159 research outputs found
The Nordic Optical Telescope
An overview of the Nordic Optical Telescope (NOT) is presented. Emphasis is
on current capabilities of direct interest to the scientific user community,
including instruments. Educational services and prospects and strategies for
the future are discussed briefly as well.Comment: 8 pages, 3 figures, 1 table, Invited talk, To appear in the
proceedings "Highlights of Spanish Astrophysics V " Proceedings of the VIII
Scientific Meeting of the Spanish Astronomical Society (SEA) held in
Santander, July 7-11, 200
Analysis of the stellar population in the central area of the HII region Sh 2-284
There is a lack of state-of-the-art information on very young open clusters,
with implications for determining the structure of the Galaxy. Our main
objective is to study the timing and location of the star formation processes
which yielded the generation of the giant HII region Sh 2-284. The analysis is
based on UBVRcIc CCD measurements and JHKs photometry in the central part of
the HII region, where the cluster Dolidze 25 is located.The determination of
cluster distance, reddening and age is carried out through comparison with
ZAMS, post-MS and PMS isochrones. Reference lines for metallicity Z=0.004 are
used, in agreement with spectroscopic metallicity determination published for
several cluster members. The results are: E(B-V)=0.78+-0.02, M=12.8+-0.2,
LogAge(yr)=6.51+-0.07. A PMS member sequence is proposed, coeval within the
errors with the post-MS cluster age (LogAge(yr)=6.7+-0.2). The mass function
for this PMS population in the mass range above 1.3-3.5 Msun is well fitted by
a Salpeter mass function.The presence of a different star generation in the
cluster with a distinctly older age, around 40 Myr, is suggested. The NIR
results indicate a large number of sources with H-Ks excess, practically
distinct from the optical PMS candidate members.
The distance determined for the cluster is distinctly lower than previously
published values. This result originates in the consistent use of low
metallicity models for ZAMS fitting, applying published metallicity values for
the cluster.Comment: gzipped tar file: 1 aa.cls, 1 tex file, 1 bbl file, 13 figures.
Accepted in Astronomy & Astrophysics (9.11.2009
Not a galaxy: IRAS 04186+5143, a new young stellar cluster in the outer Galaxy
We report the discovery of a new young stellar cluster in the outer Galaxy
located at the position of an IRAS PSC source that has been previously
mis-identified as an external galaxy. The cluster is seen in our near-infrared
imaging towards IRAS 04186+5143 and in archive Spitzer images confirming the
young stellar nature of the sources detected. There is also evidence of
sub-clustering seen in the spatial distributions of young stars and of gas and
dust.
Near- and mid-infrared photometry indicates that the stars exhibit colours
compatible with reddening by interstellar and circumstellar dust and are likely
to be low- and intermediate-mass YSOs with a large proportion of Class I YSOs.
Ammonia and CO lines were detected, with the CO emission well centred near
the position of the richest part of the cluster. The velocity of the CO and
NH lines indicates that the gas is Galactic and located at a distance of
about 5.5 kpc, in the outer Galaxy.
Herschel data of this region characterise the dust environment of this
molecular cloud core where the young cluster is embedded. We derive masses,
luminosities and temperatures of the molecular clumps where the young stars
reside and discuss their evolutionary stages.Comment: 14 pages, 15 figure
Multiple protostellar systems. II. A high resolution near-infrared imaging survey in nearby star-forming regions
(abridged) Our project endeavors to obtain a robust view of multiplicity
among embedded Class I and Flat Spectrum protostars in a wide array of nearby
molecular clouds to disentangle ``universal'' from cloud-dependent processes.
We have used near-infrared adaptive optics observations at the VLT through the
H, Ks and L' filters to search for tight companions to 45 Class I and Flat
Spectrum protostars located in 4 different molecular clouds (Taurus-Auriga,
Ophiuchus, Serpens and L1641 in Orion). We complemented these observations with
published high-resolution surveys of 13 additional objects in Taurus and
Ophiuchus. We found multiplicity rates of 32+/-6% and 47+/-8% over the 45-1400
AU and 14-1400 AU separation ranges, respectively. These rates are in excellent
agreement with those previously found among T Tauri stars in Taurus and
Ophiuchus, and represent an excess of a factor ~1.7 over the multiplicity rate
of solar-type field stars. We found no non-hierarchical triple systems, nor any
quadruple or higher-order systems. No significant cloud-to-cloud difference has
been found, except for the fact that all companions to low-mass Orion
protostars are found within 100 AU of their primaries whereas companions found
in other clouds span the whole range probed here. Based on this survey, we
conclude that core fragmentation always yields a high initial multiplicity
rate, even in giant molecular clouds such as the Orion cloud or in clustered
stellar populations as in Serpens, in contrast with predictions of numerical
simulations. The lower multiplicity rate observed in clustered Class II and
Class III populations can be accounted for by a universal set of properties for
young systems and subsequent ejections through close encounters with unrelated
cluster members.Comment: 15 pages, 6 figures, accepted for publication in Astronomy &
Astrophysic
Public health policy: taxes and subsidies to promote public health in Norway
Bacheloroppgave folkehelse, 2017Problemstilling:
Kan statlige tiltak som avgifter eller subsidier fungere som virkemidler mot et sunnere kosthold i Norge? Teori:
Beskrivelse av hva et sundt kosthold er, sosiale ulikheter, folkehelsemeldinger og ulike statlige tiltak for å fremme folkehelsen. Metode:
Oppgaven er et gjennomført litteraturstudie.
Datapresentasjon og diskusjon: Det legges frem seks ulike vitenskapeligartikler som er inkludert som litteraturstudie. Diskusjonen omhandler de seks ulik artiklenes innhold, diskutert i sammenheng med hverandre og opp mot teorien belyst i oppgaven.
Konklusjon:
Studie viser sammenheng mellom skatt som virkemiddel og inntaket av mettet fett, samt et økt inntak av frukt og grønt ved en subsidie. Skatt og subsidier anbefales og ha en kraft på mellom 15- 20 % for å vise gode nok resultater. Studie poengterer også at det trengs mer forskning på temaet for å se langtidseffekten av slike virkemidler
Hvordan kan veiledning være relevant for en leder?
Enhver organisasjon og arbeidsplass bør derfor ha en organisasjonskultur hvor det oppleves at det er rom for å kunne snakke om personlige utfordringer, følelser og andre tanker, da dette fremmer læring og utvikling hos hver enkelt. I tillegg vil enhver på arbeidsplassen føle seg ivaretatt og sett av sin nærmeste leder eller den som utfører veiledningssamtalene. Da Luftforsvaret er en organisasjon med høyt arbeidstempo som kan være involvert i krevende og stressende situasjoner som kan påvirke en i ettertid, er effekten og hensikten med veiledningen enda viktigere. Problemstillingen jeg derfor prøver å svare på er : Hvordan kan veiledning være relevant for en leder?updatedVersio
Another deep dimming of the classical T Tauri star RW Aur A
Context. RW Aur A is a classical T Tauri star (CTTS) with an unusually rich
emission line spectrum. In 2014 the star faded by ~ 3 magnitudes in the V band
and went into a long-lasting minimum. In 2010 the star suffered from a similar
fading, although less deep. These events in RW Aur A are very unusual among the
CTTS, and have been attributed to occultations by passing dust clouds. Aims. We
want to find out if any spectral changes took place after the last fading of RW
Aur A with the intention to gather more information on the occulting body and
the cause of the phenomenon. Methods. We collected spectra of the two
components of RW Aur. Photometry was made before and during the minimum.
Results. The overall spectral signatures reflecting emission from accretion
flows from disk to star did not change after the fading. However, blue-shifted
absorption components related to the stellar wind had increased in strength in
certain resonance lines, and the profiles and strengths, but not fluxes, of
forbidden lines had become drastically different. Conclusions. The extinction
through the obscuring cloud is grey indicating the presence of large dust
grains. At the same time, there are no traces of related absorbing gas. The
cloud occults the star and the interior part of the stellar wind, but not the
wind/jet further out. The dimming in 2014 was not accompanied by changes in the
accretion flows at the stellar surface. There is evidence that the structure
and velocity pattern of the stellar wind did change significantly. The dimmings
could be related to passing condensations in a tidally disrupted disk, as
proposed earlier, but we also speculate that large dust grains have been
stirred up from the inclined disk into the line-of-sight through the
interaction with an enhanced wind.Comment: 5 pages, 5 figures, Accepted for publication in A&
The extended population associated with W40
W40 is a heavily obscured bipolar HII region projected in the direction of
the Aquila Rift and ionized by hot stars in a central, partly embedded cluster.
The study of the cluster and its surroundings has been greatly hampered thus
far by the strong extinction in the region. We use the Gaia eDR3 catalog to
establish astrometric membership criteria based on the population of the W40
central cluster, reassess the distance of the region, and identify in this way
new members, both inside and outside the cluster. We obtain visible
spectroscopy in the red spectral region to classify both known and new members,
complemented with Gaia and Spitzer photometry to assess the evolutionary status
of the stellar population. We derive a high-confidence geometric distance to
the W40 region of 502 pc 4 pc and confirm the presence of a comoving
extended population of stars at the same distance, spreading over the whole
projected area of the HII region and beyond. Spectral classifications are
presented for 21 members of the W40 region, 10 of them belonging to the central
cluster. One of the newly identified B stars in the extended population is
clearly interacting with the shell surrounding the HII region, giving rise to a
small arc-shaped nebula that traces a bow shock. The infrared excess properties
suggest that the extended population is significantly older ( Myr) than
the W40 central cluster ( Myr). The area currently occupied by the W40 HII
region and its surroundings has a history of star formation extending at least
several million years in the past, of which the formation of the W40 central
cluster and the subsequent HII region is one of the latest episodes. The newly
determined distance suggests that W40 is behind, and physically detached from,
a pervasive large dust layer which is some 60 pc foreground to it as determined
by previous studies.Comment: Submitted to Astronomy and Astrophysic
First Light of Engineered Diffusers at the Nordic Optical Telescope Reveal Time Variability in the Optical Eclipse Depth of WASP-12b
We present the characterization of two engineered diffusers mounted on the
2.5 meter Nordic Optical Telescope, located at Roque de Los Muchachos, Spain.
To assess the reliability and the efficiency of the diffusers, we carried out
several test observations of two photometric standard stars, along with
observations of one primary transit observation of TrES-3b in the red (R-band),
one of CoRoT-1b in the blue (B-band), and three secondary eclipses of WASP-12b
in V-band. The achieved photometric precision is in all cases within the
sub-millimagnitude level for exposures between 25 and 180 seconds. Along a
detailed analysis of the functionality of the diffusers, we add a new transit
depth measurement in the blue (B-band) to the already observed transmission
spectrum of CoRoT-1b, disfavouring a Rayleigh slope. We also report variability
of the eclipse depth of WASP-12b in the V-band. For the WASP-12b secondary
eclipses, we observe a secondary-depth deviation of about 5-sigma, and a
difference of 6-sigma and 2.5-sigma when compared to the values reported by
other authors in similar wavelength range determined from Hubble Space
Telescope data. We further speculate about the potential physical processes or
causes responsible for this observed variabilityComment: 11 pages, 9 figure
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