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VLE14 - From the ashes: JVLA observations of water fountain nebula candidates show the rebirth of IRAS 18455+0448

Short title: Vlemmings et al. (2014)
Authors: Vlemmings, W. H. T. Amiri, N. van Langevelde, H. J. Tafoya, D.
Journal: Astronomy & Astrophysics, Volume 569, id.A92, 8 pp.
Bibcode:

Target type: pAGB_PN

Abstract
Context. The class of water fountain nebulae is thought to represent the stage of the earliest onset of collimated bipolar outflows during the post-asymptotic giant branch phase. They thus play a crucial role in the study of the formation of bipolar planetary nebulae (PNe). To date, 14 water fountain nebulae have been identified. The identification of more sources in this unique stage of stellar evolution will enable us to study the origin of bipolar PNe morphologies in more detail. Aims: Water fountain candidates can be identified based on the often double peaked 22 GHz H₂O maser spectrum with a large separation between the maser peaks (often >100 km s^-1). However, even a fast bipolar outflow will only have a moderate velocity extent in its maser spectrum when located close to the plane of the sky. In this project we aim to enhance the water fountain sample by identifying objects whose jets are aligned close to the plane of the sky. Methods: We present the results of seven sources observed with the Jansky Very Large Array (JVLA) that were identified as water fountain candidates in an Effelsberg 100 m telescope survey of 74 AGB and early post-AGB stars. Results: We find that our sample of water fountain candidates displays strong variability in their 22 GHz H₂O maser spectra. The JVLA observations show an extended bipolar H₂O maser outflow for one source, the OH/IR star IRAS 18455+0448. This source was previously classified as a dying OH/IR star based on the exponential decrease of its 1612 MHz OH maser and the lack of H₂O masers. We therefore also re-observed the 1612, 1665, and 1667 MHz OH masers. We confirm that the 1612 MHz masers have not reappeared and find that the1665/1667 MHz masers have decreased in strength by several orders of magnitude during the last decade. The JVLA observations also reveal a striking asymmetry in the red-shifted maser emission of IRAS 19422+3506. Conclusions: The OH/IR star IRAS 18455+0448 is confirmed to be a new addition to the class of water fountain nebulae. Its kinematic age is ~70 yr, but could be lower, depending on the distance and inclination. Previous observations indicate, with significant uncertainty, that IRAS 18455+0448 has a surprisingly low mass compared to available estimates for other water fountain nebulae. The available historical OH maser observations make IRAS 18455+0448 unique for the study of water fountain nebulae and the launch of post-AGB bipolar outflows. The other candidate sources appear high mass-loss OH/IR stars with partly radially beamed H₂O masers. eprintid: arXiv:1407.6709

Abstract

Context. The class of water fountain nebulae is thought to represent the stage of the earliest onset of collimated bipolar outflows during the post-asymptotic giant branch phase. They thus play a crucial role in the study of the formation of bipolar planetary nebulae (PNe). To date, 14 water fountain nebulae have been identified. The identification of more sources in this unique stage of stellar evolution will enable us to study the origin of bipolar PNe morphologies in more detail.
Aims: Water fountain candidates can be identified based on the often double peaked 22 GHz H₂O maser spectrum with a large separation between the maser peaks (often >100 km s^-1). However, even a fast bipolar outflow will only have a moderate velocity extent in its maser spectrum when located close to the plane of the sky. In this project we aim to enhance the water fountain sample by identifying objects whose jets are aligned close to the plane of the sky.
Methods: We present the results of seven sources observed with the Jansky Very Large Array (JVLA) that were identified as water fountain candidates in an Effelsberg 100 m telescope survey of 74 AGB and early post-AGB stars.
Results: We find that our sample of water fountain candidates displays strong variability in their 22 GHz H₂O maser spectra. The JVLA observations show an extended bipolar H₂O maser outflow for one source, the OH/IR star IRAS 18455+0448. This source was previously classified as a dying OH/IR star based on the exponential decrease of its 1612 MHz OH maser and the lack of H₂O masers. We therefore also re-observed the 1612, 1665, and 1667 MHz OH masers. We confirm that the 1612 MHz masers have not reappeared and find that the1665/1667 MHz masers have decreased in strength by several orders of magnitude during the last decade. The JVLA observations also reveal a striking asymmetry in the red-shifted maser emission of IRAS 19422+3506.
Conclusions: The OH/IR star IRAS 18455+0448 is confirmed to be a new addition to the class of water fountain nebulae. Its kinematic age is ~70 yr, but could be lower, depending on the distance and inclination. Previous observations indicate, with significant uncertainty, that IRAS 18455+0448 has a surprisingly low mass compared to available estimates for other water fountain nebulae. The available historical OH maser observations make IRAS 18455+0448 unique for the study of water fountain nebulae and the launch of post-AGB bipolar outflows. The other candidate sources appear high mass-loss OH/IR stars with partly radially beamed H₂O masers. eprintid:

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ID	Obs. RA	Obs. Dec	l	b	Group id	Source name	Line	V_range	V_peak	F_peak	RMS	List	Detection	Class	Dist. (parallax)	Ref.
	(J2000)	(J2000)	(deg.)	(deg.)			H₂O	(km/s)	(km/s)	(Jy)	(Jy)		Yes/No		(kpc)
1	18 48 2.3	+04 51 30.4	36.8730	2.9677	G36.873+2.968	IRAS 18455+0448	22 GHz;	14.0;48.0	22.2	2.7	0.300	ENG_H2O	+H₂O +OH	EVOLVED		VLE14
2	19 09 8.3	+08 16 33.8	42.3085	-0.1328	G42.308-0.132	IRAS 19067+0811	22 GHz;	47.2;80.0	76.4	3.1	0.300	ENG_H2O	+H₂O +OH +SiO	EVOLVED		VLE14
3	19 09 19.2	+09 21 11.5	43.2851	0.3240	G43.285+0.324	IRAS 19069+0916	22 GHz;	8.0;47.0	11.0	6.2	0.007	ENG_H2O	+H₂O +OH +SiO	GALAXY		VLE14
4	19 13 37.3	+08 24 52.5	42.9442	-1.0521	G42.944-1.052	IRAS 19112+0819	22 GHz;	19.0;59.5	54.5	2	0.300	ENG_H2O	+H₂O +OH	SFR_MIXED		VLE14
5	19 21 11.7	+03 20 57.8	39.3263	-5.0713	G39.326-5.071	IRAS 19186+0315	22 GHz;	-37.5;-11.5	-35.5	3.8	0.300	ENG_H2O	+H₂O +OH +SiO	EVOLVED		VLE14
6	19 27 42	+16 37 24.2	51.8039	-0.2248	G51.804-0.224	IRAS 19254+1631	22 GHz;	-15.0;18.5	17.0	1.8	0.007	ENG_H2O	+H₂O -CH₃OH II +OH +SiO	EVOLVED		VLE14
7	19 44 07	+35 14 8.2	69.8869	5.5926	G69.887+5.593	IRAS 19422+3506	22 GHz;	-68.5;-33.5	-37.5	18	0.007	ENG_H2O	+H₂O +OH +SiO	EVOLVED		VLE14

DSS colored	2MASS colored	WISE colored
PACS color (70-160 um)	SPIRE color (250-500 um)	GLIMPSE 360
SDSS color	IRAC color I1,I2,I4	NVSS (1.4GHz)
ATLASGAL 870 um	ATLASGAL 870 um + Planck	Bolocam 1.1 mm
UKIDSS K Download UKIDSS K FITS	2MASS K Download 2MASS K FITS

select MAX(h2o_data_all.ra_hms) as ra_hms,MAX(h2o_data_all.dec_dms) as dec_dms,MAX(h2o_data_all.source_name) as source_name,MAX(h2o_data_all.ra) as ra,MAX(h2o_data_all.dec) as dec,MAX(h2o_data_all.l) as l,MAX(h2o_data_all.b) as b,MAX(h2o_data_all.grp) as grp,MAX(h2o_data_all.other_name) as other_name,MAX(h2o_data_all.other_desc) as other_desc,BOOL_OR(thermal) as thermal,MAX(h2o_data_all.line) as line,MAX(h2o_data_all.vrange) as vrange,MAX(h2o_data_all.vpeak) as vpeak,MAX(h2o_data_all.peak) as peak,MAX(h2o_data_all.fwhm) as fwhm,MAX(h2o_data_all.int) as int,MAX(h2o_data_all.rms) as rms,MAX(h2o_data_all.units) as units,MAX(h2o_data_all.units_rms) as units_rms,MAX(h2o_data_all.date_txt) as date_txt,MAX(h2o_data_all.telescope_ref) as telescope_ref,MAX(h2o_data_all.telescope_conf) as telescope_conf,MAX(h2o_data_all.v_step) as v_step,MAX(h2o_data_all.beam) as beam,MAX(h2o_data_all.beam_maj) as beam_maj,MAX(h2o_data_all.beam_min) as beam_min,MAX(h2o_data_all.beam_pa) as beam_pa,MAX(h2o_data_all.ref) as ref,MAX(h2o_data_all.list_ref) as list_ref,MAX(h2o_data_all.ascii) as ascii,MAX(h2o_data_all.url) as url,MAX(h2o_data_all.image) as image,MAX(h2o_data_all.image2) as image2,MAX(h2o_data_all.image3) as image3,MAX(h2o_data_all.descr) as descr,MAX(h2o_data_all.id) as id,BOOL_OR(mjy_flag) as mjy_flag,BOOL_OR(rms_mjy_flag) as rms_mjy_flag,MAX(h2o_data_all.dist) as dist,1 as dist_parallax,MAX(h2o_data_all.date_txt) as date_txt,MAX(line_det) as line_det,MAX(type) as type,MAX(simbad_types_cat) as simbad_types_cat FROM h2o_data_all  LEFT JOIN all_objects_withmet ON h2o_data_all.grp=all_objects_withmet.group_name LEFT JOIN object_categories ON all_objects_withmet.group_name = object_categories.group_name_cat AND object_categories.tbl_cat = 'all_objects_withmet' LEFT JOIN transitions ON h2o_data_all.line=transitions."Line"  WHERE ref ilike 'VLE14' AND detected=true AND hide=false GROUP BY ref

select h2o_data_all.ra_hms,h2o_data_all.dec_dms,h2o_data_all.source_name,h2o_data_all.ra,h2o_data_all.dec,h2o_data_all.l,h2o_data_all.b,h2o_data_all.grp,h2o_data_all.other_name,h2o_data_all.other_desc,h2o_data_all.thermal,h2o_data_all.line,h2o_data_all.vrange,h2o_data_all.vpeak,h2o_data_all.peak,h2o_data_all.fwhm,h2o_data_all.int,h2o_data_all.rms,h2o_data_all.units,h2o_data_all.units_rms,h2o_data_all.date_txt,h2o_data_all.telescope_ref,h2o_data_all.telescope_conf,h2o_data_all.v_step,h2o_data_all.beam,h2o_data_all.beam_maj,h2o_data_all.beam_min,h2o_data_all.beam_pa,h2o_data_all.ref,h2o_data_all.list_ref,h2o_data_all.ascii,h2o_data_all.url,h2o_data_all.image,h2o_data_all.image2,h2o_data_all.image3,h2o_data_all.descr,h2o_data_all.id,h2o_data_all.mjy_flag,h2o_data_all.rms_mjy_flag,h2o_data_all.dist,h2o_data_all.dist_parallax,h2o_data_all.date_txt,line_det,type,simbad_types_cat FROM h2o_data_all   LEFT JOIN all_objects_withmet ON h2o_data_all.grp=all_objects_withmet.group_name LEFT JOIN object_categories ON all_objects_withmet.group_name = object_categories.group_name_cat AND object_categories.tbl_cat = 'all_objects_withmet' LEFT JOIN transitions ON h2o_data_all.line=transitions."Line"  WHERE ref ilike 'VLE14' AND detected=true AND hide=false ORDER BY detected DESC,id

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VLE14 - From the ashes: JVLA observations of water fountain nebula candidates show the rebirth of IRAS 18455+0448

View as list of objects

Detection table from Vlemmings et al. (2014)