You will be presented with the full text of a science research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
the supernova remnant g266.11.2 has been reported as a possible @xmath2-ray source in the 1.156 mev line of @xmath3ti ( iyudin et al .
1998 ) . the short lifetime ( @xmath090 yrs ) of this isotope , and the relatively small angular size of the remnant would imply an age of only @xmath0680 years and a small distance d@xmath0200 pc ( aschenbach et al . 1999 ) . thus g266.11.2 could be the remnant of the closest supernova event to have occurred in recent historical times .    however , _ asca _
observations showed that the x 
rays from the snr shell have a non - thermal spectrum and the fits require a high absorption value ( slane et al .
2001 ) , favoring a distance of @xmath01 - 2 kpc that would place g266.11.2 well beyond the vela snr ( see also mereghetti & pellizzoni 2001 ) .
the _ asca _
data revealed also a central point source , , surrounded by diffuse x  ray emission , that was interpreted as the neutron star associated to g266.11.2 .
a _ bepposax _ observation ( mereghetti 2001 ) of the central region of g266.11.2 showed the presence of a second source about 3@xmath4 north of that detected by _
asca _ and with a harder spectrum .
the northern source was named sax  j0852.04615 . since the _ bepposax _ error circle of contained two bright early type stars that might have produced the observed x  ray flux , while no optical counterparts brighter than v@xmath015 were visible for ,
it was unclear which of the two sources was the most likely neutron star candidate .    the puzzle has been recently solved by a _
observation that provided an arcsecond position for ( pavlov et al .
the new error box is incompatible with the two early type stars that were previously considered as possible counterparts , thus confirming that is the most likely neutron star candidate .
was not detected in the 3 ks long _ chandra _ observation reported by pavlov et al .
this might be due to variability , or to the hardness of this source , that was detected with _
bepposax _ only above 5 kev
. a deeper observation with _ xmm - newton _ confirmed the existence of , with a flux about ten times fainter than that of ( aschenbach , this conference ) .
here we present optical observations of the fields of these two x  ray sources .
optical images of the central region of g266.21.2 were obtained through the public archive of the european southern observatory ( eso ) .
these data consist of images in the r and b bands taken with the wide field imager instrument at the la silla 2.2 m telescope on july 30 , 1998 .
we derived an approximate calibration of these data based on a number of stars of the usno catalogue .
figure 1 shows the r band image of the _ bepposax _ error region ( 1@xmath4 radius ) of .
the two early type stars that were previously considered as possible counterparts are the b8 type star hd76060 ( v=7.9 ) , and wray 16 - 30 , a b[e ] star with v=13.8 ( th et al .
1994 ) also detected with iras .
the small circle indicates the new position of determined with _ chandra _ ( pavlov et al . 2001 ) .
no objects , down to limits of r@xmath022.5 and b@xmath023 are present at the _ chandra _ position , besides a star with r@xmath017 on the edge of the error circle . as discussed by pavlov et al .
this object is probably a late type star and can not be the counterpart of the x  ray source .
some diffuse emission is also visible to the west of the _ chandra _ position .
this nebula is better seen in the h@xmath1 image shown in fig.2 .
the brightest part of the h@xmath1 nebula has a roughly elliptical shape with dimensions @xmath040@xmath5@xmath620@xmath5 , and a sharply defined western edge .
some nearly parallel filaments are also visible , one of which seems to be composed by a series of aligned bright spots ( see fig.1 ) .
the field of the northern source , , is shown in the r band image of fig.3 .
the brightest stars in the _ bepposax _ error region ( 1@xmath4 radius ) have r@xmath015 , implying a ratio of x  ray to optical flux f@xmath7/f@xmath8@xmath90.1 .
none of the stars in the error region has particularly unusual colors .
the deep optical limits for the possible counterparts of confirm that this is most likely the neutron star remnant associated with g266.11.2 .
an interesting h@xmath1 nebula has also been discovered in the data presented here .
emission in the h@xmath1 has been detected around a few radio pulsars and is thought to originate in the interstellar medium shocked by the relativistic pulsar wind .
these nebulae have either a  cometary  shape with the axis of symmetry along the direction of the pulsar transverse motion ( e.g. , psr b2224 + 65 (  guitar nebula  , cordes et al .
1993 ) or psr b074028 ( stappers et al . these proceedings ) ) or an arc - like shape ( e.g. , psr j04374715 , bell et al .
1996 ) .
the morphology of the diffuse emission shown in fig.1 and fig.2 does not present any obvious connection with the location of the candidate neutron star as determined with _
it is more likely that the nebula is related to the b[e ] star wray 16 - 30 , which is located at the southern end of the nebula .
however , its peculiar morphology and the location close to the center of g266.11.2 make this nebula a potentially interesting target for more detailed investigations .
this work was based on data obtained with the eso telescopes at la silla and made available through the eso / stecf science archive facility .
we acknowledge the support of the italian space agency and of the italian ministry of university and research ( cofin-99 - 02 - 02 ) .
aschenbach , b. , iyudin a.f . , & schnfelder v. 1999 , , 350 , 997 bell j.f .
1995 , , 440 , l81 cordes j.m .
, romani r.w . &
lundgren s.c .
1993 , , 362 , 133 iyudin a.f .
1998 , nature , 396 , 142 mereghetti s. 2001 , , 548 , l213 mereghetti s. & pellizzoni a. 2001 , in proc .
gamma 2001 , s.ritz , n.gehrels & c.r.shrader eds .
n.587 , 523 pavlov g.g . , sanwal d. , kiziltan b. & garmire g.p . 2001 , , 559 , l131 slane p. et al . 2001 , , 548 , 814 th p.s . , de winter d. & perez m.r .
1994 , , 104 , 315
we present optical observations of the fields of two x  ray sources located near the center of the shell - like supernova remnant g266.11.2 . 
 no objects brighter than r@xmath022.5 and b@xmath023 are present within the small _ chandra _ error region of , besides a r@xmath017 star that has already been excluded as a possible counterpart . a bright diffuse h@xmath1 
 nebula is present close to the position of the candidate neutron star .    
 # 1_#1 _ # 1_#1 _ =    # 1 1.25 in .125 in .25 in