| 1. |
- Foley, Ryan J., et al.
(författare)
-
ON THE PROGENITOR AND SUPERNOVA OF THE SN 2002cx-LIKE SUPERNOVA 2008ge
- 2010
-
Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 140:5, s. 1321-1328
-
Tidskriftsartikel (refereegranskat)abstract
- We present observations of supernova (SN) 2008ge, which is spectroscopically similar to the peculiar SN 2002cx, and its pre-explosion site indicating that its progenitor was probably a white dwarf. NGC 1527, the host galaxy of SN 2008ge, is an S0 galaxy with no evidence of star formation or massive stars. Astrometrically matching late-time imaging of SN 2008ge to pre-explosion Hubble Space Telescope imaging, we constrain the luminosity of the progenitor star. Since SN 2008ge has no indication of hydrogen or helium in its spectrum, its progenitor must have lost its outer layers before exploding, meaning that it is a white dwarf, a Wolf-Rayet star, or a lower-mass star in a binary system. Observations of the host galaxy show no signs of individual massive stars, star clusters, or H (II) regions at the SN position or anywhere else, making a Wolf-Rayet progenitor unlikely. Late-time spectroscopy of SN 2008ge shows strong [Fe (II)] lines with large velocity widths compared to other members of this class at similar epochs. These previously unseen features indicate that a significant amount of the SN ejecta is Fe (presumably the result of the radioactive decay of Ni-56 generated in the SN), further supporting a thermonuclear explosion. Placing the observations of SN 2008ge in the context of observations of other objects in the same class of SNe, we suggest that the progenitor was most likely a white dwarf.
|
|
| 2. |
- Stritzinger, Maximilian, et al.
(författare)
-
THE DISTANCE TO NGC 1316 (FORNAX A) FROM OBSERVATIONS OF FOUR TYPE Ia SUPERNOVAE
- 2010
-
Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 140:6, s. 2036-2051
-
Tidskriftsartikel (refereegranskat)abstract
- The giant elliptical galaxy NGC 1316 (Fornax A) is a well-studied member of the Fornax Cluster and a prolific producer of Type Ia supernovae (SNe Ia), having hosted four observed events since 1980. Here, we present detailed optical-and near-infrared light curves of the spectroscopically normal SN 2006dd. These data are used, along with previously published photometry of the normal SN 1980N and SN 1981D, and the fast-declining, low-luminosity SN 2006mr, to compute independent estimates of the host reddening for each SN, and the distance to NGC 1316. From the three normal SNe, we find a distance of 17.8 +/- 0.3 (random) +/- 0.3 (systematic) Mpc for H-o = 72. Distance moduli derived from the "EBV" and Tripp methods give the values that are mutually consistent with 4%-8%. Moreover, the weighted means of the distance moduli for these three SNe for three methods agree to within 3%. This consistency is encouraging and supports the premise that Type Ia SNe are reliable distance indicators at the 5% precision level or better. On the other hand, the two methods used to estimate the distance of the fast-declining SN 2006mr both yield a distance to NGC 1316 which is 25%-30% larger. This disparity casts doubt on the suitability of fast-declining events for estimating extragalactic distances. Modest-to-negligible host galaxy reddening values are derived for all four SNe. Nevertheless, two of them (SN 2006dd and SN 2006mr) show strong Na I D interstellar lines in the host galaxy system. The strength of this absorption is completely inconsistent with the small reddening values derived from the SN light curves if the gas in NGC 1316 is typical of that found in the interstellar medium of the Milky Way. In addition, the equivalent width of the Na lines in SN 2006dd appears to have weakened significantly some 100-150 days after explosion.
|
|
