SN 2008ha: AN EXTREMELY LOW LUMINOSITY AND EXCEPTIONALLY LOW ENERGY SUPERNOVA
- Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
- Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)
We present ultraviolet, optical, and near-infrared photometry as well as optical spectra of the peculiar supernova (SN) 2008ha. SN 2008ha had a very low peak luminosity, reaching only M{sub V} = -14.2 mag, and low line velocities of only {approx}2000 km s{sup -1} near maximum brightness, indicating a very small kinetic energy per unit mass of ejecta. Spectroscopically, SN 2008ha is a member of the SN 2002cx-like class of SNe, a peculiar subclass of SNe Ia; however, SN 2008ha is the most extreme member, being significantly fainter and having lower line velocities than the typical member, which is already {approx}2 mag fainter and has line velocities {approx}5000 km s{sup -1} smaller (near maximum brightness) than a normal SN Ia. SN 2008ha had a remarkably short rise time of only {approx}10 days, significantly shorter than either SN 2002cx-like objects ({approx}15 days) or normal SNe Ia ({approx}19.5 days). The bolometric light curve of SN 2008ha indicates that SN 2008ha peaked at L {sub peak} = (9.5 {+-} 1.4) x 10{sup 40} erg s{sup -1}, making SN 2008ha perhaps the least luminous SN ever observed. From its peak luminosity and rise time, we infer that SN 2008ha generated (3.0 {+-} 0.9) x 10{sup -3} M {sub sun} of {sup 56}Ni, had a kinetic energy of {approx}2 x 10{sup 48} erg, and ejected 0.15 M {sub sun} of material. The host galaxy of SN 2008ha has a luminosity, star formation rate, and metallicity similar to those of the Large magellanic Cloud. We classify three new (and one potential) members of the SN 2002cx-like class, expanding the sample to 14 (and one potential) members. The host-galaxy morphology distribution of the class is consistent with that of SNe Ia, Ib, Ic, and II. Several models for generating low-luminosity SNe can explain the observations of SN 2008ha; however, if a single model is to describe all SN 2002cx-like objects, deflagration of carbon-oxygen white dwarfs, with SN 2008ha being a partial deflagration and not unbinding the progenitor star, is preferred. The rate of SN 2008ha-like events is {approx}10% of the SN Ia rate, and in the upcoming era of transient surveys, several thousand similar objects may be discovered, suggesting that SN 2008ha may be the tip of a low-luminosity transient iceberg.
- OSTI ID:
- 21255679
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 138, Issue 2; Other Information: DOI: 10.1088/0004-6256/138/2/376; Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
BOLOMETERS
BRIGHTNESS
CARBON
DIAGRAMS
KINETIC ENERGY
LUMINOSITY
MAGELLANIC CLOUDS
NICKEL 56
OXYGEN
PHOTOMETRY
PULSE RISE TIME
SUPERNOVAE
ULTRAVIOLET RADIATION
VELOCITY
VISIBLE RADIATION
WHITE DWARF STARS