RR Telescopii

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Double star
RR Telescopii
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation telescope
Right ascension 20 h 04 m 18.54 s
declination -55 ° 43 ′ 33.2 ″
Apparent brightness (10.8) mag
Typing
rel. Brightness
(G-band) 		(11.43 ± 0.02) mag
rel. Brightness
(J-band) 		(7.30 ± 0.04) mag
Variable star type NC 
Astrometry
Radial velocity (-61.8) km / s
Proper movement 
Rec. Share: (3.34 ± 0.31)  mas / a
Dec. portion: (-3.23 ± 0.28)  mas / a
Physical Properties
Other names
and catalog entries
2MASS catalog 2MASS J20041854-5543331 [1]
Other names RR Telescopii, Nova Telescopii 1948

Template: Infobox Star / Maintenance / MagGTemplate: Infobox Star / Maintenance / MagJ

RR Telescopii was a symbiotic nova in the southern constellation Telescope . It was recorded on photo plates as a faint variable star with a visual magnitude of 9 to 16.6 mag in the period from 1889 to 1944. At the end of 1944 the star's brightness began to increase by about 7 orders of magnitude from about 14 mag to over 8 mag. This increase in luminosity continued in early 1945 with a reduced rate of increase. The overall burst, however, was not noticed until the star was visible to the naked eye in July 1948 at around 6.0 mag. From then on, it was known as Nova Telescopii in 1948. Since mid-1949 the brightness slowly decreased again with some notable changes in the spectrum, and from August 2013 it faded to 12 mag in the visual realm.

Pre and main eruption

RR Telescopii has been repeatedly observed in surveys of the southern branch of the Harvard College Observatory since 1889 and at later times also from other southern observatories. Williamina Fleming reported differences in brightness between about 9 and 11.5 mag in 1908 and suggested that it could be the same type of star as SS Cygni . Later images showed a slight irregular scattering between 12.5 and 14 mag up to around 1930. From this time on, the periodic fluctuations in brightness between 12 and 16 mag began. The period of these fluctuations was 387 days and the star could be characterized as a giant or supergiant with medium or late spectral class . No spectra of the star were recorded prior to the outbreak as it was too faint to be included in the Henry Draper catalog and remained undetected until the outbreak.

In 1944 the periodic fluctuations stopped and RR Telescopii brightened by more than 7 orders of magnitude over the course of about four years. Starting at a brightness of 14 mag. At the end of 1944, the photographic plates showed a power of 8 mag as early as 1945, and the star was 7.4 mag in September to October 1946, 7.0 mag in March 1948 and 6.0 mag in July 1948 observed.

It was discovered in 1948 and was given the name Nova Telescopii 1948. In July 1949 the brightness slowly began to decrease. The information on the eruption behavior of RR Telescopii, as seen on Harvard photographic plates, was published in February 1949, and the already long duration of the eruption over years made it clear that RR Telescopii was very different from the novae observed previously difference. It was then referred to as a slow nova because this behavior could not be fully explained.

The first spectroscopic observations were made in June 1949 when the spectrum showed a pure absorption spectrum that resembled that of an F-type supergiant before it began to fade. Further spectra were recorded in September / October of the same year. At this point in time the character of the spectrum had changed to a continuum with many emission lines, but no recognizable absorption lines.

Decrease in brightness

In visible light, RR Telescopii has steadily faded (though not at a constant rate) since 1949. In 1977 it had a visual magnitude of around 10.0 and was around 11.8 in mid-2013. Despite this development, the visible spectrum had retained the same general character, although it increasingly included emission lines of higher excitation and showed permitted and forbidden spectral lines of many elements. Absorption features of titanium (II) oxide (the hallmark of M stars ) were observed in the RR Telescopii spectrum from the 1960s.

As technology advanced, the observation of RR Telescopii at wider wavelengths became possible. Infrared photometry showed a radiation deflection in the range from 1 to 20 µm, which indicated the presence of circumstellar dust with a temperature of a few hundred Kelvin . The observations at shorter wavelengths were also very successful. In the ultraviolet range, observations were made with the International Ultraviolet Explorer , the UV spectrometer on board Voyager 1 and the Hubble space telescope . In the X-ray spectrum, observations were made with the High Energy Astronomy Observatory 2 , EXOSAT and ROSAT . In particular, the observations in the UV range enabled a direct determination of the white dwarf in this system, which was not possible before the advent of space telescopes.

Physical model

As a symbiotic star , RR Telescopii consists of a red giant star with a late spectral class that is in orbit with a white dwarf . Both stars are surrounded by hot gas and warm dust. The red giant is often referred to as the Mira star , although the only real attempt to characterize the system before the eruption resulted in a different type of pulsating giant star. The observed visible and infrared features of the spectra suggest a star of the spectral type M5 III. Such cool, pulsating stars are known to generate circumstellar dust that flows away with the changing stellar winds. No shifts in the orbital velocities were found, so the distance between the two objects is on the order of several astronomical units and the orbital period can be assumed to be years or decades.

If the accretion rate is in the spectroscopic "low state" before an outbreak, the M-giant pulsates and loses mass. This pulsation could be seen in the visible light curve from 1930 to 1944 . Some of the matter that the M giant loses in the process arrives at the white dwarf via wind accretion . This accumulated matter is rich in hydrogen - that is, its composition corresponds to normal stellar matter. When this hydrogen-enriched accretion disk is thick enough and hot enough, the fusion reactions begin at the densest and hottest point of the disk, near the surface of the white dwarf.

Individual evidence

  1. ↑ a b c d e f RR Tel. In: SIMBAD . Center de Données astronomiques de Strasbourg , accessed on March 27, 2019 .
  2. ↑ RR Tel. In: VSX. AAVSO , accessed March 27, 2019 .
  3. ^ A b c d Margaret W. Mayall: Recent Variations of RR Telescopii . In: Harvard Observatory Bulletin . February 1949, pp. 15-17. bibcode : 1949BHarO.919 ... 15M .
  4. ↑ a b c R. P. de Kock: RR Tel. (195656) . In: Monthly Notes of the Astronomical Society of South Africa . September 7, pp. 74-75. bibcode : 1948MNSSA ... 7 ... 74D .
  5. ↑ Sergei Gaposchkin: Variable Stars in Milton Field 53 . In: Harvard Annals . 115, 1952, pp. 11-23. bibcode : 1952AnHar.115 ... 11G .
  6. ^ A b E. L. Robinson: Preeruption light curves of novae . In: Astronomical Journal . 80, September, p. 515. bibcode : 1975AJ ..... 80..515R . doi : 10.1086 / 111774 .
  7. ^ AD Thackeray: Five southern stars with emission-line spectra . In: Monthly Notices of the Royal Astronomical Society . 110, 1950, p. 45. bibcode : 1950MNRAS.110 ... 45T . doi : 10.1093 / mnras / 110.1.45 .
  8. ↑ a b A.D. Thackeray: The evolution of the nebular spectrum of the slow nova RR Telescopii . In: Memoirs of the Royal Astronomical Society . 83, 1977, pp. 1-68. bibcode : 1977MmRAS..83 .... 1T .
  9. ↑ AAVSO: AAVSO Light Curve Generator . Retrieved March 27, 2019.
  10. ^ S. Jordan, U. Mürset, K. Werner: A model for the X-ray spectrum of the symbiotic nova RR Telescopii . In: Astronomy and Astrophysics . 283, 1994, pp. 475-482. bibcode : 1994A & A ... 283..475J .
  11. ^ Hans Krimm: Accretion disks . NASA . November 6, 2000. Retrieved March 27, 2019.