TY  - JOUR
A1  - Oskinova, Lida
A1  - Sun, W.
A1  - Evans, C. J.
A1  - Henault-Brunet, V.
A1  - Chu, Y.-H.
A1  - Gallagher, J. S.
A1  - Guerrero, Martín A.
A1  - Gruendl, R. A.
A1  - Güdel, M.
A1  - Silich, S.
A1  - Chen, Y.
A1  - Naze, Y.
A1  - Hainich, Rainer
A1  - Reyes-Iturbide, J.
T1  - Discovery of x-ray emission from young suns in the small magellanic  cloud
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We report the discovery of extended X-ray emission within the young star cluster NGC 602a in the Wing of the Small Magellanic Cloud (SMC) based on observations obtained with the Chandra X-Ray Observatory. X-ray emission is detected from the cluster core area with the highest stellar density and from a dusty ridge surrounding the H II region. We use a census of massive stars in the cluster to demonstrate that a cluster wind or wind-blown bubble is unlikely to provide a significant contribution to the X-ray emission detected from the central area of the cluster. We therefore suggest that X-ray emission at the cluster core originates from an ensemble of low-and solar-mass pre-main-sequence (PMS) stars, each of which would be too weak in X-rays to be detected individually. We attribute the X-ray emission from the dusty ridge to the embedded tight cluster of the newborn stars known in this area from infrared studies. Assuming that the levels of X-ray activity in young stars in the low-metallicity environment of NGC 602a are comparable to their Galactic counterparts, then the detected spatial distribution, spectral properties, and level of X-ray emission are largely consistent with those expected from low-and solar-mass PMS stars and young stellar objects (YSOs). This is the first discovery of X-ray emission attributable to PMS stars and YSOs in the SMC, which suggests that the accretion and dynamo processes in young, low-mass objects in the SMC resemble those in the Galaxy.
KW  - Magellanic Clouds
KW  - ISM: bubbles
KW  - H II regions
KW  - stars: winds, outflows
KW  - stars: pre-main sequence
KW  - X-rays: stars
Y1  - 2013
U6  - https://doi.org/10.1088/0004-637X/765/1/73
SN  - 0004-637X
VL  - 765
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Shrader, C. R.
A1  - Hamaguchi, K.
A1  - Sturner, Steven J.
A1  - Oskinova, Lida
A1  - Almeyda, T.
A1  - Petre, R.
T1  - Hifg-energy properties of the enigmatic be STAR gamma Cassiopeiae
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present the results of a broadband X-ray study of the enigmatic Be star Gamma Cassiopeiae (herein gamma Cas) based on observations made with both the Suzaku and INTEGRAL observatories.. Cas has long been recognized as the prototypical example of a small subclass of Be stars with moderately strong X-ray emission dominated by a hot thermal component in the 0.5-12 keV energy range (L-x approximate to 10(32)-10(33) erg s(-1)). This places them at the high end of the known luminosity distribution for stellar emission, but several orders of magnitude below typical accretion-powered Be X-ray binaries. The INTEGRAL observations spanned an eight-year baseline and represent the deepest measurement to date at energies above similar to 50 keV. We find that the INTEGRAL data are consistent within statistics to a constant intensity source above 20 keV, with emission extending up to similar to 100 keV, and that searches for all of the previously reported periodicities of the system at lower energies led to null results. We further find that our combined Suzaku and INTEGRAL spectrum, which we suggest is the most accurate broadband X-ray measurement of gamma Cas to date, is fitted extremely well with a thermal plasma emission model with a single absorption component. We found no compelling need for an additional non-thermal high-energy component. We discuss these results in the context of a currently favored models for gamma Cas and its analogs.
KW  - gamma rays: stars
KW  - stars: emission-line, Be
KW  - stars: individual (gamma Cassiopeiae)
KW  - white dwarfs
KW  - X-rays: binaries
KW  - X-rays: stars
Y1  - 2015
U6  - https://doi.org/10.1088/0004-637X/799/1/84
SN  - 0004-637X
SN  - 1538-4357
VL  - 799
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -