HM Cancri (also known as HM Cnc or RX J0806.3+1527) is a binary star system about 1,600 light-years (490 pc; 1.5×1016 km) away.[2] It comprises two dense white dwarfs orbiting each other once every 5.4 minutes, at an estimated distance of only 80,000 kilometres (50,000 miles) apart (about 1/5 the distance between the Earth and the Moon). The two stars orbit each other at speeds in excess of 400 kilometres per second (890,000 mph). The stars are estimated to be about half as massive as the Sun. Like typical white dwarfs, they are extremely dense, being composed of degenerate matter, and so have radii on the order of the Earth's radius. Astronomers believe that the two stars will eventually merge, based on data from many X-ray satellites, such as Chandra X-Ray Observatory, XMM-Newton and the Swift Gamma-Ray Burst Mission. These data show that the orbital period of the two stars is steadily decreasing at a rate of 1.2 milliseconds per year as they thus are getting closer by approximately 60 centimetres (2.0 ft) per day. At this rate, they can be expected to merge in approximately 340,000 years. With a revolution period of 5.4 minutes, HM Cancri is the shortest orbital period binary white dwarf system currently known.
.jpg) An artist's depiction of J0806. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cancer |
| Right ascension | 08h 06m 22.95196s[1] |
| Declination | +15° 27′ 31.0073″[1] |
| Distance | 1,600 Light-years |
| Binary orbit | |
| Period (P) | 321.5 seconds |
| dP/dt (Pdot) | 1.1 milliseconds per year |
| Separation: | 0.0005 AU |
| Details | |
| Mass | 0.5 (primary) / 0.5 (b) M☉ |
| Other designations | |
RX J0806.3+1527, RX J0806, J0806, HM Cancri, HM Cnc | |
| Database references | |
| SIMBAD | data |
Observations
edit
As HM Cancri is a pair of white dwarfs, it has a relatively low optical luminosity. The 321.5 s modulation of HM Cancri was discovered serendipitously in 1999 thanks to the ROSAT mission working in the X-ray band. Optical follow-up observations with the ESO Very Large Telescope (VLT), Telescopio Nazionale Galileo (TNG) and Nordic Optical Telescope (NOT) allowed the counterpart to be identified, a relatively dim (20.7 magnitude in the B filter) object which shows an optical modulation at the same period detected in the X-ray band. The optical monitoring of the counterpart of HM Cancri during 2001-2004 clearly shows that the period is decreasing at a rate of about 1/1000 s each year. This result was confirmed by monitoring the source in the X-rays for several years.
Relation to general relativity
editThe decreasing separation of the components of the system mean that the system is losing orbital energy. Albert Einstein's theory of General Relativity predicts such a system will lose orbital energy through the generation of gravitational waves. Scientists believe that HM Cancri may be one of the strongest sources of gravitational waves in the Milky Way galaxy.[4][5]
Sources
edit- ^ a b Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- ^ "RX J0806.3+1527: Orbiting Stars Flooding Space with Gravitational Waves". CHANDRA X-RAY OBSERVATORY, Harvard. 2005-05-30. Archived from the original on 2011-02-25. Retrieved 2013-05-31.
{{cite web}}: CS1 maint: bot: original URL status unknown (link) - ^ Barros, S. C. C.; Marsh, T. R.; Dhillon, V. S.; Groot, P. J.; Littlefair, S.; Nelemans, G.; Roelofs, G.; Steeghs, D.; Wheatley, P. J. (1 February 2007). "ULTRACAM photometry of the ultracompact binaries V407 Vul and HM Cnc". Monthly Notices of the Royal Astronomical Society. 374 (4): 1334–1346. arXiv:astro-ph/0611117. Bibcode:2007MNRAS.374.1334B. doi:10.1111/j.1365-2966.2006.11244.x. S2CID 15741292.
- ^ "NASA Sees Orbiting Stars Flooding Space with Gravitational Waves". CHANDRA X-RAY OBSERVATORY, Harvard. 2005-05-30. Retrieved 2024-11-07.
- ^ "SPECTROSCOPIC EVIDENCE FOR A 5.4-MINUTE ORBITAL PERIOD IN HM CANCRI". arXiv. 2021-11-02. Retrieved 2024-11-07.
- NASA Astronomy Picture of the Day: White Dwarf Star Spiral (1 June 2005)
- "Orbiting Stars Flooding Space with Gravitational Waves". Chandra X-Ray Observatory. May 30, 2005. Retrieved 2024-09-07.
- RX J0806.3+1527: Orbiting Stars Flooding Space with Gravitational Waves
Further reading
edit- Irion, Robert (2002-03-15). "Stellar Pair Whirls in a 5-Minute Dash". Science. 295 (5562): 1997. doi:10.1126/science.295.5562.1997. ISSN 0036-8075. PMID 11896250.
- European southern Observatory Press Release
- Ramsay, G.; Hakala, P.; Cropper, M. (2002-05-01). "RX J0806+15: the shortest period binary?". Monthly Notices of the Royal Astronomical Society. 332 (1): L7–L10. arXiv:astro-ph/0203053. Bibcode:2002MNRAS.332L...7R. doi:10.1046/j.1365-8711.2002.05471.x. ISSN 0035-8711.
- Esposito, Paolo; Israel, Gian Luca; Dall'Osso, Simone; Covino, Stefano (January 2014). "Swift X-ray and ultraviolet observations of the shortest orbital period double-degenerate system RX J0806.3+1527 (HM Cnc)". Astronomy & Astrophysics. 561: A117. arXiv:1311.6973. Bibcode:2014A&A...561A.117E. doi:10.1051/0004-6361/201322719. ISSN 0004-6361.
- Roelofs, Gijs H. A.; Rau, Arne; Marsh, Tom R.; Steeghs, Danny; Groot, Paul J.; Nelemans, Gijs (2010-03-10). "Spectroscopic Evidence for a 5.4 Minute Orbital Period in Hm Cancri". The Astrophysical Journal. 711 (2): L138–L142. arXiv:1003.0658. Bibcode:2010ApJ...711L.138R. doi:10.1088/2041-8205/711/2/L138. ISSN 2041-8205.
- Mason, Elena; Israel, G. L.; Dall'Osso, S.; Stella, L.; Munari, U.; Marconi, G.; O'Brian, K.; Covino, S.; Fugazza, D. (2010). "VLT Phase Resolved Optical Spectroscopy of the Ultra-Compact Binary HM Cnc". Astronomy & Astrophysics. arXiv:1003.1986.
- Dall'Osso, S.; Israel, G. L.; Stella, L. (March 2007). "Unipolar inductor model coupled to GW emission: energy budget and model application to RX J0806+15 and RX J1914+24". Astronomy & Astrophysics. 464 (2): 417–427. arXiv:astro-ph/0603795. Bibcode:2007A&A...464..417D. doi:10.1051/0004-6361:20064862. ISSN 0004-6361.
- Coherent timing solution for RXJ0806
- Israel, Gian Luca; et al. (September 1999). "The discovery of 321 S pulsations in the ROSAT HRI light curves of 1BMW J080622.8+152732 = RX J0806.3+1527". Astronomy and Astrophysics. 349: L1–L4. Bibcode:1999A&A...349L...1I.
- Spectroscopic optical study of RXJ0806
- Monitoring the spin up in RX J0806+15
- Strohmayer, Tod E. (2003-08-10). "Phase Coherent Timing of RX J0806.3+1527 with ROSAT and Chandra". The Astrophysical Journal. 593 (1): L39–L42. arXiv:astro-ph/0306593. Bibcode:2003ApJ...593L..39S. doi:10.1086/378061. ISSN 0004-637X.
- RX J0806
- RX J0806.3+1527 Gravitational Wave Merger
- Roelofs, Gijs H. A.; Rau, Arne; Marsh, Tom R.; Steeghs, Danny; Groot, Paul J.; Nelemans, Gijs (2010-03-10). "Spectroscopic Evidence for a 5.4-Minute Orbital Period in HM Cancri". The Astrophysical Journal. 711 (2): L138–L142. arXiv:1003.0658. Bibcode:2010ApJ...711L.138R. doi:10.1088/2041-8205/711/2/L138. ISSN 2041-8205.