scholarly journals Revealing the “missing” low-mass stars in the S254-S258 star forming region by deep X-ray imaging

2011 ◽  
Vol 533 ◽  
pp. A121 ◽  
Author(s):  
P. Mucciarelli ◽  
T. Preibisch ◽  
H. Zinnecker
Keyword(s):  
Low Mass Stars ◽  
X Ray ◽  
Star Forming ◽  
X Ray Imaging ◽  
Low Mass

scholarly journals X-ray Emission from Young Stars in Suburban Orion

2004 ◽  
Vol 219 ◽  
pp. 228-232
Author(s):  
K. Briggs ◽  
M. Güdel ◽  
M. Audard ◽  
K. Smith ◽  
R. Mewe ◽  
...  
Keyword(s):  
Main Sequence ◽  
Rotation Period ◽  
Magnetic Activity ◽  
Young Stars ◽  
Rossby Number ◽  
Low Mass Stars ◽  
X Ray ◽  
Star Forming ◽  
Low Mass ◽  
Pms Stars

X-ray emission from > 100 pre-main sequence (PMS) stars in the Orion star-forming complex is studied in a 20-ks observation by XMM-Newton. No relation between the ratio of X-ray and bolometric luminosities, LX/Lbol, and rotation period or Rossby number is exhibited, though the action of a solar-like dynamo is not excluded because all stars would appear to be in the “saturated regime” of such a dynamo. Low-mass stars showing a strong U — V excess have lower median X-ray luminosity, suggesting that accretion suppresses magnetic activity.

scholarly journals Rotational and Candidate-Eclipsing-Binary Light Curves for Pre-Main-Sequence Stars in the Chamaeleon I Star-Forming Cloud

2009 ◽  
Vol 26 (1) ◽  
pp. 31-36 ◽  
Author(s):  
Warrick A. Lawson ◽  
Lisa A. Crause
Keyword(s):  
Angular Momentum ◽  
Main Sequence ◽  
Near Infrared ◽  
Eclipsing Binaries ◽  
Stellar Rotation ◽  
Low Mass Stars ◽  
X Ray ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass

AbstractWe present the results of a photometric survey for variability in ten X-ray-emitting low-mass stars in the Chamaeleon region. Eight of the stars we observed are bona fide pre-main-sequence members of the ∼2 Myr-old Chamaeleon I star-forming cloud. The other two stars are young with high levels of relative X-ray emission, but with discordant proper motions they are probable non-members of the cloud. In six of the stars we monitored, periodic variations on timescales of 2.5–11.5 d were detected, that we ascribe to stellar rotation and the presence of cool starspots. Two other stars, CHXR 20 and CHXR 85, show large amplitude variations at visual and near-infrared wavelengths and are candidate eclipsing binaries. Compared to the rotational properties of low-mass stars in the ≈8 Myr-old η Chamaeleontis cluster, we find that the older η Chamaeleontis stars have several times higher surface specific angular momentum than the younger Chamaeleon I stars. The apparent increase in angular momentum between ∼2 and 8 Myr might be due to changes in stellar internal structure as the stars evolve, or evidence for a different rotational history between members of the two star-forming regions.

Tracing young SMBHs in the dusty distant universe – a Chandra view of DOGs

2020 ◽  
Vol 15 (S359) ◽  
pp. 17-21
Author(s):  
Karín Menéndez-Delmestre ◽  
Laurie Riguccini ◽  
Ezequiel Treister
Keyword(s):  
Star Formation ◽  
Main Sequence ◽  
Far Infrared ◽  
Host Galaxy ◽  
X Ray ◽  
Star Forming ◽  
Near Ir ◽  
X Ray Imaging ◽  
Combined Use ◽  
Dusty Galaxies

AbstractThe coexistence of star formation and AGN activity has geared much attention to dusty galaxies at high redshifts, in the interest of understanding the origin of the Magorrian relation observed locally, where the mass of the stellar bulk in a galaxy appears to be tied to the mass of the underlying supermassive black hole. We exploit the combined use of far-infrared (IR) Herschel data and deep Chandra ˜160 ksec depth X-ray imaging of the COSMOS field to probe for AGN signatures in a large sample of >100 Dust-Obscured Galaxies (DOGs). Only a handful (˜20%) present individual X-ray detections pointing to the presence of significant AGN activity, while X-ray stacking analysis on the X-ray undetected DOGs points to a mix between AGN activity and star formation. Together, they are typically found on the main sequence of star-forming galaxies or below it, suggesting that they are either still undergoing significant build up of the stellar bulk or have started quenching. We find only ˜30% (6) Compton-thick AGN candidates (NH > 1024 cm–2), which is the same frequency found within other soft- and hard-X-ray selected AGN populations. This suggests that the large column densities responsible for the obscuration in Compton-thick AGNs must be nuclear and have little to do with the dust obscuration of the host galaxy. We find that DOGs identified to have an AGN share similar near-IR and mid-to-far-IR colors, independently of whether they are individually detected or not in the X-ray. The main difference between the X-ray detected and the X-ray undetected populations appears to be in their redshift distributions, with the X-ray undetected ones being typically found at larger distances. This strongly underlines the critical need for multiwavelength studies in order to obtain a more complete census of the obscured AGN population out to higher redshifts. For more details, we refer the reader to Riguccini et al. (2019).

scholarly journals The effect of photoionizing feedback on the shaping of hierarchically-forming stellar clusters

2020 ◽  
Vol 499 (1) ◽  
pp. 668-680
Author(s):  
Alejandro González-Samaniego ◽  
Enrique Vazquez-Semadeni
Keyword(s):  
Star Formation ◽  
Early Stage ◽  
Stellar Clusters ◽  
Low Mass Stars ◽  
Transfer Scheme ◽  
Star Forming ◽  
Secondary Star ◽  
Low Mass ◽  
Hydrodynamical Simulations ◽  
Formation Efficiency

ABSTRACT We use two hydrodynamical simulations (with and without photoionizing feedback) of the self-consistent evolution of molecular clouds (MCs) undergoing global hierarchical collapse (GHC), to study the effect of the feedback on the structural and kinematic properties of the gas and the stellar clusters formed in the clouds. During this early stage, the evolution of the two simulations is very similar (implying that the feedback from low-mass stars does not affect the cloud-scale evolution significantly) and the star-forming region accretes faster than it can convert gas into stars, causing the instantaneous measured star formation efficiency (SFE) to remain low even in the absence of significant feedback. Afterwards, the ionizing feedback first destroys the filamentary supply to star-forming hubs and ultimately removes the gas from it, thus first reducing the star formation (SF) and finally halting it. The ionizing feedback also affects the initial kinematics and spatial distribution of the forming stars because the gas being dispersed continues to form stars, which inherit its motion. In the non-feedback simulation, the groups remain highly compact and do not mix, while in the run with feedback, the gas dispersal causes each group to expand, and the cluster expansion thus consists of the combined expansion of the groups. Most secondary star-forming sites around the main hub are also present in the non-feedback run, implying a primordial rather than triggered nature. We do find one example of a peripheral star-forming site that appears only in the feedback run, thus having a triggered origin. However, this appears to be the exception rather than the rule, although this may be an artefact of our simplified radiative transfer scheme.

scholarly journals The Circumstellar Environment of Embedded Massive Stars

2002 ◽  
Vol 12 ◽  
pp. 143-145 ◽  
Author(s):  
Lee G. Mundy ◽  
Friedrich Wyrowski ◽  
Sarah Watt
Keyword(s):  
Massive Star ◽  
Massive Stars ◽  
Low Mass Stars ◽  
Submillimeter Wavelength ◽  
Star Forming ◽  
Star Forming Regions ◽  
Low Mass ◽  
Circumstellar Environments ◽  
Near Future

Millimeter and submillimeter wavelength images of massive star-forming regions are uncovering the natal material distribution and revealing the complexities of their circumstellar environments on size scales from parsecs to 100’s of AU. Progress in these areas has been slower than for low-mass stars because massive stars are more distant, and because they are gregarious siblings with different evolutionary stages that can co-exist even within a core. Nevertheless, observational goals for the near future include the characterization of an early evolutionary sequence for massive stars, determination if the accretion process and formation sequence for massive stars is similar to that of low-mass stars, and understanding of the role of triggering events in massive star formation.

scholarly journals X-Ray Detection of Brown Dwarfs with Chandra

2003 ◽  
Vol 211 ◽  
pp. 447-450 ◽  
Author(s):  
Scott J. Wolk
Keyword(s):  
Brown Dwarfs ◽  
Stellar Clusters ◽  
Brown Dwarf ◽  
Low Mass Stars ◽  
X Ray ◽  
Low Mass ◽  
Vast Range

I review recent observations of brown dwarfs by the Chandra X-ray Observatory. These observations fall in 2 categories, young stellar clusters which contain brown dwarfs and brown dwarf candidates and directed pointings at brown dwarfs and very low mass stars. Surprisingly, there are already over 60 published detections of brown dwarfs by Chandra. A review of the X–ray characteristics shows these objects are subject to flaring and their temperatures and luminosities have a vast range which is related to age.

The X-Ray View of the Low-Mass Stars in the Solar Neighborhood

1995 ◽  
Vol 450 ◽  
pp. 392 ◽  
Author(s):  
Juergen H. M. M. Schmitt ◽  
Thomas A. Fleming ◽  
Mark S. Giampapa
Keyword(s):  
Solar Neighborhood ◽  
Low Mass Stars ◽  
X Ray ◽  
Low Mass

scholarly journals NuSTAR reveals that the heavily obscured nucleus of NGC 2785 was the contaminant of IRAS 09104+4109 in the BeppoSAX/PDS hard X-rays

2018 ◽  
Vol 619 ◽  
pp. A16
Author(s):  
C. Vignali ◽  
P. Severgnini ◽  
E. Piconcelli ◽  
G. Lanzuisi ◽  
R. Gilli ◽  
...  
Keyword(s):  
X Rays ◽  
X Ray ◽  
Star Forming ◽  
Physical Description ◽  
Enhanced Sensitivity ◽  
X Ray Imaging ◽  
First Time ◽  
In Virtue Of

Context. The search for heavily obscured active galactic nuclei has been revitalized in the last five years by NuSTAR, which has provided a good census and spectral characterization of a population of such objects, mostly at low redshift, thanks to its enhanced sensitivity above 10 keV compared to previous X-ray facilities, and its hard X-ray imaging capabilities. Aims. We aim at demonstrating how NGC 2785, a local (z = 0.009) star-forming galaxy, is responsible, in virtue of its heavily obscured active nucleus, for significant contamination in the non-imaging BeppoSAX/PDS data of the relatively nearby (≈17′) quasar IRAS 09104+4109 (z = 0.44), which was originally mis-classified as Compton thick. Methods. We analyzed ≈71 ks NuSTAR data of NGC 2785 using the MYTorus model and provided a physical description of the X-ray properties of the source for the first time. Results. We found that NGC 2785 hosts a heavily obscured (NH ≈ 3 × 1024 cm−2) nucleus. The intrinsic X-ray luminosity of the source, once corrected for the measured obscuration (L2−10keV ≈ 1042 erg s−1), is consistent within a factor of a few with predictions based on the source mid-infrared flux using widely adopted correlations from the literature. Conclusions. Based on NuSTAR data and previous indications from the Neil Gehrels Swift Observatory (BAT instrument), we confirm that NGC 2785, because of its hard X-ray emission and spectral shape, was responsible for at least one third of the 20–100 keV emission observed using the PDS instrument onboard BeppoSAX, originally completely associated with IRAS 09104+4109. Such emission led to the erroneous classification of this source as a Compton-thick quasar, while it is now recognized as Compton thin.

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