Astronomy:SN 1998bw

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Short description: Supernova/gamma-ray burst in the constellation Telescopium
SN 1998bw
Occurred on the galaxy ESO 184-G82
Event typeSupernova
Spectral classType Ic
Date26 April 1998
ConstellationTelescopium
Right ascension 19h 35m 03.17s[1]
Declination−52° 50′ 46.1″[1]
Galactic coordinates344.99°, −27.72°[2]
HostESO 184-G82
[edit on Wikidata]

SN 1998bw was a rare broad-lined Type Ic[3] gamma ray burst supernova detected on 26 April 1998 in the ESO 184-G82 spiral galaxy, which some astronomers believe may be an example of a collapsar (hypernova).[4] The hypernova has been linked to GRB 980425, which was detected on 25 April 1998, the first time a gamma-ray burst has been linked to a supernova.[5] The hypernova is approximately 140 million light years away, very close for a gamma ray burst source.[6]

The region of the galaxy where the supernova occurred hosts stars 5-8 million years old and is relatively free from dust. A nearby region hosts multiple Wolf-Rayet stars less than 3 million years old, but it is unlikely that the supernova progenitor could be a runaway from that region. The implication is that the progenitor was a star that originally had a mass of 25-40 M☉, if it exploded as a single star at the end of its life.[7]

Observations

Light curves in four photometric bands for SN 1998bw, plotted from data published by Clocchiatti et al. (2011)[8]

On 25 April 1998, a gamma ray burst was detected by the BeppoSAX satellite and assigned the identifier GRB 980425. The event lasted for 30 seconds,[9] and was about average in terms of burst flux.[10] A check of images from the ESO New Technology Telescope showed a rapidly brightening point source within the error box of GRB 980425. It was located in the face-on spiral galaxy ESO 184-G82, in a spiral arm at an offset from the nucleus. This candidate supernova event lacked spectral lines of hydrogen, ruling out a normal core-collapse Type II supernova, and it was a missing line of silicon that indicated it is not a typical Type Ia supernova.[11]

A few weeks after full light, the spectrum of supernova SN 1998bw showed no clear indications of helium. This suggested the event be classed as a Type Ic supernova, although it showed some peculiarities compared to other supernovae of this type. The expansion velocity measured from calcium lines was measured as 11,700 km/s, and 9,100 km/s from silicon lines.[12] The maximum recorded expansion velocities reached 3×104 km/s.[13] Energy emissions from the supernova showed polarization, which supported a core-collapse scenario with asymmetry.[14]

Radio measurements of the supernova showed that it was unusually luminous in this band. The data suggested a shock wave moving at a relativistic velocity, whereas most supernovae ejecta are non-relativistic.[15] This was the first evidence found for a relativistic shock from a supernova.[16] The supernova light curves from radio to X-ray bands also indicated a blast wave that was highly relativistic. The data was consistent with a physical association between SN 1998bw and GRB 980425,[17][18] and supported the idea of a hypernova or collapsar event. This scenario results in the formation of a black hole from the collapse of a massive star.[17][19] Spherically-symmetrical models failed to reproduce an event with this energy level, indicating a highly asymmetrical explosion that produced the gamma-ray burst from a relativistic jet.[20] In this case, only a fraction of the progenitor's stellar mass was ejected, with the remainder collapsing to form a black hole.[3]

The supernova transitioned to the nebular phase around 100 days after the explosion.[21] Expansion velocities remained very high compared to other core-collapse supernovae at similar phases.[13] The unusual spectrum observed during the nebular phase matched a model for a strongly aspherical explosion observed from near the direction of a relativistic jet.[22][23] The radio emission from the supernova can best be explained by interaction between the relativistic shock and clumpy circumstellar medium previously ejected by a strong stellar wind.[24] Observations from the Chandra X-ray Observatory in 2004 found X-ray emission that supported this scenario.[25] It also lent support to the idea that the supernova and gamma-ray burst were the same event.[26]

Environment

Observations with the Hubble Space Telescope indicated that the host for the supernova event is a sub-luminous galaxy with a morphological classification of SBc. This indicates ESO 184-G82 is a barred spiral galaxy with loosely-wound spiral arms. The galaxy is undergoing strong star formation and the supernova occurred in an active star forming area that includes an H II region. This environment is fairly typical for Type II supernovae. The supernova afterglow was about a magnitude brighter than expected from a radioactive decay model, suggesting a contribution from a surrounding stellar cluster.[27]

The host galaxy appears morphologically disturbed, which suggests interaction from nearby galaxies. This could explain the amplified star forming process.[27] Six galaxies lie within the field of ESO 184-G82 but none of them have a matching redshift of 0.0087±0.0006. Thus, it appears to be an isolated dwarf galaxy and another explanation is needed for the star formation.[28] A 2020 study with the Atacama Large Millimeter Array discovered the galaxy has a ring of dense neutral hydrogen, which includes clumps of gas. One of these clumps was the host of SN 1998bw. The presence of a ring indicates a past collision with a companion galaxy.[29]

References

  1. ↑ 1.0 1.1 Barbon, R. et al. (2008). "Asiago Supernova Catalogue". VizieR On-line Data Catalog. 2008-Mar. Bibcode: 2008yCat.2283....0B. 
  2. ↑ "SN 1998bw". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=SN+1998bw. 
  3. ↑ 3.0 3.1 Woosley, S. E. et al. (1999). "Gamma-ray bursts and Type Ic supernova: SN 1998bw". The Astrophysical Journal 516 (2): 788–796. doi:10.1086/307131. Bibcode: 1999ApJ...516..788W. 
  4. ↑ Greiner, Jochen. "Gamma-ray burst 980425". Max-Planck-Institute for Extraterrestrial Physics. http://www.mpe.mpg.de/~jcg/grb980425.html. Retrieved 2017-06-11. 
  5. ↑ Vreeswijk, P. et al. (2000). "Gamma-ray burst afterglows: surprises from the sky". The ING Newsletter 2: 5. Bibcode: 2000INGN....2....5V. 
  6. ↑ "A strange supernova with a gamma-ray burst". European Southern Observatory. 15 October 1998. https://www.eso.org/public/news/eso9847/. Retrieved 2015-11-14. 
  7. ↑ Krühler, Thomas et al. (2017). "Hot gas around SN 1998bw - Inferring the progenitor from its environment". Astronomy & Astrophysics 602 (85): A85. doi:10.1051/0004-6361/201630268. Bibcode: 2017A&A...602A..85K. 
  8. ↑ Clocchiatti, Alejandro; Suntzeff, Nicholas B.; Covarrubias, Ricardo; Candia, Pablo (May 2011). "The Ultimate Light Curve of SN 1998bw/GRB 980425". The Astronomical Journal 141 (5): 163. doi:10.1088/0004-6256/141/5/163. Bibcode: 2011AJ....141..163C. https://iopscience.iop.org/article/10.1088/0004-6256/141/5/163/pdf. Retrieved 25 May 2025. 
  9. ↑ Soffitta, P. et al. (26 April 1998). "GRB 980425". IAU Circular (Central Bureau for Astronomical Telegrams) (6884): 1. http://www.cbat.eps.harvard.edu/iauc/06800/06884.html. Retrieved 2025-03-22. 
  10. ↑ Wang, Lifan; Wheeler, J. Craig (September 1998). "The Supernova-Gamma-Ray Burst Connection". The Astrophysical Journal 504 (2): L87–L90. doi:10.1086/311580. Bibcode: 1998ApJ...504L..87W. 
  11. ↑ Galama, T. J. et al. (7 May 1998). "GRB 980425". IAU Circulars (Central Bureau for Astronomical Telegrams) 6895: 1. http://cbat.eps.harvard.edu/iauc/06800/06895.html. Retrieved 2025-03-22. 
  12. ↑ Patat, F.; Piemonte, A. (May 1998). Green, D. W. E.. ed. "Supernova 1998bw in ESO 184-G82". IAU Circulars 6918: 1. Bibcode: 1998IAUC.6918....1P. 
  13. ↑ 13.0 13.1 Patat, Ferdinando et al. (July 2001). "The metamorphosis of SN 1998bw". The Astrophysical Journal 555 (2): 900–917. doi:10.1086/321526. Bibcode: 2001ApJ...555..900P. 
  14. ↑ Kay, L. E. et al. (July 1998). Green, D. W. E.. ed. "Supernova 1998bw in ESO 184-G82". IAU Circulars 6969: 1. Bibcode: 1998IAUC.6969....1K. 
  15. ↑ Kulkarni, S. R. et al. (October 1998). "Radio emission from the unusual supernova 1998bw and its association with the γ-ray burst of 25 April 1998". Nature 395 (6703): 663–669. doi:10.1038/27139. Bibcode: 1998Natur.395..663K. 
  16. ↑ Wieringa, M. H. et al. (September 1999). "SN 1998bw: The case for a relativistic shock". Astronomy and Astrophysics Supplement 138 (3): 467–468. doi:10.1051/aas:1999312. Bibcode: 1999A&AS..138..467W. 
  17. ↑ 17.0 17.1 Iwamoto, Koichi (February 1999). "On the Radio-to-X-Ray Light Curves of SN 1998bw and GRB 980425". The Astrophysical Journal 512 (1): L47–L50. doi:10.1086/311867. Bibcode: 1999ApJ...512L..47I. 
  18. ↑ Li, Zhi-Yun; Chevalier, Roger A. (December 1999). "Radio Supernova SN 1998bw and Its Relation to GRB 980425". The Astrophysical Journal 526 (2): 716–726. doi:10.1086/308031. Bibcode: 1999ApJ...526..716L. 
  19. ↑ Woosley, S. E.; MacFadyen, A. I. (2000). "Gamma-ray bursts, supernovae, and SN 1998bw". Memorie della Societa Astronomica Italiana 71: 357–363. Bibcode: 2000MmSAI..71..357W. 
  20. ↑ Höflich, Peter et al. (August 1999). "Aspherical Explosion Models for SN 1998BW/GRB-980425". The Astrophysical Journal 521 (1): 179–189. doi:10.1086/307521. Bibcode: 1999ApJ...521..179H. 
  21. ↑ Maeda, K. et al. (April 2006). "Nebular spectra of SN 1998bw revisited: detailed study by one- and two-dimensional models". The Astrophysical Journal 640 (2): 854–877. doi:10.1086/500187. Bibcode: 2006ApJ...640..854M. 
  22. ↑ Maeda, Keiichi et al. (January 2002). "Explosive nucleosynthesis in aspherical hypernova explosions and late-time spectra of SN 1998bw". The Astrophysical Journal 565 (1): 405–412. doi:10.1086/324487. Bibcode: 2002ApJ...565..405M. 
  23. ↑ Mazzali, Paolo A. et al. (October 2001). "The nebular spectra of the hypernova SN 1998bw and evidence for asymmetry". The Astrophysical Journal 559 (2): 1047–1053. doi:10.1086/322420. Bibcode: 2001ApJ...559.1047M. 
  24. ↑ Weiler, Kurt W. et al. (December 2001). "SN 1998bw/GRB 980425 and radio supernovae". The Astrophysical Journal 562 (2): 670–678. doi:10.1086/322359. Bibcode: 2001ApJ...562..670W. 
  25. ↑ Waxman, Eli (April 2004). "Does the detection of X-Ray emission from SN 1998bw support its association with GRB 980425?". The Astrophysical Journal 605 (2): L97–L100. doi:10.1086/420846. Bibcode: 2004ApJ...605L..97W. 
  26. ↑ Kouveliotou, C. et al. (June 2004). "Chandra observations of the X-Ray environs of SN 1998bw/GRB 980425". The Astrophysical Journal 608 (2): 872–882. doi:10.1086/420878. Bibcode: 2004ApJ...608..872K. 
  27. ↑ 27.0 27.1 Fynbo, J. U. et al. (October 2000). "HST/STIS imaging of the host galaxy of GRB980425/SN1998bw". The Astrophysical Journal 542 (2): L89–L93. doi:10.1086/312942. Bibcode: 2000ApJ...542L..89F. 
  28. ↑ Foley, S. et al. (March 2006). "The galaxies in the field of the nearby GRB 980425/SN 1998bw". Astronomy and Astrophysics 447 (3): 891–895. doi:10.1051/0004-6361:20054382. Bibcode: 2006A&A...447..891F. 
  29. ↑ Arabsalmani, M. et al. (August 2020). "Local starburst conditions and formation of GRB 980425/SN 1998bw within a collisional ring". The Astrophysical Journal 899 (2): id. 165. doi:10.3847/1538-4357/aba3c0. Bibcode: 2020ApJ...899..165A. 

Further reading

  • Mirabal, Nestor (April 2023). "Spatial coincidence between ultra-high energy cosmic rays and TeV gamma rays in the direction of GRB 980425/SN 1998bw". Research Notes of the AAS 7 (4): id. 80. doi:10.3847/2515-5172/acd006. Bibcode: 2023RNAAS...7...80M. 
  • Dessart, Luc et al. (July 2017). "Radiative-transfer models for explosions from rotating and non-rotating single WC stars. Implications for SN 1998bw and LGRB/SNe". Astronomy & Astrophysics 603: id. A51. doi:10.1051/0004-6361/201730873. Bibcode: 2017A&A...603A..51D. 
  • Michałowski, Michał J. et al. (March 2009). "The properties of the host galaxy and the immediate environment of GRB 980425/SN 1998bw from the multiwavelength spectral energy distribution". The Astrophysical Journal 693 (1): 347–354. doi:10.1088/0004-637X/693/1/347. Bibcode: 2009ApJ...693..347M. 
  • Christensen, L. et al. (October 2008). "IFU observations of the GRB 980425/SN 1998bw host galaxy: emission line ratios in GRB regions". Astronomy and Astrophysics 490 (1): 45–59. doi:10.1051/0004-6361:200809896. Bibcode: 2008A&A...490...45C. 
  • Tanaka, Masaomi et al. (October 2007). "Multidimensional simulations for early-phase spectra of aspherical hypernovae: SN 1998bw and off-axis hypernovae". The Astrophysical Journal 668 (1): L19–L22. doi:10.1086/522671. Bibcode: 2007ApJ...668L..19T. 
  • Maeda, Keiichi et al. (July 2006). "Optical emission from aspherical supernovae and the hypernova SN 1998bw". The Astrophysical Journal 645 (2): 1331–1344. doi:10.1086/504581. Bibcode: 2006ApJ...645.1331M. 
  • Nakamura, Takayoshi et al. (April 2001). "Light curve and spectral models for the hypernova SN 1998BW associated with GRB 980425". The Astrophysical Journal 550 (2): 991–999. doi:10.1086/319784. Bibcode: 2001ApJ...550..991N. 
  • Salmonson, Jay D. (January 2001). "On the kinematics of GRB 980425 and its association with SN 1998BW". The Astrophysical Journal 546 (1): L29–L31. doi:10.1086/318063. Bibcode: 2001ApJ...546L..29S. 
  • Chugai, N. N. (December 2000). "Monte Carlo simulations of supernova light curves and the hypernova SN1998bw". Astronomy Letters 26 (12): 797–801. doi:10.1134/1.1331160. Bibcode: 2000AstL...26..797C. 
  • Sollerman, J. et al. (July 2000). "SN 1998bw at late phases". The Astrophysical Journal 537 (2): L127–L130. doi:10.1086/312763. Bibcode: 2000ApJ...537L.127S. 
  • Leibundgut, B. et al. (March 2000). "The late phase of SN 1998bw". The Messenger 99: 36–38. Bibcode: 2000Msngr..99...36L. 
  • Patat, F. et al. (2000). "SN 1998bw: four months of observations at ESO". Memorie della Societa Astronomica Italiana 71: 307–315. Bibcode: 2000MmSAI..71..307P. 
  • Nakamura, T. et al. (2000). "Hypernova models for SN 1998bw & SN 1997ef: nucleosynthesis, light curves, and spectra". Memorie della Societa Astronomica Italiana 71: 345–355. Bibcode: 2000MmSAI..71..345N. 
  • Galama, T. J. et al. (September 1999). "On the possible association of SN 1998bw and GRB 980425". Astronomy and Astrophysics Supplement 138 (3): 465–466. doi:10.1051/aas:1999311. Bibcode: 1999A&AS..138..465G. 
  • McKenzie, Eric H.; Schaefer, Bradley E. (August 1999). "The Late-Time Light Curve of SN 1998BW Associated with GRB 980425". The Publications of the Astronomical Society of the Pacific 111 (762): 964–968. doi:10.1086/316404. Bibcode: 1999PASP..111..964M. 
  • Waxman, Eli; Loeb, Abraham (April 1999). "A Subrelativistic Shock Model for the Radio Emission of SN 1998BW". The Astrophysical Journal 515 (2): 721–725. doi:10.1086/307066. Bibcode: 1999ApJ...515..721W. 



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