scholarly journals A high-velocity component to the complex absorption in IRAS 13349+2438

2018 ◽  
Vol 480 (2) ◽  
pp. 2365-2376 ◽  
Author(s):  
M L Parker ◽  
G A Matzeu ◽  
M Guainazzi ◽  
E Kalfountzou ◽  
G Miniutti ◽  
...  
Keyword(s):  
Velocity Component ◽  
High Velocity

scholarly journals Spectroscopic diagnostics of T Tauri inner winds

2007 ◽  
Vol 3 (S243) ◽  
pp. 171-182 ◽  
Author(s):  
Suzan Edwards
Keyword(s):  
Velocity Component ◽  
High Velocity ◽  
T Tauri Stars ◽  
Interaction Region ◽  
Spectroscopic Diagnostics ◽  
T Tauri ◽  
Spectral Diagnostics ◽  
Launch Site ◽  
Wide Range

AbstractThe role of the star-disk interaction region in launching the high velocity component of accretion-driven outflows is examined. Spectroscopic indicators of high velocity inner winds have been recognized in T Tauri stars for decades, but identifying the wind launch site and the accompanying mass loss rates has remained elusive. A promising new diagnostic is He I λ10830, whose metastable lower level results in a powerful probe of the geometry of the outflowing gas in the interaction region. This, together with other atomic and molecular spectral diagnostics covering a wide range of excitation and ionization states, suggests that more than one launch site of the innermost wind is operational in most accreting stars.

Detection of 21-CENTIMETER Hydrogen Absorption in the High-Velocity Component of the Radio Galaxy Perseus a

1973 ◽  
Vol 185 ◽  
pp. 809 ◽  
Author(s):  
David S. de Young ◽  
Morton S. Roberts ◽  
William C. Saslaw
Keyword(s):  
Velocity Component ◽  
High Velocity ◽  
Hydrogen Absorption ◽  
Radio Galaxy

scholarly journals Connection between jets, winds and accretion in T Tauri stars

2018 ◽  
Vol 609 ◽  
pp. A87 ◽  
Author(s):  
B. Nisini ◽  
S. Antoniucci ◽  
J. M. Alcalá ◽  
T. Giannini ◽  
C. F. Manara ◽  
...  
Keyword(s):  
Mass Loss ◽  
Velocity Component ◽  
High Velocity ◽  
T Tauri Stars ◽  
Young Stars ◽  
Low Velocity ◽  
Star Forming ◽  
Average Value ◽  
T Tauri ◽  
Accretion Rates

Mass loss from jets and winds is a key ingredient in the evolution of accretion discs in young stars. While slow winds have been recently extensively studied in T Tauri stars, little investigation has been devoted on the occurrence of high velocity jets and on how the two mass-loss phenomena are connected with each other, and with the disc mass accretion rates. In this framework, we have analysed the [O i]6300 Å  line in a sample of 131 young stars with discs in the Lupus, Chamaeleon and σ Orionis star forming regions. The stars were observed with the X-shooter spectrograph at the Very Large Telescope and have mass accretion rates spanning from 10-12 to 10-7M⊙ yr-1. The line profile was deconvolved into a low velocity component (LVC, | Vr | < 40 km s-1) and a high velocity component (HVC, | Vr | > 40 km s-1), originating from slow winds and high velocity jets, respectively. The LVC is by far the most frequent component, with a detection rate of 77%, while only 30% of sources have a HVC. The fraction of HVC detections slightly increases (i.e. 39%) in the sub-sample of stronger accretors (i.e. with log (Lacc/L⊙) >−3). The [O i]6300 Å  luminosity of both the LVC and HVC, when detected, correlates with stellar and accretion parameters of the central sources (i.e. L∗, M∗, Lacc, Ṁacc), with similar slopes for the two components. The line luminosity correlates better (i.e. has a lower dispersion) with the accretion luminosity than with the stellar luminosity or stellar mass. We suggest that accretion is the main drivers for the line excitation and that MHD disc-winds are at the origin of both components. In the sub-sample of Lupus sources observed with ALMA a relationship is found between the HVC peak velocity and the outer disc inclination angle, as expected if the HVC traces jets ejected perpendicularly to the disc plane. Mass ejection rates (Ṁjet) measured from the detected HVC [O i]6300 Å  line luminosity span from ~10-13 to ~10-7M⊙ yr-1. The corresponding Ṁjet/Ṁacc  ratio ranges from ~0.01 to ~0.5, with an average value of 0.07. However, considering the upper limits on the HVC, we infer a Ṁjet/Ṁacc  ratio < 0.03 in more than 40% of sources. We argue that most of these sources might lack the physical conditions needed for an efficient magneto-centrifugal acceleration in the star-disc interaction region. Systematic observations of populations of younger stars, that is, class 0/I, are needed to explore how the frequency and role of jets evolve during the pre-main sequence phase. This will be possible in the near future thanks to space facilities such as the James Webb space telescope (JWST).

Are There Many More Small Meteors Than Hitherto Detected?

1986 ◽  
Vol 6 (4) ◽  
pp. 436-439
Author(s):  
D. I. Olsson-Steel ◽  
W. G. Elford
Keyword(s):  
Solar System ◽  
Velocity Component ◽  
High Velocity ◽  
Alternative Hypothesis ◽  
Height Distribution ◽  
Recent Past ◽  
Zodiacal Light ◽  
Low Velocity ◽  
The Past ◽  
Meteor Trails

AbstractVisual meteors, due to impinging meteoroids of radius about 1 cm, appear at a rate of a few per hour during non-shower periods. Smaller meteoroids (100 μm – 1 cm) give rise to less bright trails, but are much more abundant. These are usually detected by radars of about 10 m wavelength which, over the past 40 years, have produced a plethora of information concerning mass and height distributions, orbits, etc.Using such ‘conventional radars’, the peak of the measured height distribution is found at about 95 km, with few meteors detected above 105 km. However, the flux detected is only a few percent of the total flux (a) measured using a large (10 m) optical collector, and (b) expected from a comparison with measurements by satellite impacts and zodiacal light observations (radii < 100 μm). One possibility is that the radars detect few low-velocity (V < ~25 km s-1) meteors since these produce little ionization and thus limit their detectability: the ionizing efficiency of meteors varies as ~ V7/2. In direct opposition, our alternative hypothesis is that the undetected flux is held in a faint high-velocity component which ablates at high altitude. These are not detected by conventional radars because meteor trails have ‘initial widths’ of about 3 m at 105 km; for a radar wavelength of 10 m, components scattered from different regions of the trail therefore destructively interfere, and the probability of detecting any meteor above 105 km is small.In order to test our hypothesis we have measured the height distribution with a 150 m radar, and we are commencing ancillary observations at 50 m; compared to these wavelengths the initial width is small to at least 140 km. The results show a peak at 105 km with most meteors being above this, significant numbers occurring right up to 140 km. This suggests that the true flux is at least 10 or 20 times that previously deduced, having implications for the number of cornets in the recent past and the balance of material between the smaller bodies in the solar System.

scholarly journals Detection of a second high-velocity component in the highly ionized wind from PG 1211+143

2016 ◽  
Vol 457 (3) ◽  
pp. 2951-2957 ◽  
Author(s):  
Ken Pounds ◽  
Andrew Lobban ◽  
James Reeves ◽  
Simon Vaughan
Keyword(s):  
Velocity Component ◽  
High Velocity

scholarly journals The structure of the molecular envelope around CRL 2688

1997 ◽  
Vol 180 ◽  
pp. 375-376
Author(s):  
I. Yamamura ◽  
S. Deguchi ◽  
T. Kasuga
Keyword(s):  
Optical Depth ◽  
Opposite Direction ◽  
Velocity Component ◽  
High Velocity ◽  
Spherical Shape ◽  
Beam Size ◽  
The Core ◽  
Spherical Core ◽  
Molecular Envelope ◽  
Velocity Channel

We have observed CRL 2688 (the Egg nebula) in the 13CO J = 1–0 and CS J = 1–0 and 2–1 lines by the Nobeyama Millimeter Array with a resolution of about 4″. The 13CO velocity channel maps show that emission consists of three components; a spherical core, an extended envelope, and a bipolar high-velocity component (Yamamura et al. 1995).A spherical shape of the core despite of the maximum optical depth of about the unity indicates that the disk-like structure, expected from the shape of the bipolar nebula, is smaller than the present beam size (corresponding to about 6 × 1016cm at 1kpc). The combined maps made from the data by the NMA and the Nobeyama 45-m telescope show that emission spreads towards the south of the center more then the opposite direction.

scholarly journals High-Dispersion Spectroscopy of IC 351 and NGC 3242, Planetaries by High Internal Motion

1993 ◽  
Vol 155 ◽  
pp. 379-379
Author(s):  
Y. Yadoumaru ◽  
S. Tamura
Keyword(s):  
Velocity Component ◽  
High Velocity ◽  
Intensity Ratio ◽  
Mass Loss Rate ◽  
The Other ◽  
High Dispersion ◽  
Expansion Velocity ◽  
Internal Motions ◽  
Line Intensity Ratio ◽  
Colliding Winds

We made high-dispersion spectroscopic observations of IC 351 = PK 159 − 15°1, a compact high-excitation planetary nebula. We found the expansion velocity from Hα, [OIII] and HeII line, of 45.1kms−1, 38.7kms−1, and 33.3kms−1, respectively. Moreover, for the Hα line we detected an additional faint blue-shifted component escaping from the center of expansion with high velocity of 120kms−1. This value is larger than the usual expansion velocity (< 50kms−1) but considerably smaller than that of stellar wind. This faint blue-shifted component of Hα is also coincidently identified as the helium line, HeIIλ6560 (Pickering 6). Using the emission coefficients of recombination lines (Case B, T= 10,000K; Osterbrock 1989), and the intensity ratio, I(HeIIλ4686)/I(Hβ)=0.56±0.05 (Aller&Czyzak 1979), we can estimate the expected line intensity ratio, I(HeIIλ6560)/I(Hα)=0.026±0.002. On the other hand, the intensity ratio of faint component to Hα in the present observations is estimated as Ifaintcomp./I(Hα)=0.064±0.013, based up the Hα profile in 1988. Comparing these two estimated intensity ratios it is clearly unable to emit the all intensity of the observed faint component by HeIIλ6560 line only. Therefore, even if this component is partly polluted by HeIIλ6560 line, we can consider the rest part as an emission from high velocity component of Hα. We can also recognize the bumped feature of [OIII]λ5007 line around the same velocity to the blue-shifted component of Hα. This fact supports the idea that these components can be attributed to the high velocity flow. We discuss the three ideas for the interpretation of such component; (a) colliding winds, (b) unresolved bipolar flow, and (c) secondary formation of an expanding shell. We have investigated whether the colliding winds model gives such high velocity or not. As the results of the calculation, if we use the usual mass-loss rate, the model can not give such high velocity. Therefore, it is doubtful that we can take this model as an explanation of the high velocity components. The high velocity component of IC 351 is not uncommon; such large internal motions are reported for other planetaries by Weinberger(1989) and compiled by Grewing(1989). The article on the results of IC 351 is submitted to PASP (Yadoumaru & Tamura 1992). We also report the other analysis on NGC 3242.

scholarly journals Velocities Within 1 Arcsec of the Nucleus of NGC 4151 as Revealed by the HST Faint Object Camera

1994 ◽  
Vol 159 ◽  
pp. 441-441
Author(s):  
R.M. Catchpole ◽  
A. Boksenberg ◽  
Keyword(s):  
Velocity Component ◽  
High Velocity ◽  
Hubble Space Telescope ◽  
Position Angle ◽  
Emission Lines ◽  
Low Velocity ◽  
Strong Emission ◽  
Ngc 4151 ◽  
Zero Velocity ◽  
Faint Object

We have obtained a longslit spectrum at a position angle (PA) of 84.6° and passing within 0.38 arcsec of the nucleus of NGC 4151, using the FOC f/48 camera on the Hubble Space Telescope. The spectrum shows strong emission lines including [OII] λ 3727 and [OIII] λλ 4959, 5007. By fitting with Gaussian velocity profiles, we resolve the emission lines, within 1 arcsec of the nucleus, into a high and low velocity component. The low velocity component has a total range in radial velocity of 200 km s−1 and appears to be associated with material comprising the knots seen in the FOC, F501N [O III] image of NGC 4151, illustrated in Boksenberg (1993). The much weaker high velocity system has a range of 1000 km s−1, is more smoothly distributed in brightness and shows a peak brightness close to the nucleus. Because the slit did not intersect the nucleus it is possible to determine the PA at which the two velocity systems cross the zero velocity axis. This is at PA −26° for the low velocity system and PA +32° for the high velocity system. These PA values may be subject to a systematic error as the zero velocity is defined by the mean position of the line, in the absence of any external calibration.

scholarly journals Erratum: Detection of a second high-velocity component in the highly ionized wind from PG 1211+143

2016 ◽  
Vol 464 (2) ◽  
pp. 2377-2377
Author(s):  
Ken Pounds ◽  
Andrew Lobban ◽  
James Reeves ◽  
Simon Vaughan
Keyword(s):  
Velocity Component ◽  
High Velocity

Galactic orbits of stars

1966 ◽  
Vol 25 ◽  
pp. 93-97
Author(s):  
Richard Woolley
Keyword(s):  
Globular Cluster ◽  
Potential Field ◽  
High Velocity ◽  
Velocity Vector ◽  
Variable Stars ◽  
The Sun ◽  
Proper Motions ◽  
Rr Lyrae ◽  
The Galaxy

It is now possible to determine proper motions of high-velocity objects in such a way as to obtain with some accuracy the velocity vector relevant to the Sun. If a potential field of the Galaxy is assumed, one can compute an actual orbit. A determination of the velocity of the globular clusterωCentauri has recently been completed at Greenwich, and it is found that the orbit is strongly retrograde in the Galaxy. Similar calculations may be made, though with less certainty, in the case of RR Lyrae variable stars.

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