Exploring the substellar temperature regime down to ∼550K

被引：100

作者：

Burningham, Ben ^{[1
]}

Pinfield, D. J. ^{[1
]}

Leggett, S. K. ^{[2
]}

Tamura, M. ^{[3
]}

Lucas, P. W. ^{[1
]}

Homeier, D. ^{[4
]}

Day-Jones, A. ^{[1
]}

Jones, H. R. A. ^{[1
]}

Clarke, J. R. A. ^{[1
]}

Ishii, M. ^{[5
]}

Kuzuhara, M. ^{[6
]}

Lodieu, N. ^{[7
]}

Zapatero Osorio, M. R. ^{[7
]}

Venemans, B. P. ^{[8
]}

Mortlock, D. J. ^{[9
]}

Barrado y Navascues, D. ^{[10
]}

Martin, E. L. ^{[7
]}

Magazzu, A. ^{[11
]}

机构：

[1] Univ Hertfordshire, Ctr Astrophys Res, Sci & Technol Res Inst, Hatfield AL10 9AB, Herts, England

[2] Gemini Observ, Hilo, HI 96720 USA

[3] Natl Astron Observ, Mitaka, Tokyo 1818588, Japan

[4] Univ Gottingen, Inst Astrophys, D-37077 Gottingen, Germany

[5] Natl Inst Nat Sci, Natl Astron Observ Japan, Subaru Telescope, Hilo, HI 96720 USA

[6] Univ Tokyo, Tokyo 1130033, Japan

[7] Inst Astrofis Canarias, E-38200 San Cristobal la Laguna, Spain

[8] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England

[9] Univ London Imperial Coll Sci Technol & Med, Blackett Lab, Astrophys Grp, London SW7 2AZ, England

[10] INTA, Lab Astrofis Espacial & Fis Fundamental, E-28691 Madrid, Spain

[11] INAF, Fdn Galileo Galilei, E-38700 Santa Cruz De La Palma, Spain

来源：

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY | 2008年 / 391卷 / 01期

基金：

英国科学技术设施理事会;

关键词：

surveys; stars:; low-mass; brown dwarfs;

D O I：

10.1111/j.1365-2966.2008.13885.x

中图分类号：

P1 [天文学];

学科分类号：

0704 ;

摘要：

We report the discovery of three very late T dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS) Third Data Release: ULAS J101721.40+011817.9 (ULAS1017), ULAS J123828.51+095351.3 (ULAS1238) and ULAS J133553.45+113005.2 (ULAS1335). We detail optical and near-infrared (NIR) photometry for all three sources, and mid-IR photometry for ULAS1335. We use NIR spectra of each source to assign spectral types T8p (ULAS1017), T8.5 (ULAS1238) and T9 (ULAS1335) to these objects. ULAS1017 is classed as a peculiar T8 (T8p) due to appearing as a T8 dwarf in the J band, whilst exhibiting H- and K-band flux ratios consistent with a T6 classification. Through comparison to BT-Settl model spectra we estimate that ULAS1017 has 750K less than or similar to T(eff) less than or similar to 850 K, and 5.0 less than or similar to log g(cm s(-2)) less than or similar to 5.5, assuming solar metallicity. This estimate for gravity is degenerate with varying metallicity. We estimate that ULAS1017 has an age of 1.6-15 Gyr, a mass of 33-70M(J) and lies at a distance of 31-54 pc. We do not estimate atmospheric parameters for ULAS1238 due to a lack of K-band photometry. We extend the unified scheme of Burgasser et al. to the type T9 and suggest the inclusion of the W(J) index to replace the now saturated J-band indices. We propose ULAS1335 as the T9 spectral type standard. ULAS1335 is the same spectral type as ULAS J003402.77-005206.7 and CFBDS J005910.90-011401.3. We argue that given the similarity of the currently known > T8 dwarfs to the rest of the T dwarf sequence, the suggestion of the Y0 spectral class for these objects is premature. Comparison of model spectra with that of ULAS1335 suggest a temperature below 600 K, possibly combined with low gravity and/or high metallicity. We find ULAS1335 to be extremely red in NIR to mid-IR colours, with H - [4.49] = 4.34 +/- 0.04. This is the reddest NIR to mid-IR colour yet observed for a T dwarf. The NIR to mid-IR spectral energy distribution of ULAS1335 further supports T(eff) < 600 K, and we estimate T(eff) similar to 550-600 K for ULAS1335. We estimate that ULAS1335 has an age of 0.6-5.3 Gyr, a mass of 15-31M(J) and lies at a distance of 8-12 pc.

引用

页码：320 / 333

页数：14

共 38 条

[1]

[Anonymous], 1998, MESSENGER

[2] Subtle signatures of multiplicity in late-type dwarf spectra: The unresolved M8.5+T5 binary 2MASS J03202839-0446358 [J].

Burgasser, Adam J. ;

Liu, Michael C. ;

Ireland, Michael J. ;

Cruz, Kelle L. ;

Dupuy, Trent J. .

ASTROPHYSICAL JOURNAL, 2008, 681 (01) :579-593

[3] A unified near-infrared spectral classification scheme for T dwarfs [J].

Burgasser, AJ ;

Geballe, TR ;

Leggett, SK ;

Kirkpatrick, JD ;

Golimowski, DA .

ASTROPHYSICAL JOURNAL, 2006, 637 (02) :1067-1093

[4] The spectra of T dwarfs. I. Near-infrared data and spectral classification [J].

Burgasser, AJ ;

Kirkpatrick, JD ;

Brown, ME ;

Reid, IN ;

Burrows, A ;

Liebert, J ;

Matthews, K ;

Gizis, JE ;

Dahn, CC ;

Monet, DG ;

Cutri, RM ;

Skrutskie, MF .

ASTROPHYSICAL JOURNAL, 2002, 564 (01) :421-451

[5] Theoretical spectral models of T dwarfs at short wavelengths and their comparison with data [J].

Burrows, A ;

Burgasser, AJ ;

Kirkpatrick, JD ;

Liebert, J ;

Milsom, JA ;

Sudarsky, D ;

Hubeny, I .

ASTROPHYSICAL JOURNAL, 2002, 573 (01) :394-417

[6] The theory of brown dwarfs and extrasolar giant planets [J].

Burrows, A ;

Hubbard, WB ;

Lunine, JI ;

Liebert, J .

REVIEWS OF MODERN PHYSICS, 2001, 73 (03) :719-765

[7] The UKIRT wide-field camera [J].

Casali, M. ;

Adamson, A. ;

de Oliveira, C. Alves ;

Almaini, O. ;

Burch, K. ;

Chuter, T. ;

Elliot, J. ;

Folger, M. ;

Foucaud, S. ;

Hambly, N. ;

Hastie, M. ;

Henry, D. ;

Hirst, P. ;

Irwin, M. ;

Ives, D. ;

Lawrence, A. ;

Laidlaw, K. ;

Lee, D. ;

Lewis, J. ;

Lunney, D. ;

McLay, S. ;

Montgomery, D. ;

Pickup, A. ;

Read, M. ;

Rees, N. ;

Robson, I. ;

Sekiguchi, K. ;

Vick, A. ;

Warren, S. ;

Woodward, B. .

ASTRONOMY & ASTROPHYSICS, 2007, 467 (02) :777-784

[8]

Cruikshank D. P., 1969, Communications of the Lunar and Planetary Laboratory, V6, P275

[9] CFBDS J005910.90-011401.3: reaching the T-Y brown dwarf transition? [J].

Delorme, P. ;

Delfosse, X. ;

Albert, L. ;

Artigau, E. ;

Forveille, T. ;

Reyle, C. ;

Allard, F. ;

Homeier, D. ;

Robin, A. C. ;

Willott, C. J. ;

Liu, M. C. ;

Dupuy, T. J. .

ASTRONOMY & ASTROPHYSICS, 2008, 482 (03) :961-971

[10]

DUQUENNOY A, 1991, ASTRON ASTROPHYS, V248, P485

← 1 2 3 4 →