Optical positions of radio emitting stars

Assafin, M.; Andrei, A. H.; Puliaev, S. P.; Jilinski, E. G.; Martins, R. Vieira; Vieira, G. G.; Oliveira, W. M. de

doi:10.1051/aas:1996160

Cited by 5 publications

(2 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the objects not observed by us, we have taken data from the literature. The final sample is defined in Tables 1 and 2, respectively for the sources for which the relevant CO data have been References : (s) Simbad database; (H) Hipparcos parallaxes; (0) this paper; (1) Jura et al (1995); (2) Kelly & Latter (1995); (3) Knapp et al (1995); (4) Roddier et al (1995); (5) López et al (1995); (6) Alcolea & Bujarrabal (1991); (7) Bujarrabal et al (1992); (8) Hrivnak (1995); (9) Meixner et al (1997); (10) Dayal et al (1998); (11) Yuasa et al (1999); (12) Sánchez Contreras et al (2000); (13) Sánchez Contreras et al (1997) and Kastner et al (1992); (14) Sahai et al (1999a); (15) Bujarrabal & Bachiller (1991); (16) Allen (1978); (17) Sahai et al (1999b); (18) Allen et al (1980); (19) Olofsson & Nyman (1999); (20) Trams et al (1990); (21) Sahai & Nyman (1997); (22) Andrei et al (1999) and Assafin et al (1996); (23) Knapp et al (1990);(24) De Marco & Crowther (1998); (25) Van der Veen et al (1989); (26) Cohen et al (1978); (27) Meaburn & Walsh (1985) and Redman et al (2000); (28) Quinn et al (1996); (29) Zweigle et al (1997); (30) Calvet & Cohen (1978) and Swings & Andrillat (1979); (31) …”

Section: Iras 23541+7031mentioning

confidence: 99%

Mass, linear momentum and kinetic energy of bipolar flows in protoplanetary nebulae

Bujarrabal

Castro-Carrizo

Alcolea

et al. 2001

A&A

268

356

View full text Add to dashboard Cite

Abstract.We have studied the CO emission from protoplanetary nebulae (PPNe). Our sample is composed of 37 objects and includes, we think, all well identified PPNe detected in CO, together with the two yellow hypergiants emitting in CO and one young PN. We present a summary of the existing CO data, including accurate new observations of the 12 CO and 13 CO J = 1-0 and J = 2-1 lines in 16 objects. We identify in the nebulae a slowly expanding shell (represented in the spectra by a central core) and a fast outflow (corresponding to the line wings), that in the well studied PPNe is known to be bipolar. Excluding poor data, we end up with a sample of 32 sources (including the 16 observed by us); fast flows are detected in 28 of these nebulae, being absent in only 4. We present a method to estimate from these data the mass, "scalar" momentum and kinetic energy of the different components of the molecular outflows. We argue that the uncertainties of our method can hardly lead to significant overestimates of these parameters, although underestimates may be present in not well studied objects. The total nebular mass is often as high as ∼1 M , and the mass-loss rate, that (presumably during the last stages of the AGB phase) originated the nebula, had typical values ∼10 −4 M yr −1 . The momentum corresponding to this mass ejection process in most studied nebulae is accurately coincident with the maximum momentum that radiation pressure, acting through absorption by dust grains, is able to supply (under expected conditions). We estimate that this high-efficiency process lasts about 1000-10 000 yr, after which the star has ejected a good fraction of its mass and the AGB phase ends. On the other hand, the fast molecular outflows, that have probably been accelerated by shock interaction with axial post-AGB jets, carry a significant fraction of the nebular mass, with a very high momentum (in most cases between 10 37 and 10 40 g cm s −1 ) and very high kinetic energy (usually between 10 44 and 10 47 erg). In general, yellow hypergiants and post-AGB objects with low initial mass show nebular masses and momenta that are, respectively, higher and lower than these values. We compare the momenta of the fast outflows with those that can be supplied by radiation pressure, taking into account the expected short acceleration times and some effects that can increase the momentum transfer. We find that in about 80% of PPNe, the fast molecular flows have too high momenta to be powered by radiation pressure. In some cases the momentum of the outflow is ∼1000 larger than that carried by radiation pressure; such high factors are difficult to explain even under exceptional conditions. Wind interaction is the basic phenomenon in the PN shaping from the former AGB envelopes; we conclude that this interaction systematically takes place along a dominant direction and that this process is not powered by radiation pressure. Due to the lack of theoretical studies, the possible momentum source remains a matter of speculation.

show abstract

Section: Iras 23541+7031mentioning

confidence: 99%

Mass, linear momentum and kinetic energy of bipolar flows in protoplanetary nebulae

Bujarrabal

Castro-Carrizo

Alcolea

et al. 2001

A&A

268

356

View full text Add to dashboard Cite

show abstract

“…We note that in the optical regime time-averaged data points are shown and their error bars indicate temporal variability. The data points are from the literature (Egret et al 1992;Kislyuk et al 2000;Zacharias et al 2004;Röser et al 2008;Zacharias et al 2012;Niels Bohr Institute et al 2014;Zacharias et al 2015;Morel & Magnenat 1978;Droege et al 2006;Henden et al 2016;Herbig & Bell 1988;Ahn et al 2012;Skiff 2014;Kraus et al 2011;Ayres 2010;Folha & Emerson 2001;Grankin et al 2007;Assafin et al 1996;Richichi & Percheron 2002;Richichi et al 2005;Connelley & Greene 2010;Cutri et al 2003;Bary et al 2009;Kóspál et al 2012;Luhman et al 2006;Cieza et al 2009;Salyk et al 2013;Cutri & et al 2014;Ishihara et al 2010;Yamamura et al 2010;Di Francesco et al 2008;Andrews et al 2013;Altenhoff et al 1994;Dzib et al 2015).…”

Section: Cold Absorbing Envelope In the Line Of Sightmentioning

confidence: 99%

Mid-infrared interferometric variability of DG Tauri: Implications for the inner-disk structure

Varga

Gabányi

Ábrahám

et al. 2017

A&A

View full text Add to dashboard Cite

Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic behavior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 µm silicate feature from emission to absorption temporarily. Aims. We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods. Infrared interferometry can spatially resolve the thermal emission of the circumstellar disk, also giving information about dust processing. We study the temporal variability of the mid-infrared interferometric signal, observed with the VLTI/MIDI instrument at six epochs between 2011 and 2014. We fit a geometric disk model to the observed interferometric signal to obtain spatial information about the disk. We also model the mid-infrared spectra by template fitting to characterize the profile and time dependence of the silicate emission. We use physically motivated radiative transfer modeling to interpret the mid-infrared interferometric spectra. Results. The inner disk (r < 1 − 3 au) spectra exhibit a 10 µm absorption feature related to amorphous silicate grains. The outer disk (r > 1 − 3 au) spectra show a crystalline silicate feature in emission, similar to the spectra of comet Hale-Bopp. The striking difference between the inner and outer disk spectral feature is highly unusual among T Tauri stars. The mid-infrared variability is dominated by the outer disk. The strength of the silicate feature changed by more than a factor of two. Between 2011 and 2014 the half-light radius of the mid-infrared-emitting region decreased from 1.15 to 0.7 au. Conclusions. For the origin of the absorption we discuss four possible explanations: a cold obscuring envelope, an accretion heated inner disk, a temperature inversion on the disk surface and a misaligned inner geometry. The silicate emission in the outer disk can be explained by dusty material high above the disk plane, whose mass can change with time, possibly due to turbulence in the disk.

show abstract

Astrometry with PRAIA

Assafin

2023

Planetary and Space Science

View full text Add to dashboard Cite

Optical positions of radio emitting stars

Cited by 5 publications

References 7 publications

Mass, linear momentum and kinetic energy of bipolar flows in protoplanetary nebulae

Mass, linear momentum and kinetic energy of bipolar flows in protoplanetary nebulae

Mid-infrared interferometric variability of DG Tauri: Implications for the inner-disk structure

Astrometry with PRAIA

Contact Info

Product

Resources

About