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the enigmatic eruption of v838 mon , followed by its spectacular light echo , triggered research in different fields of astrophysics .
apart from studies of the evolution of the object , investigations of the circumstellar and interstellar neighborhood of the star can also be important for understanding the nature of the event .
we present observations undertaken to search for molecular matter in the vicinity of v838 mon .    using the results of the co
@xmath0  =  1@xmath10 galactic survey of @xcite @xcite have suggested that v838 mon is situated in a bubble of co emission of a diameter of about 1@xmath6 ( see fig .
1 ) . according to these authors the structure is of circumstellar origin due to the agb activity of the v838 mon progenitor .
several critical points against this finding and interpretation have been raised in @xcite . however , the structure in the co map reported in @xcite is quite suggestive and we have found important to obtain co observations of the same ragion with a better sensitivity and angular resolution    there are also other important reasons for observing the star and its vicinity in molecular lines .
these are the nature of the echoing matter and a search for matter lost during and after the 2002 outburst .
the detection and monitoring of the sio maser emission from v838  mon @xcite shows that a molecular activity started close to the star .
complementary observations in molecular thermal transitions would be important to better understand what is going on there .
we performed observations in the three lowest rotational transitions of co in millimeter and submillimeter wavelengths .
observations in co @xmath0  =  1@xmath10 ( 115.27 ghz ) were obtained using the delingha 13.7  m telescope in october 
november 2005 . beside the star position ,
25 points in the region around v838 mon were observed , with majority of them located in the molecular ring claimed in @xcite .
all the points observed in co ( 10 ) are marked with filled triangles in fig .
1 .    observations in the higher transitions , i.e. co @xmath0  =  2@xmath11 and 3@xmath12 ( 230.54 and 345.80 ghz , respectively ) , were obtained with the 3  m kosma telescope . in april 2005
we made two _ on - the - fly _ maps with a 1 arcmin spacing and of a total area of 3.4 squared deg .
location of the mapped region is shown on fig .  1
. we also made longer integrations on the v838  mon position in april and december 2005 in both transitions .
in all the cases heterodyne sis receivers and acousto  optical spectrographs were used as frontends and backends , respectively .
in this section we present observations of the field around v838 mon in the three transitions , starting from those obtained with the kosma telescope and followed by a discussion of the lowest transition observed with the delingha telescope .      as a result of the on - the - fly observations we have obtained a set of 12  400 spectra for each transition with typical integration time of 48 s. basic technical description of the data
is given in table  1 .
it should be noted that the sensitivity of the survey in both lines is rather poor .
furthermore , because of changing atmospheric conditions the data quality is not homogeneous .
hence , special data reduction procedures were needed to visualize the data ( e.g. clipping method ) .    from an analysis of the spectra averaged over all the positions and from the channel maps we have found that the molecular emission in the mapped region comes mainly from matter at radial velocities of @xmath7=1832 km  s@xmath4 and @xmath8=4457  km  s@xmath4 . adopting a galactic rotation curve from @xcite
the two velocity ranges correspond to kinematical distances of @xmath9=2.33.0 kpc and @xmath10=6.26.5 kpc , respectively .
these values are in good agreement with distances to two spiral arms in the direction of v838  mon , i.e. perseus arm ( 3 kpc ) and norma  cygnus arm ( 6.25 kpc ) .
we have estimated physical parameters for the clouds emitting in co. adopting @xmath9 as distances to these structures we have got values of the physical parameters typical for molecular clouds .    in fig .
2 we present the map of intensity integrated over two velocity ranges ( spectra used to obtain map were earlier clipped at @xmath11 level ) for the co  ( 21 ) transition . the co  ( 32 ) map looks similar so we do not present it here .
no significant emission can be seen around v838 mon up to a radius of about 40. in particular there is no shell - like structure around the star , contrary to the claim of @xcite .
all the significant emission west from the star position comes from ordinary giant molecular clouds in the galactic disk .
lccc co line & @xmath0 = 1@xmath10 & @xmath0 = 2@xmath11 & @xmath0 = 3@xmath12 + beam & 55  & 130 `` & 82 '' + @xmath12 [ k ] &  231 @xmath13 286 &  153 @xmath13 230 &  230 @xmath13 377 + vel . range [ km s@xmath4 ] & 139 @xmath13 189&106 @xmath13 216&121 @xmath13 231 + @xmath15 [ km
s@xmath4]&0.37&0.21&0.29 + @xmath16 [ k ] & 0.09&0.42&0.93 +     = 2@xmath11 integrated over two velocity ranges : 1832 km s@xmath4 ( contours ) and 4457 km s@xmath4 ( grey scale ) .
contours are plotted from 2.7 to 64.1 k  km  s@xmath4 by 6.8 k  km  s@xmath4 ( 4 to 94% by 10% of the maximum ) .
the v838  mon position is marked a star - like symbol .
the galactic equator is shown as a dashed line . ]
sparks et al .
( 2006 , this issue ) have concluded from polarimetric observations of the light echo that the distance to v838  mon is @xmath17  kpc .
this value is close to the distance of the outermost spiral arm in the star direction i.e. norma  cygnus arm .
thus v838  mon is likely to be situated _ in _ or at least _ close to _ this spiral arm .
this is consistent with the radial velocity of the star of @xmath18 km s@xmath4 @xcite , the existence of the b3 v companion and the proposed membership of v838  mon to a young cluster of b - type stars ( bond et al .
2006 , this issue ) .
principle technical details of our observations in co ( 10 ) are presented in table  1 .
average 3@xmath19 level for these observations is of @xmath20.3  k , which gives a better sensitivity than that of the galactic survey by @xcite in the same transition .
significant co  ( 10 ) emission is seen only for points west of the star position , in the area where we have also found emission in co ( 21 ) and ( 32 ) ( see  3.1 ) . the emission is always related to molecular clouds ( what has already been noted by * ? ? ?
* ) . among the points in the ring - like structure claimed in @xcite we have found a clear emission only at an offset @xmath20=12 , @xmath21=1 ( see upper and right axes in fig .  1 ,
the offset is given in respect to the star position ) .
the emission is weak , @xmath220.6  k , and narrow , @xmath23=1.9  km  s@xmath4 .
it is at a radial velocity of @xmath8=49.2  km  s@xmath4 , only @xmath25  km  s@xmath4 different from the velocity of v838  mon ( 54.3  km  s@xmath4 ) .
our observations in co  ( 10 ) show that the shell - like structure suggested by @xcite does not exist .
detection of the emission at 12 from the star ( 20  pc at 6  kpc ) suggests that there can be a weak extended molecular emission near v838  mon , below the sensitivity of our observations .
observations with a better sensitivity are needed to verify if this molecular matter can be related to the echoing matter .
v838 mon itself was observed in the three lowest rotational transitions of co with longer integration times .
observational details are summarized in table  2 .    in the co ( 10 )
transition the v838  mon position was observed only once .
we did not find any emission stronger than @xmath24  k ( @xmath11 ) .
we also observed 8 positions around the star , i.e. points with offsets of @xmath25 , with shorter integration times .
in all these positions we did not detect any emission higher than @xmath26  k ( @xmath11 ) .
the area covered by these 9 points corresponds to that of the light echo in the fall of 2005 .
thus the echoing matter is not seen at the sensitivity of our observations .    in co ( 21 ) and ( 32 ) we have spectra obtained in april and december 2005 . in the spring spectra
we have found emission only in the co  ( 21 ) transition at a radial velocity of @xmath27  km  s@xmath4 , almost the same as the velocity of the sio maser emission @xcite . in the spectra obtained in december with much longer integration times we have found two components in both transitions . apart from the already known component at @xmath28  km  s@xmath4 , an emission is also seen at a radial velocity of @xmath29  km  s@xmath4 .
the line intensities , widths and peak velocities are presented in table  3 .
all the lines are very narrow .
the component at @xmath30  km  s@xmath4 is stronger in the co ( 21 ) transition , while that at @xmath31  km  s@xmath4 is stronger in co ( 32 ) .
when one compares the line intensities in april and december it looks like the strength of the component at @xmath32  km  s@xmath4 decreased . however , the observed change is close to the measurment uncertainty so this finding is not conclusive .
the beam widths of our observations in co ( 21 ) and ( 32 ) are rather large ( 130  and 82  , respectively ) .
therefore we can not say whether the emission detected at the v838 mon position comes from the closest stellar vicinity or from regions which are located at a few tens of arcmin from the star .
it should be noted that a search for molecular emission ( including co and sio maser ) in 2003 gave negative result @xcite . the detected emission in the co lines may indicate that a molecular activity has started close to v838  mon , but its origin is unclear
. further observations with a better angular resolution would be of particular interest in this point .
ccccccc date&line&@xmath12&@xmath33&@xmath15&velocity range&@xmath19 + & & [ k]&[khz]&[km  s@xmath4]&[km  s@xmath4]&[k ] + 04 apr.&21&168&165.4&0.21&106.4 @xmath13 171.4&0.043 + & 32&273&339.1&0.29&121.4 @xmath13 186.4&0.083 + & & & & & & + 02 nov.&10&245&142.1&0.37&139.5 @xmath13 188.7&0.072 + & & & & & & + 26 dec.&21&310&165.4&0.21&206.8 @xmath13 233.5&0.014 + & 32&418&339.3&0.29&289.5 @xmath13 250.4&0.022 +    ccrccc date&line&&&fwhm&int .
intensity + & & [ km  s@xmath4 ] & & [ km  s@xmath4]&[k km  s@xmath4 ] + 04 apr.&21 & 53.3 & 0.553&1.174&0.691 + 26 dec.&21 & 11.1&0.099&1.075&0.114 + & & 53.3 & 0.323&1.179&0.406 + & 32 & 11.0&0.188&1.148&0.230 + & & 53.2&0.156&1.500&0.190 +      the kosma 3 m telescope is operated by the klner observatorium fr submillimeter astronomie of the i.  physikalisches institut , universitt zu kln in collaboration with the radioastronomisches institut , universitt bonn .
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we present observations of v838  mon and its close vicinity in the three lowest rotational transitions of co. the @xmath0 = 2@xmath11 and 3@xmath12 data were obtained using the 3 m kosma telescope . 
 they include on - the - fly maps covering a large area ( @xmath23.4 sq . 
 deg . ) around v838  mon and long integrations on the star position . 
 complementary observations in the co @xmath0 = 1@xmath10 transition were obtained using the 13.7 m delingha telescope . 
 the star position as well as 25 other points preselected in the near vicinity of the object have been measured in this transition .    
 we report on a detection of two narrow emission components in @xmath0 = 2@xmath11 and 3@xmath12 transitions at the position of v838  mon . 
 lines were found at radial velocities of @xmath3  km  s@xmath4 and @xmath5  km  s@xmath4 . 
 their origin is unclear . 
 we also shortly discuss results of the observations of the vicinity of v838  mon .