Accretion, Kinematics, and Rotation in the Orion Nebula Cluster: Initial Results from Hectochelle

Sicilia‐Aguilar, A.; Hartmann, L.; Szentgyorgyi, Andrew; Fabricant, Daniel G.; Fürész, Gábor; Roll, John; Conroy, Maureen A.; Calvet, Nuria; Tokarz, S.; Hernández, Jesús

doi:10.1086/426327

Cited by 78 publications

(122 citation statements)

References 50 publications

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“…Contrary to the case of more massive stars where disklocking is supported by rotation-color excess and rotationaccretion correlations (Herbst et al 2002;Sicilia-Aguilar et al 2005), the lack of strong concordance between Fig. 12 and Fig.…”

Section: Is There Any Evidence Supporting Disk-locking?mentioning

confidence: 62%

Evidence of early disk-locking among low-mass members of the Orion Nebula Cluster

Biazzo

Melo

Pasquini

et al. 2009

A&A

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Context. We present new high-resolution spectroscopic observations for 91 pre-main sequence stars in the Orion Nebular Cluster (ONC) with masses in the range 0.10−0.25 M carried out with the multi-fiber spectrograph flames attached to the UT2 at the Paranal Observatory. Aims. Our aim is to better understand the disk-locking scenario in very low-mass stars. Methods. We have derived radial velocities, projected rotational velocities, and full width at 10% of the Hα emission peak. Using published measurements of infrared excess (Δ(I C − K)), as disk tracer and equivalent width of the nead-infrared Ca ii line λ8542, mid-infrared difference [3.6]-[8.0] μm derived by Spitzer data, and 10% Hα width as diagnostic of the level of accretion, we looked for any correlation between projected angular rotational velocity divided by the radius (v sin i/R) and presence of disk and accretion. Results. For 4 low-mass stars, the cross-correlation function is clearly double-lined, indicating that the stars are SB2 systems. The distribution of rotation periods derived from our v sin i measurements is unimodal with a peak of a few days, in agreement with previous results for M < 0.25 M . The photometric periods were combined with our v sin i to derive the equatorial velocity and the distribution of rotational axes. Our sin i is lower than the one expected for a random distribution, as previously found. We find no evidence of a population of fast rotators close to the break-up velocity. A clear correlation between v sin i/R and Δ(I C − K) has been found. While a spread in the rotation rates is seen for stars with no circumstellar disk (Δ(I C − K) < 0.3), stars with a circumstellar disk (Δ(I C − K) > 0.3) show an abrupt drop in their rotation rates by a factor of ∼5. On the other hand, only a partial correlation between v sin i and accretion is observed when other indicators are used. The X-ray coronal activity level (log L X /L bol ) shows no dependence on v sin i/R, suggesting that all stars are in a saturated regime limit. The critical velocity is probably below our v sin i detection limit of 9 km s −1 . Conclusions. The ONC low-mass stars in our sample, close to the hydrogen burning limit, at present do not seem to be locked, but the clear correlation we find between rotation and infrared color excess suggests that they were locked once. In addition, the percentage of accretors seems to scale inversely to the stellar mass.

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Section: Is There Any Evidence Supporting Disk-locking?mentioning

confidence: 62%

Evidence of early disk-locking among low-mass members of the Orion Nebula Cluster

Biazzo

Melo

Pasquini

et al. 2009

A&A

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“…Nevertheless, an impressive correlation between NIR excess and mass accretion indicators such as the Hα emission line width has been found for many YSOs over a broad mass range (e.g. Sicilia-Aguilar et al 2005. This strong correlation allows us to use NIR excess as a good accretion disk indicator in this study, since a more direct accretion indicator (e.g.…”

Section: Are Nir Excesses Good Accretion Disks Indicators?mentioning

confidence: 75%

“…However, a remarkable correlation between mass accretion indicators such as Hα emission line widths and NIR excess has been reported in the literature (e.g. Sicilia-Aguilar et al 2005 and therefore using NIR excess as a mass accretion indicator is a reasonable approach. Muench et al (2001) found that about 50% of their brown dwarf candidates in the Trapezium region show near-infrared (NIR) excesses indicative of a circumstellar disk.…”

Section: Introductionmentioning

confidence: 99%

Rotation-disk connection for very low mass and substellar objects in the Orion Nebula Cluster

Rodríguez-Ledesma

Mundt²,

Eislöffel

2010

A&A

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Aims. Angular momentum (J) loss requires magnetic interaction between the forming star and both the circumstellar disk and the magnetically driven outflows. In order to test these predictions many authors have investigated a rotation-disk connection in pre-main sequence objects with masses larger than about 0.4 M . For brown dwarfs (BDs) this connection was not investigated as yet because there are very few samples available. We aim to extend this investigation well down into the substellar regime for our large sample of ≈80 BDs in the Orion Nebula Cluster, for which we have recently measured rotational periods. Methods. In order to investigate a rotation-disk correlation, we derived near-infrared (NIR) excesses for a sample of 732 periodic variables in the Orion Nebula Cluster with masses ranging between ≈1.5-0.02 M and whose IJHK colors are available. Circumstellar NIR excesses were derived from the Δ[I − K] index. We performed our analysis in three mass bins (>0.4 M , 0.4-0.075 M , and <0.075 M ). Results. We found a rotation-disk correlation in the high and intermediate mass regime, in which objects with NIR excess tend to rotate slower than objects without NIR excess. Interestingly, we found no correlation in the substellar regime. A tight correlation between the peak-to-peak (ptp) amplitude of the rotational modulation and the NIR excess was found however for all objects with available ptp values (<0.4 M ). We discuss possible scenarios which may explain the lack of rotation-disk connection in the substellar mass regime. One possible reason could be the strong dependence of the mass accretion rateṀ on stellar mass in the investigated mass range (Ṁ ∝ M 2 − 2.8 star ), which is expected to result in a corresponding mass dependence ofJ/J.

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“…There have been a number of measurements of these quantities for the ONC with proper-motion and radial velocity studies. Recent spectroscopic observations of stars in the cluster by Sicilia-Aguilar et al (2005) show a mean heliocentric velocity of 25 km s À1 , with a $2 km s À1 uncertainty in the zero point and a dispersion of ¼ 2:3 km s À1 . Bower et al (2003) measured a heliocentric radial velocity of 14 AE 5 km s À1 for GMR A.…”

Section: The Membership Of Gmr a In The Orion Nebula Clustermentioning

confidence: 98%

A Parallactic Distance of \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMat

Sandström

Peek

Bower

et al. 2007

ApJ

139

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We determine the parallax and proper motion of the flaring, nonthermal radio star GMR A, a member of the Orion Nebula Cluster, using Very Long Baseline Array observations. Based on the parallax, we measure a distance of 389 þ24 À21 pc to the source. Our measurement places the Orion Nebula Cluster considerably closer than the canonical distance of 480 AE 80 pc determined by Genzel et al. A change of this magnitude in distance lowers the luminosities of the stars in the cluster by a factor of $1.5. We briefly discuss two effects of this change -an increase in the age spread of the premain-sequence stars, and better agreement between the zero-age main sequence and the temperatures and luminosities of massive stars.

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Accretion, Kinematics, and Rotation in the Orion Nebula Cluster: Initial Results from Hectochelle

Cited by 78 publications

References 50 publications

Evidence of early disk-locking among low-mass members of the Orion Nebula Cluster

Evidence of early disk-locking among low-mass members of the Orion Nebula Cluster

Rotation-disk connection for very low mass and substellar objects in the Orion Nebula Cluster

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