Related papers: Spin up in RX J0806+15 - the shortest period binar…

The X-ray source RX J0806+15 was discovered using ROSAT, and shows an X-ray light curve with a prominent modulation on a period of 321.5 sec. We present optical observations in which we report the detection of its optical counterpart. We…

RX J0806.3+1527 is thought to be a 321s orbital period (the shortest known) double white dwarf binary system. According to the double degenerate binary (DDB) scenario this source is expected to be one of the strongest gravitational wave…

RX J0806+15 shows a prominent intensity variation on a period of 321.5 sec. This has widely been interpreted as the binary orbital period, although this remains controversial. We have been monitoring the precise period of RX J0806+15 for a…

We carried out optical observations of the field of the X-ray pulsator RXJ0806.3+1527. A blue V=21.1 star was found to be the only object consistent with the X-ray position. VLT FORS spectra revealed a blue continuum with no intrinsic…

RX J0806.3+1527 is a candidate double degenerate binary with possibly the shortest known orbital period. The source shows an 100% X-ray intensity modulation at the putative orbital frequency of 3.11 mHz (321.5 s). If the system is a…

Following the suggestion of Schwope et al that the magnetic cataclysmic variable RX J2115-5840 maybe a near-synchronous polar, we obtained optical polarimetry of this system over a 2 week period. From a power spectrum of the circular…

RX J1914.4+2456 is a candidate double-degenerate binary (AM CVn) with a putative 569 s orbital period. If this identification is correct, then it has one of the shortest binary orbital periods known, and gravitational radiation should drive…

We report the discovery of a rare close binary system, SMSS J160639.78-100010.7, comprised of a magnetic white dwarf with a field of about 30 MG and a brown dwarf. We measured an orbital period of 92 min which is consistent with the…

We present the discovery of the orbital period of Swift J1626.6-5156. Since its discovery in 2005, the source has been monitored with Rossi X-ray Timing Explorer, especially during the early stage of the outburst and into the X-ray…

We report the detection of orbital decay in the 12.75-min, detached binary white dwarf (WD) SDSS J065133.338+284423.37 (hereafter J0651). Our photometric observations over a 13-month baseline constrain the orbital period to 765.206543(55) s…

Following the detection of a bright new X-ray source, MAXI J1659-152, a series of observations was triggered with almost all currently flying high-energy missions. We report here on XMM-Newton, INTEGRAL and RXTE observations during the…

We report XTE and SAX observations of the X-ray pulsar RX J0146.9+612, the neutron star/Be binary system with the longest known spin period. Data obtained one month after the most recent outburst (July 1997), show that the source has…

RX J0806.3+1527 is an ultra-compact, double degenerate binary with the shortest known orbital period (321.5 s). Hakala et al. (2003) have recently reported new optical measurements of the orbital frequency of the source which indicate that…

A new cataclysmic variable is identified as the optical counterpart of the faint and hard X-ray source RX J0757.0+6306 discovered during the ROSAT all-sky survey. Strong double-peaked emission lines bear evidence of an accretion disc via an…

ZTF J213056.71+442046.5 is the prototype of a small class of recently discovered compact binaries composed of a white dwarf and a hot subdwarf that fills its Roche-lobe. Its orbital period of only 39 min is the shortest known for the…

We review the current observational status of the ROSAT sources RX J1914.4+2456 and RX J0806.3+1527, and the evidence that these are ultra-short period (<10min) binary systems. We argue that an Intermediate Polar interpretation can be ruled…

We present new photometric and spectroscopic observations of the transient supersoft X-ray source RX J0537.7-7034 and find a periodicity of approximately 3.5 hrs. This establishes RX J0537.7-7034 as the supersoft X-ray source with the…

We report the results of long-term time series photometry on RX J2133.7+5107 (also known as 1RXS J213344.1+510725) obtained at several observatories. Using data taken during 17 years, we determined the current value of the spin period of…

In recent years there has been much interest in the nature of two stars, V407 Vul and RXJ0806+1527, which are widely thought to be binary white dwarfs of very short orbital period, 570 and 321 seconds respectively. As such they should be…

We identify SDSS J010657.39-100003.3 (hereafter J0106-1000) as the shortest period detached binary white dwarf (WD) system currently known. We targeted J0106-1000 as part of our radial velocity program to search for companions around known…