Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userA detached double degenerate with a 1.4 hr orbital period
106
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We have discovered that the detached double degenerate binary WD 0957-666 has an orbital period of 1.46 hours, rather than the 1.15 day orbital period reported earlier. This is the shortest period example of such a system yet discovered. We obtain a unique period, which fits both our and earlier data. At this period the emission of gravitational radiation will cause the binary to merge within approximately 2.0 x 10*8 years. This system represents a population of short orbital period binaries which will merge within a Hubble time, and so could account for type Ia supernovae, although due to the low mass of both stars (0.3 to 0.4 solar masses), it is unlikely to become a supernova itself. We have detected the companion star and have measured a mass ratio of q = 1.15. This is the third double degenerate for which q has been measured and all three have q close to 1, which is in conflict with the predicted mass ratio distribution which peaks at 0.7. This system is viewed close to edge on, and we estimate that the probability of this system undergoing eclipses is 15 %.
rate research
Read More
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 absorption lines. Broad (v~1500 km/s), low equivalent width (about -1/-6A) emission lines from the HeII Pickering series were clearly detected. B, V and R time-resolved photometry revealed the presence of about 15% pulsations at the 321s X-ray period, confirming the identification. These findings, together with the period stability and absence of any additional modulation in the 1min-5hr period range, argue in favour of the orbital interpretation of the 321s pulsations. The most likely scenario is thus that RXJ0806.3+1527 is a double degenerate system of the AM CVn class. This would make RXJ0806.3+1527 the shortest orbital period binary currently known and one of the best candidates for gravitational wave detection.
We report the discovery of ZTF J2243+5242, an eclipsing double white dwarf binary with an orbital period of just $8.8$ minutes, the second known eclipsing binary with an orbital period less than ten minutes. The system likely consists of two low-mass white dwarfs, and will merge in approximately 400,000 years to form either an isolated hot subdwarf or an R Coronae Borealis star. Like its $6.91, rm min$ counterpart, ZTF J1539+5027, ZTF J2243+5242 will be among the strongest gravitational wave sources detectable by the space-based gravitational-wave detector The Laser Space Interferometer Antenna (LISA) because its gravitational-wave frequency falls near the peak of LISAs sensitivity. Based on its estimated distance of $d=2120^{+131}_{-115},rm pc$, LISA should detect the source within its first few months of operation, and should achieve a signal-to-noise ratio of $87pm5$ after four years. We find component masses of $M_A= 0.349^{+0.093}_{-0.074},M_odot$ and $M_B=0.384^{+0.114}_{-0.074},M_odot$, radii of $R_A=0.0308^{+0.0026}_{-0.0025},R_odot$ and $R_B = 0.0291^{+0.0032}_{-0.0024},R_odot$, and effective temperatures of $T_A=22200^{+1800}_{-1600},rm K$ and $T_B=16200^{+1200}_{-1000},rm K$. We determined all of these properties, and the distance to this system, using only photometric measurements, demonstrating a feasible way to estimate parameters for the large population of optically faint ($r>21 , m_{rm AB}$) gravitational-wave sources which the Vera Rubin Observatory (VRO) and LISA should identify.
We report the discovery of a 1201 s orbital period binary, the third shortest-period detached binary known. SDSS J232230.20+050942.06 contains two He-core white dwarfs orbiting with a 27 deg inclination. Located 0.76 kpc from the Sun, the binary has an estimated LISA 4-yr signal-to-noise ratio of 40. J2322+0509 is the first He+He white dwarf LISA verification binary, a source class that is predicted to account for one-third of resolved LISA ultra-compact binary detections.
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 out, that they are indeed compact binaries with a degenerate secondary, and that the period seen in the X-ray and optical is the orbital period. A white dwarf primary is preferred, but a neutron star cannot be excluded. We examine the capability of the three current double-degenerate models (Polar, Direct Accretor and Electric Star) to account for the observational characteristics of these systems. All models have difficulties with some aspects of the observations, but none can be excluded with confidence at present. The Electric Star model provides the best description, but the lifetime of this phase requires further investigation. These ultra-short period binaries will be strong gravitational wave emitters in the LISA bandpass, and because of their known source properties will be important early targets for gravitational wave studies.
We use ASAS V-band and ASAS-SN g-band observations to model the long-period detached eclipsing binary ASASSN-21co. ASAS observations show an eclipse of depth V ~ 0.6 mag in April of 2009. ASAS-SN g-band observations from March of 2021 show an eclipse of similar duration and depth, suggesting an orbital period of 11.9 years. We combine the g-band observations with additional BVRI photometry taken during the eclipse to model the eclipse using PHOEBE. We find that the system is best described by two M giants with a ratio of secondary radius to primary radius of ~0.61. Optical spectra taken during the eclipse are consistent with at least one component of the binary being an M giant, and we find no temporal changes in the spectral features. The eclipse itself is asymmetric, showing an increase in brightness near mid-eclipse, likely due to rotational variability that is too low amplitude to be observed out-of-eclipse.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
