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281. VLTI observations of V4334 Sgr
ID:
ivo://CDS.VizieR/J/A+A/493/L17
Title:
VLTI observations of V4334 Sgr
Short Name:
J/A+A/493/L17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high spatial resolution observations in the mid-infrared of the Sakurai's object (V4334 Sgr) obtained with the Very Large Telescope Interferometer (VLTI) of ESO's Paranal Observatory and MIDI, the MID-infrared Interferometric recombiner. MIDI combines the light of two telescopes and provides spectrally resolved visibilities in the N band atmospheric window. The optical interferometry data are used in the paper from Chesneau et al. entitled "A dense disk of dust around the born-again Sakurai's object" and are available in OI-FITS format. The data were recorded in June 2007 under rather good atmospheric conditions and were reduced with the EWS package. The data set contains 6 spectrally dispersed calibrated visibilities and 6 differential phases. The files include all visibility data recorded from these observations as well as all the characteristics concerning the observations in the form of two OI-FITS files, for each night of observation. The log of the observations is shown in Table 1. The data products are stored in the FITS-based, optical interferometry data exchange format (OI-FITS), described in Pauls et al. (2005PASP..117.1255P). The OI Exchange Format is a standard for exchanging calibrated data from optical (visible/infrared) stellar interferometers. The standard is based on the Flexible Image Transport System (FITS), and supports storage of the optical interferometric observations including visibilities and differential phases. Several routines to read and write this format in various languages can be found in: Webpage http://www.mrao.cam.ac.uk/~jsy1001/exchange .
282. Water maser emission toward post-AGB and PN
ID:
ivo://CDS.VizieR/J/A+A/578/A119
Title:
Water maser emission toward post-AGB and PN
Short Name:
J/A+A/578/A119
Date:
21 Oct 2021
Publisher:
CDS
Description:
Water maser emission at 22GHz is a useful probe for studying the transition between the nearly spherical mass loss in the asymptotic giant branch (AGB) to a collimated one in the post-AGB phase. In their turn, collimated jets in the post-AGB phase could determine the shape of planetary nebulae once photoionization starts. We intend to find new cases of post-AGB stars and planetary nebulae (PNe) with water maser emission, including some especially interesting and rare types: water fountains (evolved objects with high velocity collimated jets traced by water masers) or water-maser-emitting PNe. Since previous studies have shown a higher detection rate of water maser emission in evolved objects that are optically obscured, we selected a sample that contains a significant fraction of post-AGB and young PN candidate sources showing signs of strong obscuration. We searched for water maser emission in 133 evolved objects using the radio telescopes in Robledo de Chavela, Parkes, and Green Bank. We detected water maser emission in 15 sources of our sample, of which seven are reported here for the first time (IRAS 13483-5905, IRAS 14249-5310, IRAS 15408-5413, IRAS 17021-3109, IRAS 17348-2906, IRAS 17393-2727, and IRAS 18361-1203). We identified three water fountain candidates: IRAS 17291-2147, with a total velocity spread of =~96km/s in its water maser components and two sources (IRAS 17021-3109 and IRAS 17348-2906) that show water maser emission whose velocity lies outside the velocity range covered by OH masers. We have also identified IRAS 17393-2727 as a possible new water-maser-emitting PN. The detection rate is higher in obscured objects (14%) than in those with optical counterparts (7%), which is consistent with previous results. Water maser emission seems to be common in objects that are bipolar in the near-IR (43% detection rate in such sources). The water maser spectra of water fountain candidates like IRAS 17291-2147 show significantly fewer maser components than others (e.g., IRAS 18113-2503). We speculate that most post-AGBs may show water maser emission with wide enough velocity spread (>=100km/s) when observed with enough sensitivity and/or for long enough periods of time. Therefore, it may be necessary to single out a special group of "water fountains", probably defined by their high maser luminosities. We also suggest that the presence of both water and OH masers in a PN is a better tracer of its youth, than is the presence of just one of these species.

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