"The 1001 Nights of SN 1987A" Compiled by P

ing spent the night in La Serena, they and Telescope of July 1969 (Vol. 38 (7] Cou. Doc. Chi-12 and 14 in EHA­ flew back to Santiago on March 27 [18]. No. 1). 1.A.2.14. and letters of Heckmann to Oort of 4 and 13 Oet. 1964 in EHA­ References and Notes 1.A.2.10. The Dedication Symposium on [8] ESO Basic Texts, Seetion B4. Abbreviations used: (9] See the sketches included in the Annual the Magellanic Clouds EC = ESO Committee, the committee that Report 1965. preceded the ESO Council. The dedications also induced ESO to [10] See, for instance, Ann. Rep. 1968, p. 10. EHA = ESO Historical Archives. See the de­ organize its first broad scientific sym­ The realization of this teleseope beeame scription in the Messenger No. 54 of De­ posium at the Headquarters in Santiago part of the task of the ESO TP-Division. cember 1988. on March 28 and 29. Subject were the [11] See FHA File 2.9.2. The last one of the EHPA = ESO Historical Photographs Archive. signatures was on Sept. 11, 1969, by the Magellanic Clouds, one of those objects FHA Files belonging to the Office of the = Chancellor of the Uno of Bochum. of research at which ESO had aimed Head of Administration of ESO. from its very beginnings. Participants [12] See FHA File 2.9.3. [1] EHA-I.A.2.14. [13] See Doe. Cou-205 of Nov. 7, 1975 in came from Argentina, Australia, Chile, (2] Frank Middelburg became an ESO em­ FHA File 2.9.3. Mexico, South Africa, the United States ployee in 1967. By the time of his un­ [14] See Couneil Minutes Deeember 1968. and, naturally, from the ESO member timely death in the year 1985 he had [15] "Problemes poses cl I'ESO par I'implan­ states. The Proceedings of the sym­ become a specialist in the fields of im­ tation sur ses terrains d'lnstruments posium, edited by Andre Muller, were age processing and software systems. etrangers". published in 1971 [19]. The symposium See the obituary by A. Ardeberg in the [16] See Minutes 13th Cou Meeting, p. 12. underlined ESO's taking up its tasks in Messenger No. 42 of December 1985. [17] Cou-doc No. 55 of May 30, 1969 in FHA astronomical research - although at that (3] See the ESO Annual Report for 1968. 1.1 .1/1 .2.1. time modest observing programmes [4] A copy of this report occurs in the Oort [18] Details of the programme of the Council Archives of the Leiden University Li­ visit are in EHA-1. A.2.16. See also B. E. had been underway with the first tele­ brary; a duplicate from this has been put Westerlund's report in Sky and Tele­ scopes, as we shall see in the next in EHA-I.A.1.18. scope, Vol. 37, No. 6 of June 1969. article. An early report on the sub­ (5] EHA-1. A.1.22. (19] A. B. Muller, ed., The Magellanic Clouds, jects discussed at the symposium was (6] Cou. Doc. Chi-7 in EHA-I.A.2.14. and Astrophysics and Spaee Library, given by Bengt Westerlund in Sky minutes of the 2nd Cou Meeting. Vol. 23, Reidel Dordreeht 1971.

REPORT ON THE FOURTH JOINT ESO/CTIO COLLOQUIUM "The 1001 Nights of SN 1987A" Compiled by P. BOUCHET, ESO

1. Introduction 2. VISIBLE 5 11. SPECTROPHOTOMETRY: I The fourth joint ESO/CTIO colloquium Day 190 SN 1907A Mark M. Phillips/CTIO [0 I [Ca IIJ was held at La Silla on November 20, Ca 11 Hp Na 1" I P6 1989, in order to celebrate properly the SN 1987 A in the Large Magellanic III I results of the 1001 nights spent after the Cloud has provided a unique opportuni­ 4 outburst of SN 1987 A. This colloquium ty to study the spectral evolution of a consisted of informal talks followed by Type 11 supernova. Taking advantage of ~ debates and a round-table discussion the superb observing conditions that dealing with the acquired experience in characterize the "Norte Chico" of Chile, Day 589 a supernova follow-up, the current ob­ astronomers at ESO and CTIO have led servations of SN 1987 A, the future joint the way in obtaining precise spec­ ESO/CTIO monitoring of SNs, and the trophotometry of this important object DaY714 [FaIlJ preparation for the next bright super­ at visual wavelengths. These observa­ - 111 nova(e?) (observations in Chile). tions have yielded a number of impor­ ~[F~ IIJ Most of the statt astronomers and tant findings, a few of which are listed I visitors from the three observatories of below: Day 907 the IVth region of Chile (La Silla, CTIO, [Oellt) Las Campanas) were able to attend the 2. 1 Abundance Anomalies meeting, which largely contributed to its o in the Hydrogen Envelope success. 4000 6000 0000 10000 The colloquium ended in the gym­ The first spectra obtained of SN Aoo. (A) nasium of La Silla where the ESO As­ 1987 A were characterized by strong H tronomy volleyball team brilliantly de­ and He P-Cygni emission lines. feated the CTIO one, in an intense Attempts to model these early spectra Figure 1: Seleeted optieal speetra of SN 1987 A obtained at CTIO whieh iIIustrate the game. To conclude in the very best way have suggested that the helium abun­ evolution from days 198-907. Identifications this pleasant and fruitful day, a cocktail dance in the outer envelope of the of the most prominent emission and absorp­ was then ottered to everybody. supernova may have been as much as a tion features are indicated. The narrow [Oll/J We present in the following a factor of 2-3 times the solar value. As and [S II/J lines visible in the speetrum for day summary of the talks given during the the supernova expanded and cooled 907 are due to the eireumstellar material that meeting. over the following weeks, strong ab- surrounded the progenitor Sk -69202.

34 sorption lines of Ba, Sr, and Sc were r -I observed, indicating similar enhance­ 0- "~."'M- ... ments of the s-process elements. These ...... ,-...... ~ findings suggest that the progenitor of '.."K...... SN 1987 A, Sk -69202, may have "....-. --..... f ~ undergone a phase where the products ..."...... of a He-burning shell were mixed in sig­ -. -. "Z I .... ~ nificant quantities to the surface. 5 - -...... -. , ~... --... Ii 2.2 The "Bochum Event" -...... • 'z \ I 1- I I Approximately three weeks after the ... t outburst of SN 1987A, two emission "bumps" appeared in the blue and red 1II1 I 10 lIt wings of H-a and several other emission lines. It seems likely that these bumps ''!i..... I were the first observable consequence of the arrival, at the photosphere, of --L.----"----''--1--L~---' energy associated with the radioactive L.-..J'---'---L-.J.. __._L1---'----I_L.-LI--1.--1.---1_ .L decay of 56Ni and 56CO. For this to have ?,oo 40n 600 000 1000 Occurred less than a month after out­ burst implies significant mixing of radioactive materialoutwards into the hydrogen envelope.

2.3 {Fell] Emission During the "Nebular" Phase Emission lines of [Fell] became clearly visible in optical spectra of SN 1987 A around 200 days after outburst, growing in strength until approximately day 650 l1l 1-0 ::l (Fig. 1). Forbidden emission Iines of Fe, o Ni, and Co were observed in the infrared Ö at approximately the same time. These u observations represent the first unam­ I biguous detection of the products of explosive nucleosynthesis in a type 11 supernova. 6 - o 0 0° 2.4 Emission Une Profile Variations

At the beginning of the nebular phase 1000 (day 200 or so), the peaks of the H I, Nal, Ca 11, and [Fell] lines all displayed a prominent redshift, apparently due to scattering by electrons in the hydrogen I I I -2 '} 1 1- jI 0011 ~f ,I ~ I@ N:t~ 11 II \I I I 60 ~ o -, "'" •: N2'~ © '0 [Ca 11] 0 0 0 ~ : Nl~~ CDoo 0 @ I 00 @ l§© l1l Rj;11!!l~ ca I i ~ 20 QJ ~ ~ •.. ~. "Cl ~:..E 0l§ 0 ;:l 2 10 0: .... '2 x ~ ~ 60 E-t-f-+-I I I III f-t tlJJ N2'= N2 - 0.5 'Sc 0 0 l1l N:J'= N:J - 0.5 .0 x c i5 Ha ;:;; QO'= QO - 0.6 x § -', 'I - 00 . x 0 20 0 IU 10 6 200 .00 .00 .00 x x TIME SINCE CORE COLLAPSE Figure 2: The contribution of the Ha (Iower I I I I I panel) and[Ca 11] 7291,7323 (top panel) emis­ o 200 400 6no 000 1000 sion lines in SN 1987A to the f1ux in the CTiO Days after explosion R band, plotted as a function of time. Figure 3: The lightcurves in the broad band filters, as indicated. 35 -', ".,"I ~ '... April. 1907 ~ \, .,... "\

lE 1

III 11

10 20 10 20 § I I li i 111 1::~ L.. ~ , ,§ ! 11"1,1 1 10 20 1 10 20 1 10 20 1 10 20 1 10 20 1 10 20 Figure 4: The evolution of the spectral energy distribution from 1 to 20 !J.m deduced from ESO broad band photometry, and the evolution of the spectrum obtained through CVF filters, for the indicated dates (X-axis: wavelength in !J.m; Y-axis: f1ux density in erg S-I cm-2 !J.m-I). .

envelope. The peaks of the [0 I] 6300, obtained have been used together with account when deriving the bolometric 6364, [Ca "] 7291, 7323, and [C I] 9824, the ESO infrared observations to con­ light curve of SN 1987 A. 9850 lines lacked such a redshift during struct the ESO/CTIO bolometric light­ the same period, proving conclusively curve. 4. INFRARED OBSERVATIONS: that these emission lines originated in a Large discrepancies have been found Patrice BouchetlESO physically distinct zone. Between days between the observations of UBVRI 525-590, however, the peaks of all of photoelectric photometry of SN 1987 A An infrared monitoring programme of the observed emission lines underwent carried out a CTIO and at SAAO. In SN 1987 A was started at La Silla on a sudden blueshift, coinciding nearly ex­ order to clear up the origin of these February 27, 1987, and is still going on. actly in time with the development of a differences we calculated synthetic The observations carried out (at the far-infrared excess in the flux distribu­ magnitudes using different bandpasses 1-m, 2.2-m and 3.6-m telescopes) con­ tion of the supernova. These two from our spectrophotometric database. cern broad band photometry from J phenomena have been successfully in­ For this purpose we made laboratory (1.24 ftm) to Q 0 (20 ftm), as weil as terpreted (by ESO astronomers at first) measurements of the bandpasses used spectrophotometry in the four atmo­ as observable consequences of the for­ at CTIO, with which we were able to spheric windows (1.4-2.4 ftm; mation of dust in the ejecta. Although successfu/ly reproduce the CTIO photo­ 2.9-4.2 ftm; 4.7-5.4 ftm; 8-13 ftm) the blueshifted peaks have persisted to electric photometry. On the other hand, with CVFs (/J ~A. - 80). The ESO team the present, further changes have con­ the SAAO photometry could be synthet­ working on this programme include I.J. tinued to occur in the profiles of at least ica/ly reproduced using the standard Danziger and L. B. Lucy from ESO­ some emission lines. Most prominent of Kron-Cousins band functions. We con­ Garehing and, familiar to all ESO in­ these has been a broadening of the [0 I] clude that the discrepancies between frared users, our observer R. Vega, 6300, 6364 Iines which occurred be­ both data sets are due only to the whose active and enthusiastic participa­ tween days 700-800, the cause of which differences between the photometrie tion has been crucial for the pro­ is not yet fully understood. systems used at both observatories. In gramme. T. Le Bertre and A. Moneti also addition, we found that the contribution collaborated for some of the observa­ of the emission lines in the spectrum of tions. 3. UBVRI PHOTOMETRY: SN 1987 A to the Rand I magnitudes is Since we started this work, a large Mario Hamuy/CTIO non-negligible for the purpose of trans­ amount of observing time has been de­ Since the announcement of the out­ forming the broad-band magnitudes to dicated to it, resulting in the most com­ burst of SN 1987 A, the CTIO staff has monochromatic fluxes (see Fig. 2). The p/ete set of such data ever co/lected on undertaken a regular photometrie effect of the emission lines in the UBVRI a supernova (including SN 1987 A!). Fig­ monitoring of the Supernova. The data photometry must be carefully taken into ures 3 and 4 iIIustrate our results. 36 2- ,-,-, (the only one available which takes into account the measured infrared flux up to 20 11m), is by now weil known and understood (see the curve on page 41 of this issue of the Messenger) as UlJ DIJD folIows: o • During the first 10 days the high tem­ perature plasma produced by the o passage of the shock, cooled to a tem­ perature typical of hydrogen recombina­ tion (T - 5500 K), which produces a rapid decline of the lightcurve. -2 • Between days 10 to 125, there was a slow brightening to maximum followed by a rapid decline as the hydrogen re­ o combination front propagated inward o into material that was being heated by radioactive decay of 56Ni and 56CO. At --1 [1- L-....l--'---'-_L-....l--'---'-_L-....l--'---'-_L-....l--'--J.._L_-'-----'---'-_ that time, the radioactive decay energy o 200 -100 GOO [JOO 1(JOD was trapped behind the hydrogen re­ Doys since oulbuC'sl combination front and produced both Figure 5: The spectral index a as function of time. mechanical work in accelerating the plasma and later a diffusion wave of energy that was seen as the broad max­ imum (mixing of the radioactive material 4. 1 The IR Exeess and Exeess Emission while (V-K) suddenly changed evolution outward, and of hydrogen inward into atM from blue to red, even though there has the core). Note that the light curve been no corresponding change in the slowed its rise around day 30 at the time Even in the earliest photometry, there bolometric lightcurve (see next section). when SN 1987 A began to be powered was a clear excess in the far IR. By day The simultaneity of these events can be by energy released from the diffusion 100, an emission started to develop in most easily explained by the formation wave of thermalized radioactive energy, the M band (4.8 11m), which was attri­ of dust (or the accelerated formation of rather than the recombination of the hy­ buted to CO. By day 260, an excess dust, if the early IR excess is due to drogen ionized purely by the shock, as appeared at N 1 (8.4 11m), probably due dust) local to the Supernova. The ESO discussed by M. Phillips in his talk (see to SiO. We define the infrared spectral team (Danziger et al. 1989, and Lucy et also Lucy, 1988). index a by fitting from L (3.8 11m) to Q 0, al. 1989, 1990) were first to announce • Between' days 125 and 800, the re­ excluding M and N 1, the function: and discuss the formation of dust in the combination front had passed through

Fv = Fa v" ejecta of SN 1987 A. These authors the diffusion wave of trapped energy, have estimated the dust extinction in and the observed bolometric flux be­ Figure 5 shows the evolution of the a various optical emission lines, and using came due to the fraction of the radioac­ index: it started near the Rayleigh-Jeans these line optical depths, have shown tive energy from the decay of 56Co that law (a = 2) and decreased rather uni­ that the inflection in the V lightcurve at was thermalized by inverse Compton formly. Such a continuous temporal var­ around day 500 can be modelIed by a scattering. iation argues for a single physical cause, simple extrapolation of this lightcurve • After day 800, measurements made in the most obvious explanation being the from the linear decline phase, reddened August and November 1989, showed a early and continuous formation of dust according to the estimated extinction levelling off of the lightcurve. Subse­ (starting at about day 100). However, from the emission Iines. They have also quent observations made in December with these data alone it is not possible to shown that the line optical depths and January confirmed the reality of the rule out that several effects may have appear to provide evidence for selective levelling off. This result, and its interpre­ conspired to produce the uniform varia­ extinction. tation as probably due to the presence tion. The IR excess till day 300 could be of a pulsar, has been communicated due just to the gradual transformation recenfly in I. A. U. Circular 4933 (Janu­ 4.3 The Bolametrie Lighteurve from a dense and optically thick plasma ary, 1990) and the ESO Press Release radiating like a black body to a low The CTIO UBVRI photometry together PR 01/90. It is presented in this issue of density optically thin plasma radiating with the ESO infrared photometry have the Messenger (page 41). by free-free emission (a = 0). Indeed, a been used to derive the bolometric Iight­ In conclusion, the main results con­ leveled out a 0 between days 200 and curve (Suntzeff and Bouchet, 1990). In cerning the ESO/CTIO bolometric light 300. After that time, a resumed its de­ order to estimate the luminosity of the curve are: crease as a cool component appeared. thermal component (discussed in the At least up to day 800: previous section) a black body fitted The sum of the observed flux (be­ between Land QO (with an interpolation tween 3200 and 20 11m) with the ob­ 4.2 The Thermal Component A at M to avoid the contamination by CO) served high-energy flux as fit by the Around day 550, our broad band pho­ has been integrated up to zero frequen­ models, is consistent with SN 1987 A tometry reveals the emergence of a cool cy. Since the actual f1ux in the far IR is being powered purely by the decay of component (Fig. 4). When the thermal probably a combination of line emis­ - 0.07 MG:> of 56CO. emission rapidly dominated the total ob­ sions and thermal re-radiation from No more than 30 % of the thermal flux served flux, the optical magnitudes be­ dust, the estimated total flux from the can be due to an infrared echo without gan to accelerate their dec\ine in bright­ fits is an upper limit to the thermal radia­ violating the energy budget. Any pulsar, ness. (U-V) decreased roughly uniformly tion. The resulting bolometric lightcurve IR echo or radioactive source other than

37 56CO must have a luminosity inferior to scopes where the installation of a Large Magellanic Cloud). On about day 1.5 x 1038 erg S-1 . photometer was possible: 300 the optical continuum had faded At least from day 900 on, the • The 3.6-m telescope and the Danish sufficiently that nebular lines could be bolometric lightcurve lies above a linear 1.54 were the most used. seen in the optical spectral region, and extrapolation from earlier epochs, which • The acquisition programme allowed the extension of the nebular lines be­ implies that a hitherto undetected ener­ us a time resolution of 1 msec. yond the width of the supernova con­ gy source started to contribute signifi­ • The famous Crab Pulsar (wh ich has a tinuum spectrum indicated the presence cantly to the total energy output. period of rotation of 33 msec and is of a small bright nebula, about 2 arcsec bright enough to be detectable with cer­ in diameter (Wampler and Richichi, tainty in a few seconds integration at the 1989). It was already expected that the 4.4 The Spectrophotometry 3.6-m telescope) was observed when blue supergiant phase of SN 1987 A that The infrared range is perfectly suited possible to check our acquisition pro­ occurred just before SN 1987 A ex­ for spectroscopic studies of super­ gramme. ploded would produce a high density novae: in fact, whereas optical emission After the announcement in January shell of shocked gas around the pro­ lines are strongly temperature and den­ 1989 by Middleditch et al. (lAU Circular genitor star. The UV flash that accom­ sity dependent, the infrared forbidden 4735) of the discovery of a nearly 2-KHz panied shock break-out in the first line fluxes depend only weakly on tem­ periodic signal from SN 1987 A, we minutes of the explosion would then perature (for T 2: 1000 K). In addition, modified our equipment in order to get a ionize the shell; the observed nebular for several years after the explosion, the sampie rate of 10KHz. In February lines are a signature of the recombining densities in the ejecta exceed the critical 1989, SN 1987 A was observed at the gas. densities of most of the fine-structure 3.6-m telescope. The data, which were On August 29,1989, UT, the ND was levels, so the line fluxes are independent immediately sent to Garching (Max­ used to obtain images of the supernova of the density in the emitting region. Planck-Institut für Physik und Astrophy­ in conditions of 0.4 arcsec seeing; some Once the transitions become optically sik) to be analysed, did not show any of these were published in the De­ thin, the masses of heavy elements in significant signal, giving an upper limit of cember issue of the Messenger. A com­ the ejecta can be directly determined magnitude 20 for the pulsar (Ögelman et posite of more recent images taken on from the IR line fluxes. Moreover, the al. , lAU Circular 4743). December 18 by Sandro D'Odorico and major IR continuum opacity in the H/He We continue our monitoring at a rate Massimo Tarenghi is shown here in Fig­ gas envelope is free-free absorption, of approximatively 1-2 nights per ure 6. We are indebted to them for per­ which becomes small after several month. A Fast Fourier Aigorithm de­ mission to publish their data here. With months. In the mantle, where the heavy veloped by P. Grosb01 from ESO is used the stellar images subtracted, it is seen elements are ionized, the total free-free at La Silla at the Sun computers to have that the nebula consists of three main optical depth is small at infrared a quick look at the data a few hours after structural components: an inner oval wavelengths after - 6 months, and the their acquisition and react immediately if nebula, an outer filamentary loop north formation of optically thick dust in the something is wrong in the acquisition and south of the inner nebula and a envelope produces a continuum (and programme or in case we detect some­ "light echo" that is shaped Iike "Napo­ alters the gas phase abundances in the thing ... leon's hat" and extends to about 6 light­ ejecta). Our CVF spectra have been At the moment of writing, no signifi­ years to the north of the supernova. The used to determine the masses of the cant signal has been detected from SN inner structure of the nebula appears to heavy metals in the mantle, and particu­ 1987 A in the many hours of observa­ be morphologically very similar to galac­ larly for 56CO, through the observation of tions that we got. Even for this 1001 tic planetary nebula. the [CoII] line at 10.52 f.tm. nights meeting no significant signal It has been supposed that planetary The modelling of the spectrum leads came out. nebulae begin during the red giant to the conclusion that, at t 2: 1000 days, The recent infrared observations (P. phase of a star's evolution, but that their an "Infrared catastrophe" should occur Bouchet, this article) that show a level­ complex structure results from an in­ as the radioactive heating rate drops ling off of the bolometric lightcurve en­ teraction between the red giant wind below the saturated, high temperature courages us to continue our effort. and the wind and radiation from the cooling produced by fine structure lines. subdwarf nucleus (Balick, 1987; Balick At the time of this writing (January 1990) and Preston, 1987). Because SN 1987 A 6. THE NEBULOSITY NEAR this "catastrophe" has not yet occurred. never became a subdwarf and after its SN 1987 A: E. Joseph Wamplerl red giant phase it was only a blue giant ESO for a short period of time these observa­ 5. SEARCHING FOR THE PUL­ Because the progenitors of type 11 tions may prove useful for constraining SAR: Christian Gouiffes/ESO supernovae were expected to be red models of planetary nebula formation. The duration of the neutrino burst de­ supergiant stars, there have been a Even if the nebulosity around SN 1987 A tected by the Kamiokande and the 1MB number of studies of the expected in­ is classified as a planetary nebula, it is groups as weil as its energy suggest teraction of a supernova explosion on not likely that SN 1987 A is the first that a neutron star was born after the the remnant red supergiant wind (see observed supernova to explode inside a explosion of the supernova SN 1987 A in Chevalier, 1987 for an early discussion planetary nebula. Dickel and Jones the LMC. If the conditions are not too of the SN 1987A situation and other (1985) have suggested, on the bases of unfavourable (optical thickness too high references). Beginning on about day 80, modelling Tycho's supernova remnant, or a pulsar beam not pointing in the narrow nebular lines were seen in IUE that Tycho's supernova (a type-I super­ direction of the earth for example) one spectra of SN 1987 A (Wamsteker et al., nova) exploded inside a planetary might expect to detect optical pulses 1987, Fransson et al., 1989). These lines nebula. from the Pulsar. grew in strength for about 400 days and We are very fortunate to have had a We have started at ESO a continuous then faded. This suggested that the nearby supernova explode in our search in order to look for the possible supernova is surrounded by a thin nebu­ lifetimes. At the present time the studies emergence of this pulsar. The observa­ lar shell with a radius of about 400 light­ of the expanding envelope and the tions were carried out at different tele- days (-1.3 arcsec at the distance of the surrounding nebulosity can proceed in- 38 dependently, but soon the two will begin to interacl and we can expect even more fireworks!

7. WHAT THE STORY TEACHES US: Patrice BouchetlESO lhe following is certainly not inlended to be a complete review 01 the subject (for this purpose, Ihe reader may reler to Ametl et al., 1989 and Hillebrandt and Höllich. 1989), but ralher abrief summary, from an observer's poir,t of view, of the highlights 01 SN 1987 A. (Note that additional relerences can be lound in these two reviews.)

7.1 The "Pecllliarities" lhe lact thai (he progenitor was a blue supergianl has certainly been the lirst surprise 01 SN 1987 A. However, it was already known before SN 1987 A exploded, thaI a low rnetatlicily andJor an extensive mass loss could lead mas­ sive slars 10 such a blue phase. Or,ly lhe eflects 01 an appropriate mixing seem to have been sludied alter the explosion of the supernova. The blue appearance 01 the progenitor is probably due 10 these Figura 6: A composl/e lIn.1ge In {Dill] I)nd (Nil) ligl1f of IM nebulosJly near SN /987 A nIe three interconnected effects, and it is Jmages were takell wlth IIle NTT by S. O'OdOfiCO ,1nd M, Tarenglu Oll December 18. /989. The therefore not considered anymore as an Images of SN 1987 A and ilS (WO fleld stars htWe beeil rernoved m order 10 show Ille nebular slfllclure more clearly. NOit/! 15 up and E,1SI IS 10 Ille left. Tlle sjze of Oie figure IS 14 x 13 extraordinary characteristic 01 SN arcsec, 1987 A. but rather as one possible road in the stellar evolution. However, it is Worth nOling that it is thanks 10 SN 1987 A lhat we are now aware 01 il! inslance.lhe use 01 SN 1987 A 10 check Anolher importanl new concepl inlro­ The second surprise was Ihe relatively the reliabilily 01 Ihe absolute f1uxes de­ duced by Ihe observalions of SN 1987 A low luminosity 01 SN 1987 A relative 10 duced from Iheory. showed Ihal the relers 10 lhe presence of an in­ other "normal" SN IIS: Ihis has been ex­ models have 10 be quile sophislicated, homogeneous mixing of shells 01 differ­ plained as a consequence of lhe more and lhal a large amount 01 observational ent chemical composilion, In fact, mix· COmpact structure of the progenilor. dala has 10 be available. It !lOW seems ing occurred: Moreover. as we have seen above, the dangerous to use SN IIs as a kind 01 • Before the explosion (induced by bolometric Iighlcurve is periectly inler­ slandard candles. large-scale molions due to the rolation preted in lhe same frame and wilh Ihe 01 lhe progeniIOr). Tl1ls makes Ihe same mechanism as those used for academic dogma 01 an onion-shell-tike 1.2 Tlle New Concepls olher SN IIs. In particular lhe role of Ihe struclure (before Ihe explosion) quile radioaclive decay of 56Co 10 power Ihe The deleclion 01 Ihe neulrinos a few obsolete. lightcurve is a confirmalion of Ihe lirsl hours belore (he explosion indicates lhe • During and after Ihe explosion (due 10 suggestions made by Weaver and formalion 01 a neutron slar: Ihis is lhe Rayleigh-Taylor instabllilies or to Ihe ex­ WOOSl ey (1980). lirst direcl evidence Ihal Ihis can really pansion of hol bubbles of radioaclive Illurns Out. Ihen, that lhe main "pecu­ occur! These direct observalions have Nickel): This was realized because 01 Ihe liarity" 01 SN 1987 A is that il could be been used 10 place new conslraints on early deleclion of X and y rays. Ihe need Seen! Seleclion effecls (Iike eXlinction Ihe fundamenlai properties 01 such par­ 10 match lhe theoretical models 10 and dlslance) lavour. indeed, the delec­ licles (resl masses. Iifelimes, magnelic Ihe observed bolomelric lighlcurve lion 01 brighl explosions (in visible fight). momenls. mixing angles, elc.), on im­ ("plaleau"). and Ihe inlerpretation 01 lhe And, lor inslance, if Ihe same supernova portant physical quanlilies such as lhe visible and infrared spectra. wOuld explode l1ear Cass A (which is nuclear equalion of stale, and on Ihe Finally, a major discovery was Ihe deo closer but in a region 01 high exlinclion). exiSlence 01 exotic particles (axions and leclion by lhe ESO leam of dust conden­ 1I could only be delected as a neutrino majorons). This is especially inleresling salion In (he melal rich eJecta wilh a emiller and (perllaps) as al1 inlrared as axions call be 01 importance in cos­ clumpy distribulion (Danziger el al.. SOurce, This leads one 10 question Ihe mology as candidates for Ihe dark mal­ 1989, Lucyet al.. 1989. 1990). One 01 Ihe presenl supernova rates. ler. However. although numerical simu­ first implicalions of lhis discovery may be lhe (relalive) proximity and low ex­ lalions have reproduced lhe luminosily Ihal the isolopic anomafies observed in tinclion of Ihis supernova allowed inten­ and the spectrum 01 those neuIrinos. meleoriles can be explained in terms of sive and complele sludies. which none could accounl lor Ihe energy ba­ dust 01 elementary and isolopic com­ proved Ihe absolule necessily of such lance of Ihe explosion. Clearly, some­ position characleristics of the ejecta 01 a Observations in order 10 gel a Iruslwor­ thing is still missing in Ihe currenl supernova which has condensed belore Ihy piclure of whal was gOlng on. For models. being diluled into Ihe primilive nebula of 39 normal isotopic composition (Clayton, As one can see, future topics of inter­ Mueller, M.W., Amett, W.D., 1976: Astro­ 1982). It seems then plausible that at est are not missing! Much has still to be phys. J., 210, 670. least one supernova exploded in the done to exhaust all the information col­ Öpik, 1953: The lrish Astron. Journal, 2, 219. vicinity of the proto-sun, some 106 years lected during these first 1001 nights of Ostriker, J.P., Cowie, L.L., 1981: Astrophys. J. (Lett.), 243, L127. before its formation (Lee, Pappanas­ observing SN 1987 These observa­ A. Suntzeff and Bouchet, 1990: Astron. J., to stassiou and Wasserburg, 1976). tions will be continued at La Silla, espe­ appear in February 1990. cially in the infrared and sub-millimetre Wampler, E.J. and Richichi, A, 1989: Astr. ranges, where more than 80 % of the 7.3 The Open Questions Ap., 217, L21. energy is now concentrated. We will Wamsteker, W., Gilmozzi, R, Cassatella, A, Although the appearance of SN also witness the birth of the remnant, and Panagia, N., 1987: lAU Cir., No. 4410. 1987 A has led to new concepts as weil watching for any kind of surprise. New Weaver, T.A, Woosley, S. E., 1980: in as an extraordinary improvement in our telescopes and new detectors will soon "Supernova Spectra", AlP Cont. proc. 63, understanding of type-li supernovae, be in operation, and new exciting results p. 15; ed. R Meyerott, New York, AlP. some points remain obscure: will certainly be obtained. • The amount of dust condensed and its possible contribution to the total References amount of dust in the galaxies. As pointed out by J. Wampler during this Arnett, W.O., Bahca/l, J. N., Kirshner, R P., The Bolometric Light colloquium, the dust formed in the ejec­ and Woosley, S.E., 1989: Ann. Rev. As­ tron. and Astrophys. 27, 1. ta is expe/led at great velocity and soon­ Balick, B., 1987: AJ., 94, 671. Curve of SN 1987 A er or later will have to slow down, with a Balick, B. and Preston, H.L., 1987, AJ., 94, high probability of being destroyed. 1641. Continuing IR photometry in the J, H, • The enrichment of the circumstellar Bartei, 1990: Proceedings of Santa Cruz K, L, M, N 1, N2, N3, Q bands at ESO­ and interstellar matter in heavy elements Workshop, S. Woosley ed. La Silla combined with UBVRI photome­ (Oanziger et aL, 1990 were first to deter­ Branch, 1977: Mon. Not. R. A S., 179, 401. try reported from CTIO (IAUC 4881, mine abundances and they show that Chevalier, RA, 1987: in Proc. ESO Work­ 4910) shows that the bolometric light there are large uncertainties in the quan­ shop on the SN 1987A, ed. I.J. Oanziger curve on 10 November 1989 (day 991) (Munieh: ESO Garehing), p. 481. titative estimates which are strongly lies 1 x 1038 ergs S-1 above a linear ex­ Clayton, 0.0., 1982: Q.J. Roy. Astron. Soc., model dependent). trapolation from earlier epochs (Suntzeff 23,174. • The stimulating role in star formation Oanziger, I.J., Gouiffes, C., Bouchet, P., and Bouchet, A. J. 1989, in press). This in dense interstellar clouds (Öpik, 1953; Lucy, L.B., 1989: LAU. Circ. 4746. levelling off was already apparent for the Herbst, 1977). Klein (1990) showed that Danziger, I.J., Lucy, L.B., Bouchet, P., previously observed day 14 August the clouds could be destroyed in Ray­ Gouiffes, C., 1990; Proceedings of Santa 1989 (day 903) though at a lower level of leigh-Taylor time scales, and give rise to Cruz Workshop, S. Woosley ed. significance and is confirmed by obser­ fragmented small clouds which could Dickei, J. R. and Jones, E. M., 1985: Ap. J., vations in less than ideal conditions on prevent star formation. 288,707. 20 Oecember 1989 (day 1030) when Fransson, C., Cassatella, A, Gilmozzi, R, • The determination of Ho through a black body fitting gives T = 160 K and Kirshner, R.P., Panagia, N., Sonneborn, G. thermal interpretation at maximum visi­ log L = 38.30 0.05. Because more and Wamsteker, W., 1989: Ap. J., 336, ± ble light (Branch, 1977, found Ho = 49 ± 429. than 80 per cent of the flux is now 1 1 8 kms- Mpc- ). With the VLBI, Bartel Gerola, H., Seiden, P.E., 1978: Astrophys. J., emitted red ward of the M band, the (1990) estimated the distance to the 223, 129. levelling off is almost completely due to LMC and deduced Ho = 60 ± 20 kms-1 Herbst, W., 1977: in "Supernovae", Proc. ofa the near constancy of the flux integrated 1 Mpc- , which in itself is not so new. special lAU session on supernovae, held over the M, N, Q bands for days 903, However, Bartel stressed the point that on September 1976, at Grenoble, France; 991 and 1030. This implies that a hither­ he could get a far higher accuracy ed. D. N. Schramm; Astrophysics and to undetected energy source is now (-20 %) by radio interferometry with Space Science Library, Vol. 66, D. Reidel contributing significantly to the total Publishing Company. energy output. If it were due to 57Co, the Arecibo and VLBI. Hillebrandt and Höflich, 1990: Preprint Max­ On the other hand, some points tradi­ Planck-Institut für Physik und Astrophysik, original amount would have to be 20-25 tionally related to the supernova MPA 458, May 1989; to appear in Progress times the anticipated 0.0017 solar phenomenon, or still speculative in Physics. masses (Woosley and Pinto, Workshop theories, have not received any input yet (keuchi, S., 1981: In "Fundamental Problems on Gamma-ray Spectroscopy, 1988), from SN 1987 A. Among them are the in the Theory of Stellar Evolution", lAU but this is contradicted by the observed following ones: Symposium 93, p. 103; O. Sugimoto, O. Q. [CoII] 10.52 f.t line strength on day 526 • The relation between supernovae and Lamb and D. N. Schramm eds.; D. Reidel (Oanziger et aL, Proceedings of Santa phenomena observed in quasars; Publishing Company. Cruz Workshop, July 1989). A thermal Klein, 1990: Proceedings of Santa Cruz • The acceleration of galactic cosmic Workshop, S. Woosley ed. echo from external dust seems unlikely rays in the shock wave fronts created by Lee, Pappanasstassiou and Wasserburg, since it would coincidentally need to the explosion; 1976: Bull. Am. Astron. Soc., 8, 457. have a colour temperature (150-180 K) • The role of supernova induced star Lucy, L. B., 1988: in "Supernova 1987 A in the similar to that of the SN's emission. formation in producing and sustaining LMC"; Proceedings of the 4th George Ma­ Moreover, the corresponding scattering spiral structures in galaxies (Mueller and son Astrophysics Workshop, eds., M. echo (cf. IAUC 4746) is not evident in the Arnett, 1976; Gerola and Seiden, 1978); Kafatos and A Michalitsianos. smooth UBVR light curves (IAUC 4881, • The possibility that supernova explo­ Lucy, L. B., Danziger, I. J., Gouiffes, C., and 4910). Nevertheless, CCO frames sions that took place during the first Bouchet, P., 1989: in lAU Colloquium 120, should be inspected for new echoes "Structure and Dynamics of Interstellar billion years or so after the big-bang (at Medium"; Eds. G. Tenorio-Tagle, M. Moles within 5 arcsec of the SN. a time when the galaxies we see today and J. Melnick (Springer-Verlag). Uncertainties in luminosities derived had not yet formed) impressed on the Lucy, L.B., Danziger, I.J., Gouiffes, C., and by fitting black body curves to the far-IR universe its large-scale structure (Os­ Bouchet, P., 1990: Proceedings of Santa data have been checked using emission triker and Cowie, 1981; Ikeuchi, 1981). Cruz Workshop, S. Woosley ed. curves for isothermal dust clouds of as- 40