A survey for variable young stars with small telescopes – V. Analysis of TX Ori, V505 Ori, and V510 Ori, the <i>HST</i> ULLYSES targets in the σ Ori cluster

Froebrich, D.; Eislöffel, J.; Stecklum, B.; Herbert, Carys; Hambsch, Franz-Josef

doi:10.1093/mnras/stab3450

Cited by 5 publications

(4 citation statements)

References 53 publications

(89 reference statements)

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“…The estimated WM in parallax, * m a , and μ δ are 2.45 ± 0.12 mas, 1.23 ± 0.91 mas yr −1 , and -0.47 ± 0.80 mas yr −1 , respectively. From the median parallax we find the distance to the cluster to be 408 ± 8 pc, which is consistent with other Gaia-based distance estimated in Monteiro et al (2020) and Froebrich et al (2022).…”

Section: Member Selection Using Gaia Dr3supporting

confidence: 90%

“…This region was first described by Garrison (1967) and later several photometric and spectroscopic studies have been carried out (Béjar et al 1999(Béjar et al , 2001Zapatero Osorio et al 2002;Kenyon et al 2005;Lodieu et al 2009;Peña Ramírez et al 2012;Hernández et al 2014;Zapatero Osorio et al 2017;Caballero et al 2019). The kinematic study by Froebrich et al (2022), using photometric and astrometric data from Gaia EDR3, showed that the cluster has a main population of young stellar objects at ∼403 pc. The cluster is affected by almost negligible extinction A V < 1 mag (Lee 1968;Béjar et al 2004), which enables identification of the coolest objects in the region.…”

Section: Introductionmentioning

confidence: 90%

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A Novel Survey for Young Substellar Objects with the W-band Filter. VI. Spectroscopic Census of Substellar Members and the IMF of the σ Orionis Cluster

Damian

Jose

Biller

et al. 2023

ApJ

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Low-mass stars and substellar objects are essential in tracing the initial mass function (IMF). We study the nearby young σ Orionis cluster (d ∼ 408 pc, age ∼ 1.8 Myr) using deep near-infrared (NIR) photometric data in the J, W, and H bands from WIRCam on the Canada–France–Hawaii Telescope. We use the water absorption feature to select brown dwarfs photometrically and confirm their nature spectroscopically with IRTF-SpeX. Additionally we select candidate low-mass stars for spectroscopy and analyze their membership and those of literature sources using astrometry from Gaia DR3. We obtain NIR spectra for 28 very-low-mass stars and brown dwarfs and estimate their spectral type between M3 and M8.5 (masses ranging between 0.3 and 0.01 M ⊙). Apart from these, we also identify five new planetary-mass candidates which require further spectroscopic confirmation of youth. We compile a comprehensive catalog of 170 spectroscopically confirmed members in the central region of the cluster, for a wide mass range of ∼19–0.004 M ☉. We estimate the star-to-brown-dwarf ratio to be ∼4, within the range reported for other nearby star-forming regions. With the updated catalog of members we trace the IMF down to 4 M Jup and we find that a two-segment power law fits the substellar IMF better than a log-normal distribution.

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Section: Member Selection Using Gaia Dr3supporting

confidence: 90%

Section: Introductionmentioning

confidence: 90%

A Novel Survey for Young Substellar Objects with the W-band Filter. VI. Spectroscopic Census of Substellar Members and the IMF of the σ Orionis Cluster

Damian

Jose

Biller

et al. 2023

ApJ

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“…However, for several of the clusters our values are in agreement with previous works using earlier versions of Gaia data, such as DR2 and EDR3. These are for example: NGC 1333 and IC 348 (Pavlidou et al 2021); M 42 and other regions in the Orion complex (Chen et al 2020); 𝜎-Ori (Froebrich et al 2022); IC 5070 (Kuhn et al 2020);IC 1396(Pelayo-Baldárrago et al 2023. Several of our regions are also included in Mendigutía et al (2022).…”

Section: Discussionmentioning

confidence: 99%

“…This field has already been analysed in detail in Froebrich et al (2022) using GaiaEDR3 data. Hence, our results are very similar to these.…”

Section: 𝜎-Orimentioning

confidence: 99%

A survey for variable young stars with small telescopes: VI – Analysis of the outbursting Be stars NSW 284, gaia 19eyy, and VES 263

Froebrich

Hillenbrand

Herbert

et al. 2023

Monthly Notices of the Royal Astronomical Society

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This paper is one in a series reporting results from small telescope observations of variable young stars. Here, we study the repeating outbursts of three likely Be stars based on long-term optical, near-infrared, and mid-infrared photometry for all three objects, along with follow-up spectra for two of the three. The sources are characterised as rare, truly regularly outbursting Be stars. We interpret the photometric data within a framework for modelling light curve morphology, and find that the models correctly predict the burst shapes, including their larger amplitudes and later peaks towards longer wavelengths. We are thus able to infer the start and end times of mass loading into the circumstellar disks of these stars. The disk sizes are typically 3 – 6 times the areas of the central star. The disk temperatures are ∼40 %, and the disk luminosities are ∼10 % of those of the central Be star, respectively. The available spectroscopy is consistent with inside-out evolution of the disk. Higher excitation lines have larger velocity widths in their double-horned shaped emission profiles. Our observations and analysis support the decretion disk model for outbursting Be stars.

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Penellope

Sperling,

Eislöffel,

Manara

et al. 2024

A&A

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The physical mechanism leading to the formation of the blue loop in the Hertzsprung-Russell (HR) diagram is not satisfactorily explained by the evolutionary track of single stars. Rapid rotation and low metallicity drastically modify the internal structures and surface compositions of stars. Therefore, they provide a very significant pattern to investigate the evolutionary properties of the blue loop. In this paper, we mainly explore how rapid rotation and low metallicity have an important impact on the occurrence and extension of the blue loop. To this end, we implemented the rotating stellar evolution model, including the angular momentum transportation and chemical element mixing. We incorporated several initial rotational velocities and two characteristic metallicities in various models to explore the blue loop extension. The blue loop can occur when the hydrogen burning shell merges with the hydrogen--helium abundance discontinuity. We find that the blue loop extension strongly depends on the amplitude and gradient of the hydrogen--helium discontinuity. The hydrogen--helium discontinuity is created by the intermediate convective region or the convective dredge-up. A steeper hydrogen gradient in association with a greater amplitude of the hydrogen abundance discontinuity may favour a hotter star. Both the low metallicity and rapid rotation tend to restrain the development of the outer convective envelope and thus disfavour the occurrence and extension of the blue loop. There are three main reasons for this occurrence. Firstly, the helium core and its core potential can be enlarged by rotational mixing or low metallicity. Secondly, rapid rotation reduces the convective dredge-up depth in the star with $ Z=0.014$ and the mass extension of the intermediate convective region in the star with $ Z=0.0008$. Both of these phenomena lead to a reduction of the amplitude of the hydrogen abundance gradient. Thirdly, strong rotational mixing in the model (i.e. $ ini =350$ Km/s) with $ Z=0.0008$ reduces the energy generation rate from the hydrogen burning shell. Without bending towards higher effective temperature in the HR diagram, the additional helium brought near the H-burning shell associated with the larger He core can cause the star to expand towards becoming a red giant star directly after the core hydrogen burning. Rapid rotation and low metallicity tend to produce surface enrichment of the ratio of nitrogen to carbon and reduce the $ C$ left in the core; this has an important influence on the stellar compactness of the supernovae progenitor.

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A survey for variable young stars with small telescopes – V. Analysis of TX Ori, V505 Ori, and V510 Ori, the HST ULLYSES targets in the σ Ori cluster

Cited by 5 publications

References 53 publications

A Novel Survey for Young Substellar Objects with the W-band Filter. VI. Spectroscopic Census of Substellar Members and the IMF of the σ Orionis Cluster

A Novel Survey for Young Substellar Objects with the W-band Filter. VI. Spectroscopic Census of Substellar Members and the IMF of the σ Orionis Cluster

A survey for variable young stars with small telescopes: VI – Analysis of the outbursting Be stars NSW 284, gaia 19eyy, and VES 263

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