ZTF Discovers a New Mass-Transferring Brown Dwarf Binary System
by Tomasz Nowakowski, Phys.org
Astronomers from the California Institute of Technology (Caltech) and elsewhere have reported the discovery of a binary system consisting of two brown dwarfs undergoing stable mass transfer. The detection of the system, designated ZTF J1239+8347, was made with the Zwicky Transient Facility (ZTF) and is detailed in a paper published March 18 in The Astrophysical Journal Letters.
Key Characteristics of Brown Dwarfs
Brown dwarfs (BDs) are intermediate objects between planets and stars, occupying a mass range of approximately 13 to 80 Jupiter masses (0.012 to 0.076 solar masses). While many BDs have been detected to date, those orbiting other stars or each other in binary systems are relatively rare discoveries. The following table summarizes some important characteristics of brown dwarfs:
| Characteristic | Description |
|---|---|
| Mass Range | 13 to 80 Jupiter masses |
| Temperature | Typically range from 1,200 K to 2,500 K |
| Formation | Formed through the same processes as stars but do not fuse hydrogen in their cores |
| Lifespan | Can last for billions of years but cool and fade over time |
New Rare Double Brown Dwarf
Recent observations with ZTF, conducted by a team of astronomers led by Caltech's Samuel Whitebook, have revealed the presence of a new system of this rare type. The newly discovered BD binary was found at a distance of some 1,100 light years and has been designated ZTF J1239+8347.
"ZTF has undertaken a comprehensive search for periodic variable stars in the ZTF Variability survey (ZVAR). Within the ZVAR survey, we undertook a targeted search for accreting brown dwarf binaries. In this search, we identified ZTF J1239+8347," explained the researchers.
Accretor and Donor on a Stable Mass Transfer
The newfound binary consists of two BDs with estimated masses between 60 and 80 Jupiter masses. The system has an orbital period of approximately 57.41 minutes and is currently undergoing a stable mass transfer.
According to the paper, the accretor in ZTF J1239+8347 has a radius of 1.2 Jupiter radii and an atmospheric temperature of about 1,500 K. The donor's radius is estimated to be within the range of 0.9–1.4 Jupiter radii, while its atmospheric temperature is likely lower than 1,200 K.
Variable and Worth Further Monitoring
Further optical observations of ZTF J1239+8347 reveal that it showcases an extremely high amplitude variability at short wavelengths. This finding suggests an orbiting hotspot that is slightly buried inside the atmosphere of the accretor BD.
However, although ZTF J1239+8347 is highly variable in the optical band, it turns out that in near and mid-infrared, the accretion luminosity of the system is dim enough that the thermal emission from the BD atmospheres contributes significantly to the spectrum.
The study authors propose further monitoring of ZTF J1239+8347 to better constrain its properties. "Future observations of the system with the James Webb Space Telescope (JWST) could better constrain the temperature of the accretor atmosphere and could detect the atmosphere of the donor system. Such observations will be necessary to directly measure the mass ratio of the system, as it is not feasible for ground-based near-infrared spectra to be phase resolved for systems at this brightness," the scientists state.
For More Information
Continue exploring these related topics and articles that provide detailed insights into our universe:
- Understanding Brown Dwarfs
- The Impact of Binary Stars
- Exploring Extrinsic Variable Stars
- Brown Dwarfs: New Insights and Discoveries
- Research in The Astrophysical Journal
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