298 research outputs found
Warm and hot circumstellar gas in V1647 Ori during the 2008-2009 outburst
The pre-main sequence star V1647 Ori started a new outburst in August 2008. From October 2008 to February 2009 we monitored V1647 Ori, obtaining quasi-simultaneous VLT-CRIRES near-IR spectroscopy, VLT-VISIR mid-IR spectroscopy and VLT-FORS2 optical spectroscopy. We studied the evolution of H2 and CO emission from hot and warm gas and Hα and forbidden line-emission during the initial outburst phase of V1647 Ori. Hα is observed in emission displaying P-Cygni profiles with blue-shifted absorption up to -700 km/s, suggesting the presence of a high velocity wind (Fig. 1a). [OI] emission at 6300 Å is observed displaying a blue-shifted emission shoulder, indicating the presence of material moving away from the star (Fig. 1b). We detect H2 1-0 S(1) and CO (P4 to P14 and P30-P38) ro-vibrational lines centered at the velocity of the star at all epochs (Fig. 1c & d). This strongly suggests that the H2 and CO emission originates from a disk and not from a warm outflow. The H2 1-0 S(0) and 2-1 S(1) ro-vibrational lines at 2.22 and 2.24 μm and the pure-rotational H2 0-0 S(1) and 0-0 S(2) lines at 17 and 12 μm were not detected in our spectra. Changes in the Hα and [OI] profiles and the H2 and CO emission observed do not correlate. We modeled the H2 and CO line profiles assuming emission from a flat disk in keplerian rotation with line intensity decreasing with radius (I ~ I0(R/Rmin)−α). We found that the disk of V1647 Ori is observed nearly face-on and that the line emission is produced within a fraction of an AU of the star (Fig. 1d
A survey for near-infrared H2 emission in Herbig Ae/Be stars: emission from the outer disks of HD 97048 and HD 100546
Evidence for CO depletion in the inner regions of gas-rich protoplanetary disks
We investigate the physical properties and spatial distribution of Carbon
Monoxide (CO) gas in the disks around the Herbig Ae/Be stars HD 97048 and HD
100546.
Using high-spectral-resolution 4.588-4.715 m spectra containing
fundamental CO emission taken with CRIRES on the VLT, we probe the
circumstellar gas and model the kinematics of the emission lines. By using
spectro-astrometry on the spatially resolved targets, we constrain the physical
size of the emitting regions in the disks. We resolve, spectrally and
spatially, the emission of the CO v(1-0) vibrational band and the
CO and vibrational bands in both targets,
as well as the CO band in HD 100546. Modeling of the CO emission
with a homogeneous disk in Keplerian motion, yields a best fit with an inner
and outer radius of the CO emitting region of 11 and 100 AU for HD
97048. HD 100546 is not fit well with our model, but we derive a lower limit on
the inner radius of 8 AU. The fact that gaseous [OI] emission was previously
detected in both targets at significantly smaller radii suggests that CO may be
effectively destroyed at small radii in the surface layers of these disksComment: v2: Letter format has been changed to Paper format; Change in the
focus of the paper towards CO depletion; Major changes in text; Change of
title. Submitted to A&A, 14/10/2008. Accepted by A&A, 17/04/200
The structure of the protoplanetary disk surrounding three young intermediate mass stars. II. Spatially resolved dust and gas distribution
[Abridged] We present the first direct comparison of the distribution of the
gas, as traced by the [OI] 6300 AA emission, and the dust, as traced by the 10
micron emission, in the protoplanetary disk around three intermediate-mass
stars: HD 101412, HD 135344 B and HD 179218. N-band visibilities were obtained
with VLTI/MIDI. Simple geometrical models are used to compare the dust emission
to high-resolution optical spectra in the 6300 AA [OI] line of the same
targets. The disks around HD 101412 and HD 135344 B appear strongly flared in
the gas, but self-shadowed in the dust beyond ~ 2 AU. In both systems, the 10
micron emission is rather compact (< 2 AU) while the [OI] brightness profile
shows a double peaked structure. The inner peak is strongest and is consistent
with the location of the dust, the outer peak is fainter and is located at 5-10
AU. Spatially extended PAH emission is found in both disks. The disk around HD
179218 is flared in the dust. The 10 micron emission emerges from a double
ring-like structure with the first ring peaking at ~ 1 AU and the second at ~
20 AU. No dust emission is detected between ~ 3 -- 15 AU. The oxygen emission
seems also to come from a flared structure, however, the bulk of this emission
is produced between ~ 1 -- 10 AU. This could indicate a lack of gas in the
outer disk or could be due to chemical effects which reduce the abundance of OH
-- the parent molecule of the observed [OI] emission -- further away from the
star. The three systems, HD 179218, HD 135344 B and HD 101412, may form an
evolutionary sequence: the disk initially flared becomes flat under the
combined action of gas-dust decoupling, grain growth and dust settling.Comment: Accepted for publication in A&
A survey for near-infrared H2 emission in Herbig Ae/Be stars: emission from the outer disks of HD 97048 and HD 100546
We report on a sensitive search for H2 1-0 S(1), 1-0 S(0) and 2-1 S(1)
ro-vibrational emission at 2.12, 2.22 and 2.25 micron in a sample of 15 Herbig
Ae/Be stars employing CRIRES, the ESO-VLT near-infrared high-resolution
spectrograph, at R~90,000. We detect the H2 1-0 S(1) line toward HD 100546 and
HD 97048. In the other 13 targets, the line is not detected. The H2 1-0 S(0)
and 2-1 S(1) lines are undetected in all sources. This is the first detection
of near-IR H2 emission in HD 100546. The H2 1-0 S(1) lines observed in HD
100546 and HD 97048 are observed at a velocity consistent with the rest
velocity of both stars, suggesting that they are produced in the circumstellar
disk. In HD 97048, the emission is spatially resolved and it is observed to
extend at least up to 200 AU. We report an increase of one order of magnitude
in the H2 1-0 S(1) line flux with respect to previous measurements taken in
2003 for this star, which suggests line variability. In HD 100546 the emission
is tentatively spatially resolved and may extend at least up to 50 AU. Modeling
of the H2 1-0 S(1) line profiles and their spatial extent with flat keplerian
disks shows that most of the emission is produced at a radius >5 AU. Upper
limits to the H2 1-0 S(0)/ 1-0 S(1) and H2 2-1 S(1)/1-0 S(1) line ratios in HD
97048 are consistent with H2 gas at T>2000 K and suggest that the emission
observed may be produced by X-ray excitation. The upper limits for the line
ratios for HD 100546 are inconclusive. Because the H2 emission is located at
large radii, for both sources a thermal emission scenario (i.e., gas heated by
collisions with dust) is implausible. We argue that the observation of H2
emission at large radii may be indicative of an extended disk atmosphere at
radii >5 AU. This may be explained by a hydrostatic disk in which gas and dust
are thermally decoupled or by a disk wind caused by photoevaporation.Comment: Accepted by A&A. 16 pages, 7 figure
The Structure of Protoplanetary Disks Surrounding Three Young Intermediate Mass Stars. I. Resolving the disk rotation in the [OI] 6300 \AA line
We present high spectral resolution optical spectra of three young
intermediate mass stars, in all of which we spectrally resolve the 6300
Angstrom [OI] emission line. Two of these have a double peaked line profile. We
fit these data with a simple model of the [OI] emission caused by
photo-dissociation of OH molecules in the upper layer of a circumstellar disk
by stellar UV radiation and thus translate the Doppler broadened [OI] emission
profile into an amount of emission as a function of distance from the central
star. The resulting spectra are in agreement with the expected disk shapes as
derived from their spectral energy distribution. We find evidence for shadowing
by an inner rim in the disk surrounding HD101412 and see a flaring disk
structure in HD179218 while the [OI] spectrum of HD135344 is more complex. The
[OI] emission starts for all three targets at velocities corresponding to their
dust sublimation radius and extends up to radii of 10 -- 90 AU. This shows that
this method can be a valuable tool in the future investigation of circumstellar
disks.Comment: 11 pages, 19 figures, accepted in A&A on 04/02/2008; added reference
High-resolution Br γ spectro-interferometry of the transitional Herbig Ae/Be star HD 100546: a Keplerian gaseous disc inside the inner rim
We present spatially and spectrally resolved Br γ emission around the planet-hosting, transitional Herbig Ae/Be star HD 100546. Aiming to gain insight into the physical origin of the line in possible relation to accretion processes, we carried out Br γ spectro-interferometry using AMBER/VLTI from three different baselines achieving spatial and spectral resolutions of 2–4 mas and 12 000. The Br γ visibility is larger than that of the continuum for all baselines. Differential phases reveal a shift between the photocentre of the Br γ line – displaced ∼0.6 mas (0.06 au at 100 pc) NE from the star – and that of the K-band continuum emission – displaced ∼0.3 mas NE from the star. The photocentres of the redshifted and blueshifted components of the Br γ line are located NW and SE from the photocentre of the peak line emission, respectively. Moreover, the photocentre of the fastest velocity bins within the spectral line tends to be closer to that of the peak emission than the photocentre of the slowest velocity bins. Our results are consistent with a Br γ-emitting region inside the dust inner rim ( ≲ 0.25 au) and extending very close to the central star, with a Keplerian, disc-like structure rotating counter-clockwise, and most probably flared (∼25°). Even though the main contribution to the Br γ line does not come from gas magnetically channelled on to the star, accretion on to HD 100546 could be magnetospheric, implying a mass accretion rate of a few 10−7 M⊙ yr−1. This value indicates that the observed gas has to be replenished on time-scales of a few months to years, perhaps by planet-induced flows from the outer to the inner disc as has been reported for similar systems
Effect of the consumption of a fermented dairy product containing Bifidobacterium lactis DN-173 010 on constipation in childhood: a multicentre randomised controlled trial (NTRTC: 1571)
<p>Abstract</p> <p>Background</p> <p>Constipation is a frustrating symptom affecting 3% of children worldwide. Randomised controlled trials show that both polyethylene glycol and lactulose are effective in increasing defecation frequency in children with constipation. However, in 30–50%, these children reported abdominal pain, bloating, flatulence, diarrhoea, nausea and bad taste of the medication. Two recent studies have shown that the fermented dairy product containing <it>Bifidobacterium lactis </it>strain DN-173 010 is effective in increasing stool frequency in constipation-predominant irritable bowel syndrome patients with a defecation frequency < 3/week and in constipated women with a defecation frequency < 3/week. Goal of this study is to determine whether this fermented dairy product is effective in the treatment of constipated children with a defecation frequency < 3/week.</p> <p>Methods/design</p> <p>It is a two nation (The Netherlands and Poland) double-blind, placebo-controlled randomised multicentre trial in which 160 constipated children (age 3–16 years) with a defecation frequency <3/week will be randomly allocated to consume a fermented dairy product containing <it>Bifidobacterium lactis </it>DN-173 010 or a control product, twice a day, for 3 weeks. During the study all children are instructed to try to defecate on the toilet for 5–10 minutes after each meal (3 times a day) and daily complete a standardized bowel diary. Primary endpoint is stool frequency. Secondary endpoints are stool consistency, faecal incontinence frequency, pain during defecation, digestive symptoms (abdominal pain, flatulence), adverse effects (nausea, diarrhoea, bad taste) and intake of rescue medication (Bisacodyl). Rate of success and rate of responders are also evaluated, with success defined as ≥ 3 bowel movements per week and ≤1 faecal incontinence episode over the last 2 weeks of product consumption and responder defined as a subject reporting a stool frequency ≥ 3 on the last week of product consumption. To demonstrate that the success percentage in the intervention group will be 35% and the success percentage in the control group (acidified milk without ferments, toilet training, bowel diary) will be 15%, with alpha 0.05 and power 80%, a total sample size of 160 patients was calculated.</p> <p>Conclusion</p> <p>This study is aimed to show that the fermented dairy product containing <it>Bifidobacterium lactis </it>strain DN-173 010 is effective in increasing stool frequency after 3 weeks of product consumption in children with functional constipation and a defecation frequency < 3/week.</p
Resolving the inner regions of the HD97048 circumstellar disk with VLT/NACO polarimetric differential imaging
Circumstellar disks are the cradles of planetary systems and their physical
and chemical properties directly influence the planet formation process. As
most planets supposedly form in the inner disk regions, i.e., within a few tens
of AU, it is crucial to study circumstellar disk on these scales to constrain
the conditions for planet formation. Our aims are to characterize the inner
regions of the circumstellar disk around the young Herbig Ae/Be star HD97048 in
polarized light. We use VLT/NACO to observe HD97048 in polarimetric
differential imaging (PDI) mode in the H and Ks band. We spatially resolve the
disk around HD97048 in polarized flux in both filters on scales between
~0.1"-1.0" corresponding to the inner ~16-160 AU. Fitting isophots to the flux
calibrated H-band image between 13 - 14 mag/arcsec^2 and 14 - 15 mag/arcsec^2
we derive a apparent disk inclination angle of 34+-5 deg and 47+-2 deg,
respectively. The disk position angle in both brightness regimes is almost
identical and roughly 80 deg. Along the disk major axis the surface brightness
of the polarized flux drops from ~11 mag/arcsec^2 at ~0.1" (~16 AU) to ~15.3
mag/arcsec^2 at ~1.0" (~160 AU). The brightness profiles along the major axis
are fitted with power-laws falling off as ~r^(-1.78+-0.02) in H and
~r^(-2.34+-0.04) in Ks. As the surface brightness drops off more rapidly in Ks
compared to H the disks becomes relatively bluer at larger separations possibly
indicating changing dust grain properties as a function of radius. For the
first time the inner ~0.1"-1.0" (~16-160 AU) of the surface layer of the
HD97048 circumstellar disk have been imaged in scattered light demonstrating
the power of ground-based imaging polarimetry. Our data fill an important gap
in a large collection of existing data including resolved thermal dust and PAH
emission images as well as resolved gas emission lines.Comment: Accepted for publication in Astronomy & Astrophysics; 6 pages incl. 5
figures and 2 table
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