Becklin-Neugebauer Research Articles

The Orion Protostellar Explosion and Runaway Stars Revisited: Stellar Masses, Disk Retention, and an Outflow from the Becklin–Neugebauer Object

Abstract The proper motions of the three stars ejected from Orion’s OMC1 cloud core are combined with the requirement that their center of mass is gravitationally bound to OMC1 to show that radio source I (Src I) is likely to have a mass around 15 M ⊙ consistent with recent measurements. Src I, the star with the smallest proper motion, is suspected to be either an astronomical-unit-scale binary or a protostellar merger remnant produced by a dynamic interaction ∼550 yr ago. Near-infrared 2.2 μm images spanning ∼21 yr confirm the ∼55 km s−1 motion of “source x” (Src x) away from the site of stellar ejection and point of origin of the explosive OMC1 protostellar outflow. The radial velocities and masses of the Becklin–Neugebauer (BN) object and Src I constrain the radial velocity of Src x to be km s−1. Several high proper-motion radio sources near BN, including Zapata 11 ([ZRK2004] 11) and a diffuse source near IRc 23, may trace a slow bipolar outflow from BN. The massive disk around Src I is likely the surviving portion of a disk that existed prior to the stellar ejection. Though highly perturbed, shocked, and reoriented by the N-body interaction, enough time has elapsed to allow the disk to relax with its spin axis roughly orthogonal to the proper motion.

High Spectral Resolution Observations toward Orion BN at 6 μm: No Evidence for Hot Water

Abstract The Becklin–Neugebauer (BN) object in Orion has a large proper motion and radial velocity with respect to the gas and other stars in the region where it is presumed to have formed. Multiple dynamical interaction scenarios have been proposed to explain this motion. In one case BN is thought to have interacted with stars in the Trapezium cluster, while in another it is thought to have interacted with source I while deeply embedded in molecular gas. If there is dense gas that has been retained in close proximity to BN, it may be evidence that the latter scenario is favored. We observed BN at high spectral resolution in three windows near 6 μm using the Echelon-Cross-Echelle Spectrograph on board the Stratospheric Observatory for Infrared Astronomy targeting the ν 2 vibrational band of H2O. Absorption from only three transitions of H2O is detected, and through kinematic analysis is associated with cool, dense foreground gas, not BN itself. We find no evidence for H2O absorption or emission at the systemic velocity of BN.

ALMA and VLA observations of recombination lines and continuum toward the Becklin-Neugebauer object in Orion

Compared to their centimeter-wavelength counterparts, millimeter recombination lines (RLs) are intrinsically brighter and are free of pressure broadening. We report observations of RLs (H30alpha at 231.9 GHz, H53alpha at 42.9 GHz) and the millimeter and centimeter continuum toward the Becklin-Neugebauer (BN) object in Orion, obtained from the Atacama Large Millimeter/submillimeter Array (ALMA) Science Verification archive and the Very Large Array (VLA). The RL emission appears to be arising from the slowly-moving, dense (Ne=8.4x10^6 cm^-3) base of the ionized envelope around BN. This ionized gas has a relatively low electron temperature (Te<4900 K) and small (<<10 km s^-1) bulk motions. Comparing our continuum measurements with previous (non)detections, it is possible that BN has large flux variations in the millimeter. However, dedicated observations with a uniform setup are needed to confirm this. From the H30alpha line, the central line-of-sight LSR velocity of BN is 26.3 km s^-1.

GRAVITATIONAL SLINGSHOT OF YOUNG MASSIVE STARS IN ORION

The Orion Nebula Cluster (ONC) is the nearest region of massive star formation and thus a crucial testing ground for theoretical models. Of particular interest amongst the ONC's ~1000 members are: \theta^1 Ori C, the most massive binary in the cluster with stars of masses 38 and 9 MSun (Kraus et al. 2009); the Becklin-Neugebauer (BN) object, a 30 km/s runaway star of ~8 MSun (Tan 2004); and the Kleinmann-Low (KL) nebula protostar, a highly-obscured, ~15 MSun object still accreting gas while also driving a powerful, apparently "explosive" outflow (Allen & Burton 1993). The unusual behavior of BN and KL is much debated: How did BN acquire its high velocity? How is this related to massive star formation in the KL nebula? Here we report the results of a systematic survey using ~ 10^7 numerical experiments of gravitational interactions of the \theta^1C and BN stars. We show that dynamical ejection of BN from this triple system at its observed velocity leaves behind a binary with total energy and eccentricity matching those observed for \theta^1C. Five other observed properties of \theta^C are also consistent with it having ejected BN and altogether we estimate there is only a <~ 10^{-5} probability that \theta^1C has these properties by chance. We conclude that BN was dynamically ejected from the \theta^1C system about 4,500 years ago. BN has then plowed through the KL massive-star-forming core within the last 1,000 years causing its recently-enhanced accretion and outflow activity.

Circular polarimetry and the line of sight to the Becklin-Neugebauer object

The 3.1-μm absorption feature of water-ice has been observed spectroscopically in many molecular clouds and, when it has been observed spectropolarimetrically, usually a corresponding polarization feature is seen. Typically, on these occasions, and particularly for the Becklin–Neugebauer (BN) object, a distinct position angle shift between the feature and continuum is seen, which indicates both a fractionation of the icy material and a changing alignment direction along the line of sight. Here, the dependence of circular polarimetry on fractionation along the line of sight is investigated and it is shown that the form of its spectrum, together with the sign of the position angle shift, indicates where along the line of sight the icy material lies. More specifically, a coincidence between the sign of the position angle displacement in the ice feature, measured north through east, and that of the circular polarization ice feature means that the icy grains are overlaid by bare grains. Some preliminary circular polarimetry of BN has this characteristic, and a similar situation is found in the only two other cases for which relevant observations so far exist.

The Becklin-Neugebauer Object as a Runaway B Star, Ejected 4000 Years Ago from the 1 Orionis C System

We attempt to explain the properties of the Becklin-Neugebauer (BN) object as a runaway B star, as originally proposed by Plambeck et al. This is one of the best-studied bright infrared sources, located in the Orion Nebula Cluster—an important testing ground for massive star formation theories. From radio observations of the BN object's proper motion, we trace its trajectory back to Trapezium star θ1 Ori C, the most massive (45 M☉) in the cluster and a relatively tight (17 AU) visual binary with a B star secondary. This origin would be the most recent known runaway B star ejection event, occurring only ~4000 years ago and providing a unique test of ejection models. Although highly obscured, we can constrain the BN object's mass (7 M☉) from both its bolometric luminosity and the recoil of θ1 Ori C. Interaction of a runaway B star with dense ambient gas should produce a compact wind bow shock. We suggest that X-ray emission from this shocked gas may have been seen by Chandra: the offset from the radio position is 300 AU in the direction of the BN object's motion. Given this model, we constrain the ambient density, wind mass-loss rate, and wind velocity. The BN object made its closest approach to the massive protostar, source I, 500 years ago. This may have triggered enhanced accretion and thus outflow, consistent with previous interpretations of the outflow being a recent (~103 yr) explosive event.

Spectropolarimetry of the 3 Micron Ice Feature toward the Becklin-Neugebauer Object

view Abstract Citations (33) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectropolarimetry of the 3 Micron Ice Feature toward the Becklin-Neugebauer Object Hough, J. H. ; Chrysostomou, A. ; Messinger, D. W. ; Whittet, D. C. B. ; Aitken, D. K. ; Roche, P. F. Abstract We present spectropolarimetry of the 3.1 μm water-ice feature in the Becklin-Neugebauer (BN) object in OMC-1, with spectral resolution and signal-to-noise ratios substantially improved over previous observations. The well-known increase in polarization within the ice feature is interpreted in terms of a model for aligned graphite and silicate grains with ice mantles. We identify polarization structure in the long-wavelength (3.3-3.6 μm) wing of the ice profile, including a feature at 3.47 μm which matches closely the spectroscopic feature discovered in several protostars and attributed to carbonaceous material with diamond-like structure. We also show, for the first time, the occurrence of a systematic variation in the position angle of polarization across the ice feature in BN, indicating systematic differences in the relative numbers of core-mantle and unmantled grains along the line of sight, and a twist in the magnetic field orientation. Publication: The Astrophysical Journal Pub Date: April 1996 DOI: 10.1086/177111 Bibcode: 1996ApJ...461..902H Keywords: ISM: DUST; EXTINCTION; INFRARED: ISM: LINES AND BANDS; ISM: INDIVIDUAL ALPHANUMERIC: OMC-1; POLARIZATION full text sources ADS | data products SIMBAD (2)

Infrared extinction and polarization due to partially aligned spheroidal grains - Models for the dust toward the BN object

We describe methods for computing the extinction and polarization due to partially aligned, precessing, spheroidal grains in the dipole approximation regime. These techniques are applied to develop models for the dust on th line of sight to the Becklin-Neugebauer (BN) object. The models, utilizing a mixture of graphite and silicate particles, some coated with ice mantles, are found to be capable of reproducing all important features of spectroscopic and polarimetric observations in the spectral range 2< or approx. =lambda< or approx. =13 ..mu..m. The models suggest, however, that the abundance of graphite grains relative to silicate grains may be somewhat smaller than suggested by the Mathis-Rumpl-Nordsieck model for the dust in diffuse clouds; possible reasons for this are discussed. The observed polarization variation across the 9.7 ..mu..m silicate feature appears to require silicate grains of oblate, rather than prolate, shape. The core/mantle grains are generally required to be more highly aligned than bare grains. We are able to place limits on the mean size of the graphite grains (0.1< or approx. =a< or approx. =0.3 ..mu..m) and on the mantle-to-core volume ratio (0.5< or approx. =V/sub m//V/sub c/< or approx. =5) for core/mantle grains. The intrinsic spectrum of the BNmore » object is inferred from the observed flux distribution and calculation and calculated optical depths; the inferred intrinsic spectrum may be satisfactorily represented by blackbody radiation with Troughly-equal1100 K plus optically thin emission from dust with Troughly-equal450 K. The total luminosity of the BN object is estimated to be about 5 x 10/sup 3/ L/sub sun/.« less

Observations of Brackett-alpha emission in the region of the BN object

view Abstract Citations (19) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of Brackett-alpha emission in the region of the BN object. Joyce, R. R. ; Simon, M. ; Simon, T. Abstract The hydrogen B-alpha emission around the region of the Becklin-Neugebauer (BN) object has been mapped. An extended distribution of B-alpha emission around the BN object has been found. This emission appears to arise in the foreground nebula M42. A local maximum of B-alpha emission at the BN object has been observed whose strength is in quantitative agreement with previous observations by Grasdalen (1976). A marginal detection of the B-gamma line toward BN suggests the visual extinction may be approximately 35 mag to the object. Publication: The Astrophysical Journal Pub Date: February 1978 DOI: 10.1086/155890 Bibcode: 1978ApJ...220..156J Keywords: Infrared Radiation; Nebulae; Radiation Distribution; Spectral Emission; Astronomical Maps; Hydrogen Atoms; Interstellar Extinction; Radiative Recombination; Astronomy; Infrared Sources:Brackett Alpha full text sources ADS |

Detection of molecular hydrogen quadrupole emission in the Orion Nebula

view Abstract Citations (244) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Detection of molecular hydrogen quadrupole emission in the Orion nebula. Gautier, T. N., III ; Fink, U. ; Treffers, R. R. ; Larson, H. P. Abstract Seven lines of the 1-0 vibration-rotation quadrupole spectrum of H2 were detected around the Becklin-Neugebauer (BN) object and in a part of the Kleinmann-Low nebula 10" south of BN. The surface brightness of the S(1) line was found to be 3.0+-0.5 x 1e-3 ergs cm-2 s-1 sr-1 for the region around BN. Analysis showed that a thermal excitation model gives a good fit to the observed line intensities with a temperature of approximately 2000K. A column density for H2 of 9.4 +- 1.5 x 1e18 cm-2 was derived with this temperature. Publication: The Astrophysical Journal Pub Date: July 1976 DOI: 10.1086/182195 Bibcode: 1976ApJ...207L.129G Keywords: Emission Spectra; Hydrogen Clouds; Interstellar Gas; Molecular Gases; Nebulae; Astronomical Models; Brightness; Gas Density; Molecular Excitation; Astrophysics full text sources ADS |

2.2- and 3.5-MICRON Polarization Measurements of the Becklinneugebauer Object in the Orion Nebula

Independent measurements of the Becklin-Neugebauer (BN) object in the Orion Nebula yield large values of linear polarization in wavelength bands centered at 2.2 and 3.4 microns. The 10 to 15% polarization at 2.2 microns of the BN object is larger than any yet measured for an extraterrestrial object. The large polarization probably originates from the scattering of the radiation by dust grains.