R Crateris

R Crateris

A visual band light curve for R Crateris, plotted from ASAS data.[1]
Observation data
Epoch J2000      Equinox J2000
Constellation Crater
Right ascension 11h 00m 33.85257s[2]
Declination −18° 19′ 29.5827″[2]
Apparent magnitude (V) 8.1 - 9.5[3]
Characteristics
Evolutionary stage AGB[4]
Spectral type M7/8III[5]
Variable type SRb[6]
Astrometry
Radial velocity (Rv)20.94±1.50[2] km/s
Proper motion (μ) RA: −29.373±0.180[2] mas/yr
Dec.: −2.499±0.172[2] mas/yr
Parallax (π)4.7027 ± 0.1528 mas[2]
Distance690 ± 20 ly
(213 ± 7 pc)
Details
Mass1.91[7] M☉
Radius633[8] R☉
Luminosity8,151[8] L☉
Surface gravity (log g)−0.86[8] cgs
Temperature3,295[9] K
Other designations
HD 95384, HIP 53809, SAO 156389, IRC −20222, RAFGL 1450[10]
Database references
SIMBADdata

R Crateris is a star about 700 light years from the Earth in the constellation Crater. It is a semiregular variable star, ranging in brightness from magnitude 8.1 to 9.5 over a period of about 160 days.[3] It is not visible to the naked-eye, but can be seen with a small telescope, or binoculars.[11] R Crateris is a double star; the variable star and its magnitude 9.9 F8V companion are separated by 65.4 arcseconds.[12]

Although the period for large brightness changes in R Crateris is listed as ~160 days, in 1982 Silvia Livi and Thaisa Bergmann reported small (~0.1 magnitude) variations on timescales of less than one hour. The rapid variations seem to be more regular when the star is near maximum brightness.[13]

R Crateris is an oxygen-rich asymptotic giant branch star, losing mass at a rate of 8×10−7 solar masses per year via a stellar wind.[4] At large distances from the star, the wind is expanding into space at 11.7±0.3 km/sec.[14]

Near-infrared radiation from R Crateris was detected in the first Two-Micron Sky Survey, published in 1969.[15] It was detected in the far-infrared by the IRAS satellite, and that emission was resolved by IRAS, showing that the star is surrounded by a large circumstellar shell containing dust.[16] High resolution far-infrared images of R Crateris taken by the Herschel Space Observatory show that the emitting region of the shell, roughly 280 arcseconds (0.94 light year) across, consists primarily of two non-concentric arcs well separated from the star itself. The arcs are probably bowshocks formed as the dusty stellar wind collides with the interstellar medium.[17] The total mass of the shell, including both dust and gas, is estimated to be about (6.4±2)×10−2 solar masses.[18] Infrared imaging of the innermost (sub-arcsecond) portion of the dust shell shows a bipolar structure.[4][19]

In the early 1970s, maser emission from OH and H2O was detected in R Cratoris' circumstellar shell.[20] SiO maser emission was detected in 1985.[21] Thermal (non-maser) emission from CO was detected in 1986.[22]

With the high angular resolution provided by Very Long Baseline Interferometry, the H2O maser emission is seen to arise from small (milli-arcsecond) blobs, whose proper motions through the inner region of the circumstellar shell can be measured. These observations give additional evidence that R Cratoris has developed a bipolar stellar wind.[23]

  1. ^ Cite error: The named reference ASASServer was invoked but never defined (see the help page).
  2. ^ a b c d e f Cite error: The named reference dr3 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Jura1992 was invoked but never defined (see the help page).
  4. ^ a b c Cite error: The named reference Khouri2020 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference Houk1988 was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference gcvs was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference kervella2022 was invoked but never defined (see the help page).
  8. ^ a b c Cite error: The named reference mcdonald2017 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference tonry2018 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Taylor was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference Halbedel1985 was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Livi1982 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference Brand2020 was invoked but never defined (see the help page).
  15. ^ Cite error: The named reference Neugebauer1969 was invoked but never defined (see the help page).
  16. ^ Cite error: The named reference Young1993 was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference Cox2012 was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference CoxError was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Paladini2017 was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Dickinson1973 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Jewell1985 was invoked but never defined (see the help page).
  22. ^ Cite error: The named reference Zuckerman1986 was invoked but never defined (see the help page).
  23. ^ Cite error: The named reference Ishitsuka2001 was invoked but never defined (see the help page).