CMDs. In the more massive and complex GC NGC2808 three groups
of stars with different chemical abundances occupy different locations on the
so-called "chromosome map" photometric diagram. The spectroscopic+photometric
comparison of stellar populations along the AGB and the red giants of this GC
suggests that the AGB hosts stellar populations with a range in helium
abundances spanning from primordial up to high contents of Y~0.32. On the other
hand, from our dataset, there is no evidence for stars with extreme helium
abundance (Y~0.38) on the AGB, suggesting that the most He-rich stars of
NGC2808 do not reach this phase.Comment: 33 pages, 8 figures, accepted for publication in Ap
Exploring the origin of the extended main sequence turn off in M37 through the white dwarf cooling sequence
We use new observations from the Canada-France-Hawaii Telescope to study the
white dwarf cooling sequence of the open cluster M37, a cluster that displays
an extended main sequence turn-off and, according to a recent photometric
analysis, also a spread of initial chemical composition. By taking advantage of
a first epoch collected in 1999 with the same telescope, we have been able to
calculate proper motions for sources as faint as g ~ 26 (about ~ 6 magnitudes
fainter than the Gaia limit), allowing us to separate cluster members from
field stars. This has enabled us to isolate a sample of the white dwarf
population of M37, reaching the end of the cooling sequence (at g ~ 23.5). The
here-derived atlas and calibrated catalogue of the sources in the field of view
is publicly released as supplementary on-line material. Finally, we present an
exhaustive comparison of the white dwarf luminosity function with theoretical
models, which has allowed us to exclude the age-spread scenario as the main
responsible for the extended turnoff seen in the cluster
colour-magnitude-diagram.Comment: 10 pages, 13 figures. Accepted for publication in MNRAS on 2023, June
1
A possibly inflated planet around the bright, young star DS Tuc A
The origin of the observed diversity of planetary system architectures is one
of the main topic of the exoplanetary research. The detection of a
statistically significant sample of planets around young stars allows us to
study the early stages of planet formation and evolution, but only a handful of
them is known so far. In this regard, a considerable contribution is expected
from the NASA TESS satellite, which is now performing a survey of
of the sky to search for short-period transiting planets In its first month of
operations, TESS found a planet candidate with an orbital period of 8.14 days
around a member of the Tuc-Hor young association ( 40 Myr), the G6V main
component of the binary system DS\,Tuc. If confirmed, it would be the first
transiting planet around a young star suitable for radial velocity and/or
atmospheric characterization. We aim to validate the planetary nature of this
companion and to measure its orbital and physical parameters. We obtain
accurate planet parameters by coupling an independent reprocessing of the TESS
light curve with improved stellar parameters and the dilution caused by the
binary companion; we analyse high precision archival radial velocities to
impose an upper limit of about 0.1 M on the planet mass; we finally
rule out the presence of external companions beyond 40 au with adaptive optics
images. We confirm the presence of a young, giant ( R) planet having a not negligible possibility to be inflated (theoretical
mass M) around DS\,Tuc~A. We discuss the feasibility
of mass determination, Rossiter-McLaughlin analysis and atmosphere
characterization, allowed by the brightness of the star.Comment: 12 pages, 11 figures. Accepted for publication in A&
Investigation of fennel protein extracts by shot-gun Fourier transform ion cyclotron resonance mass spectrometry
A rapid shot-gun method by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is proposed for the characterization of fennel proteins. After enzymatic digestion with trypsin, few microliters of extract were analyzed by direct infusion in positive ion mode. A custom-made non-redundant fennel-specific proteome database was derived from the well-known NCBI database; additional proteins belonging to recognized allergenic sources (celery, carrot, parsley, birch, and mugwort) were also included in our database, since patients hypersensitive to these plants could also suffer from fennel allergy. The peptide sequence of each protein from that derived list was theoretically sequenced to produce calculated m/z lists of possible m/z ions after tryptic digestions. Then, by using a home-made Matlab algorithm, those lists were matched with the experimental FT-ICR mass spectrum of the fennel peptide mixture. Finally, Peptide Mass Fingerprint searches confirmed the presence of the matched proteins inside the fennel extract with a total of 70 proteins (61 fennel specific and 9 allergenic proteins)
The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIII. ACS/WFC Parallel-Field Catalogues
As part of the Hubble Space Telescope UV Legacy Survey of Galactic Globular
Clusters, 110 parallel fields were observed with the Wide Field Channel of the
Advanced Camera for Surveys, in the outskirts of 48 globular clusters, plus the
open cluster NGC 6791. Totalling about square degrees of observed sky,
this is the largest homogeneous Hubble Space Telescope photometric survey of
Galalctic globular clusters outskirts to date. In particular, two distinct
pointings have been obtained for each target on average, all centred at about
arcmin from the cluster centre, thus covering a mean area of about
for each globular cluster. For each field, at least one
exposure in both F475W and F814W filters was collected. In this work, we
publicly release the astrometric and photometric catalogues and the
astrometrised atlases for each of these fields.Comment: 30 pages, 23 figures. Accepted by MNRA
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