Browsing by Author "Heinke, C. O."

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An arcsecond view at 1-2 GHz into the Galactic Bulge
(2024) Pattie, E. C. (TTU); Maccarone, T. J. (TTU); Britt, C. T.; Heinke, C. O.; Jonker, P. G.; Lorimer, D. R.; Sivakoff, G. R.; Steeghs, D.; Strader, J.; Torres, M. A.P.; Wijnands, R.
We present the results of a high angular resolution (1.1 arcsec) and sensitivity (maximum of ∼0.1 mJy) radio survey at 1-2 GHz in the Galactic Bulge. This complements the X-ray Chandra Galactic Bulge Survey, and investigates the full radio source population in this dense Galactic region. Radio counterparts to sources at other wavelengths can aid in classification, as there are relatively few types of objects that are reasonably detectable in radio at kiloparsec distances, and even fewer that are detected in both X-rays and radio. This survey covers about 3 sq deg of the Galactic Bulge Survey area (spanning the Galactic coordinate range of -3° < l < +3° and +1.6° < b < +2.1°) as a first look into this region of the Galaxy with this combination of frequency, resolution, and sensitivity. Spectral indices within the observed band of 1-2 GHz were calculated for each source to assist in determining its emission mechanism. We find 1617 unique sources in the survey, 25 of which are radio counterparts to X-ray sources, and about 100 of which are steep-spectrum (α ≲ -1.4) point sources that are viable pulsar candidates. Four radio sources are of particular interest: a compact binary; an infrared transient with an inverted radio spectrum; a potential transitional millisecond pulsar candidate; and a very steep spectrum radio source with an X-ray and bright infrared counterpart. We discuss other notable sources, including possible radio transients, potential new planetary nebulae, and active galactic nuclei.
Chandra reveals a possible ultrafast outflow in the super-Eddington Be/X-ray binary Swift J0243.6+6124
(2019) Van Den Eijnden, J.; Degenaar, N.; Schulz, N. S.; Nowak, M. A.; Wijnands, R.; Russell, T. D.; Herńandez Santisteban, J. V.; Bahramian, A.; Maccarone, T. J. (TTU); Kennea, J. A.; Heinke, C. O.
Accretion at super-Eddington rates is expected to be accompanied by strong outflows. Such outflows are observed inGalactic X-ray binaries and extragalactic ultraluminous X-ray sources (ULXs). However, due to their large source distances, ULX outflows are challenging to detect and study in detail. Galactic neutron stars accreting from a Be-star companion at super- Eddington rates show many similarities to ULX pulsars, and therefore offer an alternative approach to study outflows in this accretion regime. Here, we present Chandra high-resolution spectroscopy of such a super-Eddington accreting neutron star, Swift J0243.6+6124, to search for wind outflow signatures during the peak of its 2017/2018 giant outburst.We detect narrow emission features at rest from Ne, Mg, S, Si, and Fe. In addition, we detect a collection of absorption features which can be identified in two ways: Either as all Fe transitions at rest (with a possible contribution from Mg), or a combination of three blue-shifted Ne and Mg lines at ∼0.22c, while the remaining lines are at rest. The second scenario would imply an outflow with a velocity similar to those seen in ULXs, including the ULX pulsar NGC 300 ULX-1. This result would also imply that Swift J0243.6+6124 launches both a jet, detected in radio and reported previously, and an ultrafast wind outflow simultaneously at super-Eddington accretion rates.