scholarly journals Discovery of a mid-infrared protostellar outburst of exceptional amplitude

2020 ◽  
Vol 499 (2) ◽  
pp. 1805-1822
Author(s):  
P W Lucas ◽  
J Elias ◽  
S Points ◽  
Z Guo ◽  
L C Smith ◽  
...  
Keyword(s):  
Thermal Instability ◽  
Accretion Rate ◽  
Wide Field ◽  
Apparent Absence ◽  
Mid Infrared ◽  
Dark Clouds ◽  
Low Mass ◽  
Infrared Dark Clouds ◽  
Cloud Core ◽  
Infrared Survey

ABSTRACT We report the discovery of a mid-infrared outburst in a young stellar object (YSO) with an amplitude close to 8 mag at λ ≈ 4.6 μm. WISEA J142238.82−611553.7 is one of 23 highly variable Wide-field Infrared Survey Explorer (WISE) sources discovered in a search of infrared dark clouds (IRDCs). It lies within the small IRDC G313.671−0.309 (d ≈2.6 kpc), seen by the Herschel/Hi-Gal survey as a compact massive cloud core that may have been measurably warmed by the event. Pre-outburst data from Spitzer in 2004 suggest it is a class I YSO, a view supported by observation of weak 2.12 μm H2 emission in an otherwise featureless red continuum spectrum in 2019 (6 mag below the peak in Ks). Spitzer, WISE, and VISTA Variables in the Via Lactea (VVV) data show that the outburst began by 2006 and has a duration >13 yr, with a fairly flat peak from 2010 to 2014. The low pre-outburst luminosity implies a low-mass progenitor. The outburst luminosity of a few × 102 L⊙ is consistent with an accretion rate $\dot{M} \approx 10^{-4}$ M⊙yr−1, comparable to a classical FU Orionis event. The 4.6 μm peak in 2010 implies T = 800–1000 K and a disc radial location R ≈ 4.5 au for the emitting region. The colour evolution suggests subsequent progression outwards. The apparent absence of the hotter matter expected in thermal instability or MRI models may be due to complete obscuration of the innermost disc, e.g. by an edge-on disc view. Alternatively, disc fragmentation/infalling fragment models might more naturally explain a mid-infrared peak, though this is not yet clear.

scholarly journals A Census of the Circumstellar Disk Populations in the Sco-Cen Complex*

2021 ◽  
Vol 163 (1) ◽  
pp. 25
Author(s):  
K. L. Luhman
Keyword(s):  
Spectral Type ◽  
Circumstellar Disks ◽  
Circumstellar Disk ◽  
Wide Field ◽  
Low Mass Stars ◽  
Mid Infrared ◽  
Low Mass ◽  
Ir Photometry ◽  
Infrared Survey

Abstract I have used mid-infrared (IR) photometry from the Wide-field Infrared Survey Explorer (WISE) to perform a census of circumstellar disks among ∼10,000 candidate members of the Sco-Cen complex that were recently identified with data from the Gaia mission. IR excesses are detected for more than 1200 of the WISE counterparts that are within the commonly adopted boundary for Sco-Cen, ∼400 of which are newly reported in this work. The richest population in Sco-Cen, UCL/LCC, contains the largest available sample of disks (>500) for any population near its age (∼20 Myr). UCL/LCC also provides the tightest statistical constraints to date on the disk fractions of low-mass stars for any single age beyond that of Upper Sco (∼11 Myr). For Upper Sco and UCL/LCC, I have measured the disk fractions as a function of spectral type. The disk fraction in Upper Sco is higher at later spectral types, which is consistent with the results for previous samples of candidate members. In UCL/LCC, that trend has become more pronounced; the disk fractions in UCL/LCC are lower than those in Upper Sco by factors of ∼10, 5.7, and 2.5 at B7–K5.5, K6–M3.5, and M3.75–M6, respectively. The data in UCL/LCC also demonstrate that the disk fraction for low-mass stars remains nonnegligible at an age of 20 Myr (0.09 ± 0.01). Finally, I find no significant differences in the ages of disk-bearing and diskless low-mass stars in Upper Sco and UCL/LCC based on their positions in color–magnitude diagrams.

scholarly journals Massive and low-mass protostars in massive “starless” cores

2019 ◽  
Vol 622 ◽  
pp. A54 ◽  
Author(s):  
Thushara Pillai ◽  
Jens Kauffmann ◽  
Qizhou Zhang ◽  
Patricio Sanhueza ◽  
Silvia Leurini ◽  
...  
Keyword(s):  
Star Formation ◽  
Detection Limit ◽  
High Mass ◽  
Mass Star ◽  
Core Mass ◽  
Filamentary Structure ◽  
Dark Clouds ◽  
Low Mass ◽  
Infrared Dark Clouds ◽  
Dense Clump

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 μm. Such seemingly quiescent massive dense clumps have been speculated to harbor cores that are precursors of high-mass stars and clusters. We observed these two “prestellar” regions at 1 mm with the Submillimeter Array (SMA) with the aim of characterizing the nature of such cores. We show that the clumps fragment into several low- to high-mass cores within the filamentary structure of the enveloping cloud. However, while the overall physical properties of the clump may indicate a starless phase, we find that both regions host multiple outflows. The most massive core though 70 μm dark in both clumps is clearly associated with compact outflows. Such low-luminosity, massive cores are potentially the earliest stage in the evolution of a massive protostar. We also identify several outflow features distributed in the large environment around the most massive core. We infer that these outflows are being powered by young, low-mass protostars whose core mass is below our detection limit. These findings suggest that low-mass protostars have already formed or are coevally formed at the earliest phase of high-mass star formation.

A Search for Brown Dwarfs in the Alpha Persei Cluster

2003 ◽  
Vol 211 ◽  
pp. 179-180
Author(s):  
Nicolas Lodieu ◽  
Mark McCaughrean ◽  
Jérôme Bouvier ◽  
David Barrado y Navascués ◽  
John R. Stauffer
Keyword(s):  
Near Infrared ◽  
Open Cluster ◽  
Brown Dwarfs ◽  
Wide Field ◽  
Brown Dwarf ◽  
Young Open Cluster ◽  
Low Mass ◽  
Alpha Persei ◽  
Calar Alto ◽  
Infrared Survey

We present preliminary results from a deep near-infrared survey of a ~ 1 square degree area in the young open cluster Alpha Persei using the wide-field Omega-Prime camera on the Calar Alto 3.5m telescope, yielding a list of new low-mass cluster members, including brown dwarf candidates.

scholarly journals Characterizing the chemical pathways for water formation – a deep search for hydrogen peroxide

2014 ◽  
Vol 168 ◽  
pp. 349-367 ◽  
Author(s):  
Bérengère Parise ◽  
Per Bergman ◽  
Karl Menten
Keyword(s):  
Hydrogen Peroxide ◽  
Dark Clouds ◽  
Chemical Models ◽  
Upper Limits ◽  
Low Mass ◽  
And Shifts ◽  
First Time ◽  
Infrared Dark Clouds ◽  
Very High ◽  
High Column

In 2011, hydrogen peroxide (HOOH) was observed for the first time outside the solar system (Bergman et al., Astron. Astrophys., 2011, 531, L8). This detection appeared a posteriori to be quite natural, as HOOH is an intermediate product in the formation of water on the surface of dust grains. Following up on this detection, we present a search for HOOH in a diverse sample of sources in different environments, including low-mass protostars and regions with very high column densities, such as Infrared Dark Clouds (IRDCs). We do not detect the molecule in any other source than Oph A, and derive 3σ upper limits for the abundance of HOOH relative to H2 lower than that in Oph A for most sources. This result sheds a different light on our understanding of the detection of HOOH in Oph A, and shifts the question of why this source seems to be special. Therefore we rediscuss the detection of HOOH in Oph A, as well as the implications of the low abundance of HOOH, and its similarity with the case of O2. Our chemical models show that the production of HOOH is extremely sensitive to temperature, and is favored only in the range 20–30 K. The relatively high abundance of HOOH observed in Oph A suggests that the bulk of the material lies at a temperature in the range 20–30 K.

scholarly journals Observational Studies of Pre-Stellar Cores and Infrared Dark Clouds

2011 ◽  
Vol 7 (S280) ◽  
pp. 19-32 ◽  
Author(s):  
Paola Caselli
Keyword(s):  
Molecular Cloud ◽  
Chemical Structure ◽  
Initial Conditions ◽  
Theoretical Work ◽  
High Mass ◽  
Mass Star ◽  
Stellar Cluster ◽  
Dark Clouds ◽  
Low Mass ◽  
Infrared Dark Clouds

AbstractStars like our Sun and planets like our Earth form in dense regions within interstellar molecular clouds, called pre-stellar cores (PSCs). PSCs provide the initial conditions in the process of star and planet formation. In the past 15 years, detailed observations of (low-mass) PSCs in nearby molecular cloud complexes have allowed us to find that they are cold (T < 10K) and quiescent (molecular line widths are close to thermal), with a chemistry profoundly affected by molecular freeze-out onto dust grains. In these conditions, deuterated molecules flourish, becoming the best tools to unveil the PSC physical and chemical structure. Despite their apparent simplicity, PSCs still offer puzzles to solve and they are far from being completely understood. For example, what is happening to the gas and dust in their nuclei (the future stellar cradles) is still a mystery that awaits for ALMA. Other important questions are: how do different environments and external conditions affect the PSC physical/chemical structure? Are PSCs in high-mass star forming regions similar to the well-known low-mass PSCs? Here I review observational and theoretical work on PSCs in nearby molecular cloud complexes and the ongoing search and study of massive PSCs embedded in infrared dark clouds (IRDCs), which host the initial conditions for stellar cluster and high-mass star formation.

scholarly journals Primeval very low-mass stars and brown dwarfs – VI. Population properties of metal-poor degenerate brown dwarfs

2019 ◽  
Vol 486 (1) ◽  
pp. 1260-1282 ◽  
Author(s):  
Z H Zhang (张曾华) ◽  
A J Burgasser ◽  
M C Gálvez-Ortiz ◽  
N Lodieu ◽  
M R Zapatero Osorio ◽  
...  
Keyword(s):  
Transition Zone ◽  
Spectral Type ◽  
Near Infrared ◽  
Brown Dwarfs ◽  
Absolute Magnitude ◽  
Wide Field ◽  
Low Mass Stars ◽  
Low Mass ◽  
Infrared Survey ◽  
K Band

ABSTRACT We presented 15 new T dwarfs that were selected from UKIRT Infrared Deep Sky Survey, Visible and Infrared Survey Telescope for Astronomy , and Wide-field Infrared Survey Explorer surveys, and confirmed with optical to near-infrared spectra obtained with the Very Large Telescope and the Gran Telescopio Canarias. One of these new T dwarfs is mildly metal-poor with slightly suppressed K-band flux. We presented a new X-shooter spectrum of a known benchmark sdT5.5 subdwarf, HIP 73786B. To better understand observational properties of brown dwarfs, we discussed transition zones (mass ranges) with low-rate hydrogen, lithium, and deuterium burning in brown dwarf population. The hydrogen burning transition zone is also the substellar transition zone that separates very low-mass stars, transitional, and degenerate brown dwarfs. Transitional brown dwarfs have been discussed in previous works of the Primeval series. Degenerate brown dwarfs without hydrogen fusion are the majority of brown dwarfs. Metal-poor degenerate brown dwarfs of the Galactic thick disc and halo have become T5+ subdwarfs. We selected 41 T5+ subdwarfs from the literature by their suppressed K-band flux. We studied the spectral-type–colour correlations, spectral-type–absolute magnitude correlations, colour–colour plots, and HR diagrams of T5+ subdwarfs, in comparison to these of L–T dwarfs and L subdwarfs. We discussed the T5+ subdwarf discovery capability of deep sky surveys in the 2020s.

scholarly journals A mid-infrared study of RR Lyrae stars with the Wide-field Infrared Survey Explorer all-sky data release

2014 ◽  
Vol 441 (1) ◽  
pp. 715-725 ◽  
Author(s):  
Tatyana Gavrilchenko ◽  
Christopher R. Klein ◽  
Joshua S. Bloom ◽  
Joseph W. Richards
Keyword(s):  
Wide Field ◽  
Infrared Study ◽  
Rr Lyrae Stars ◽  
Mid Infrared ◽  
Rr Lyrae ◽  
Data Release ◽  
Lyrae Stars ◽  
Infrared Survey

scholarly journals Unveiling the Unseen: The Mid-IR Galactic Disk

2009 ◽  
Vol 5 (H15) ◽  
pp. 787-787
Author(s):  
Ed Churchwell
Keyword(s):  
Galactic Disk ◽  
Young Stellar Objects ◽  
Physical Processes ◽  
Stellar Objects ◽  
Mid Infrared ◽  
Dark Clouds ◽  
The Galaxy ◽  
Polycyclic Aromatic ◽  
Star Formation Regions ◽  
Infrared Dark Clouds

AbstractThe Spitzer mid-infrared (MIR) surveys, Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) and MIPSGAL have revealed a new view of the disk of the Milky Way. Hallmarks of the Galactic disk at MIR wavelengths with spatial resolution <2″ are bubbles/HII regions, infrared dark clouds, young stellar objects (YSOs)/star formation regions, diffuse dust and extended polycyclic aromatic hydrocarbons (PAHs), and more than 100 million publically available archived stars with measured flux densities at 7 wavelengths and positions accurate to 0.1″. At mid-IR wavelengths, the cool components in the Galaxy are preferentially bright and highlight physical processes that are not obvious at other wavelength regimes.

scholarly journals Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs). IX. Identification of two red quasars at z > 5.6

2020 ◽  
Vol 72 (5) ◽  
Author(s):  
Nanako Kato ◽  
Yoshiki Matsuoka ◽  
Masafusa Onoue ◽  
Shuhei Koyama ◽  
Yoshiki Toba ◽  
...  
Keyword(s):  
Rest Frame ◽  
Spectral Energy Distribution ◽  
Spectral Energy ◽  
Wide Field ◽  
Imaging Data ◽  
Mid Infrared ◽  
Dust Extinction ◽  
Infrared Wavelengths ◽  
Strategic Program ◽  
Infrared Survey

Abstract We present the first discovery of dust-reddened quasars (red quasars) in the high-z universe (z &gt; 5.6). This is a result from the Subaru High-z Exploration of Low-Luminosity Quasars (SHELLQs) project, which is based on the sensitive multi-band optical imaging data produced by the Hyper Suprime-Cam (HSC) Subaru Strategic Program survey. We identified four red quasar candidates from the 93 spectroscopically confirmed high-z quasars in the SHELLQs sample, based on detections in the Wide-field Infrared Survey Explorer (WISE) data at 3.4 and 4.6 μm (rest-frame ∼5000–6500 Å). The amount of dust reddening was estimated with spectral energy distribution (SED) fits over optical and mid-infrared wavelengths. Two of the four candidates were found to be red quasars with dust reddening of E(B − V) &gt; 0.1. The remaining SHELLQs quasars without individual WISE detections are significantly fainter in the WISE bands and bluer than the red quasars, although we did detect them in the W1 band in a stacked image. We also conducted the same SED fits for high-z optically-luminous quasars, but no red quasar was found. This demonstrates the power of Subaru HSC to discover high-z red quasars, which are fainter than the limiting magnitudes of past surveys in the rest-frame ultraviolet, due to dust extinction.

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