Kelu-1/ˈkeɪluː/is a system of twobrown dwarfsofspectral typesL2 and L4[2]located in constellationHydraat approximately 60.6light-yearsfromEarth.[4]It is among the first free-floating later-than-M-type brown dwarfs discovered, and sometimes considered as prototype of L-type brown dwarfs.[10]
  Kelu-1 Location of Kelu-1 in the constellationHydra | |
| Observation data EpochJ2000[1]EquinoxJ2000[1] | |
|---|---|
| Constellation | Hydra |
| Right ascension | 13h05m40.196s[1] |
| Declination | −25° 41′ 05.99″[1] |
| Characteristics | |
| Spectral type | L2:[2]/ L4:[2] |
| Apparent magnitude(J) | 13.83 ± 0.08 / 14.65 ± 0.12[3] |
| Apparent magnitude(H) | 12.92 ± 0.03 / 13.44 ± 0.04[3] |
| Apparent magnitude(KS) | 12.32 ± 0.02 / 12.72 ± 0.03[3] |
| Apparent magnitude(L') | 11.42 ± 0.15 / 11.66 ± 0.15[3] |
| Astrometry | |
| Proper motion(μ) | RA:−299.2 ± 1.2[2]mas/yr Dec.:−4.1 ± 1.4[2]mas/yr |
| Parallax(π) | 53.8492 ± 0.7107mas[4] |
| Distance | 60.6 ± 0.8ly (18.6 ± 0.2pc) |
| Orbit[3] | |
| Primary | A |
| Companion | B |
| Period(P) | 38+8 −6yr |
| Semi-major axis(a) | 0.339+0.129 −0.066" (6.4+2.4 −1.3AU) |
| Eccentricity(e) | 0.82+0.1 −0.1 |
| Inclination(i) | 84.9+1.0 −2.0° |
| Longitude of the node(Ω) | 39.4+2.0 −2.0° |
| Periastronepoch(T) | 2452079+200 −400(Jun 18, 2001) |
| Argument of periastron(ω) (secondary) | 57.8+15.0 −20.0° |
| Details | |
| Kelu-1 A | |
| Mass | 0.060 ± 0.01[5]M☉ |
| Radius | 0.098R☉ |
| Luminosity (bolometric) | 1.35–1.74 · 10−4[6]L☉ |
| Temperature | ≈ 2020[6]K |
| Age | 0.3–0.5[3]Gyr |
| Kelu-1 B | |
| Mass | 0.055 ± 0.01[5]M☉ |
| Radius | 0.0976R☉ |
| Luminosity (bolometric) | 0.91–1.12 · 10−4[6]L☉ |
| Temperature | ≈ 1840[6]K |
| Age | 0.3–0.5[3]Gyr |
| Other designations | |
| Database references | |
| SIMBAD | Kelu-1 AB |
History of observations
edit
Discovery
editIn 1987María Teresa Ruizdecided to start The Calán-ESO proper-motion survey using red plates taken (starting from the 1970s) with the 1-m ESO Schmidt Camera atLa Silla Observatory,Chile.The survey was not specially designed for search for brown dwarfs, but in the main for search for another type of celestial bodies—white dwarfs.Pairs of plates, separated by long span of time, were compared withblink comparatorto detect objects with highproper motion.Objects with high proper motion, which were found, were selected for follow-upspectroscopyusing the 3.6-m telescope, equipped with EFOSC1, at the same observatory.
In March 1997 was carried out spectroscopy with the 3.6-m telescope of the next object, discovered from the pair of plates, separated by 14 years (1979–1993) (at the limit of sensitivity: itsapparent magnitudein R band was about 19.5), through its large proper motion, and its spectrum was found very red, very peculiar and very odd-looking. The object's spectrum and its extremely low luminosity led to conclusion that this probably is a brown dwarf. Ruiz et al. named this brown dwarf Kelu-1: «kelu» means «red» in theMapuche language(the origin of the second part of the name—the number «1»—is unexplained in the article).[~ 1]
Follow-up observations of Kelu-1 include: optical spectroscopy using theESO3.6 m telescope at La Silla (1997 March),infraredspectroscopy using IRCAM3 and CGS4 onUKIRTat theMauna Kea Observatory,Hawaii(1997 April), and finding chart for Kelu-1 was kindly taken by R. Covarrubias of theCerro Tololo Inter-American Observatory (CTIO)with the CTIO 0.9 m telescope.
The discovery paper of Kelu-1 by Ruiz et al. was received 1997 September 5, accepted for publication 1997 October 16 and published 1997 November 6 inThe Astrophysical Journal Letters.[7][12]
Inclusion to CE Catalog
editIn 2001 Ruiz et al. published The Calán-ESO Proper-Motion Catalog (CE Catalog), containing 542 high proper motion stars, detected with ESO 1-m Schmidt Camera plates taken with intervals of time between 6.4 and 16 years. Kelu-1 also was included in this catalog (as object number 298), hence one of its identifiers isCE 298.[8][1]
Assignment of spectral class
editRuiz et al. did not assign anyspectral classto Kelu-1—in 1997 the latest used in astronomy spectral class was M, but type of Kelu-1 was later than M. In 1999J. Davy Kirkpatricket al. published a paper inThe Astrophysical Journal,in which they introduced two new spectral classes later than M for recently discovered cool objects—brown dwarfs:LandT.At the same time in this paper they assigned spectral classes to 26 later-than-M-type brown dwarfs, discovered by 1999: 25 brown dwarfs were assigned class L, including Kelu-1, and one, the coolest, brown dwarfGliese 229 Bwas assigned class T. Kelu-1 was assigned spectral class L2 V.[9]
2nd component hypothesis
editIn 1997 Ruiz et al. had made two estimates of distance of Kelu-1—from its proper motion, assuming its observed motion is due to Solar System's motion only (about 12 parsecs), and from its apparent magnitude in J band, assuming it is same with that ofGD 165 B—another L-type brown dwarf with similar spectral properties, discovered in 1988 in the system ofwhite dwarfGD 165[13](about 10 parsecs).[7]
But in 1999 preliminarytrigonometric parallaxof Kelu-1, measured underUSNOfaint-star parallax program, was obtained, and it turned out that it is located further—at about 19 parsecs, and so it is more luminous than GD 165 B. There were two possible explanations of overluminosity of Kelu-1: it is either young (age less than 0.1Gyr) or binary.[14]However, observations of Kelu-1 with near-infraredcamera NICMOS onHubble Space Telescopecarried out on 1998 August 14, did not reveal the presence of any companion with separation greater than 300masand magnitude difference less than 6.7mag.[15][5]
2nd component discovery
edit
In 2005 the binarity hypothesis proved true: the second component (Kelu-1 B) was discovered with theLaser Guide StarAdaptive Optics(LGS AO) system on 10-meterKeckII Telescope,Mauna Kea Observatory,Hawaii,by Gelino et al.[5]and independently by Liu and Leggett.[6]
Gelino et al.observed Kelu-1 with infrared camera NIRC2 using LGS AO system on 2005 March 4 and 2005 April 30, and it appeared to be a binary object with a separation about 290mas.The binarity was confirmed withHSTobservations on 2005 July 31 by W. Brandner that were present in the public archive. HST did not detect the companion in 1998 August observations, as it turned out, because its separation increased for 1998–2005 due to orbital motion, and in 1998 it was several times smaller. However, Gelino et al. re-analyzed a 1998 HST observation of Kelu-1 and found that it is best fit by a binary object separated by 45 ± 18 mas. The discovery paper by Gelino et al. was submitted toThe Publications of the Astronomical Society of the Pacificon 5 August 2005, and it was published in 2006 April.[5]
Liu & Leggett independently observed Kelu-1 on 2005 May 1 also with NIRC2 using LGS AO system on Keck II Telescope, and also discovered the companion Kelu-1 B (a separation was 291 ± 2 mas). Despite Liu & Leggett had conducted their observations slightly later than Gelino et al., they published their discovery paper of Kelu-1 B earlier—it was received 2005 June 2, accepted for publication 2005 August 1 and published inThe Astrophysical Journal2005 November 20.[6]
3rd component hypothesis
editIn 2005–2008, Stumpf et al. observed Kelu-1 with NICMOS camera ofHSTand with theadaptive opticssystem NACO at theESO8.2-meter telescopeVLT/UT4 (Yepun) atParanal Observatory,Chile(they also used observations withSpitzer Space Telescope,retrieved from the SPITZER Science Archive).
They obtained orbital parameters and total mass estimate of Kelu-1 system: 177+113
−55MJup.The mass is too high for a system of two brown dwarfs: an upper limit for brown dwarf mass is 72–75 MJup,so a maximum mass for a system of two brown dwarfs is about 150 MJup.Moreover, presence ofLiabsorption in the unresolved spectrum of Kelu-1 indicates that at least one of its components has mass below lithium-burning limit, which is 65 MJup.
This may indicate presence of the third component in the system. Another possible explanation of too high mass: it may be an under-prediction of the masses of brown dwarfs, which is already the case for other objects (AB Dor C,GJ 802 bandEpsilon Indi Ba, Bb).
Also Stumpf et al. revealed a peculiarity in the spectrum of Kelu-1 A, indicating it itself may be an unresolved binary with spectral types of L0.5 ± 0.5 for Kelu-1 Aa and T7.5 ± 1 for Kelu-1 Ab (corresponding to a mass of 18.5 MJup)[3]
X-rays and attempt of detection in radio
editKelu-1 system is also a source ofX-rays,which was revealed in 2007 by Audard et al. usingChandra X-ray Observatory.Theluminosityof Kelu-1 in X-rays is LX= 2.9+1.8
−1.3· 1025erg·s−1.
This was the first detection of X-rays from an L dwarf.
In the same time Audard et al. attempted to detect Kelu-1 in the radio usingVery Large Array,but it remained undetected in radio.[16]
Distance
editCurrently the most precise distance estimate of Kelu-1 istrigonometric parallax,measured underUSNOfaint-star parallax program and published by Dahn et al. in 2002: 53.6 ± 2.0mas,corresponding to a distance 18.7 ± 0.7pc,or 60.9 ± 2.3ly.[17]
Kelu-1 distance estimates
| Source | Parallax,mas | Distance,pc | Distance,ly | Ref. |
|---|---|---|---|---|
| Ruiz et al. (1997) (from proper motion) |
~12 | ~39.1 | [7] | |
| Ruiz et al. (1997) (spectrophotometric) |
~10 | ~32.6 | [7] | |
| Dahn (1999) (private communication); Ruiz (1999) (private communication) |
19 ± 1 | 62.0 ± 3.3 | [14] | |
| Dahn et al. (2002) | 53.6 ± 2.0 | 18.7 ± 0.7 | 60.9 ± 2.3 | [17] |
| Dupuy & Liu (2012) | 49.7 ± 2.4 | 20.1+1.0 −0.9 |
65.6+3.3 −3.0 |
[18][2] |
Non-trigonometric distance estimates are marked initalic.The best estimate is marked inbold.
Early discoveries of brown dwarfs
editAlthough Kelu-1 is among the first free-floating L dwarfs discovered, it is actually not the first. Three free-floating L dwarfs were found by Xavier Delfosse et al. using theDENISsurvey (the article was submitted and published in the same 1997, but it was submitted earlier than Ruiz et al. (1997)):[19]
And one free-floating L dwarf was announced by Kirkpatrick et al. using2MASSprototype observations ( "MASP" ) (the article was submitted in 1996 and published in 1997):[20]
In addition, several free-floating brown dwarfs candidates have been found in thePleiades clusterby Rebolo et al. (1996).[7]
Two early discoveries of not free-floating L and T dwarfs:
- Gliese 229 B(a T6.5-[21]type companion to ared dwarf,detected in 1995 by Nakajima et al.)[22]
- GD 165 B(an L4-[9]type companion to awhite dwarf,detected in 1988 by Becklin and Zuckerman)[13]
Furthermore, some of late M-type stars are also considered as brown dwarfs now. Such objects were known even earlier: some of them were included to theNLTTCatalogue in 1979, for example,LP 944-020.
See also
editNotes
edit- ^This is not the only case of usingMapuchewords in modern astronomy: names of four 8.2-meterVLTtelescopes ofParanal Observatory(Antu,Kueyen,MelipalandYepun) are also originated from Mapuche.
References
edit- ^abcdefghijklmnopqrst"NAME Kelu-1 -- Double or multiple star".SIMBAD.Centre de Données astronomiques de Strasbourg.Retrieved2013-08-12.
- ^abcdefDupuy, Trent J.; Liu, Michael C. (2012). "The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition".The Astrophysical Journal Supplement.201(2): 19.arXiv:1201.2465.Bibcode:2012ApJS..201...19D.doi:10.1088/0067-0049/201/2/19.S2CID119256363.
- ^abcdefghStumpf, M. B.; Brandner, W.; Henning, Th.; Bouy, H.; Koehler, R.; Hormuth, F.; Joergens, V.; Kasper, M. (2008). "Kelu-1 AB - A possible brown dwarf triple system".arXiv:0811.0556v1[astro-ph].
- ^abBrown, A. G. A.;et al. (Gaia collaboration) (August 2018)."GaiaData 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 sourceatVizieR.
- ^abcdeGelino, Christopher R.; Kulkarni, S. R.; Stephens, Denise C. (2006). "Evidence of Orbital Motion in the Binary Brown Dwarf Kelu-1AB".The Publications of the Astronomical Society of the Pacific.118(842): 611–616.arXiv:astro-ph/0508164.Bibcode:2006PASP..118..611G.doi:10.1086/502985.S2CID17426298.
- ^abcdefLiu, Michael C.; Leggett, S. K. (2005). "Kelu-1 Is a Binary L Dwarf: First Brown Dwarf Science from Laser Guide Star Adaptive Optics".The Astrophysical Journal.634(1): 616–624.arXiv:astro-ph/0508082.Bibcode:2005ApJ...634..616L.doi:10.1086/496915.S2CID16185006.
- ^abcdefRuiz, Maria Teresa; Leggett, S. K.; Allard, France (1997)."Kelu-1: A Free-floating Brown Dwarf in the Solar Neighborhood".The Astrophysical Journal Letters.491(2): L107.Bibcode:1997ApJ...491L.107R.doi:10.1086/311070.
- ^abRuiz, Maria Teresa; Wischnjewsky, Marina; Rojo, Patricio M.; Gonzalez, Luis E. (2001)."Calán-ESO Proper-Motion Catalog".The Astrophysical Journal Supplement Series.133(1): 119–160.Bibcode:2001ApJS..133..119R.doi:10.1086/319188.
- ^abcKirkpatrick, J. Davy; Reid, I. Neill; Liebert, James; Cutri, Roc M.; Nelson, Brant; Beichman, Charles A.; Dahn, Conard C.; Monet, David G.; Gizis, John E.; Skrutskie, Michael F. (10 July 1999)."Dwarfs Cooler than M: the Definition of Spectral Type L Using Discovery from the 2-µ ALL-SKY Survey (2MASS)"(PDF).The Astrophysical Journal.519(2): 802–833.Bibcode:1999ApJ...519..802K.doi:10.1086/307414.[permanent dead link]
- ^Kelu 1 - A Brief History
- ^abClarke, F. J.; Tinney, C. G.; Covey, K. R. (May 2002)."Periodic photometric variability of the brown dwarf Kelu-1".Monthly Notices of the Royal Astronomical Society.332(2): 361–366.arXiv:astro-ph/0201162.Bibcode:2002MNRAS.332..361C.doi:10.1046/j.1365-8711.2002.05308.x.
- ^A Faint and Lonely Brown Dwarf in the Solar Vicinity
- ^abBecklin, E. E.; Zuckerman, B. (1988). "A low-temperature companion to a white dwarf star".Nature.336(Dec. 15, 1988): 656–658.Bibcode:1988Natur.336..656B.doi:10.1038/336656a0.S2CID4358564.
- ^abMartín, Eduardo L.; Delfosse, Xavier; Basri, Gibor; Goldman, Bertrand; Forveille, Thierry; Zapatero-Osorio, María Rosa (1999)."Spectroscopic Classification of Late-M and L Field Dwarfs".The Astronomical Journal.118(5): 2466–2482.Bibcode:1999AJ....118.2466M.doi:10.1086/301107.
- ^Martín, Eduardo L.; Brandner, W.; Basri, Gibor (1999). "A Search for Companions to Nearby Brown Dwarfs: The Binary DENIS-P J1228.2-1547".Science.283(5408): 1718–1720.Bibcode:1999Sci...283.1718M.doi:10.1126/science.283.5408.1718.PMID10073933.
- ^Audard, M.; Osten, R. A.; Brown, A.; Briggs, K. R.; Güdel, M.; Hodges-Kluck, E.; Gizis, J. E. (2007). "A Chandra X-ray detection of the L dwarf binary Kelu-1. Simultaneous Chandra and Very Large Array observations".Astronomy and Astrophysics.471(3): L63–L66.arXiv:0707.1882.Bibcode:2007A&A...471L..63A.doi:10.1051/0004-6361:20078093.S2CID14200111.
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- ^Dupuy, Trent J.; Liu, Michael C. (2012). "The Hawaii Infrared Parallax Program. I. Ultracool Binaries and the L/T Transition".The Astrophysical Journal Supplement Series.201(2): 19.arXiv:1201.2465v1.Bibcode:2012ApJS..201...19D.doi:10.1088/0067-0049/201/2/19.S2CID119256363.
- ^Delfosse, Xavier; Tinney, Chris G.; Forveille, Thierry; Epchtein, Nicolas; Bertin, Emmanuel; Borsenberger, Jean; Copet, Éric; de Batz, Bertrand; Fouqué, Pascal; Kimeswenger, Stefan; Le Bertre, Thibaut; Lacombe, François; Rouan, Daniel; Tiphène, Didier (1997). "Field brown dwarfs found by DENIS".Astronomy and Astrophysics.327:L25–L28.Bibcode:1997A&A...327L..25D.
- ^Kirkpatrick, J. Davy;Beichman, Charles A.; Skrutskie, Michael F. (1997)."The Coolest Isolated M Dwarf and Other 2MASS Discoveries".The Astrophysical Journal.476(1): 311–318.Bibcode:1997ApJ...476..311K.doi:10.1086/303613.
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