scholarly journals First L band detection of hot exozodiacal dust with VLTI/MATISSE

2020 ◽  
Vol 499 (1) ◽  
pp. L47-L52
Author(s):  
Florian Kirchschlager ◽  
Steve Ertel ◽  
Sebastian Wolf ◽  
Alexis Matter ◽  
Alexander V Krivov
Keyword(s):  
Temporal Variability ◽  
Spectral Energy Distribution ◽  
Flux Ratio ◽  
Spectral Energy ◽  
Large Telescope ◽  
Very Large Telescope ◽  
New Instrument ◽  
L Band ◽  
First Time ◽  
Dust Ring

ABSTRACT For the first time, we observed the emission of hot exozodiacal dust in L band. We used the new instrument MATISSE at the Very Large Telescope Interferometer to detect the hot dust around κ Tuc with a significance of 3σ to 6σ at wavelengths between 3.37 and $3.85\, {\mu {\rm m}}$ and a dust-to-star flux ratio of 5 to $7{{{\ \rm per\ cent}}}$. We modelled the spectral energy distribution based on the new L band data alone and in combination with H band data published previously. In all cases we find $0.58\, {\mu {\rm m}}$ grains of amorphous carbon to fit the κ Tuc observations the best, however, also nanometre or micrometre grains and other carbons or silicates reproduce the observations well. Since the H band data revealed a temporal variability, while our Lband data were taken at a different epoch, we combine them in different ways. Depending on the approach, the best fits are obtained for a narrow dust ring at a stellar distance in the 0.1–029 au range and thus with a temperature between 940 and $1430\, {\rm K}$. Within the 1σ uncertainty dust location and temperature are confined to $0.032{\!-\!}1.18\, {\rm au}$ and $600{\!-\!}2000\, {\rm K}$.

scholarly journals Orbital and atmospheric characterization of the planet within the gap of the PDS 70 transition disk

2018 ◽  
Vol 617 ◽  
pp. L2 ◽  
Author(s):  
A. Müller ◽  
M. Keppler ◽  
Th. Henning ◽  
M. Samland ◽  
G. Chauvin ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Near Infrared ◽  
Direct Detection ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Infrared Range ◽  
Data Set ◽  
Cloud Properties ◽  
Spectrophotometric Data ◽  
First Time

Context. The observation of planets in their formation stage is a crucial but very challenging step in understanding when, how, and where planets form. PDS 70 is a young pre-main sequence star surrounded by a transition disk, in the gap of which a planetary-mass companion has recently been discovered. This discovery represents the first robust direct detection of such a young planet, possibly still at the stage of formation. Aims. We aim to characterize the orbital and atmospheric properties of PDS 70 b, which was first identified on May 2015 in the course of the SHINE survey with SPHERE, the extreme adaptive-optics instrument at the VLT. Methods. We obtained new deep SPHERE/IRDIS imaging and SPHERE/IFS spectroscopic observations of PDS 70 b. The astrometric baseline now covers 6 yr, which allowed us to perform an orbital analysis. For the first time, we present spectrophotometry of the young planet which covers almost the entire near-infrared range (0.96–3.8 μm). We use different atmospheric models covering a large parameter space in temperature, log g, chemical composition, and cloud properties to characterize the properties of the atmosphere of PDS 70 b. Results. PDS 70 b is most likely orbiting the star on a circular and disk coplanar orbit at ~22 au inside the gap of the disk. We find a range of models that can describe the spectrophotometric data reasonably well in the temperature range 1000–1600 K and log g no larger than 3.5 dex. The planet radius covers a relatively large range between 1.4 and 3.7 RJ with the larger radii being higher than expected from planet evolution models for the age of the planet of 5.4 Myr. Conclusions. This study provides a comprehensive data set on the orbital motion of PDS 70 b, indicating a circular orbit and a motion coplanar with the disk. The first detailed spectral energy distribution of PDS 70 b indicates a temperature typical of young giant planets. The detailed atmospheric analysis indicates that a circumplanetary disk may contribute to the total planetflux.

scholarly journals A Search for Submillimeter Galaxy Counterparts

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Ariana Blair
Keyword(s):  
Energy Distribution ◽  
Spectral Energy Distribution ◽  
Flux Ratio ◽  
Spectral Energy ◽  
Ratio Versus

In this paper, we look to find counterparts to our 450µm sources found in our SCUBA-2 imaging of the Chandra Deep Field – South (CDF-S). We chose sources greater than 4σ and found 21 sources. We then matched the sources to a published 850µm ALMA catalog. We matched the sources within a 4 arcsecond radius and found 12 matches to our 450µm sources. Using the fluxes from the SCUBA-2 CDF-S map and the ALMA 850µm fluxes from the catalog. We created a 450µm to 850µm flux ratio versus redshift plotted against an Arp220 spectral energy distribution (SED) at varying temperatures.

scholarly journals The UVMag space project: UV and visible spectropolarimetry of massive stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 389-390
Author(s):  
Coralie Neiner ◽  
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Massive Stars ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Medium Size ◽  
Space Project ◽  
First Time ◽  
The Magnetic Field ◽  
Circumstellar Environment

AbstractUVMag is a medium-size space telescope equipped with a high-resolution spectropolarimetrer working in the UV and visible domains. It will be proposed to ESA for a future M mission. It will allow scientists to study all types of stars as well as e.g. exoplanets and the interstellar medium. It will be particularly useful for massive stars, since their spectral energy distribution peaks in the UV. UVMag will allow us to study massive stars and their circumstellar environment (in particular the stellar wind) spectroscopically in great details. Moreover, with UVMag's polarimetric capabilities we will be able, for the first time, to measure the magnetic field of massive stars simultaneously at the stellar surface and in the wind lines, i.e. to completely map their magnetosphere.

scholarly journals Metallicity, temperature, and gravity scales of M subdwarfs,

2019 ◽  
Vol 628 ◽  
pp. A61 ◽  
Author(s):  
N. Lodieu ◽  
F. Allard ◽  
C. Rodrigo ◽  
Y. Pavlenko ◽  
A. Burgasser ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
M Dwarfs ◽  
Low Mass Stars ◽  
Very Large Telescope ◽  
Wide Range ◽  
Solar Metallicity ◽  
Effective Temperatures

Aims. The aim of the project is to define metallicity/gravity/temperature scales for different spectral types of metal-poor M dwarfs. Methods. We obtained intermediate-resolution ultraviolet (R ∼ 3300), optical (R ∼ 5400), and near-infrared (R ∼ 3900) spectra of 43 M subdwarfs (sdM), extreme subdwarfs (esdM), and ultra-subdwarfs (usdM) with the X-shooter spectrograph on the European Southern Observatory Very Large Telescope. We compared our atlas of spectra to the latest BT-Settl synthetic spectral energy distribution over a wide range of metallicities, gravities, and effective temperatures to infer the physical properties for the whole M dwarf sequence (M0–M9.5) at sub-solar metallicities and constrain the latest atmospheric models. Results. The BT-Settl models accurately reproduce the observed spectra across the 450–2500 nm wavelength range except for a few regions. We find that the best fits are obtained for gravities of log (g) = 5.0–5.5 for the three metal classes. We infer metallicities of [Fe/H] = −0.5, −1.5, and −2.0 ± 0.5 dex and effective temperatures of 3700–2600 K, 3800–2900 K, and 3700–2900 K for subdwarfs, extreme subdwarfs, and ultra-subdwarfs, respectively. Metal-poor M dwarfs tend to be warmer by about 200 ± 100 K and exhibit higher gravity than their solar-metallicity counterparts. We derive abundances of several elements (Fe, Na, K, Ca, Ti) for our sample but cannot describe their atmospheres with a single metallicity parameter. Our metallicity scale expands the current scales available for mildly metal-poor planet-host low-mass stars. Our compendium of moderate-resolution spectra covering the 0.45–2.5 micron range represents an important resource for large-scale surveys and space missions to come.

scholarly journals Detection of a flaring blazar coincident with an IceCube high-energy neutrino

2019 ◽  
Vol 207 ◽  
pp. 02001
Author(s):  
Anna Franckowiak
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Neutrino Flux ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
High Energy Neutrino ◽  
Energy Neutrino ◽  
Radio Wavelength ◽  
First Time

In September 22, 2017, IceCube released a public alert announcing the detection of a 290 TeV neutrino track event with an angular uncertainty of one square degree (90% containment). A multi-messenger follow-up campaign was initiated resulting in the detection of a GeV gamma-ray flare by the Fermi Large Area Telescope positionally consistent with the location of the known Bl Lac object, TXS 0506+056 , located only 0.1 degrees from the best-fit neutrino position. The probability of finding a GeV gamma-ray flare in coincidence with a high-energy neutrino event assuming a correlation of the neutrino flux with the gamma-ray energy flux in the energy band between 1 and 100 GeV was calculated to be 3σ (after trials correction). Following the detection of the flaring blazar the imaging air Cherenkov telescope MAGIC detected the source for the first time in the > 100 GeV gamma-ray band. The activity of the source was confirmed in X-ray, optical and radio wavelength. Several groups have developed lepto-hadronic models which succeed to explain the multi-messenger spectral energy distribution.

scholarly journals Mid-infrared evolution of η Carinae from 1968 to 2018

2019 ◽  
Vol 630 ◽  
pp. L6 ◽  
Author(s):  
A. Mehner ◽  
W.-J. de Wit ◽  
D. Asmus ◽  
P. W. Morris ◽  
C. Agliozzo ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Circumstellar Dust ◽  
Spectral Energy ◽  
Short Term ◽  
Dust Extinction ◽  
Bolometric Luminosity ◽  
Very Large Telescope ◽  
Optical Wavelengths ◽  
The Mean

η Car is one of the most luminous and massive stars in our Galaxy and is the brightest mid-IR source in the sky outside our solar system. Since the late 1990s, the central source has dramatically brightened at UV and optical wavelengths. This might be explained by a decrease in circumstellar dust extinction. We aim to establish the mid-IR flux evolution and further our understanding of the star’s UV and optical brightening. Mid-IR images from 8−20 μm were obtained in 2018 with VISIR at the Very Large Telescope. Archival data from 2003 and 2005 were retrieved from the ESO Science Archive Facility, and historical records were collected from publications. We present mid-IR images of η Car with the highest angular resolution to date at the corresponding wavelengths (≥0.22″). We reconstruct the mid-IR evolution of the spectral energy distribution of the spatially integrated Homunculus nebula from 1968 to 2018 and find no long-term changes. The bolometric luminosity of η Car has been stable over the past five decades. We do not observe a long-term decrease in the mid-IR flux densities that could be associated with the brightening at UV and optical wavelengths, but circumstellar dust must be declining in our line of sight alone. Short-term flux variations within about 25% of the mean levels could be present.

scholarly journals HELP: a catalogue of 170 million objects, selected at 0.36–4.5 μm, from 1270 deg2 of prime extragalactic fields

2019 ◽  
Vol 490 (1) ◽  
pp. 634-656 ◽  
Author(s):  
Raphael Shirley ◽  
Yannick Roehlly ◽  
Peter D Hurley ◽  
Veronique Buat ◽  
María del Carmen Campos Varillas ◽  
...  
Keyword(s):  
Near Infrared ◽  
Spectral Energy Distribution ◽  
Value Added ◽  
Far Infrared ◽  
Spectral Energy ◽  
Distribution Modelling ◽  
Sigma Point ◽  
Photometric Redshift ◽  
First Time ◽  
Cross Match

ABSTRACT We present an optical to near-infrared (NIR) selected astronomical catalogue covering 1270 deg2. This is the first attempt to systematically combine data from 23 of the premier extragalactic survey fields – the product of a vast investment of telescope time. The fields are those imaged by the Herschel Space Observatory that form the Herschel Extragalactic Legacy Project (HELP). Our catalogue of 170 million objects is constructed by a positional cross-match of 51 public surveys. This high-resolution optical, NIR, and mid-infrared catalogue is designed for photometric redshift estimation, extraction of fluxes in lower resolution far-infrared maps, and spectral energy distribution modelling. It collates, standardizes, and provides value added derived quantities including corrected aperture magnitudes and astrometry correction over the Herschel extragalactic wide fields for the first time. $grizy$ fluxes are available on all fields with g-band data reaching $5\sigma$ point-source depths in a 2 arcsec aperture of 23.5, 24.4, and 24.6 (AB) mag at the 25th, 50th, and 75th percentiles, by area covered, across all HELP fields. It has K or $K_s$ coverage over 1146 deg2 with depth percentiles of 20.2, 20.4, and 21.0 mag, respectively. The IRAC Ch 1 band is available over 273 deg2 with depth percentiles of 17.7, 21.4, and 22.2 mag, respectively. This paper defines the ‘masterlist’ objects for the first data release (DR1) of HELP. This large sample of standardized total and corrected aperture fluxes, uniform quality flags, and completeness measures provides large well-understood statistical samples over the full Herschel extragalactic sky.

scholarly journals Optical polarised phase function of the HR 4796A dust ring

2019 ◽  
Vol 626 ◽  
pp. A54 ◽  
Author(s):  
J. Milli ◽  
N. Engler ◽  
H. M. Schmid ◽  
J. Olofsson ◽  
F. Ménard ◽  
...  
Keyword(s):  
Phase Function ◽  
Scattered Light ◽  
Dust Particles ◽  
Cometary Dust ◽  
Very Large Telescope ◽  
Wide Range ◽  
Alternative Scenarios ◽  
First Time ◽  
Dust Ring ◽  
Compact Spheres

Context. The scattering properties of the dust originating from debris discs are still poorly known. The analysis of scattered light is however a powerful remote-sensing tool to understand the physical properties of dust particles orbiting other stars. Scattered light is indeed widely used to characterise the properties of cometary dust in the solar system. Aims. We aim to measure the morphology and scattering properties of the dust from the debris ring around HR 4796 A in polarised optical light. Methods. We obtained high-contrast polarimetric images of HR 4796 A in the wavelength range 600–900 nm with the SPHERE/ZIMPOL instrument on the Very Large Telescope. Results. We measured for the first time the polarised phase function of the dust in a debris system over a wide range of scattering angles in the optical. We confirm that it is incompatible with dust particles being compact spheres under the assumption of the Mie theory, and propose alternative scenarios compatible with the observations, such as particles with irregular surface roughness or aggregate particles.

scholarly journals A multiwavelength study of the debris disc around 49 Cet

2019 ◽  
Vol 488 (3) ◽  
pp. 3507-3525 ◽  
Author(s):  
Nicole Pawellek ◽  
Attila Moór ◽  
Julien Milli ◽  
Ágnes Kóspál ◽  
Johan Olofsson ◽  
...  
Keyword(s):  
Thermal Emission ◽  
Scattered Light ◽  
Spectral Energy Distribution ◽  
Outer Region ◽  
Transport Processes ◽  
Spectral Energy ◽  
Distribution Fitting ◽  
Emission Data ◽  
Very Large Telescope ◽  
Radial Extent

Abstract In a multiwavelength study of thermal emission and scattered light images we analyse the dust properties and structure of the debris disc around the A1-type main-sequence star 49 Cet. As a basis for this study, we present new scattered light images of the debris disc known to possess a high amount of both dust and gas. The outer region of the disc is revealed in former coronagraphic H-band and our new Y-band images from the Very Large Telescope SPHERE instrument. We use the knowledge of the disc’s radial extent inferred from ALMA observations and the grain size distribution found by spectral energy distribution fitting to generate semidynamical dust models of the disc. We compare the models to scattered light and thermal emission data and find that a disc with a maximum surface density at 110 au and shallow edges can describe both the thermal emission and the scattered light observations. This suggests that grains close to the blow-out limit and large grains stem from the same planetesimal population and are mainly influenced by radiation pressure. The influence of inward transport processes could not be analysed in this study.

Constraining convection across the AGB with high-angular-resolution observations

2018 ◽  
Vol 14 (S343) ◽  
pp. 27-30
Author(s):  
Claudia Paladini ◽  
Fabien Baron ◽  
A. Jorissen ◽  
J.-B. Le Bouquin ◽  
B. Freytag ◽  
...  
Keyword(s):  
Angular Resolution ◽  
Granule Size ◽  
Scaling Relations ◽  
High Angular Resolution ◽  
Large Telescope ◽  
Horizontal Scale ◽  
Very Large Telescope ◽  
Convective Pattern ◽  
Surface Convection ◽  
First Time

AbstractWe present very detailed images of the photosphere of an AGB star obtained with the PIONIER instrument, installed at the Very Large Telescope Interferometer (VLTI). The images show a well defined stellar disc populated by a few convective patterns. Thanks to the high precision of the observations we are able to derive the contrast and granulation horizontal scale of the convective pattern for the first time in a direct way. Such quantities are then compared with scaling relations between granule size, effective temperature, and surface gravity that are predicted by simulations of stellar surface convection.

Sign in / Sign up

Export Citation Format

Share Document