Related papers: Ultracompact X-Ray Binaries with Neon-Rich Degener…

We present high-resolution spectroscopy of the neutron star/low-mass X-ray binaries (LMXBs) 4U 1850-087 and 4U 0513-40 as part of our continuing study of known and candidate ultracompact binaries. The LMXB 4U 1850-087 is one of four systems…

Ultra-compact X-ray binaries consist of a neutron star or black hole that accretes material from a white dwarf-donor star. The ultra-compact nature is expressed in very short orbital periods of less than 1 hour. In the case of 4U 0614+091…

We report the discovery of a broad emission feature at ~0.7 keV in the spectra of the ultra-compact X-ray binary 4U 1543-624, obtained with the high-resolution spectrographs of the XMM-Newton and Chandra satellites. We confirm the presence…

We report the results of two XMM-Newton observations of the ultra-compact low-mass X-ray binary 4U1850-087 located in the galactic globular cluster NGC6712. A broad emission feature at 0.7keV was detected in an earlier ASCA observation and…

We present new medium-resolution high-S/N optical spectra of the ultracompact low-mass X-ray binaries 4U0614+091 and 4U1626-67, taken with the ESO Very Large Telescope. They are pure emission line spectra and the lines are identified as due…

We report on a 39 ks observation of the 7.7-s low-mass X-ray binary pulsar 4U1626-67 with the High Energy Transmission Grating Spectrometer (HETGS) on the Chandra X-Ray Observatory. This ultracompact system consists of a disk-accreting…

We observed the ultra-compact binary candidate 4U 0614+091 for a total of 200 ksec with the high-energy transmission gratings onboard the \chandra X-ray Observatory. The source is found at various intensity levels with spectral variations…

4U 0614+09 is a low-mass X-ray binary with a weakly magnetized neutron star primary. It shows variability on time scales that range from years down to ~0.8 milliseconds. Before the Chandra and XMM-Newton era, emission features around 0.7…

We present optical spectroscopy of several (candidate) ultra-compact X-ray binaries (UCXBs) obtained with the ESO VLT and Gemini-North telescopes. In only one of five observed UCXB candidates did we find evidence for H in its spectrum (4U…

The persistent, low-luminosity neutron star X-ray binary 4U 1812-12 is a potential member of the scarce family of ultra-compact systems. We performed deep photometric and spectroscopic optical observations with the 10.4 m Gran Telescopio…

We present high-resolution spectroscopy of the neutron-star/low-mass X-ray binaries 2S 0918-549 and 4U 1543-624 with the High Energy Transmission Grating Spectrometer onboard the Chandra X-ray Observatory and the Reflection Grating…

We have obtained Hubble Space Telescope/STIS low-resolution ultraviolet spectra of the X-ray pulsar 4U 1626-67 (=KZ TrA); 4U 1626-67 is unusual even among X-ray pulsars due to its ultra-short binary period (P=41.4 min) and remarkably low…

We present optical spectra in the range 4600 -- 8600 A for three low-mass X-ray binaries which have been suggested to belong to the class of ultra-compact X-ray binaries based on their X-ray spectra. Our spectra show no evidence for…

We study the formation of neon-enriched donor stars in ultracompact X-ray binaries (orbital periods P<80 min) and show that their progenitors have to be low-mass (0.3 - 0.4 solar mass) ``hybrid'' white dwarfs (with CO cores and thick helium…

Spitzer observations of the neutron star (ultra-compact) X-ray binary (XRB) 4U 0614+091 with the Infrared Array Camera reveal emission of non-thermal origin in the range 3.5-8 um. The mid-infrared spectrum is well fit by a power law with…

We present spectroscopic X-ray data of two candidate ultra-compact X-ray binaries: 4U~0614+091 and 4U~1543$-$624. We confirm the presence of a broad O VIII Ly$\alpha$ reflection line (at $\approx18\ \AA$) using {\it XMM-Newton} and {\it…

We report on X-ray and radio observations of the ultra-compact X-ray binary 4U 1543-624 taken in August 2017 during an enhanced accretion episode. We obtained NICER monitoring of the source over a $\sim10$ day period during which…

Symbiotic X-ray binaries form a subclass of low-mass X-ray binary systems consisting of a neutron star accreting material from a red giant donor star via stellar wind or Roche lobe overflow. Only a few confirmed members are currently known;…

We search for the Fe K${\alpha}$ line in spectra of Ultra Compact X-ray Binaries (UCXBs). For this purpose we have analyzed XMM-Newton observations of five confirmed UCXBs. We find that the object 2S 0918-549 - whose optical spectrum bears…

We present the first joint NuSTAR and NICER observations of the ultra-compact X-ray binary (UCXB) 4U 1543$-$624 obtained in 2020 April. The source was at a luminosity of $L_{0.5-50\ \mathrm{keV}} = 4.9 (D/7\ \mathrm{kpc})^{2}\times10^{36}$…