NOT Stockholm Supernovae

This proceeding contribution is a short summary of the invited talk about observational supernova science at Stockholm University that has been conducted at the Nordic Optical Telescope over the past 25 years, and some expectations for the future.Comment: Conference proceeding for NOT - a telescope for the futur

High Resolution Spectroscopy of Balmer-Dominated Shocks in the RCW 86, Kepler and SN 1006 Supernova Remnants

We report results from high resolution optical spectroscopy of three non-radiative galactic supernova remnants, RCW 86, Kepler's supernova remnant and SN 1006. We have measured the narrow component H-alpha line widths in Balmer-dominated filaments in RCW 86 and SN 1006, as well as the narrow component width in a Balmer-dominated knot in Kepler's SNR. The narrow component line widths measured in RCW 86 and Kepler's SNR show FWHM of 30-40 km/s, similar to what has been seen in other Balmer-dominated remnants. Of the remnants in our sample, SN 1006 is the fastest shock (~3000 km/s). The narrow component H-alpha and H-beta lines in this remnant have a FWHM of merely 21 km/s. Comparing the narrow component widths measured in our sample with those measured in other remnants shows that the width of the narrow component does not correlate in a simple way with the shock velocity. The implications for the pre-heating mechanism responsible for the observed line widths are discussed.Comment: Accepted by A&

Deep optical imaging of the gamma-ray pulsar J1048-5832 with the VLT

(abridged) PSR J1048-5832 is a young Vela-like pulsar that was recently detected in gamma-rays with Fermi, and also in X-rays with Chandra and XMM-Newton. It powers a compact PWN visible in X-rays. We present deep optical observations with the ESO Very Large Telescope to search for optical counterparts of the pulsar and its nebula and to explore their multi-wavelength emission properties. The data were obtained in V and R bands and compared with archival data in other spectral domains. We do not detect the pulsar in the optical and derive informative upper limits of R > 28.1 mag and V > 28.4 mag for its brightness. Using a red-clump star method, we estimate an interstellar extinction towards the pulsar of 2 mag, which is consistent with the absorbing column density derived form X-rays. The respective distance agrees with the dispersion measure distance. We reanalyse the Chandra X-ray data and compare the dereddened upper limits with the unabsorbed X-ray spectrum of the pulsar. We find that regarding its optical-X-ray spectral properties this gamma-ray pulsar is not distinct from other pulsars detected in both ranges. However, like the Vela pulsar, it is very inefficient in the optical and X-rays. Among a dozen optical sources overlapping with the pulsar X-ray nebula we find one with V = 26.9 and R = 26.3 mag, whose colour is slightly bluer then that of the field stars and consistent with the peculiar colours typical for pulsar nebula features. It positionally coincides with a relatively bright feature of the pulsar X-ray nebula, resembling the Crab wisp and locating in 2 arcsec from the pulsar. We suggest this source as a counterpart candidate to the feature. Based on the substantial interstellar extinction towards the pulsar and its optical inefficiency, further optical studies should be carried out at longer wavelengths.Comment: 8 pages, 7 figures, 3 tables, accepted for publication in Astronomy and Astrophysic

Optical and Infrared Observations of Radioactive Elements in Supernovae

At late phases the powering of supernova light curves is often provided by the decay of radioactive elements synthesized in the explosions. This is unambiguously revealed when the light curve decline follows the half life time of the decaying elements, and the bolometric luminosity then directly provides the mass of ejected radioactive material. I will focus on the best observed element, Nickel-56, and demonstrate that different supernovae eject different amounts of this element. SN 1994W ejected very small amounts of nickel, possibly caused by black hole formation. SN 1998bw may instead have ejected more Nickel-56 than any other supernova to date. I will also discuss our ISO non-detection of [Fe II] 26 micron in SN 1987A, which can be used to estimate an upper limit on the mass of ejected radioactive Titanium-44.Comment: 9 pages, 3 figures, In press in New Astronomy Review