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THE 1959 SUPERNOVA, SN 64 Jesse L. Greenstein and F. Zwicky Mount

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THE 1959 SUPERNOVA, SN 64 Jesse L. Greenstein and F. Zwicky Mount THE 1959 SUPERNOVA, SN 64 Jesse L. Greenstein and F. Zwicky Mount Wilson and Palomar Observatories Carnegie Institution of Washington California Institute of Technology The 48-inch Schmidt telescope on Palomar Mountain has been used since September 1957 as the most powerful instrument in the international supernova search, now being supported by the Na- tional Science Foundation and by observatories in the United States, Mexico, Argentina, France, Italy, Belgium, the U.S.S.R., and Switzerland. The supernova discussed here was discovered in Anon Barred Spiral at 1308.8 +0340 (1950) by M. L. Humason on June 28, 1959, at an estimated photographic magnitude mPg= 14.0. A brief description was given in the report on the 1959 Palomar supernova search by Humason and Gates.1 In the continuation of the master list published by Zwicky,2 this supernova is assigned the number 64. THE GALAXY AND THE SUPERNOVA The galaxy in which the supernova appeared is an open barred spiral of integrated photographic apparent magnitude ntpg =15.4 (see Plate I). With the indicative absolute distance of 29.90 mil- lion parsecs, as derived below, the indicative3 photographic abso- lute magnitude of the galaxy thus is ^(galaxy) =-17.0 (1) The apparent dimensions of the galaxy in seconds of arc are ^ = 83'/4 , d2 = lOrO . (2) The indicative absolute dimensions normal to the line of sight are therefore D1 = 12,100 parsecs , = 1450 parsecs . (3) The apparent distances of the supernova from the center of the galaxy are Τι — 6'!67 west, ^ = 6^11 south. (4) 35 © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 36 J. L. GREENSTEIN AND F. ZWICKY THE SPECTRUM OF THE SUPERNOVA Four nights after the discovery by Humason, a spectrum of 190 Â/mm dispersion on Kodak Ila-O baked emulsion was ob- tained at the prime focus of the Hale reflector, July 3.2, 1959 (see Plate II). The estimated visual magnitude was about 14; reob- servation at an extreme hour angle on August 6.2 at about mag- nitude 16.5 could provide only a weak un widened spectrum. A linear microphotometer record of the first plate is shown in Figure 1, where no attempt was made to rectify for plate sensitivity and atmospheric transmission. The spectrum is that of an early phase of a type I supernova. Fig. 1.—Tracing on a linear scale of the supernova spectrum, IIa-0 emulsion. The indicated wavelengths of maxima and minima are corrected for redshift. Intensities are on an arbitrary scale, uncorrected for trans- mission or sensitivity as a function of wavelength. Quartz optics and grating would provide a nearly constant response down to 3300 Â for a hot star. The observed wavelengths on the microphotometer tracings are derivable from Figure 1, but the actual labeled wavelengths of the maxima and minima are corrected for the redshift. Min- kowski has reproduced tracings of prismatic spectra of type I supernovae as a function of phase, useful for recognition of the features and showing their variation with time.5 A general sys- tematic trend of the maxima to shift toward longer wavelengths exists in his data and is confirmed by an unpublished study (J.L.G.) of recent type I supernovae. The redshift, 2990 km/sec, © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System PLATE I Ν ' » MIN. ARC. , Photographs of Anon Galaxy 1308.8, +0304 200-inch telescope: (a) July 3, 1959, on Kodak 103a-D, with supernova bright and (b) March 31, 1960, on Kodak 103a-O, with supernova faint. (For the use of 1(a) we are indebted to Mr. William Miller of the Mount Wilson Observatory.) © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System QI09 < G a <v Κ u(V d £\¿t W (¾ <v C H fe C o OCAI 'Π ci o C. S o w υ PH in S o co o < On ω ffi C .2 H o (Λ < 0021? tuU -i ρ (ΛΤ> Ph Pi • v-H H O W Ρ-ι .S m 3 ''SΠ 9201? § o <υ χ +-» a ou 688€ H tS) O c Ph a; <vS ubß < W Ή<u C aJ -M(U jû <L) 029£ Λ H ^ίΛ** Í í¿ ■ .>·ΐ © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System THE 1959 SUPERNOVA, SN 64 37 of the galaxy containing S Ν 64 is greater than that of Minkow- ski's brighter objects in IC4182 and NGC 1003, but after this correction, no evidence of an intrinsic redwards shift is found on the plate taken July 3. Therefore, both from the relative intensity of the bands and from their wavelengths, this spectrum seems to have been obtained within 10 days after maximum. The spectrum taken August 6 shows one dominant feature, a very broad (prob- ably complex) maximum at λ 4680, about 140 Â wide, with weaker, sharper maxima at λ 4880 and λ 5025. The longward shift described by Minkowski is confirmed, and these wavelengths corrected for the redshift of the galaxy correspond to a phase be- TABLE I Wavelengths of Features in Early Phases, Spectra of Supernovae of Type I (Corrected for Redshift) Maxima Minima Interval after NGC NGC IC Maximum NGC NGC IC SN 64 5668 4496 4182 (days) SN64 5668 4496 4182 3630 3680 3680 3670 3720: 3790 3800 3790 3770N 4000 4000 4010 4030 3960d 3950 3950 3970 7-20 4140: 4110 4090 4090 4100 6-13 43001 — — Γ4280: 4170: 4190 4200 4210 8-20 4380 4360 4390? — — 4310: ? 4440 — 4410 4510NN 4520 4520 — 4-8 — 4670 — 4560 4590 4610: 4590' ^ 4660 — 4720: 15-20 4790: 4790 — 4810 9-20 tween 40 and 70 days after maximum. The possible dates of max- imum suggested by the second plate are between May 28 and June 27, while the first plate suggests the interval including June 13 to June 28 as the probable maximum. Minkowski has also prepared an unpublished chart of the drift of wavelengths with phase in typical type I supernovae. In the fifth column of Table I we give the probable interval after maximum indicated by the positions of © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System 38 J. L. GREENSTEIN AND F. ZWICKY various maxima for S Ν 64 on the assumption that all supernovae of type I are identical. Table I also includes corrected wavelengths of features in two other supernovae of type I (J.L.G.), wavelengths of some minima, and wavelengths given by Popper.6 The similarities are quite striking, especially since the data in Table I are derived from only one plate of S Ν 64. It is certain, moreover, that some of the broad bands are complex and that their structure, origin, and relative intensities vary strongly within a few days. There are especially complex changes within the broad maxima λλ 3950-4200 and λλ 4390-4609. (See also the spectra of the supernova in NGC 4496 by Bloch, Chalonge, and Dufay.4) Minkowski's data stop below λ 3900, but Popper6 noted the strong ultraviolet maximum we find located approximately at λ 3660, and its associated mini- mum at λ 3770. This very characteristic feature should be useful for the redshifts of supernovae at quite large values, up to Δλ/λ = 0.6, although at certain phases a sharp peak is superposed. THE SPECTRUM OF THE GALAXY The prime-focus spectrograph of the Hale telescope with a 370 Â/mm-dispersion grating yielded the spectrum of the galaxy shown in Plate III. The spectrum is of type G2, but almost com- pletely washed out and showing no measurable absorption line. The slit was laid along the bar which has several pronounced knots overlapping each other, producing a strong bright line at λ 3727. The average symbolic velocity of recession obtained from the red displacement of this line is observed to be Fs = 2990 km/sec (6) with an estimated uncertainty of about 40 km/sec. The correc- tion for solar motion is small. The width of the bright line, λ 3727, in the two brightest emission knots of the bar indicates a velocity spread of about 600 km/sec, that is, AFS = ±300 km/sec around the mean F8 of 2990 km/sec. The bright line λ 3727 is not measurably inclined and the bar of the spiral is therefore not observably rotating around an axis normal to it and normal to the line of sight. © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System PLATE III 1 r- Osi t- ro Spectrum of Anon Galaxy 1308.8, +0304 Obtained with the prime-focus spectrograph of the 200-inch telescope at a dispersion of 370 Â/mm. Comparison lines are H and He. © Astronomical Society of the Pacific · Provided by the NASA Astrophysics Data System THE 1959 SUPERNOVA, SN 64 39 ABSOLUTE BRIGHTNESS OF THE SUPERNOVA The photographic apparent magnitude of the supernova on June 28, 1959, was mPg= 14.1 as derived from a comparison with stars in Selected Area 57. On June 3, 1959, the supernova was fainter than mPg = 20.5, while on July 1 it was about mPg = 14.2. From this and the subsequent rapid decline* we may as- sume that the maximum occurred on about June 23 and that the photographic magnitude was wmax = 14.0, corresponding to an absolute indicative magnitude of the supernova at maximum Mp^max) = —18.4, (7) a value that is in close agreement with the average absolute bright- ness at maximum for typical supernovae of type I.
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