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the class of type  iin supernovae ( sne  iin hereafter ) , whose narrow h lines indicate strong interaction with dense circumstellar material ( csm ) , have challenged our understanding of stellar evolution and death . their dense h - rich csm , progenitor instability , and high initial masses inferred from various clues suggest a link to the class of luminous blue variables ( lbvs ) , which are not supposed to be anywhere near core collapse in the standard scenario of massive single - star evolution ( see @xcite for a general review ) . among well - studied examples of sne  iin , the explosion of sn  2009ip in mid-2012 ( note that its discovery in 2009 was deemed to be a sn impostor ) is one of the most interesting , with by far the best observational characterization of a directly detected progenitor among any sn in history ( even sn  1987a ) . it had a ( presumably ) quiescent progenitor star candidate detected in archival _ hubble space telescope _ ( _ hst _ ) images , with a luminosity that implied a very high initial mass of at least 50 - 60 @xmath2 @xcite . this source also showed a series of outbursts in the few years before the sn @xcite that were reminiscent of both s  dor outbursts and giant eruptions of lbvs . unlike any progenitor source so far , high - quality spectra of these precursor outbursts were obtained , with a detailed analysis before the sn indicating a strong similarity to lbvs @xcite . with a quiescent and very luminous progenitor , an s  dor outburst , several bright but brief sn impostor eruptions , and progenitor spectra resembling lbvs , sn  2009ip provides a strong link between lbvs and sne  iin . the repeating variable source at the position of sn  2009ip began to brighten again in mid-2012 , but this time things were different . spectra of the fainter 2012a peak showed very broad p cygni profiles with velocities of 13,000 km s@xmath3 , suggesting that the event was a core - collapse sn and not another lbv outburst @xcite . the subsequent and brighter 2012b event showed a high peak luminosity and a spectrum typical of sne  iin with strong csm interaction . the 2012 sn - like event has already been discussed extensively in the literature @xcite . in these publications and in discourse at meetings , there was some uncertainty and controversy about whether the 2012 event was a true core - collapse sn , since ( 1 ) csm interaction can provide bright transients even from relatively low - energy explosions , ( 2 ) the initial sn was somewhat fainter than standard sne  ii - p , and ( 3 ) the rich observational dataset for the progenitor presented mysteries that were not easily explained by any existing model . these are , however , expressions of the challenge in understanding sne  iin and csm interaction , rather than arguments against a core - collapse event . while it is difficult to prove definitively that the event was a core collapse because of the masking of csm interaction , a sn is the most straightforward explanation of the data . @xcite showed that all available evidence was consistent with the core collapse sn explosion of a blue supergiant that encountered strong csm interaction . moreover , both line - profile evolution @xcite and spectrapolarimetry @xcite show that the csm interaction was highly aspherical and probably disk - like , forcing the kinetic energy budget of the event to be @xmath110@xmath4 ergs . @xcite also argued for a disk - like csm based on narrow line ratios . @xcite showed that the source at + 2 yr was consistent with steady ongoing csm interaction with no additional outbursts , adding further evidence in favor of a core - collapse event . sn  2009ip provides our clearest example of pre - sn instability that leads to eruptive pre - sn mass loss in the few years before explosions , which may be associated with the final nuclear burning sequences in the last years of a massive star s life @xcite . alternative non - terminal models involving binary mergers and accretion were also proposed for the 2012 event @xcite , but these can not supply the required 10@xmath4 ergs of kinetic energy .    in this paper , we are mainly concerned with the host galaxy environment around sn  2009ip . a fundamental interesting mystery was that while progenitor detections pointed to a very massive unstable star , the location of sn  2009ip was in the remote outskirts of its spiral host , far away from obvious signs of recent star formation and young stellar populations @xcite . it was located about 5 kpc from the center of its relatively small host spiral galaxy ngc  7259 . by extrapolating the apparent metallicity gradient measured in the inner @xmath11.5 kpc out to the 5 kpc radius of sn  2009ip , @xcite infer a mildly subsolar metallicity at the sn site of @xmath5 . sn  2009ip s progenitor can therefore be compared with populations of massive stars observed in the milky way and large magellanic cloud ( lmc ) . an interesting result is that despite their high luminosities and high inferred initial masses , lbvs in the milky way and lmc appear to be relatively isolated compared to expectations for their presumed role in stellar evolution . @xcite demonstrated that lbvs selectively avoid clusters of o - type stars , especially early o - types that are their presumed progenitors . more importantly , lbvs are more dispersed on the sky than wr stars ; this rules out the standard picture wherein lbvs are a transitional phase between massive o - type stars and wr stars . instead , @xcite suggested that most lbvs may be the result of interacting binary evolution , getting rejuvenated by either mass transfer or mergers . this would make them stand out as anomolously young compared to their surrounding populations . in other words , _ they are evolved massive blue stragglers_. they may become even more isolated upon receiving a kick from their companion star s sn , although it is not yet clear if a kick is required to explain their environments . also relevant to this story is that sne  iin in general appear to be less correlated with bright h@xmath0 in their host galaxies than other types of sne @xcite . while this has been interpreted as signifying lower initial masses by those authors , that interpretation has been a topic of debate @xcite . as described below , sn  2009ip seems to follow a similar trend of not having bright h@xmath0 nearby , despite having a detection of a very massive and luminous progenitor star . .new _ hst _ wfc - uvis images of sn  2009ip , including st magnitudes for sn  2009ip and background 3@xmath6 upper limits [ cols="<,^,^,^,^,^",options="header " , ]     [ tab : s99 ]     compared to a roughly contemporaneous spectrum of sn  2009ip ( blue ) taken with the mmt in 2015 november , as well as a late - time day 905 spectrum of sn  2005ip ( black ) from @xcite . sn  2005ip had stronger csm interaction at almost 3 yr after explosion , and a spectrum with much higher signal to noise showing the fainter emission features that are expected to accompany strong h@xmath0 emission . this sn  2005ip spectrum has been scaled to match the same h@xmath0 flux as sn  2009ip.,width=307 ]    10@xmath7 ergs s@xmath3 @xmath8 arcsec@xmath9 , but there are negative residuals at a similar level , so these could be subtraction artifacts . there is no extended emission beyond 0@xmath104 ( 40 pc ) from the sn site brighter than @xmath10.2@xmath1110@xmath7 ergs s@xmath3 @xmath8 arcsec@xmath9.,width=307 ] the new _ hst _ images show a clearly detected point source at the location of sn  2009ip . based on the measured offset from a nearby bright star in the field , this source is coincident with the position of the 1999 progenitor to within 0.043 arcsec ( roughly 10% of a wfc3 pixel ) . the late - time source has a profile consistent with the point spread function in all the broad filters . figure  [ fig : psf ] shows the result of subtracting a model point spread function ( psf ) from the f657n image of sn  2009ip . the model psf was generated using the tiny tim program . there is residual emission after the psf subtraction at a typical brightness level of 0.5@xmath1110@xmath7 ergs s@xmath3 @xmath8 arcsec@xmath9 located within 0@xmath104 ( 40 pc ) of the sn site . this could indicate some faint extended h  ii region emission from a fading star forming region . however , there are negative residuals at a similar level , so these are also consistent with being simple subtraction artifacts due to an imperfect psf match . there is no detected emission brighter than @xmath12@xmath1110@xmath12 ergs s@xmath3 @xmath8 arcsec@xmath9 beyond 40 pc from the sn site . we also tried using a psf made from a bright star on the same image , with similar results . psf subtraction of the broadband images ( not shown ) yielded similarly inconclusive results . in the continuum images , the residuals allow for the presence of a faint sn light echo or extended and very faint ob association that is 2 - 5% as bright as the sn point source , but as with f657n , the residuals are also consistent with subtraction artifacts from an imperfect psf match . the f555w source is slightly fainter than the f606w progenitor , but consistent with no change in the continuum level within the uncertainty . in a preliminary report of ground - based photometry , @xcite also reported that sn  2009ip continued to fade , and by a few months after our _ hst_images were taken , it was fainter than the progenitor .    the faint emission detected in the broad filters could be dominated by continuum from an underlying star cluster , late - time csm interaction emission from the fading sn itself , or a combination of these two . in fact , there must be some contribution from csm interaction emission , due to the strong and broad h@xmath0 detected in the late - time spectrum ( fig . [ fig : spec ] ) . @xcite showed that there was still strong csm interaction at around 2 yr after explosion . we can therefore rule out the possibility that there is no change in the brightness of the progenitor candidate ( as would be the case if it was a chance alignment with an unrelated star ) , and so the progenitor must have faded by whatever amount is now contributed by csm interaction luminosity . the possibility that a progenitor survived but is now obscured by dust is hard to rule out because it requires some arbitrary amount of extinction to compensate for csm interaction . however , @xcite noted that there was no clear indication of new dust formation in the late - time data for sn  2009ip , so this would argue that the progenitor candidate has in fact faded . figure  [ fig : sed ] compares the observed spectral energy distribution ( sed ) in the _ hst _ photometry to the hypothetical emission from underlying young star clusters using examples from starburst99 models @xcite . we show models with ages of 5 , 10 , and 20 myr scaled to the f275w point only ( assuming the the optical / red emission is dominated by the sn ) , as well as these same cluster model spectra with reddening to match both the f275w and the f814w flux . clusters much older than 20 myr would have turn off masses too low ( less than 12 @xmath2 ) . the associated cluster terminal - age main sequence masses ( @xmath13 ) , absolute @xmath14 mags , and total cluster stellar masses are listed in table  [ tab : s99 ] . the corresponding absolute @xmath14 mag and total cluster mass corrected for extinction are also shown , along with the corresponding @xmath15 value .    if we assume that the csm interaction dominates the optical / red emission , the unreddened clusters allowed by the f275w photometry imply total clutser masses that are unreasonably low ( lower than the progenitor mass of an individual star ; this is because they have been artificially scaled to match the photometry ) . we discount these . adding reddening to the host cluster , we can account for the f275w and f814w fluxes reasonably well , but there is a f555w excess flux of about a factor of 2 above the model spectra , which could perhaps be accounted for by sn emission ( see below ) . the stellar masses implied are more reasonable , but the problem with these reddened clusters is that the required reddening is larger than the value of the total @xmath15 inferred for the line of sight ( @xmath15=0.019 mag ; @xcite ) . a dominant contribution from a reddened cluster therefore seems unlikely as well . overall , we find that an underlying star cluster does not provide a compelling explanation for the observed photometry , but we can not rule out some contribution from a small cluster or association hidden by sn  2009ip . another possibility is that the current photometry of sn  2009ip is dominated by late - time sn emission from ongoing csm interaction . figure  [ fig : spec ] shows the sn  2009ip photometry compared to a spectrum that we obtained at the mmt several months later in 2015 november . this spectrum indicates that very strong h@xmath0 emission with a resolved width of about 2000 km s@xmath3 continued to be observed , requiring the presence of strong ongoing csm interaction at these late times . for comparison , figure  [ fig : spec ] shows a late time ( day 905 ) spectrum of sn  2005ip from @xcite . sn  2005ip was a type  iin with very strong late - time csm interaction , and this has much higher signal to noise across a wide wavelength range that demonstrates the lower - level emission in many lines that may accompany bright h@xmath0 . many of these fainter emission lines blend together to make a blue `` pseudo - continuum '' @xcite . the sn  2005ip spectrum has been scaled to match the same h@xmath0 flux as measured in the spectrum of sn  2009ip , providing a rough indication of the pseudo - continuum emission we might expect from sn  2009ip . we do not necessarily expect the late - time spectrum of sn  2009ip to be exactly the same as that of sn  2005ip . the point of this comparison is to illustrate that the level of csm interaction we detect via the h@xmath0 emission in sn  2009ip should be accompanied by a host of other emission lines across a wide wavelength range that should contribute to the broad - band filters . using sn  2005ip as a guide , it seems possible that csm interaction alone may account for the broadband flux and relatively blue color . a deeper spectrum of the late - time emission can confirm this hypothesis .    because the late - time csm interaction emission must make some contribution to the observed f555w photometry in 2015 , we conclude that any underlying continuum source other than csm interaction should be fainter than the f606w progenitor seen in 1999 . it is likely that we will need to wait several more years to confirm that this source has actually faded enough to place strong constraints on the progenitor . the main goal of our proposed observations was to investigate the environment around sn  2009ip , as discussed next . the comparison between photometry of sn  2009ip and starburst99 model spectra in figure  [ fig : sed ] shows that our broad - band images could easily detect any massive young clusters or ob associations in these images . the sensitivity determined from 3@xmath6 upper limits in the background of these images indicates that we would have detected sources with @xmath16 of @xmath174.7 mag , almost 100 times fainter than the sn  2009ip point source . this limit corresponds to a single mid to late o - type main sequence star , or a single red supergiant . the f275w image rules out even relatively small clusters with ages younger than 10 myr or any early o - type main sequence stars ( initial masses above 40 @xmath2 ) ; these would be easily detected in the @xmath11 kpc environment around sn  2009ip . no such bright clusters or luminous stars are seen . there is only one source about 100 pc to the south east , which is , however , more than 10 times fainter than sn  2009ip at most wavelengths , and not detected in f275w . we take this as indicating a remarkable lack of recent massive star formation in the vicinity over the past @xmath110 myr . h@xmath0 also serves as a tracer of any recent or ongoing nearby star formation . our f657n image was designed to be sensitive to even relatively modest h  ii regions . indeed , the f657n image reveals dozens of h  ii regions with a wide range of surface brightness in the interior few kpc of the host galaxy nucleus , but there is a marked absence of any h  ii emission in the outer regions of the galaxy beyond 34 kpc from the center . the new f657n image of sn  2009ip and its surroundings is shown in figure  [ fig : carina ] . this image reveals no detectable h@xmath0 emission from any young h  ii regions in the surrounding @xmath11 kpc around sn  2009ip , which is found about 5 kpc from the galaxy center . there is a bright point source to the north east ( possibly a foreground star ) and two very faint point sources as well , but all these other sources have similar brightness in broadband continuum filters and so these are unlikely to be h  ii regions . sn  2009ip itself is much brighter in the f657n filter , consistent with its bright h@xmath0 emission detected in the spectrum ( fig . [ fig : spec ] ) .    to illustrate how the lack of h@xmath0 detection indicates a dearth of recent or ongoing massive star formation in the vicinity , figure  [ fig : carina ] shows two panels that zoom - in on the surrounding @xmath11 kpc around sn  2009ip . one of these is the observed f657n image , and the other is the same image with some fake comparison sources injected . as noted earlier in section 2 , we used h@xmath0 images of the orion nebula , the carina nebula , and the 30 dor complex , and scaled them to the appropriate pixel size as they would appear in these images if they resided at the distance of ngc  7259 . these sources were then convolved to the fwhm of the f657n images and added to the fits files of the _ hst _ data at the appropriate surface brightness for the flux calibration in the _ hst _ images . we also added these fake images to the left side of the larger scale image in the same figure . all three nebulae would have been easily detected in the images , although the orion nebula is so small that it would have been an unresolved point source ( note however , that the orion nebula is in a larger complex of star formation that we did not include this in the fake injected image ) . it is evident that the eastern side of ngc  7259 has no extreme mini - starbursts comparable to 30 dor , although there are a few detected h@xmath0 sources that have a scale in between 30 dor and carina , and several comparable to carina in the inner spiral arms of the galaxy . there are a few dozen smaller h  ii regions comparable to orion scattered around ngc  7259 , but none in the vicinity of sn  2009ip .    with a presumed initial mass of 50 - 80 @xmath2 @xcite , and a lifetime of only @xmath14 myr , one would expect sn  2009ip to reside in a massive young cluster with many other o - type stars , and to be surrounded by bright extended h  ii region emission . this is clearly not the case , nor are there any such h  ii regons in the vicinity . we dod not attempt to obtain deep radio data to search for free - free emission from h  ii regions or sn remnants , although this may be interesting future observation to make . we discuss implications corresponding to each type of region below . _ 30 dor : _ big h  ii region complexes like 30 dor can have ongoing massive star formation for 10 - 20 myr @xcite . 30 dor contains the very young ( 12 myr ) cluster r136 , as well as the @xmath110 myr old population that gave rise to sn  1987a . if sn  2009ip were in such a region , the new _ hst _ images would clearly detect bright extended h@xmath0 emission in the few 10@xmath18 pc surrounding sn  2009ip . we can rule out the presence of such a large complex at the position of sn  2009ip or within several kpc . _ carina : _ the carina nebula has birthed about 70 o - type stars @xcite , and is of sufficient scale to sample the upper part of the main sequence . there are a handful of extremely massive stars in carina , including @xmath19 carinae and three very massive wnh stars . moderately large h  ii regions like carina fade in 5 myr ( carina is now @xmath13 myr old ) when the most massive o stars have died and the bulk of the ionizing photons shut off . with a presumed initial mass of 50 - 80 @xmath2 , one would expect sn  2009ip to come from a region that is no older than than this ( if it is a single star ) . however , we can clearly rule out a bright extended h@xmath0 nebula like carina at the position of sn  2009ip . after about 5 myr , there may be a larger and fainter h@xmath0 bubble . this is harder to rule out , and depends on an adopted escape fraction of ionizing photons . as noted earlier , our psf subtraction residuals allow for some faint emission within 40 pc of the sn site , but these could also be artifacts . the lack of bright extended emission to a surface brightness about 10 times fainter than carina s outer shells @xcite would imply a region significantly older than 5 or 6 myr , and would also therefore cause us to expect that any stars with initial masses above 40 @xmath2 are long since dead . the lack of any carina - like h  ii region in the 1 kpc surrounding sn  2009ip also suggests that it is unlikely to be a runaway from such a region .    _ orion : _ the orion nebula contains only one o - type star ( with an initial mass around 30 @xmath2 ) . smaller h  ii regions like this with only a couple o stars die after 5 - 6 myr as well , when any mid - o - type stars evolve off the main sequence and most of the ionizing photons shut off . the surrounding gas shells become neutral and get much fainter and diffuse as they age . moreover , even when young and bright , such a region would be very small in terms of angular extent and would be unresolved by _ hst _ at 20 mpc . such an h  ii region could easily be the birth environment of sn  2009ip and may be hiding under the sn emission . it would be unusual ( although perhaps not impossible with stochastic sampling of the initial mass function ; @xcite ) to find such a massive 50 - 80 @xmath2 progenitor being born in this type of region . it seems more plausible that such an h  ii region might give rise to a single very massive star like the progenitor of sn  2009ip through binary evolution ( see below ) . although an orion - like region could be hiding underneath the current photometry of sn  2009ip , it is important to note that such regions are rarely found in complete isolation . massive star formation tends to propagate from one region of a molecular cloud complex to another @xcite , leading to chains and complexes of h  ii region emission in disk galaxies . orion is part of a larger complex of star formation in the orion region , but no sign of any other nearby h   ii regions are seen in the images of sn  2009ip . therefore , we have the additional unusual circumstance that sn  2009ip s birth environment would need to be a singular instance of star formation , or the last such episode of massive star formation in the vicinity . all of these considerations point to ages that are longer than 5 myr , and more likely around 10 myr or more , suggesting initial masses around 20 @xmath2 . this is in apparent contradiction with the high luminosity of the progenitor star in its early phase before the series of bright pre - sn eruptive events ( at least 50 - 60 @xmath2 ) . one way to close the gap between the massive progenitor that was detected and the surprising lack of recent massive star formation in the vicinity would be to invoke binary evolution . either sn  2009ip was a runaway star born at some other location , or it has been rejuvenated by binary interaction .    if it is a runaway , the nearest indications of massive star formation in ngc  7259 are found at least 1.5 kpc away . to cover this distance in a time of @xmath13 myr would require a kick speed of 400 - 500 km s@xmath3 . this would be a very fast kick for a massive companion of a sn . moreover , such high runaway speeds seem hard to reconcile with the narrow emission lines in the spectrum of sn  2009ip ( arising in the pre - shock csm ) , whose centroid radial velocities are consistent to within @xmath20100 km s@xmath3 with the redshift of the host galaxy @xcite . a more likely alternative may be that the progenitor of sn  2009ip increased its mass and luminosity late in life by accreting mass in a mass transferring interacting binary system , or by a stellar merger event ( see @xcite ) . this would allow the stars to live a longer core h - burning main sequence lifetime of a lower - mass star , and to then get rejuvenated by mass accretion or merging to produce the luminous progenitor source that was detected in 1999 . this is the sort of evolutionary scenario suggested for lbvs based on their remote environments @xcite , although it should be noted that sn  2009ip s environment seems unusually remote even among known lbvs . the most isolated lbv known in nearby galaxies is r71 in the lmc , which is 300 pc from any o - type stars , but still on the outskirts of 30 dor @xcite . @xcite pointed out , however , that rejuvenation by mass accetion or merging might produce an lbv - like star that appears very isolated even without a kick if it is a blue straggler in a relatively small , isolated , and aging star cluster . this scenario requires the presence of a relatively modest @xmath110 myr - old star cluster or association at the position of sn  2009ip , which could be hidden by the current ongoing csm interaction . observations after the csm interaction luminosity fades ( this may take several years ) can eventually test this hypothesis .    a binary scenario for the progenitor of sn  2009ip was invoked previously , independent of the remote environment . the disk - like csm inferred to exist around sn  2009ip @xcite would be consistent with the notion that some strong binary interaction had occurred in the recent past . the repeating brief luminosity spikes in 2009 - 2011 we also attributed to binary close encouters @xcite , either through direct stellar collisions at periaston in an eccentric system as in the @xmath19 car system @xcite or potentially due to periastron accretion events @xcite . the remote environment discussed here strengthens the argument for a binary progenitor . if the sort of binary rejuvenation discussed above is appropriate for sn  2009ip , then it is important to remember that the companion should still be there if the binary system did not merge . this companion might be combined with any host cluster light in the late time photometry after the csm interaction luminosity fades . if this sort of binary rejuvenation scenario is _ not _ the origin of sn  2009ip , then its very luminous progenitor source is difficult to understand . to produce such a luminous , h - rich progenitor with a strong wind and eruptive variability may require a more exotic scenario invoving a binary system with a massive compact object accreting from a companion , for example , which might then lead to a core - collapse sn explosion .    a pulsational pair instability ( ppi ) eruption @xcite is the only proposed single - star mechanism to produce a non - terminal eruption that could account for the total energetics of sn  2009ip s 2012 event , which has been shown to require a kinetic energy well above 10@xmath21 ergs because of the asymmetric csm and the large ejecta mass implied by the sustained broad - lined spectrum @xcite . however , typically the ppi will have a large ejecta mass and expansion speeds @xmath205,000 km s@xmath3 @xcite , slower than the observed 13,000 km s@xmath3 broad lines in sn  2009ip s 2012a event @xcite . the most energetic ppi events approaching 10@xmath4 ergs would require extremely high initial masses in excess of 100 @xmath2 , and it is uncertain if they occur at all at 0.5  @xmath22 due to mass loss . it seems very unlikely that there would be no evidence whatsoever of recent massive star formation in the vicinity of sn  2009ip if it originated from a star born with an initial mass above 100 @xmath2 . support was provided by the national aeronautics and space administration ( nasa ) through hst grant go-13787 from the space telescope science institute , which is operated by aura , inc . , under nasa contract nas5 - 26555 . support was also provided by the national science foundation ( nsf ) through grants ast-1210599 and ast-1312221 to the university of arizona . this study used data products from the southern h - alpha sky survey atlas ( shassa ) , which is supported by the national science foundation .
we present late - time _ hubble space telescope _ ( _ hst _ ) images of the site of supernova ( sn ) 2009ip taken almost 3 yr after its bright 2012 luminosity peak . 
 sn  2009ip is now slightly fainter in broad filters than the progenitor candidate detected by _ hst _ in 1999 . 
 the current source continues to be dominated by ongoing late - time csm interaction that produces strong h@xmath0 emission and a weak pseudo - continuum , as found previously for 1 - 2 yr after explosion . 
 the intent of these observations was to search for evidence of recent star formation in the local ( @xmath11kpc ; 10 ) environment around sn  2009ip , in the remote outskirts of its host spiral galaxy ngc  7259 . 
 we can rule out the presence of any massive star - forming complexes like 30 dor or the carina nebula at the sn site or within a few kpc . 
 if the progenitor of sn  2009ip was really a 50 - 80 @xmath2 star as archival _ hst _ images suggested , then it is strange that there is no sign of this type of massive star formation anywhere in the vicinity . 
 a possible explanation is that the progenitor was the product of a merger or binary mass transfer , rejuvenated after a lifetime that was much longer than 4 - 5 myr , allowing its natal h  ii region to have faded 
 . a smaller region like the orion nebula would be an unresolved but easily detected point source . 
 this is ruled out within @xmath11.5 kpc around sn  2009ip , but a small h  ii region could be hiding in the glare of sn  2009ip itself . later 
 images after a few more years have passed are needed to confirm that the progenitor candidate is truly gone and to test for the presence of a small h  ii region or cluster at the sn position . 
 [ firstpage ]    circumstellar matter  stars : evolution  stars : winds , outflows  supernovae : general  supernovae : individual ( 2009ip )