Thursday, February 28, 2019

JCMT/SCUBA-2 Continuum Observations of Pre-protostellar Evolution

SCOPE: SCUBA-2 Continuum Observations of Pre-protostellar Evolution - Survey Description and Compact Source Catalogue

We present the first release of the data and compact-source catalogue for the JCMT Large Program SCUBA-2 Continuum Observations of Pre-protostellar Evolution (SCOPE). SCOPE consists of 850-um continuum observations of 1235 Planck Galactic Cold Clumps (PGCCs) made with the Submillimetre Common-User Bolometer Array 2 on the James Clerk Maxwell Telescope. These data are at an angular resolution of 14.4 arcsec, significantly improving upon the 353-GHz resolution of Planck at 5 arcmin, and allowing for a catalogue of 3528 compact sources in 558 PGCCs.

http://arxiv.org/abs/1902.10180

Wednesday, February 20, 2019

Methylamine and other N-bearing species in NGC 6334I MM1-3

Methylamine and other simple N-bearing species in the hot cores NGC 6334I MM1-3

In the search for the building blocks of life, nitrogen-bearing molecules are of particular interest since nitrogen-containing bonds are essential for the linking of amino acids and ultimately the formation of larger biological structures. The elusive molecule methylamine (CH3NH2) is thought to be a key pre-biotic species but has so far only been securely detected in the giant molecular cloud Sgr B2. We identify CH3NH2 and other simple nitrogen-bearing species towards three hot cores in NGC 6334I. Column density ratios are derived in order to investigate the relevance of the individual species as precursors of biotic molecules.

http://arxiv.org/abs/1902.07060

Thursday, February 14, 2019

Prebiotic relevance of interstellar ices

Interstellar ices: a possible scenario for symmetry breaking of extraterrestrial chiral organic molecules of prebiotic interest

In the laboratory, the photo-and thermochemical evolution of ices, made of simple molecules of astrophysical relevance, always leads to the formation of semi-refractory water-soluble organic residues. Targeted searches for specific molecules do reveal the notable presence of two families of important molecular ''bricks of life'': amino acids, key molecules in metabolism, and sugars, including ribose, the backbone of RNA molecules which support the genetic information in all living entities.

http://arxiv.org/abs/1902.04575

Tuesday, February 5, 2019

New brown dwarf candidates from Gaia DR2

New ultra-cool and brown dwarf candidates in Gaia DR2

Context. The second Gaia data release (Gaia DR2) contains high precision positions, parallaxes and proper motions for 1.3 billion sources. The resulting Hertzsprung-Russell diagram reveals fine structures all over the mass range. Aims. This paper aims to investigate the content of Gaia DR2 at the low-mass end and to characterize ultra-cool and brown dwarfs.

https://arxiv.org/abs/1809.08244

Monday, February 4, 2019

Carbon and oxygen in metal-poor halo stars

Carbon and oxygen are key tracers of the Galactic chemical evolution; in particular, a reported upturn in [C/O] towards decreasing [O/H] in metal-poor halo stars could be a signature of nucleosynthesis by massive Population III stars. We reanalyse carbon, oxygen, and iron abundances in thirty-nine metal-poor turn-off stars.

https://arxiv.org/abs/1901.03592

Tuesday, January 29, 2019

Discovery of Galactic dwarf satellite Antila 2

The hidden giant: discovery of an enormous Galactic dwarf satellite in Gaia DR2

We report the discovery of a Milky-Way satellite in the constellation of Antlia. The Antlia 2 dwarf galaxy is located behind the Galactic disc at a latitude of $b\sim 11^{\circ}$ and spans 1.26 degrees, which corresponds to $\sim2.9$ kpc at its distance of 130 kpc.

https://arxiv.org/abs/1811.04082

Monday, January 28, 2019

G11.92-0.61 MM1b: a star forming like a planet

A young star caught forming like a planet

Astronomers have captured one of the most detailed views of a young star taken to date, and revealed an unexpected companion in orbit around it. The main object, referred to as MM 1a, is a young massive star surrounded by a rotating disc of gas and dust that was the focus of the scientists' original investigation.
https://phys.org/news/2019-01-star-flips-planet-forming-disk-pole.html

Circumbinary disk perpendicular to orbital plane

Double star system flips planet-forming disk into pole position

New research led by an astronomer at the University of Warwick has found the first confirmed example of a double star system that has flipped its surrounding disc to a position that leaps over the orbital plane of those stars...

https://phys.org/news/2019-01-star-flips-planet-forming-disk-pole.html

Friday, January 25, 2019

Cloud fragmentation and star formation

As clouds fall apart, a new star is born

Using the ALMA observatory in Chile, a group of astronomers led by MPIA's Henrik Beuther has made the most detailed observation yet of the way that a giant gas cloud fragments into dense cores, which then act as the birthplaces ...

https://phys.org/news/2019-01-clouds-fall-star-born.html

Thursday, January 24, 2019

Planet 9 or an icy disc? Complementary hypotheses

Shepherding in a Self-Gravitating Disk of Trans-Neptunian Objects

A relatively massive and moderately eccentric disk of trans-Neptunian objects (TNOs) can effectively counteract apse precession induced by the outer planets, and in the process shepherd highly eccentric members of its population into nearly-stationary configurations which are anti-aligned with the disk itself.

https://arxiv.org/abs/1804.06859

Protostars in massive "starless" cores

Massive and low-mass protostars in massive "starless" cores

The infrared dark clouds (IRDCs) G11.11$-$0.12 and G28.34$+$0.06 are two of the best-studied IRDCs in our Galaxy. These two clouds host clumps at different stages of evolution, including a massive dense clump in both clouds that is dark even at 70 and 100$μ$m.

https://arxiv.org/abs/1901.07582

Thursday, January 17, 2019

Binarity of massive young stellar objects

A pilot survey of the binarity of Massive Young Stellar Objects with $K$ band adaptive optics

We present the first search for binary companions of Massive Young Stellar Objects (MYSOs) using AO-assisted $K$ band observations, with NaCo at the VLT. We have surveyed 32 MYSOs from the RMS catalogue, probing the widest companions, with a physical separation range of 400 - 46,000 au, within the predictions of models and observations for multiplicity of MYSOs.

https://arxiv.org/abs/1901.04716

An O-type protostar forming in an accretion disk

An Asymmetric Keplerian Disk Surrounding the O-type Protostar IRAS16547$-$4247

During the last decades, a great interest has emerged to know if even the most massive stars in our galaxy (namely the spectral O-type stars) are formed in a similar manner as the low- and intermediate-mass stars, that is, through the presence of accreting disks and powerful outflows.

https://arxiv.org/abs/1901.04896

The most massive binary star known

Weighing Melnick 34: the most massive binary system known

Here we confirm Melnick 34, an X-ray bright star in the 30 Doradus region of the Large Magellanic Cloud, as an SB2 binary comprising WN5h+WN5h components. We present orbital solutions using 26 epochs of VLT/UVES spectra and 22 epochs of archival Gemini/GMOS spectra.

https://arxiv.org/abs/1901.04769

Tuesday, January 15, 2019

Wide co-moving binary and multiple stars

A catalog of wide binary and multiple systems of bright stars from Gaia-DR2 and the Virtual Observatory

Binary and multiple stars have long provided an effective empirical method of testing stellar formation and evolution theories. In particular, the existence of wide binary systems (separations $>$20,000 au) is particularly challenging to binary formation models as their physical separations are beyond the typical size of a collapsing cloud core ($\sim$5,000$-$10,000 au).

https://arxiv.org/abs/1901.03730

Dissolving star cluster Ruprecht 147

Ruprecht 147: a paradigm of dissolving star cluster

We employed recent Gaia/DR2 data to investigate the dynamical status of the nearby (300 pc), old (2.5 Gyr) open cluster Ruprecht~147. We found prominent leading and trailing tails of stars along the cluster orbit, which demonstrates that Ruprecht~147 is losing stars at fast pace.

https://arxiv.org/abs/1901.04253

Monday, January 14, 2019

Stars surrounded by iron dust

Discovery of stars surrounded by iron dust in the LMC

We consider a small sample of oxygen-rich, asymptotic giant branch stars in the Large Magellanic Cloud, observed by the Spitzer Space Telescope, exhibiting a peculiar spectral energy distribution, which can be hardly explained by the common assumption that dust around AGB stars is primarily composed of silicate grains.

https://arxiv.org/abs/1901.03621

Thursday, January 10, 2019

First detection of interstellar glycolonitrile

First detection of the pre-biotic molecule glycolonitrile (HOCH2CN) in the interstellar medium

Theories of a pre-RNA world suggest that glycolonitrile (HOCH$_2$CN) is a key species in the process of ribonucleotide assembly, which is considered as a molecular precursor of nucleic acids. In this Letter, we report the first detection of this pre-biotic molecule in the interstellar medium (ISM) by using ALMA data obtained at frequencies between 86.5$\,$GHz and 266.5$\,$GHz toward the Solar-type protostar IRAS16293-2422 B.

https://arxiv.org/abs/1901.02576

Evidence for crystallisation in white dwarfs

Astronomers discover first direct evidence of white dwarf stars solidifying into crystals

The first direct evidence of white dwarf stars solidifying into crystals has been discovered by astronomers at the University of Warwick, and our skies are filled with them. Observations have revealed that dead remnants of stars like our Sun, called white dwarfs, have a core of solid oxygen and carbon due to a phase transition during their lifecycle similar to water turning into ice but at much higher temperatures.

https://phys.org/news/2019-01-astronomers-evidence-white-dwarf-stars.html

Helium flash origin of heavy isotopes

Stellar corpse reveals clues to missing stardust

Everything around you - your desk, your laptop, your coffee cup - in fact, even you - is made of stardust, the stuff forged in the fiery furnaces of stars that died before our sun was born. Probing the space surrounding ...

https://phys.org/news/2018-12-stellar-corpse-reveals-clues-stardust.html

Saturday, December 22, 2018

Substellar mass function of the field

Preliminary Trigonometric Parallaxes of 184 Late-T and Y Dwarfs and an Analysis of the Field Substellar Mass Function into the "Planetary" Mass Regime

We present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), USNO (18), NTT (14), and UKIRT (9). To complete the 20-pc census of $\ge$T6 dwarfs, we combine these measurements with previously published trigonometric parallaxes for an additional 44 objects and spectrophotometric distance estimates for another 7.

https://arxiv.org/abs/1812.01208

Tuesday, December 18, 2018

A method to analyse velocity structure

We present a new method of analysing and quantifying velocity structure in star forming regions suitable for the rapidly increasing quantity and quality of stellar position-velocity data. The method can be applied to data in any number of dimensions, does not require the centre or characteristic size (e.g.

https://arxiv.org/abs/1812.05628

Wednesday, December 12, 2018

Consistent modelling of proto-planetary disks

Consistent dust and gas models for protoplanetary disks III. Models for selected objects from the FP7 DIANA project

The European FP7 project DIANA has performed a coherent analysis of a large set of observations from protoplanetary disks by means of thermo-chemical disk models. The collected data include extinction-corrected stellar UV and X-ray input spectra (as seen by the disk), photometric fluxes, low and high resolution spectra, interferometric data, emission line fluxes, line velocity profiles and line maps.

http://arxiv.org/abs/1812.02741