Supernova Environments in Hubble Space Telescope Images

The locations of supernovae in the local stellar and gaseous environment in galaxies contain important clues to their progenitor stars. Access to this information, however, has been hampered by the limited resolution achieved by ground-based observations. High spatial resolution Hubble Space Telescope (HST) images of galaxy fields in which supernovae had been observed can improve the situation considerably. We have examined the immediate environments of a few dozen supernovae using archival post-refurbishment HST images. Although our analysis is limited due to signal-to-noise ratio and filter bandpass considerations, the images allow us for the first time to resolve individual stars in, and to derive detailed color-magnitude diagrams for, several environments. We are able to place more rigorous constraints on the masses of these supernovae. A search was made for late-time emission from supernovae in the archival images, and for the progenitor stars in presupernova images of the host galaxies. In particular, we highlight the results for the Type II SN 1979C in M100. In addition, we have identified the progenitor of the Type IIn SN 1997bs in NGC 3627. We also add to the statistical inferences that can be made from studying the association of SNe with recent star-forming regions

On The Progenitor of the Type II-Plateau Supernova 2003gd in Messier 74

HST WFPC2 archival F606W and F300W images obtained within one year prior to the explosion of the nearby Type II supernova (SN) 2003gd in Messier 74 (NGC 628) have been analyzed to isolate the progenitor star. The SN site was located using precise astrometry applied to the HST images. Two plausible candidates are identified within 0.6" of the SN position in the F606W image. Neither candidate was detected in the F300W image. SN 2003gd appears to be of Type II-plateau (II-P), with age ~87 d on June 17 UT and with low reddening [E(B-V) = 0.13 mag]. The most likely of the two progenitor candidates has M_V_0 ~ -3.5 mag (for an extinction-corrected distance modulus of 29.3 mag) and, based on additional color information derived from a high-quality, archival ground-based I-band image, we estimate that this star was a red supergiant with initial mass M_ZAMS ~ 8 -- 9 Msun. This mass estimate is somewhat lower than, but relatively consistent with, recent limits placed on the progenitor masses of other SNe II-P, using HST data. Future HST imaging with the Advanced Camera for Surveys, when the SN has faded considerably, will be extremely useful in pinpointing the exact SN location and securing identification of the progenitor. If our proposed candidate is confirmed, it will be only the sixth SN progenitor ever directly identified.Comment: 10 pages, 6 figures, to appear now in PASP, 2003 Nov. This update includes more detailed light and color curves for the S

Possible Recovery of SN 1961V In Hubble Space Telescope Archival Images

SN 1961V in NGC 1058 was originally classified by Fritz Zwicky as a ``Type V'' supernova. However, it has been argued that SN 1961V was not a genuine supernova, but instead the superoutburst of an eta Carinae-like luminous blue variable star. In particular, Filippenko et al. (1995, AJ, 110, 2261) used pre-refurbishment HST WFPC images and the known radio position of SN 1961V to conclude that the star survived the eruption and is likely coincident with a V \~ 25.6 mag, V-I ~ 1.9 mag object. Recently, Stockdale et al. (2001, AJ, 122, 283) recovered the fading SN 1961V at radio wavelengths and argue that its behavior is similar that of some Type II supernovae. We have analyzed post-refurbishment archival HST WFPC2 data and find that the new radio position is still consistent with the Filippenko et al. object, which has not changed in brightness or color, but is also consistent with an adjacent, fainter (I ~ 24.3 mag) and very red (V-I > 1.0 mag) object. We suggest that this fainter object could be the survivor of SN 1961V. Forthcoming HST observations may settle this issue.Comment: 8 pages, 6 figures, to appear in the PASP (2002 July issue

On the Progenitor System of the Type Iax Supernova 2014dt in M61

We present pre-explosion and post-explosion Hubble Space Telescope images of the Type Iax supernova (SN Iax) 2014dt in M61. After astrometrically aligning these images, we do not detect any stellar sources at the position of the SN in the pre-explosion images to relatively deep limits (3 sigma limits of M_F438W > -5.0 mag and M_F814W > -5.9 mag). These limits are similar to the luminosity of SN 2012Z's progenitor system (M_F435W = -5.43 +/- 0.15 and M_F814W = -5.24 +/- 0.16 mag), the only probable detected progenitor system in pre-explosion images of a SN Iax, and indeed, of any white dwarf supernova. SN 2014dt is consistent with having a C/O white-dwarf primary/helium-star companion progenitor system, as was suggested for SN 2012Z, although perhaps with a slightly smaller or hotter donor. The data are also consistent with SN 2014dt having a low-mass red giant or main-sequence star companion. The data rule out main-sequence stars with M_init > 16 M_sun and most evolved stars with M_init > 8 M_sun as being the progenitor of SN 2014dt. Hot Wolf-Rayet stars are also allowed, but the lack of nearby bright sources makes this scenario unlikely. Because of its proximity (D = 12 Mpc), SN 2014dt is ideal for long-term monitoring, where images in ~2 years may detect the companion star or the luminous bound remnant of the progenitor white dwarf.Comment: 5 pages, 3 figures, submitted to ApJ

Asphericity, Interaction, and Dust in the Type II-P/II-L Supernova 2013ej in Messier 74

SN 2013ej is a well-studied core-collapse supernova (SN) that stemmed from a directly identified red supergiant (RSG) progenitor in galaxy M74. The source exhibits signs of substantial geometric asphericity, X-rays from persistent interaction with circumstellar material (CSM), thermal emission from warm dust, and a light curve that appears intermediate between supernovae of Types II-P and II-L. The proximity of this source motivates a close inspection of these physical characteristics and their potential interconnection. We present multi-epoch spectropolarimetry of SN 2013ej during the first 107 days, and deep optical spectroscopy and ultraviolet through infrared photometry past ~800 days. SN 2013ej exhibits the strongest and most persistent continuum and line polarization ever observed for a SN of its class during the recombination phase. Modeling indicates that the data are consistent with an oblate ellipsoidal photosphere, viewed nearly edge-on, and probably augmented by optical scattering from circumstellar dust. We suggest that interaction with an equatorial distribution of CSM, perhaps the result of binary evolution, is responsible for generating the photospheric asphericity. Relatedly, our late-time optical imaging and spectroscopy shows that asymmetric CSM interaction is ongoing, and the morphology of broad H-alpha emission from shock-excited ejecta provides additional evidence that the geometry of the interaction region is ellipsoidal. Alternatively, a prolate ellipsoidal geometry from an intrinsically bipolar explosion is also a plausible interpretation of the data, but would probably require a ballistic jet of radioactive material capable of penetrating the hydrogen envelope early in the recombination phase (abridged).Comment: Post-proof edit. Accepted to ApJ on Nov. 23 2016; 21 pages, 16 figure

Constraints on the Progenitor of SN 2010jl and Pre-Existing Hot Dust in its Surrounding Medium

A search for the progenitor of SN~2010jl, an unusually luminous core-collapse supernova of Type~IIn, using pre-explosion {\it Hubble}/WFPC2 and {\it Spitzer}/IRAC images of the region, yielded upper limits on the UV and near-infrared (IR) fluxes from any candidate star. These upper limits constrain the luminosity and effective temperature of the progenitor, the mass of any preexisting dust in its surrounding circumstellar medium (CSM), and dust proximity to the star. A {\it lower} limit on the CSM dust mass is required to hide a luminous progenitor from detection by {\it Hubble}. {\it Upper} limits on the CSM dust mass and constraints on its proximity to the star are set by requiring that the absorbed and reradiated IR emission not exceed the IRAC upper limits. Using the combined extinction-IR emission constraints we present viable $M_d-R_1$ combinations, where $M_d$ and $R_1$ are the CSM dust mass and its inner radius. These depend on the CSM outer radius, dust composition and grain size, and the properties of the progenitor. The results constrain the pre-supernova evolution of the progenitor, and the nature and origin of the observed post-explosion IR emission from SN~2010jl. In particular, an $\eta$~Car-type progenitor will require at least 4~mag of visual extinction to avoid detection by the {\it Hubble}. This can be achieved with dust masses $\gtrsim 10^{-3}$~\msun\ (less than the estimated 0.2-0.5~\msun\ around $\eta$~Car) which must be located at distances of $\gtrsim 10^{16}$~cm from the star to avoid detection by {\it Spitzer}.Comment: Accepted for publication in the ApJ. 14 pages 10 figures. The complete figure set for Figure 10 (24 images) is available in the online journa

The Light Echo Around Supernova 2003gd in Messier 74

We confirm the discovery of a light echo around the Type II-plateau Supernova 2003gd in Messier 74 (NGC 628), seen in images obtained with the High Resolution Channel of the Advanced Camera for Surveys on-board the Hubble Space Telescope (HST), as part of a larger Snapshot program on the late-time emission from supernovae. The analysis of the echo we present suggests that it is due to the SN light pulse scattered by a sheet of dust grains located about 113 pc in front of the SN, and that these grains are not unlike those assumed to be in the diffuse Galactic interstellar medium, both in composition and in size distribution. The echo is less consistent with scattering off carbon-rich grains, and, if anything, the grains may be somewhat more silicate-rich than the Galactic dust composition. The echo also appears to be more consistent with a SN distance closer to 7 Mpc than 9 Mpc. This further supports the conclusion we reached elsewhere that the initial mass for the SN progenitor was relatively low (about 8--9 M_suns). HST should be used to continue to monitor the echo in several bands, particularly in the blue, to better constrain its origin.Comment: 8 pages, 4 figures, To appear in PASP (2006 March); disregard previous versio

Supernova 2008bk and its red supergiant progenitor

Indexación: ISIHemos obtenido pocos datos fotométricos y espectroscópicos de supernova (SN) 2008bk en NGC 7793, principalmente a 150 días después de la explosión. Nos parece que se trata de un tipo II-Plateau (II-P) SN que más se asemeja a la de baja luminosidad SN 1999br en NGC 4900. Dada la similitud general entre las curvas de luz observadas y colores de SNs 2008bk y 1999br, inferimos que la extinción total visual a SN 2008bk ( A V = 0,065 mag) debe ser casi en su totalidad debido a un primer plano galáctico, similar a lo que ha supuesto para SN 1999br. Confirmamos la identificación de la supergigante roja putativo (RSG) estrella progenitora de SN en la alta calidad de g ' r ' i imágenes "que había obtenido en 2007 en el Gemini-Sur 8 telescopio m. Existe poca ambigüedad en esta identificación progenitor, calificándolo como el mejor ejemplo hasta la fecha, junto con la identificación de la estrella Sk -69 ° 202 como el progenitor de SN 1987A. A partir de una combinación de fotometría de las imágenes de Gemini con el de archivo, pre-SN, el Telescopio Muy Grande de JHK s imágenes, derivamos una precisa distribución observada energía espectral (SED) para el progenitor. Nos encontramos con índices de nebulares fuerte intensidad de emisiones de línea para varios H II regiones cercanas a la SN que la metalicidad en el medio ambiente es probable subsolar ( Z 0.6 Z ☉ ). El SED observado de la estrella concuerda bastante bien con SED sintéticos obtenidos a partir de modelos de atmósferas RSG eficaz con temperatura T eff = 3600 ± 50 K. Nos encontramos, por tanto, que la estrella tenía una luminosidad bolométrica con respecto al Sol de log ( L bol / L ☉ ) = 4,57 ± 0,06 y el radio R = 496 ± 34 R ☉ a ~ 6 meses antes de la explosión. Al comparar las propiedades del progenitor con teóricos masiva estrella modelos evolutivos, llegamos a la conclusión de que el progenitor RSG tenía una masa inicial en el rango de 8-8,5 M ☉ . Esta masa es consistente con, aunque en el extremo bajo de la gama inferido de masas iniciales para SN II-P progenitores. También es coherente con el límite superior estimado de la masa inicial de la progenitora de SN 1999br, y concuerda con las masas iniciales bajos encontrados para los progenitores RSG de otras supernovas de baja luminosidad II-P.http://www.sherpa.ac.uk/romeo/issn/0004-6256/es/http://iopscience.iop.org/1538-3881/143/1/19

The Progenitor of Supernova 2011dh Has Vanished

We conducted Hubble Space Telescope (HST) Snapshot observations of the Type IIb Supernova (SN) 2011dh in M51 at an age of ~641 days with the Wide Field Camera 3. We find that the yellow supergiant star, clearly detected in pre-SN HST images, has disappeared, implying that this star was almost certainly the progenitor of the SN. Interpretation of the early-time SN data which led to the inference of a compact nature for the progenitor, and to the expected survival of this yellow supergiant, is now clearly incorrect. We also present ground-based UBVRI light curves obtained with the Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory up to SN age ~70 days. From the light-curve shape including the very late-time HST data, and from recent interacting binary models for SN 2011dh, we estimate that a putative surviving companion star to the now deceased yellow supergiant could be detectable by late 2013, especially in the ultraviolet. No obvious light echoes are detectable yet in the SN environment.Comment: 6 pages, new versions of the 3 figures, improved U-band SN photometry, to appear in ApJ Letter