scholarly journals Activity and Rotation in the Young Cluster h Per

2013 ◽  
Vol 9 (S302) ◽  
pp. 102-105
Author(s):  
C. Argiroffi ◽  
M. Caramazza ◽  
G. Micela ◽  
E. Moraux ◽  
J. Bouvier
Keyword(s):  
Main Sequence ◽  
Activity Relationship ◽  
Central Field ◽  
Activity Levels ◽  
Rotational Period ◽  
Main Sequence Stars ◽  
Lower Mass ◽  
Significant Evidence ◽  
X Ray ◽  
Low Mass

AbstractWe study the rotation-activity relationship for low-mass members of the young cluster h Persei, a ~13 Myr old cluster. h Per, thanks to its age, allows us to link the rotation-activity relation observed for main-sequence stars to the still unexplained activity levels of very young clusters.We constrained the activity levels of h Per members by analyzing a deep Chandra/ACIS-I observation pointed to the central field of h Per. We combined this X-ray catalog with the catalog of h Per members with measured rotational period, presented by Moraux et al. (2013). We obtained a final catalog of 202 h Per members with measured X-ray luminosity and rotational period. We investigate the rotation-activity relation of h Per members considering different mass ranges. We find that stars with 1.3 M⊙ > M 1.4 M⊙ show significant evidence of supersaturation for short periods. This phenomenon is instead not observed for lower mass stars.

scholarly journals Non thermal emission from T Tauri stars

2010 ◽  
Vol 6 (S275) ◽  
pp. 404-405
Author(s):  
María V. del Valle ◽  
Gustavo E. Romero
Keyword(s):  
Main Sequence ◽  
Thermal Emission ◽  
High Energy ◽  
Magnetic Activity ◽  
T Tauri Stars ◽  
Main Sequence Stars ◽  
High Energy Radiation ◽  
X Ray ◽  
T Tauri ◽  
Low Mass

AbstractT Tauri stars are low mass, pre-main sequence stars. These objects are surrounded by an accretion disk and present strong magnetic activity. T Tauri stars are copious emitters of X-ray emission which belong to powerful magnetic reconnection events. Strong magnetospheric shocks are likely outcome of massive reconnection. Such shocks can accelerate particles up to relativistic energies through Fermi mechanism. We present a model for the high-energy radiation produced in the environment of T Tauri stars. We aim at determining whether this emission is detectable. If so, the T Tauri stars should be very nearby.

scholarly journals Comment on “A noninteracting low-mass black hole–giant star binary system”

Science ◽  
2020 ◽  
Vol 368 (6491) ◽  
pp. eaba3282 ◽  
Author(s):  
Ed P. J. van den Heuvel ◽  
Thomas M. Tauris
Keyword(s):  
Black Hole ◽  
Main Sequence ◽  
Close Binary ◽  
Main Sequence Stars ◽  
Solar Mass ◽  
Giant Star ◽  
X Ray ◽  
Low Mass ◽  
Red Giant ◽  
Star Binary

Thompson et al. (Reports, 1 November 2019, p. 637) interpreted the unseen companion of the red giant star 2MASS J05215658+4359220 as most likely a black hole. We argue that if the red giant’s mass is ~1 solar mass, its companion can be a close binary consisting of two main-sequence stars. This would explain why no x-ray emission is detected from the system.

scholarly journals X-RAY PROPERTIES OF LOW-MASS PRE-MAIN SEQUENCE STARS IN THE ORION TRAPEZIUM CLUSTER

2015 ◽  
Vol 810 (1) ◽  
pp. 55 ◽  
Author(s):  
Norbert S. Schulz ◽  
David P. Huenemoerder ◽  
Moritz Günther ◽  
Paola Testa ◽  
Claude R. Canizares
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
X Ray ◽  
Low Mass ◽  
Orion Trapezium

Low-Mass Pre-Main Sequence Stars and Their X-ray Emission

Science ◽  
1997 ◽  
Vol 276 (5317) ◽  
pp. 1363-1370 ◽  
Author(s):  
R. Neuhauser
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
X Ray ◽  
Low Mass

scholarly journals Magnetic Activity of Pre-main Sequence Stars near the Stellar-Substellar Boundary

2015 ◽  
Vol 10 (S314) ◽  
pp. 126-127
Author(s):  
David Principe ◽  
Joel. H. Kastner ◽  
David Rodriguez
Keyword(s):  
Spectral Type ◽  
Main Sequence ◽  
Brown Dwarfs ◽  
Magnetic Activity ◽  
Main Sequence Stars ◽  
Coronal Emission ◽  
Low Mass Stars ◽  
X Ray ◽  
Low Mass ◽  
Age Range

AbstractX-ray observations of pre-main sequence (pre-MS) stars of M-type probe coronal emission and offer a means to investigate magnetic activity at the stellar-substellar boundary. Recent observations of main sequence (MS) stars at this boundary display a decrease in fractional X-ray luminosity (LX/Lbol) by almost two orders of magnitude for spectral types M7 and later. We investigate magnetic activity and search for a decrease in X-ray emission in the pre-MS progenitors of these MS stars. We present XMM-Newton X-ray observations and preliminary results for ~10 nearby (30-70 pc), very low mass pre-MS stars in the relatively unexplored age range of 10-30 Myr. We compare the fractional X-ray luminosities of these 10-30 Myr old stars to younger (1-3 Myr) pre-MS brown dwarfs and find no dependence on spectral type or age suggesting that X-ray activity declines at an age later than ~30 Myr in these very low-mass stars.

scholarly journals Are sdAs helium core stars?

2017 ◽  
Vol 26 (1) ◽  
Author(s):  
Ingrid Pelisoli ◽  
S. O. Kepler ◽  
Detlev Koester
Keyword(s):  
Main Sequence ◽  
Galactic Disk ◽  
Physical Nature ◽  
Sloan Digital Sky Survey ◽  
Distance Modulus ◽  
Main Sequence Stars ◽  
Sky Survey ◽  
Balmer Lines ◽  
Low Mass ◽  
Binary Evolution

AbstractEvolved stars with a helium core can be formed by non-conservative mass exchange interaction with a companion or by strong mass loss. Their masses are smaller than 0.5 M⊙. In the database of the Sloan Digital Sky Survey (SDSS), there are several thousand stars which were classified by the pipeline as dwarf O, B and A stars. Considering the lifetimes of these classes on the main sequence, and their distance modulus at the SDSS bright saturation, if these were common main sequence stars, there would be a considerable population of young stars very far from the galactic disk. Their spectra are dominated by Balmer lines which suggest effective temperatures around 8 000-10 000 K. Several thousand have significant proper motions, indicative of distances smaller than 1 kpc. Many show surface gravity in intermediate values between main sequence and white dwarf, 4.75 < log g < 6.5, hence they have been called sdA stars. Their physical nature and evolutionary history remains a puzzle. We propose they are not H-core main sequence stars, but helium core stars and the outcomes of binary evolution. We report the discovery of two new extremely-low mass white dwarfs among the sdAs to support this statement.

scholarly journals The discovery of low-mass pre-main-sequence stars in Cepheus OB3b

2003 ◽  
Vol 341 (3) ◽  
pp. 805-822 ◽  
Author(s):  
M. Pozzo ◽  
T. Naylor ◽  
R. D. Jeffries ◽  
J. E. Drew
Keyword(s):  
Main Sequence ◽  
Main Sequence Stars ◽  
Low Mass

scholarly journals The low-mass pre-main sequence population of Scorpius OB1

2018 ◽  
Vol 615 ◽  
pp. A148 ◽  
Author(s):  
Francesco Damiani
Keyword(s):  
Total Mass ◽  
Main Sequence ◽  
Near Infrared ◽  
Large Population ◽  
X Ray ◽  
Uv Excess ◽  
Low Mass ◽  
Ob Associations ◽  
The Rich ◽  
A New Technique

Context. The low-mass members of OB associations, expected to be a major component of their total population, are in most cases poorly studied because of the difficulty of selecting these faint stars in crowded sky regions. Our knowledge of many OB associations relies on only a relatively small number of massive members. Aims. We study here the Sco OB1 association, with the aim of a better characterization of its properties, such as global size and shape, member clusters and their morphology, age and formation history, and total mass. Methods. We use deep optical and near-infrared (NIR) photometry from the VPHAS+ and VVV surveys, over a wide area (2.6° × 2.6°), complemented by Spitzer infrared (IR) data, and Chandra and XMM-Newton X-ray data. A new technique is developed to find clusters of pre-main sequence M-type stars using suitable color-color diagrams, complementing existing selection techniques using narrow-band Hα photometry or NIR and ultraviolet (UV) excesses, and X-ray data. Results. We find a large population of approximately 4000 candidate low-mass Sco OB1 members whose spatial properties correlate well with those of Hα-emission, NIR-excess, UV-excess, and X-ray detected members, and unresolved X-ray emission. The low-mass population is spread among several interconnected subgroups: they coincide with the HII regions G345.45+1.50 and IC4628, and the rich clusters NGC 6231 and Trumpler 24, with an additional subcluster intermediate between these two. The total mass of Sco OB1 is estimated to be ~ 8500 M⊙. Indication of a sequence of star-formation events is found, from South (NGC 6231) to North (G345.45+1.50). We suggest that the diluted appearance of Trumpler 24 indicates that the cluster is now dissolving into the field, and that tidal stripping by NGC 6231 nearby contributes to the process.

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