Small Nebula Research Articles

A Binary Star in the Superbubble N160 in the Large Magellanic Cloud

Abstract We have made a spectroscopic investigation of the nature of 053949.17−693747.4, a blue star with mid-infrared excess, projected within a superbubble in the H ii complex N160 in the Large Magellanic Cloud (LMC). Analyses of photometric and spectrophotometric data of this star indicate that it is an O7 ± 1 V in the LMC. The radial velocity of this star from a 2010 spectrum shows an offset of ∼150 km s−1 from that of the background interstellar medium (ISM), while the spectra taken in 2020 show stellar velocity similar to the ISM velocity. The velocity variations indicate that 053949.17−693747.4 must be a binary system. The lack of spectroscopic features from a stellar companion and the large radial velocity variations of the primary O7 star imply that the companion is most likely an early-type B star. Hubble Space Telescope Hα and [O iii] images of 053949.17−693747.4 show a small nebula around the star with the southern rim resembling a blow-shock-like structure. While the physical nature as a bow shock cannot be robustly established, this small nebula is likely the cause of 053949.17−693747.4's mid-infrared excess. Spectroscopic monitoring over an entire binary period is needed to establish the period and systemic velocity to determine the properties of the binary companion and whether this binary system is a runaway.

Industrialiser l’Indochine (1898–1900)?:Entre “petite patrie” lyonnaise et réseaux à l’échelle du monde

Abstract The mooring of the Third French Republic, at the beginning of the 1880s, depended as much on the will of the Opportunistes—for the most part men linked to Gambetta—as on the Modérés, given that colonial expansionism represented a neutral terrain on which these men could meet. The local level, that of the petites patries, here Lyon, provides a methodological space to attempt to understand how this République des hommes d’affaires, to use Jean Garigue’s expression, constructed both the French Imperial project and the way to run this project. It allows us also to understand how the liberal lyonnaises elites—mercantile, industrial, and financial—played a role in shaping its economic implantation in Indochina, particularly in Tonkin and Annam. At the turn of the century, a small nebula of patrons and local politiques, of national and imperial dimension, gathered around Ulysse Pila—the Lyonnais paragon of colonization in East Asia and Southeast Asia—played a crucial role in the first phase of Indochinese industrialization. Their dynamism reveals a play which can be read on three levels: local (Lyon/Tonkin), national (France/Indochina), and international (Colonial empire/East Asia and Southeast Asia). More than a mere form of municipal imperialism, their commitment, both financial and ideological, allows the elucidation of a constructive network of the French patronat, on the eve of the Belle Époque.

A Morphological Study of UV-Bright Stars and Emission Nebulae in a Selection of Star Formation Regions in M31

ABSTRACTUsing the data from the NOAO Local Group Survey, we have measured the Hα fluxes of 291 nebulae associated with 21 of the van den Bergh OB associations. We have combined these data together with six-color HST WFPC2 photometry, in order to identify the most UV-bright stars in the region. The simple purpose of this article is to explore the spatial relationships between these components. We find that there are basically three types of Hα-hot star morphology. One type consists of a very bright H II region, with a tightly spaced group of hot stars at or near its center; we refer to these as monolithic structures. A second common arrangement is that of a ringlike bubble structure with an often-empty central area, where the hot stars are concentrated. We construct simple models of these objects, which show that their photometric profiles are like those of spherical shells. We refer to these as bubble structures A third morphology is a scattered distribution of small nebulae with a few hot stars that are widely spaced; these are called dispersed structures. We suggest that this sequence may be an evolutionary one.

Young Stars Associated with the Reflection Nebula NGC 2626

ABSTRACTWe have conducted a search for Hα emission‐line stars within the field containing the reflection nebula NGC 2626 and the associated dark cloud DC 259.9−0.0. Thirty‐two Hα stars, most of them newly discovered, have been identified. Magnitudes and colors for these stars are listed. Some are found to be variable and are possible T Tauri stars. Changes between 1991 and 1999 in the brightness and appearance of a small reflection nebula in the region are shown. These are caused by an unevenly obscured young stellar object which is the probable source of IRAS 08337−4028 and the Herbig‐Haro object HH 132. The overall morphology of the small nebula is strikingly similar to that of the well‐studied HH 46–47 configuration, but the NGC 2626 region is at about twice the distance.

Near‐Infrared Polarimetric Study of Monoceros R2 IRS

We present H- and Ks-band imaging polarimetry for the star-forming region Mon R2 IRS, and spectropolarimetry from 1.2 to 4.2 μm for the infrared sources IRS 2 and IRS 3. The nebular complex in Mon R2 IRS is revealed to be composed of four domains dominated by the infrared sources IRS 1, IRS 2, IRS 3, and IRS 6. IRS 2 is the predominant illuminating source in the region and dominates the emission of the IR ring and most of the western part of the nebulosity. IRS 1 is responsible for the enhanced unpolarized intensity in the southeast part of the IR ring and inside the IR ring. IRS 3 illuminates the bright eastern nebula, and together with IRS 2 illuminates the eastern region inside the IR ring. IRS 6 illuminates a small nebula to the south of the IR ring. An arc structure of polarized intensity is observed abutting the northwest IR ring, consistent with the outflow cavity structure inferred from millimeter-wave observations. IRS 3 is associated with a disklike condensation oriented southeast-northwest, perpendicular to the elongated eastern nebula. The magnetic field in the core region exhibits an hourglass structure oriented north-south.

IRAS Sources Associated With Small Nebulae in Star Forming Regions: Optical and Near Infrared Images

view Abstract Citations (42) References (51) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS IRAS Sources Associated With Small Nebulae in Star Forming Regions: Optical and Near Infrared Images Tapia, Mauricio ; Persi, Paolo ; Bohigas, Joaquin ; Ferrari-Toniolo, Marco Abstract Optical CCD and near-IR broad and narrow-band imaging have been obtained of a sample of 11 small optical nebula associated with IRAS sources in star forming regions in order to perform a morphological and photometric study. More than 130 sources were detected in K. The J-H versus H-K diagram was used to establish their nature. The most massive regions, Gy 2-18, Gy 4-2 and Gy 3-7, have embedded clusters of early-type stars and their associated nebulae were found to be photoionized. The IRAS sources in L1455, L1473, L1165 and Gy 4-1 with near-IR reflection nebulae were found to be Class I young stellar objects with associated molecular outflows. The results for each region is discussed in detail. Publication: The Astronomical Journal Pub Date: May 1997 DOI: 10.1086/118390 Bibcode: 1997AJ....113.1769T full text sources ADS | data products SIMBAD (67)

The nature of the compact X-ray source in the supernova remnant G27.4+0.0

High-resolution X-ray imaging data obtained with ROSAT is used to constrain the nature of the central compact source in the supernova remnant G27.4+0.0. Diffuse emission is seen from throughout the approximately 4 min diameter radio shell, while the central source remains unresolved at approximately 3 sec. We combine archival data from the Einstein HRI, IPC, and MPC with the ROSAT HRI data to define the X-ray spectra of the diffuse and point-like emission. The bulk of the shell radiation is consistent with that of a approximately 10(exp 7) K plasma, although a higher temperature component is also suggested by the data; coupled with the remnant's size and distance, we derive an age of between 500 and 2500 yr. The point source has a substantially harder spectrum, with a power-law photon index less than or approximately equal to 1. A search for periodic modulation from the point source yields upper limits ranging from 10%-35% for periods between 0.025 and 1000 s, depending on the assumed pulse shape. No aperiodic variability on timescales of from 10(exp 3) to 10(exp 8) s is required, although a factor of approximately 2 change between the Einstein and ROSAT eras is possible. We show that the point source cannot represent thermal emission from the surface of a young neutron star and is unlikely to be explained as nonthermal, Crab-like X-ray pulses or a small synchrotron nebula. The most likely models involve accretion-powered systems -- either a wind-fed neutron star with a massive companion or a low-mass X-ray binary. In all probability, this is the youngest X-ray binary in the Galaxy.

Distribution of Planetary Nebulae Perpendicular to the Disk

From an analytical solution to the Boltzmann-Poisson equations for a thin, vertically isothermal self-gravitating disk with the assumptions that the mass spectrum of stars is expressible as an inverse power-law and the velocity dispersion perpendicular to the plane follows a law of the form we have obtained a vertical height distribution of planetary nebulae: where being the potential at z. Figure 1 shows a normalised height distribution for various values of V0 where we have assumed a Salpeter slope, a ρ(o) = 0.10M⊙pc−3 and set m∗ = ml = 1.0m⊙. Figure 2 shows filled circles obtained from the observational sample of Daub (1982, ApJ 260, 612) superposed on the theoretical distributions. Although there is agreement for large values of z, closer to the plane the observational sample falls below the theoretical curves. Since the observational sample is size-limited, we may be missing a larger fraction of small nebulae closer to the plane. It is also possible a single value of Vo is not a correct representation of reality as these nebulae originate from stars of greatly differing ages and Vo may have changed over the lifetime of the Galactic disk.

On the nature of the symbiotic binary CI Cygni

An analysis of ultraviolet and optical spectroscopy is presented for the symbiotic binary CI Cyg. This system contains an M5 II asymptotic branch giant Mg of about 1.5 solar mass, transfering material at a few times 0.00001 solar mass/yr into a large accretion disk surrounding a main-sequence star with Mh of about 0.5 solar mass. A boundary layer at the inner edge of the disk photoionizes a small nebula approximately confined to the Roche volume of the accreting star. An extended, more highly ionized region forms when material ejected from the disk interacts with the red giant wind. 115 refs.

Bernes 48: An example of optically observed anisotropic outflow. I

The results are given of spectral investigation of the object Bernes 48 (RNO 129), which is an emission star with a very small cometary nebula. The star has spectral class G-K and has a moderately developed emission spectrum of T Tau type with conspicuous forbidden lines. The spectrum of the nebula differs from that of the star by a pronounced enhancement of the absorption lines of the Balmer series and reduction of all emissions. On the basis of the radial velocities, all the lines in the spectra of the star and the nebula can be divided into two systems, namely, all the allowed emission lines have a velocity of about +40 km/sec, while the forbidden emission lines and all absorption lines have one of about -140 km/sec. A preliminary phenomenological model of the object is proposed: a star with anisotropic ejection of matter and a bipolar nebula oriented almost along the line of sight.

CO and CS Observations in the Eastern Part of W5

At galactic longitudes between 132 and 139 degrees and distances of 2 to 2.5 kpc, the galactic disk contains an unusual concentration of gas clouds, young clusters and OB associations (W3, W4 and W5). The small nebula S 201 is situated to the east of W5, which contains the young open cluster IC 1848. Probably associated with S 201 is one of the originally proposed Bok globules; the region also contains three infrared sources.

First light from a young star?

The early phases of stellar evolution are frequently characterized by vigorous interaction between the nascent star and its environment, resulting in the formation of molecular outflows, highly collimated jets, Herbig-Haro objects and small emission or reflection nebulae. A deep survey of such small nebulae around young stars in the Orion molecular clouds has recently been completed1. We report here the sudden appearance of a highly variable, conical nebula (Object 50) 1.5 arc min south of a 250L⊙ infrared source in the southern part of the L1641 cloud in Orion. The nebula coincides with the edge of the approaching lobe of a 105-yr-old bipolar molecular outflow. Variability of the infrared source generates light pulses observed to propagate through the surrounding ambient cloud, producing a fluctuating illumination pattern. This emission may represent the first optical radiation to have emerged from this newborn star.

New Results on Eta Carinae. Evidence for an Asymmetric, Inhomogeneous Wind

The very peculiar object Eta Car is one of the best laboratory for the study of those physical processes - such as mass loss, superionization, dust condensation, wind interaction with the i.s. medium - that presently are of great astrophysical interest, especially for the study of the most luminous stars. For its light history and high luminosity Eta Car may also be considered as the galactic counterpart of the Hubble-Sandage variables. Eta Car is one of the rare astrophysical objects with evidence of dust condensation from ejected stellar matter (Andriesse et al. 78) On the other side the star is also producing a strong, hard X-ray flux (Chlebowski et al. 1984), and the problem is whether there is any physical reason to have these two quite different processes in the same stellar environment. In any case rather extreme physical conditions are required which cannot be verified in a uniformly, spherically symmetric atmospheric enevelope. Andriesse et al. in fact suggested the presence of strong inhomogeneities, such as filaments, possibly related to the presence of a strong magnetic field. This may also explain the X-ray emission. In the following we shall present new optical and UV observations of Eta Car and its small nebula with the aim of clearfying the physical nature of its wind.

Sandqvist 187 - A dense molecular cloud in Norma

Observations of Sandqvist 187, an elongated dust cloud in the southern constellation Norma are presented and discussed. The cloud contains two Herbig-Haro objects, HH 56 and HH 57. HH 57 currently displays on its NE edge a 17th mag variable star of the FU Ori type. Using the Columbia University 1.2 m millimeter-wave telescope at Cerro Tololo, the region is mapped and an extended CO cloud which envelops and is elongated along the optical dust cloud is found. The position of maximum CO emission coincides with HH 56 and HH 57. Assuming a distance of 0.7 kpc, the total mass of the cloud is found to be close to 500 solar masses. The CO spectra show evidence of a molecular flow. Photographs and CCD images obtained mostly with the CTIO 4 m telescope show the detailed optical structure of the dark cloud's core region. The Herbig-Haro object HH 56 appears to be related to an emission-line star embedded in the small nebula Reipurth 13, not to the FU Ori star in HH 57.

Einstein observations of VELA X and the VELA pulsar

The imaging detectors of the Einstein X-ray observatory have been used to study the Vela pulsar and its surrounding region. Although the pulsar is a relatively strong source of X-rays, there are not detectable pulsations at the pulsar period; the pulsed X-ray luminosity is less than approximately 10 to the 31st ergs/s in the 0.1-4.5 keV band. Nor is there evidence for other types of variability in the pulsar's X-ray emission. The images reveal structure on four spatial scales: (1) a pointlike object coincident with the pulsar; (2) a relatively bright, approximately 4-arcmin nebula of diffuse emission about the pulsar; (3) an approximately 1-degree nebula of hard emission that lies between the pulsar and the radio feature Vela X; and (4) thermal emission from the entire approximately 5-degree Vela supernova remnant. Spectral data from the small nebula are well fitted by a synchrotron model. Under the assumption that emission from the pulsar itself is thermal blackbody radiation, the surface temperature of the neutron star is calculated to be 1 million K.

High-spatial-resolution observation of the small planetary nebula IC 2165

The use of a rather large equivalent focal length in an attempt to obtain two-dimensional monochromatic images of the planetary nebula IC 2165, catalogued as a small, high-excitation object of 8 arcsec diameter, with a very faint and very hotcentral star, is reported. Due to the high spatial resolution of 0.047 arcsec/pixel and the seeing of 0.8 arcsec, detailed structures less than 1 arcsec could be distinguished. The nebula exhibits a more or less homogeneous spheroidal H-alpha image, while the forbidden N II isophote map displays four symmetrical condensations well separated in two lobes. It is concluded that the relative enhancement of forbidden N II in the peripheral zones could be explained by an abundance effect together with the strong collisional excitation due to the high electron density. 23 references.

EXOSAT LE-CMA observations of the Vela supernova remnant

Presented here are Exosat LE1-CMA images of fields in the Vela SNR. Soft X-ray emission is observed in the north of the remnant indicating a filamentry structure. No X-ray emission was seen in two fields to the west and south-west which have optical filaments but were not studied by Einstein. The Vela pulsar is observed and is significantly broader than a point source indicating the presence of a small nebula as seen by the Einstein HRI. The flux seen from the point source in the CMA is consistent with blackbody radiation from a 106 degree neutron star of approx. 10 km radius. A bright ridge of emission is seen north of the pulsar which may be part of the extended synchroton nebula seen in the 2–10 keV range.

Spectroscopic Observations of Z Andromedae and CI Cygni from 1968 to 1973

A description is given of the spectral changes observed in the symbiotic stars Z And and CI Cyg during the nova-like outbursts of 1968 and 1971–73. The observed features can be interpreted by assuming that transient shells are formed around the hot component of a binary system, imbedded in a small nebula.

INFRARED OBSERVATIONS OF NEW COMETARY NEBULAE

ABSTRACT An infrared photometric survey of small nebulae selected from the Palomar Sky Survey prints reveals that long wavelength radiation ( 10 ) is only detected from those objects with "cometary" morphology. The structure of the nebulae and the infrared properties of their associated stars suggest that cometary nebulae are young stars surrounded by a disk-like distribution of dust, which may be viewed at various inclinations. Key words: infrared radiation - cometary nebulae - dust disks

Small Nebulae Associated with Wolf-Rayet Stars.

view Abstract Citations (4) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Small Nebulae Associated with Wolf-Rayet Stars. Smith, Lindsey F. Abstract We now know of six Woif-Rayet (WR) stars that are situated at the center of curvature of an arc or arcs of nebulosity. All of these are WX stars; none are believed to be binary systems. Total masses have been derived for three of the nebulae from (a) total fluxes 9btained from 11-cm observations with the 2 10-ft radio telescope of the Australian X ational Radio Astronomical Observatory, (b) electron densities derived from spectra of the N3727 doublet, (c) photometric distances for the central WR stars. Similar data are given by Johnson and Hogg (Astrophys. J. 142, 1033, 1965) for two other nebulae, and their mass estimates have been revised in accord with the new photometric distances for the stars concerned. The derived masses range from 7 to 700 solar masses. The conclusions drawn by Johnson and Hogg are confirmed: (1) that the nebulae are in the form of extremely thin shells, and (2) that this characteristic shape may arise from a situation in which the interstellar matter is swept up by matter ejected from the WR star. Assuming that the nebulae are formed in this way, and assuming continuous ejection, the ages of the nebulae may be calculated for a range of values of the assumed rate of mass loss and velocity of ejection. The derived ages lie in the range 10~ to 106 yr for rates of mass loss between 10-~ and 10-6 solar masses per year. There is a monotonic relationship between the derived ages of the nebulae and their observed masses, in the sense that the more massive nebulae are older. This is reasonable since the formation, persistence and total mass of such a nebula will depend on the density of the interstellar medium in which the star is situated. The absence of nebulae associated with WC stars therefore implies either that the WC stars do not eject matter, or that they are situated in regions of low density of the interstellar gas. The latter explanation is favored. Publication: The Astronomical Journal Pub Date: September 1967 DOI: 10.1086/110559 Bibcode: 1967AJ.....72S.829S full text sources ADS |