SN 2005gj

{{Short description|Supernova event observed on September 29, 2005}}

{{Supernova

| name = SN 2005gj

| image = SN2005gjLightCurve.png

| caption = Light curves for SN 2005gj in four photometric bands, plotted from data published by Prieto et al. (2007){{cite arXiv|eprint=0706.4088 |last1=Prieto |first1=J. L. |last2=Garnavich |first2=P. M. |last3=Phillips |first3=M. M. |last4=DePoy |first4=D. L. |last5=Parrent |first5=J. |last6=Pooley |first6=D. |last7=Dwarkadas |first7=V. V. |last8=Baron |first8=E. |last9=Bassett |first9=B. |last10=Becker |first10=A. |last11=Cinabro |first11=D. |last12=DeJongh |first12=F. |last13=Dilday |first13=B. |last14=Doi |first14=M. |last15=Frieman |first15=J. A. |last16=Hogan |first16=C. J. |last17=Holtzman |first17=J. |last18=Jha |first18=S. |last19=Kessler |first19=R. |last20=Konishi |first20=K. |last21=Lampeitl |first21=H. |last22=Marriner |first22=J. |last23=Marshall |first23=J. L. |last24=Miknaitis |first24=G. |last25=Nichol |first25=R. C. |last26=Riess |first26=A. G. |last27=Richmond |first27=M. W. |last28=Romani |first28=R. |last29=Sako |first29=M. |last30=Schneider |first30=D. P. |title=A Study of the Type Ia/IIn Supernova 2005gj from X-ray to the Infrared: Paper I |date=2007 |class=astro-ph |display-authors=1 }}

| epoch = J2000.0

| type = Ia/IIn "hybrid"

| SNRtype =

| host =

| constellation =

| ra =

| dec =

| gal =

| discovery = September 27, 2005

| iauc = IAUC 8633 {{cite journal | bibcode = 2005ATel..663....1S | title = SAO/NASA ADS Astronomy Abstract Service | last1 = Soderberg | first1 = A. M. |author1-link=Alicia M. Soderberg | last2 = Frail | first2 = D. A. | journal = The Astronomer's Telegram | year = 2005 | volume = 663 | page = 1 }}

| mag_v =

| progenitor = White dwarf

| distance = 864 million light years (265 million parsecs)

| notes = Proposed "quark nova".

}}

SN 2005gj was a supernova located approximately 864 million light years (265 million parsecs) away from Earth. It was discovered on September 27, 2005, by the Sloan Digital Sky Survey and the Nearby Supernova Factory.{{cite web

|url=http://sdssdp47.fnal.gov/sdsssn/talks/AAS-1-07/aas07_prieto.pdf

|title=Peculiar Supernovae in SDSS-II

|author=J. L. Prieto

|display-authors=etal

|accessdate=2009-04-26

|archive-date=2011-08-26

|archive-url=https://web.archive.org/web/20110826215841/http://sdssdp47.fnal.gov/sdsssn/talks/AAS-1-07/aas07_prieto.pdf

|url-status=dead

}}

{{cite web

|url=http://repositories.cdlib.org/cgi/viewcontent.cgi?article=4934&context=lbnl

|title=Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope

|author=G. Aldering

|display-authors=etal

|accessdate=2009-04-26

|pages=2

}} 2005gj was noted because it had qualities of both type Ia and type IIn supernovae, and because hydrogen emission lines were found in its spectrum (see hydrogen spectral series). These hydrogen lines, which were found on the spectrum at redshift z=0.0613, are thought to be indicative of interactions with a circumstellar medium (CSM; a donut-shaped, nebula-like ring of matter around a star) by the supernova's ejected matter or white dwarf progenitor.{{cite web

|url=http://sdssdp47.fnal.gov/sdsssn/talks/AAS-1-07/aas07_prieto.pdf

|title=Peculiar Supernovae in SDSS-II

|author=J. Priesto

|display-authors=etal

|accessdate=2009-04-26

|archive-date=2011-08-26

|archive-url=https://web.archive.org/web/20110826215841/http://sdssdp47.fnal.gov/sdsssn/talks/AAS-1-07/aas07_prieto.pdf

|url-status=dead

}} Such emission lines are extremely rare in Type Ia supernovae – only one other Type Ia, SN 2002ic, has been observed to exhibit the same properties.

{{cite web

|url=http://repositories.cdlib.org/cgi/viewcontent.cgi?article=4934&context=lbnl

|title=Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope

|author=G. Aldering

|display-authors=etal

|accessdate=2009-04-26

|pages=4

}}

{{cite web

|url=http://cbat.eps.harvard.edu/cbet/000300/CBET000302.txt

|title=SUPERNOVA 2005gj

|accessdate=2009-04-25

|date=2005-11-23

}} However, 2005gj's CSM interaction was much stronger and more clearly observed than 2002ic's. The mass-loss history 2005gj's hydrogen lines suggest has been cited as evidence that luminous blue variable (LBV) hypergiants can be progenitors of thermonuclear supernovae.

{{cite web

|url=http://www.astroscu.unam.mx/massive_stars/submission/2008/08041866444.pdf

|title=SN 2005gj: Evidence for LBV supernovae progenitors?

|accessdate=2009-04-26

}}

2005gj was also noted for its overluminosity. With a light curve that maximised 14–47 days after the initial observation, it was three times more luminous than SN 1991T (which was, at the time of its 1991 discovery, the brightest Ia supernova on record), 1.5 times more luminous than SN 2002ic, and close to 100 times more luminous than previously thought possible.

{{cite book

|title=The extravagant universe

|author=R. P. Kirshner

|page=[https://archive.org/details/extravagantunive00kirs/page/173 173]

|publisher=Princeton University Press

|date=2002

|isbn=0-691-05862-8

|url-access=registration

|url=https://archive.org/details/extravagantunive00kirs/page/173

}} Scientists Denis Leahy and Rachid Ouyed from the University of Calgary contend that the incidence of a quark nova, a very luminous process involving the degeneration of neutrons into their constituent quarks, could explain the unusual magnitude of the luminosity.

{{cite web

|url=http://astronomynow.com/080604Secondsupernovaepointtoquarkstars.html

|title=Second supernovae point to quark stars

|author=K. S. Chadhar

|accessdate=2009-04-26

|date=2009-06-04

}}