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This paper presents the idea of an automatic forward-collision warning system based on a decentralized radio sensing (RS) approach. In this framework, a vehicle in receiving mode employs a continuous waveform (CW) transmitted by a second vehicle as a probe signal to detect oncoming vehicles and warn the driver of a potential forward collision. Such a CW can easily be incorporated as a pilot signal within the data frame of current multicarrier vehicular communication systems. Detection of oncoming vehicles is performed by a deep learning (DL) module that analyzes the features of the Doppler signature imprinted on the CW probe signal by a rapidly approaching vehicle. This decentralized CW RS approach was assessed experimentally using data collected by a series of field trials conducted in a two-lanes high-speed highway. Detection performance was evaluated for two different DL models: a long short-term memory network and a convolutional neural network. The obtained results demonstrate the feasibility of the envisioned forward-collision warning system based on the fusion of DL and decentralized CW RS.

OH231.8+4.2 is an archetypal pre-planetary nebulae (pPN). It is a binary system surrounded by bipolar nebula. Some years ago the authors extensively studied it and performed several VLBI observations from which they obtained mas-resolution maps of the SiO (7 mm) and H2O (1.3 cm) maser emissions. H2O masers were found to be distributed in two areas along the symmetry axis of the nebulae oriented nearly north-south delineating a bipolar outflow and their astrometric positions were accurately measured. SiO masers, indicating the position of the Mira component of the binary system, form a structure perpendicular to the axis of the nebulae. The general picture of the source looked satisfactory, except for the relative position of the two masers. Surprisingly, SiO masers, were tentatively placed 250 mas away (370 AU) from the apparent center of the outflow. Using the ALMA we observed the SiO maser emission at 86 GHz and accurately derived the position of the Mira component. Combining our previous VLBA data and our new ALMA observations we are now able to give a more complete and detailed description of the inner part of this amazing pPN., Comment: Accepted 6 pages, 2 figures 14th European VLBI Network Symposium & Users Meeting (EVN 2018)8-11 October 2018Granada, Spain - POS(EVN2018)-074

VLBI observations of SiO masers recover at most 40-50% of the total flux obtained by single dish observations at any spectral channel. Some previous studies seems to indicate that, at least, part of the lost flux is divided up into many weak components rather than in a large resolved emission area. Taking benefit of the high sensitivity and resolution of the HSA, we investigate the problem of the missing flux in VLBI observations of SiO maser emission at 7mm in the AGB stars and obtain a high dynamic range map of IRC+10011. We conclude that the missing flux is mostly contained in many very weak maser components., Comment: 2 pages, 1 figure, to appear in proceedings of IAU Symposium 336 "Astrophysical Masers: Unlocking the Mysteries of the Universe", Editors: A. Tarchi, M. J. Reid & P. Castangia

Very long baseline interferometry at millimetre/submillimetre wavelengths (mmVLBI) offers the highest achievable spatial resolution at any wavelength in astronomy. The anticipated inclusion of ALMA as a phased array into a global VLBI network will bring unprecedented sensitivity and a transformational leap in capabilities for mmVLBI. Building on years of pioneering efforts in the US and Europe the ongoing ALMA Phasing Project (APP), a US-led international collaboration with MPIfR-led European contributions, is expected to deliver a beamformer and VLBI capability to ALMA by the end of 2014 (APP: Fish et al. 2013, arXiv:1309.3519). This report focuses on the future use of mmVLBI by the international users community from a European viewpoint. Firstly, it highlights the intense science interest in Europe in future mmVLBI observations as compiled from the responses to a general call to the European community for future research projects. A wide range of research is presented that includes, amongst others: - Imaging the event horizon of the black hole at the centre of the Galaxy - Testing the theory of General Relativity an/or searching for alternative theories - Studying the origin of AGN jets and jet formation - Cosmological evolution of galaxies and BHs, AGN feedback - Masers in the Milky Way (in stars and star-forming regions) - Extragalactic emission lines and astro-chemistry - Redshifted absorption lines in distant galaxies and study of the ISM and circumnuclear gas - Pulsars, neutron stars, X-ray binaries - Testing cosmology - Testing fundamental physical constants, Comment: Replaced figures 2 and 3: corrected position SRT. Corrected minor typo in 5.1

The v=1 and v=2 J=1-0 (43 GHz), and v=1 J=2-1 (86 GHz) SiO masers are intense in AGB stars and have been mapped using VLBI showing ring-like distributions. Those of the v=1, v=2 J=1-0 masers are similar, but the spots are rarely coincident, while the v=1 J=2-1 maser arises from a well separated region farther out. These relative locations can be explained by models tools that include the overlap of two IR lines of SiO and H2O. The v=3 J=1-0 line is not directly affected by any line overlap and its spot structure and position, relative to the other lines, is a good test to the standard pumping models. We present single-dish and simultaneous VLBI observations of the v=1, v=2, and v=3 J=1-0 maser transitions of 28SiO in several AGB stars. The spatial distribution of the SiO maser emission in the v=3 J=1-0 transition from AGB stars is systematically composed of a series of spots that occupy a ring-like structure. The overall ring structure is extremely similar to that found in the other 43 GHz transitions and is very different from the structure of the v=1 J=2-1 maser. The positions of the individual spots of the different 43 GHz lines are, however, very rarely coincident, which in general is separated by about 0.3 AU (between 1 and 5 mas). These results are very difficult to reconcile with standard pumping models, which predict that the masers of rotational transitions within a given vibrational state require very similar excitation conditions, while the transitions of different vibrational states should appear in different positions. However, models including line overlap tend to predict v=1, v=2, v=3 J=1-0 population inversion to occur under very similar conditions, while the requirements for v=1 J=2-1 appear clearly different, and are compatible with the observational results., Comment: 9 pages, 4 figures accepted by A&A

Aims. We investigate the different manifestations of AGN feedback in the evolved, powerful radio source 3C293 and their impact on the molecular gas of its host galaxy, which harbors young star-forming regions and fast outflows of HI and ionized gas. Methods. We study the distribution and kinematics of the molecular gas of 3C293 using high spatial resolution observations of the CO(1-0) and CO(2-1) lines, and the 3 and 1mm continuum taken with the IRAM PdBI. We mapped the molecular gas of 3C293 and compared it with the dust and star-formation images of the host. We searched for signatures of outflow motions in the CO kinematics, and reexamined the evidence of outflowing gas in the HI spectra. We also derived the star formation rate (SFR) and efficiency (SFE) of the host with all available SFR tracers from the literature, and compared them with the SFE of young and evolved radio galaxies and normal star-forming galaxies. Results. The CO(1-0) emission line shows that the molecular gas in 3C293 is distributed along a massive (2.2E10 Msun) warped disk with diameter of 21 kpc that rotates around the AGN. Our data show that the dust and the star formation are clearly associated with the CO disk. The CO(2-1) emission is located in the inner 7 kpc (diameter) region around the AGN, coincident with the inner part of the CO(1-0) disk. Both the CO(1-0) and CO(2-1) spectra reveal the presence of an absorber against the central regions of 3C293 that is associated with the disk. We do not detect any fast (>500 km/s) outflow motions in the cold molecular gas. The host of 3C293 shows an SFE consistent with the Kennicutt-Schmidt law. The apparently low SFE of evolved radio galaxies may be caused by an underestimation of the SFR and/or an overestimation of the molecular gas densities in these sources. We find no signatures of AGN feedback in the molecular gas of 3C293., Comment: Accepted in A&A. 18 pages, 15 figures

We study the physical properties and molecular excitation of the different warm gas components found in the protoplanetary nebula CRL 618. We revise our previous Herschel/HIFI observations, which consist of several 12CO and 13CO lines in the far-infrared/sub-mm band. These data have been re-analyzed in detail by improving calibration, the signal-to-noise-ratio, and baseline substraction. We identify the contributions of the different nebular components to the line profiles. We have used a spatio-kinematical model to better constrain the temperature, density, and kinematics of the molecular components probed by the improved CO observations. The 12CO and 13CO J=16-15, J=10-9, and J=6-5 transitions are detected in this source. The line profiles present a composite structure showing spectacular wings in some cases, which become dominant as the energy level increases. Our analysis of the high-energy CO emission with the already known low-energy J=2-1 and J=1-0 lines confirms that the high-velocity component, or fast bipolar outflow, is hotter than previously estimated with a typical temperature of ~300 K. This component may then be an example of a very recent acceleration of the gas by shocks that has not yet cooled down. We also find that the dense central core is characterized by a very low expansion velocity, ~5 km/s, and a strong velocity gradient. We conclude that this component is very likely to be the unaltered circumstellar layers that are lost in the last AGB phase, where the ejection velocity is particularly low. The physical properties of the other two nebular components, the diffuse halo and the double empty shell, more or less agrees with the estimations derived in previous models., Comment: Accepted for publication in Astronomy & Astrophysics. 8 pages, 3 figures

Aims: We study the emission of molecular gas in 3C236, a FR II radio source at z~0.1, and search for the footprints of AGN feedback. 3C236 shows signs of a reactivation of its AGN triggered by a recent minor merger episode. Observations have also previously identified an extreme HI outflow in this source. Methods: The IRAM PdBI has been used to study the distribution and kinematics of molecular gas in 3C236 by imaging with high spatial resolution the emission of the 12CO(2-1) line in the nucleus of the galaxy. We have searched for outflow signatures in the CO map. We have also derived the SFR in 3C236 using data available from the literature at UV, optical and IR wavelengths, to determine the star-formation efficiency of molecular gas. Results: The CO emission in 3C236 comes from a spatially resolved 2.6 kpc disk with a regular rotating pattern. Within the limits imposed by the sensitivity and velocity coverage of the CO data, we do not detect any outflow signatures in the cold molecular gas. The disk has a cold gas mass M(H2)~2.1x10^9 Msun. We determine a new value for the redshift of the source zCO=0.09927. The similarity between the CO and HI profiles indicates that the deep HI absorption in 3C236 can be accounted for by a rotating HI structure, restricting the evidence of HI outflow to the most extreme velocities. In the light of the new redshift, the analysis of the ionized gas kinematics reveals a 1000 km/s outflow. As for the CO emitting gas, outflow signatures are nevertheless absent in the warm molecular gas emission traced by infrared H2 lines. The star-formation efficiency in 3C236 is consistent with the value measured in normal galaxies, which follow the canonical KS-law. This result, confirmed to hold in other young radio sources examined in this work, is in stark contrast with the factor of 10-50 lower SFE that seems to characterize evolved powerful radio galaxies., Comment: 14 pages, 11 figures, 2 tables. Accepted for publication in A&A

We present the results of SiO maser observations at 43GHz toward two AGB stars using the VLBA. Our preliminary results on the relative positions of the different J=1-0 SiO masers (v=1,2 and 3) indicate that the current ideas on SiO maser pumping could be wrong at some fundamental level. A deep revision of the SiO pumping models could be necessary., Comment: poster, 2 pages, 2 figures, Proc. IAU Symp. 287 "Cosmic Masers: from OH to H0", R.S. Booth, E.M.L. Humphreys and W.H.T. Vlemmings, eds

Red supergiant stars (RSGs) and yellow hypergiant stars (YHGs) are believed to be the high-mass counterparts of stars in the AGB and early post-AGB phases. We study the mass-loss in the post main-sequence evolution of massive stars, through the properties of their envelopes in the intermediate and warm gas layers. These are the regions where the acceleration of the gas takes place and the most recent mass-loss episodes can be seen. We used the HIFI instrument on-board the Herschel Space Observatory to observe sub-mm and FIR transitions of CO, water, and their isotopologues in a sample of two RSGs (NML Cyg and Betelgeuse) and two YHGs (IRC+10420 and AFGL 2343) stars. We present an inventory of the detected lines and analyse the information revealed by their spectral profiles. On the basis of the results presented in an earlier study, we model the CO and 13CO emission in IRC+10420 and compare it to a set of lines ranging from the mm, to the FIR. Red supergiants have stronger high-excitation lines than the YHGs, indicating that they harbour dense and hot inner shells contributing to these transitions. Consequently, these high-J lines in RSGs originate from acceleration layers that have not yet reached the circumstellar terminal velocity and have narrower profiles than their flat-topped lower-J counterparts. The YHGs tend to lack this inner component, in line with the picture of detached, hollow envelopes derived from studies at longer wavelengths. NH3 is only detected in two sources (NML Cyg, IRC+10420), which are also observed to be the strongest water-line emitters of the studied sample. In contrast, OH is detected in all sources and does not seem to correlate with the water line intensities. We show that the IRC+10420 model derived solely from mm low-J CO transitions is capable of reproducing the high-J transitions when the temperature in the inner shell is simply lowered by about 30%., Comment: 14 pages, 13 figures, accepted in Astronomy and Astrophysics

We performed Herschel/HIFI observations of intermediate-excitation molecular lines in the far-infrared/submillimeter range in a sample of ten protoplanetary nebulae and young planetary nebulae. The high spectral resolution provided by HIFI yields accurate measurements of the line profiles. The observation of these high-energy transitions allows an accurate study of the excitation conditions, particularly in the warm gas, which cannot be properly studied from the low-energy lines. We have detected FIR/sub-mm lines of several molecules, in particular of 12CO, 13CO, and H2O. Emission from other species, like NH3, OH, H2^{18}O, HCN, SiO, etc, has been also detected. Wide profiles showing sometimes spectacular line wings have been found. We have mainly studied the excitation properties of the high-velocity emission, which is known to come from fast bipolar outflows. From comparison with general theoretical predictions, we find that CRL 618 shows a particularly warm fast wind, with characteristic kinetic temperature Tk >~ 200 K. In contrast, the fast winds in OH 231.8+4.2 and NGC 6302 are cold, Tk ~ 30 K. Other nebulae, like CRL 2688, show intermediate temperatures, with characteristic values around 100 K. We also discuss how the complex structure of the nebulae can affect our estimates, considering two-component models. We argue that the differences in temperature in the different nebulae can be due to cooling after the gas acceleration (that is probably due to shocks); for instance, CRL 618 is a case of very recent acceleration, less than ~ 100 yr ago, while the fast gas in OH 231.8+4.2 was accelerated ~ 1000 yr ago. We also find indications that the densest gas tends to be cooler, which may be explained by the expected increase of the radiative cooling efficiency with the density., Comment: 24 pages, 31 figures

We performed Herschel/HIFI observations of several CO lines in the far-infrared/sub-mm in the protoplanetary nebula CRL618. The high spectral resolution provided by HIFI allows measurement of the line profiles. Since the dynamics and structure of the nebula is well known from mm-wave interferometric maps, it is possible to identify the contributions of the different nebular components (fast bipolar outflows, double shells, compact slow shell) to the line profiles. The observation of these relatively high-energy transitions allows an accurate study of the excitation conditions in these components, particularly in the warm ones, which cannot be properly studied from the low-energy lines. The 12CO J=16-15, 10-9, and 6-5 lines are easily detected in this source. 13CO J=10-9 and 6-5 are also detected. Wide profiles showing spectacular line wings have been found, particularly in 12CO 16-15. Other lines observed simultaneously with CO are also shown. Our analysis of the CO high-J transitions, when compared with the existing models, confirms the very low expansion velocity of the central, dense component, which probably indicates that the shells ejected during the last AGB phases were driven by radiation pressure under a regime of maximum transfer of momentum. No contribution of the diffuse halo found from mm-wave data is identified in our spectra, because of its low temperature. We find that the fast bipolar outflow is quite hot, much hotter than previously estimated; for instance, gas flowing at 100 km/s must have a temperature higher than ~ 200 K. Probably, this very fast outflow, with a kinematic age < 100 yr, has been accelerated by a shock and has not yet cooled down. The double empty shell found from mm-wave mapping must also be relatively hot, in agreement with the previous estimate., Comment: 5 pages, 4 figures

The first images of 6.7-GHz methanol masers in the massive star-forming regions DR21(OH) and DR21(OH)N are presented. By measuring the shapes, radial velocities and polarization properties of these masers it is possible to map out the structure, kinematics and magnetic fields in the molecular gas that surrounds newly-formed massive stars. The intrinsic angular resolution of the observations was 43 mas (~100 AU at the distance of DR21), but structures far smaller than this were revealed by employing a non-standard mapping technique. This technique was used in an attempt to identify the physical structure (e.g. disc, outflow, shock) associated with the methanol masers. Two distinct star-forming centres were identified. In DR21(OH) the masers had a linear morphology, and the individual maser spots each displayed an internal velocity gradient in the same direction as the large-scale structure. They were detected at the same position as the OH 1.7-GHz ground-state masers, close to the centre of an outflow traced by CO and class I methanol masers. The shape and velocity gradients of the masers suggests that they probably delineate a shock. In DR21(OH)N the methanol masers trace an arc with a double-peaked profile and a complex velocity gradient. This velocity gradient closely resembles that of a Keplerian disc. The masers in the arc are 4.5% linearly polarized, with a polarization angle that indicates that the magnetic field direction is roughly perpendicular to the large-scale magnetic field in the region (indicated by lower angular resolution measurements of the CO and dust polarization). The suitability of channel-by-channel centroid mapping is discussed as an improved and viable means to maximise the information gained from the data., Comment: Accepted by MNRAS

The study of the innermost circumstellar layers around AGB stars is crucial to understand how these envelopes are formed and evolve. The SiO maser emission occurs at a few stellar radii from the central star, providing direct information on the stellar pulsation and on the chemical and physical properties of these regions. Our data also shed light on several aspects of the SiO maser pumping theory that are not well understood yet. We aim to determine} the relative spatial distribution of the 43 GHz and 86 GHz SiO maser lines in the oxygen-rich evolved star R Leo. We have imaged with milliarcsecond resolution, by means of Very Long Baseline Interferometry, the 43 GHz (28SiO v=1, 2 J=1-0 and 29SiO v=0 J=1-0) and 86 GHz (28SiO v=1 J=2-1 and 29SiO v=0 J=2-1) masing regions. We confirm previous results obtained in other oxygen-rich envelopes. In particular, when comparing the 43 GHz emitting regions, the 28SiO v=2 transition is produced in an inner layer, closer to the central star. On the other hand, the 86 GHz line arises in a clearly farther shell. We have also mapped for the first time the 29SiO v=0 J=1-0 emission in R Leo. The already reported discrepancy between the observed distributions of the different maser lines and the theoretical predictions is also found in R Leo., Comment: accepted for publication in A&A

We report the first VLBI map of the v=0 J=1-0 maser line of 29SiO in the long-period variable star IRC+10011. We have found that this maser emission is composed of multiple spots distributed in an incomplete ring, suggesting that this maser is also amplified tangentially, as already proposed in other SiO circumstellar masers. We present also VLBI maps for the 7 mm 28SiO v=1 and 2 J=1-0 and the 3 mm v=1 J=2-1 lines. The 29SiO masing region appears to be located in a layer in between the 28SiO v=1 J=1-0 and 28SiO v=1 J=2-1 lines. In addition, we confirm that the 86 GHz maser v=1 J=2-1 forms in an outer region of the circumstellar envelope compared to the other 28SiO masers studied. Finally, we discuss the possible implications of the observational results on the SiO maser pumping theory., Comment: 4 pages, 2 figures. Accepted for publication in A&A Letters

We report the first VLBI map of the 7 mm v=0 J=1-0 maser line of the 29-SiO isotopic substitution in the long period variable star IRC+10011. We have found that this maser emission is composed of multiple features distributed in an incomplete ring, suggesting that this maser is also amplified tangentially as already proposed in other SiO circumstellar masers. We present also the results for some 28-SiO 7 mm and 3 mm maser lines. We confirm in this epoch that the 86 GHz maser v=1 J=2-1 in IRC+10011 is formed in an outer region of the circumstellar envelope compared to the other SiO masers studied. The 29-SiO masing region appears to be located in a layer in between the 28-SiO v=1 J=1-0 and 28-SiO v=1 J=2-1 lines. Finally, we discuss the possible implications of the observational results in the SiO maser pumping theory., Comment: 4 pages. 7 figures. Proceedings of the 7th European VLBI Network Symposium held in Toledo, Spain on October 12-15, 2004. Editors: R. Bachiller, F. Colomer, J.-F. Desmurs, P. de Vicente (Observatorio Astronomico Nacional), p. 205-208. Needs evn2004.cls

We present sub-milliarcsecond observations of SiO masers in the late-type stars IRC +10011 and Chi Cyg. We have used the NRAO Very Long Baseline Array (VLBA) to map the 43 GHz (v=1, 2 J=1-0) and the 86 GHz (v=1, 2 J=2-1) SiO masers. All the transitions have been imaged except the v=2 J=2-1 in IRC +10011. We report the first VLBI map of the v=1 J=2-1 28SiO maser in IRC +10011 as well as the first VLBA images of SiO masers in an S-type Mira variable, Chi Cyg. In this paper we have focused on the study of the relative spatial distribution of the different observed lines. We have found that in some cases the observational results are not reproduced by the current theoretical pumping models, either radiative or collisional. In particular, for IRC +10011, the v=1 J=1-0 and J=2-1 28SiO lines have different spatial distributions and emitting region sizes, the J=2-1 emission being located in an outer region of the envelope. For Chi Cyg, the distributions also differ, but the sizes of the masing regions are comparable. We suggest that the line overlaps between ro-vibrational transitions of two abundant molecular species, H2O and 28SiO, is a possible explanation for the discrepancies found between the observations and the theoretical predictions. We have introduced this overlapping process in the calculations of the excitation of the SiO molecule. We conclude that the line overlaps can strongly affect the excitation of SiO and may reproduce the unexpected observational results for the two sources studied., Comment: 16 pages, 12 figures

On this paper, we present simultaneous VLBA observations of the J=1-0 and J=2-1 rotational lines in the v=1 and v=2 vibrationally excited states of SiO (at 7 and 3 mm wavelengths). We have mapped these four maser lines in the circumstellar envelopes of three AGB stars: IRC +10011, Chi Cyg and TX Cam. We study the relative spatial distribution between these maser lines. In particular, for the two v=1 transitions, we found that the J=1-0 and J=2-1 maser spot distributions are unalike, challenging all the current theoretical pumping mechanisms for SiO masers (which predict quite similar distribution for maser lines in the same vibrational excited state)., Comment: 5 page, 6 figures. To be published in "Future Directions in High Resolution Astronomy", ASP Conference Series

We present the first VLBI images of SiO masers in the circumstellar envelope of an S-type star obtained with the newly developed capabilities of the Very Long Baseline Array (VLBA) at 86 GHz. We combine these data with those obtained quasy simultaneously at 43 GHz. These observations provide information on the structure and dynamics of the innermost circumstellar shells, where the return of large quantities of stellar material to the interstellar medium starts. Despite of the fact that these are prelimininary results, we report that the maser emission of the $v$=1 J=1--0 and J=2--1 present a very different emission distribution, being not coincident in most case., Comment: Proceedings of the 6th European VLBI Network Symposium, Ros, E., Porcas, R.W., Lobanov, A.P., & Zensus, J.A. (eds.), MPIfR, Bonn, Germany (2002). 2 pages, 2 figures