SN 1999em

SN 1999em
Event type	Supernova
	Type II-P
Instrument	Katzman Automatic Imaging Telescope
Constellation	Eridanus
Right ascension	04h 41m 27.04s
Declination	−02° 51′ 45.2″
Epoch	J2000
Distance	38.2 ± 3.0 million light-years (11.71 ± 0.92 Mpc).
Host	NGC 1637
	Related media on Commons
	[ edit on Wikidata]

Last updated January 08, 2025

SN 1999em was a well-observed^[2] type II-P supernova in the spiral galaxy NGC 1637,^[3] which lies within the mostly southern constellation of Eridanus. It was discovered on October 29, 1999 at a visual magnitude of 13.3.^[4] Using a corrected version of the expanding photosphere method (EPM), the distance to the supernova is estimated as 37.5 ± 3.3 million light-years (11.5 ± 1 Mpc ).^[5] This is in good agreement with the Cepheid method, which yields a distance of 38.2 ± 3.0 million light-years (11.71 ± 0.92 Mpc ).^[1]

Observations

Light curves in four photometric bands, plotted from data published by Galbany et al. (2016) SN1999emLightCurve.png — Light curves in four photometric bands, plotted from data published by Galbany *et al.* (2016)

This supernova event was first detected by the Lick Observatory Supernova Search from a CCD frame taken October 29, 1999 with the Katzman Automatic Imaging Telescope (KAIT). The discovery was confirmed by the Beijing Astronomical Observatory the same day. It showed an apparent visual magnitude of 13.5. A KAIT image of the same area taken October 20th showed nothing at the position of this supernova.^[4] SN 1999em was positioned 15.4″ west and 17.0″ south of the NGC 1637 nucleus. A spectrum taken October 30 showed this to be a type II supernova event. The early expansion velocity of the photosphere was measured at 10,300 km/s. Interstellar lines in the spectrum indicated the event may be partially obscured by dust.^[7]

X-ray emission was detected from this source on November 1–2 and 11–12 using the Chandra X-ray Observatory. The number of photons detected suggested a luminosity of 1×10³⁸ erg/s for the source.^[8] A compact radio source at this position was detected on December 1 from the NRAO Very Large Array.^[9] This was the first type II-p supernova to be detected at both X-ray and radio wavelengths.^[10] By now the target was identified as a type II-P supernova,^[9] based on the shape of the light curves and spectral properties.^[11] Spectrapolarimetry measured between November 1999 and January 2000 showed an increasing level of polarization at later dates. This implied asphericity toward the core of the explosion – meaning a deviation from spherical symmetry.^[12]

Photometric observations showed that SN 1999em remained in its plateau phase for approximately 90 days, indicating that the progenitor possessed a massive hydrogen envelope when the explosion occurred.^[11] The explosion date was estimated to be 5.3±1.4 d before discovery.^[13]^[11] By day 161, the spectrum was dominated by emission lines, indicating that the remnant was transitioning to the nebular phase.^[11] Evidence showed that dust formation began at around day 500. The exponential decay rate of the light curve tail was mainly powered by the radioactive decay of ⁵⁶Co to ⁵⁶Fe. Ejecta mass is estimated at approximately 10 to 11 M_☉ and the surviving neutron star has 1.5 M_☉.^[2]

The host galaxy is close enough that individual bright supergiants can be resolved. However, no such object was detected at the position of the event.^[14] Supernova models indicate a progenitor mass in the range of 11 to 13 M_☉ , with near solar metallicity and an explosive energy of 1.2 foe .^[15] This star had a radius of about 120 to 150 R_☉ .^[2] Radio and X-ray emission indicate the progenitor was surrounded by clumpy or filamentary circumstellar material that was fed by a low stellar mass loss rate of about 2×10⁻⁴ M_☉·yr⁻¹ with a wind velocity of 10 km/s.^[10]^[2] The light curve for this event is nearly identical to that of SN 1999gi, suggesting they may have similar progenitor stars.^[15]

Related Research Articles

Messier 83 or M83, also known as the Southern Pinwheel Galaxy and NGC 5236, is a barred spiral galaxy approximately 15 million light-years away in the constellation borders of Hydra and Centaurus. Nicolas-Louis de Lacaille discovered M83 on 17 February 1752 at the Cape of Good Hope. Charles Messier added it to his catalogue of nebulous objects in March 1781.

Messier 61 is an intermediate barred spiral galaxy in the Virgo Cluster of galaxies. It was first discovered by Barnaba Oriani on May 5, 1779, six days before Charles Messier discovered the same galaxy. Messier had observed it on the same night as Oriani but had mistaken it for a comet. Its distance has been estimated to be 45.61 million light years from the Milky Way Galaxy. It is a member of the M61 Group of galaxies, which is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster.

Messier 74 is a large spiral galaxy in the equatorial constellation Pisces. It is about 32 million light-years away from Earth. The galaxy contains two clearly defined spiral arms and is therefore used as an archetypal example of a grand design spiral galaxy. The galaxy's low surface brightness makes it the most difficult Messier object for amateur astronomers to observe. Its relatively large angular size and the galaxy's face-on orientation make it an ideal object for professional astronomers who want to study spiral arm structure and spiral density waves. It is estimated that M74 hosts about 100 billion stars.

Messier 84 or M84, also known as NGC 4374, is a giant elliptical or lenticular galaxy in the constellation Virgo. Charles Messier discovered the object in 1781 in a systematic search for "nebulous objects" in the night sky. It is the 84th object in the Messier Catalogue and in the heavily populated core of the Virgo Cluster of galaxies, part of the local supercluster.

NGC 6946, sometimes referred to as the Fireworks Galaxy, is a face-on intermediate spiral galaxy with a small bright nucleus, whose location in the sky straddles the boundary between the northern constellations of Cepheus and Cygnus. Its distance from Earth is about 25.2 million light-years or 7.72 megaparsecs, similar to the distance of M101 in the constellation Ursa Major. Both were once considered to be part of the Local Group, but are now known to be among the dozen bright spiral galaxies near the Milky Way but beyond the confines of the Local Group. NGC 6946 lies within the Virgo Supercluster.

SN 2005df was a Type Ia supernova in the barred spiral galaxy NGC 1559, which is located in the southern constellation of Reticulum. The event was discovered in Australia by Robert Evans on the early morning of August 5, 2005 with a 13.8 magnitude, and was confirmed by A. Gilmore on August 6. The supernova was classified as Type Ia by M. Salvo and associates. It was positioned at an offset of 15.0″ east and 40.0″ north of the galaxy's nucleus, reaching a maximum brightness of 12.3 on August 18. The supernova luminosity appeared unreddened by dust from its host galaxy.

NGC 1637 is an isolated, non-interacting intermediate spiral galaxy in the constellation Eridanus, about a degree to the WNW of the star Mu Eridani. It was discovered by German-British astronomer William Herschel on 1 February 1786. It is located at a distance of about 9.77 ± 1.82 Mpc (31.9 ± 5.9 Mly) from the Milky Way. The galaxy is inclined at an angle of 31.1° to the line of sight from the Earth and the long axis is oriented along a position angle of 16.3°.

NGC 2841 is an unbarred spiral galaxy in the northern circumpolar constellation of Ursa Major. It was discovered on 9 March, 1788 by German-born astronomer William Herschel. J. L. E. Dreyer, the author of the New General Catalogue, described it as, "very bright, large, very much extended 151°, very suddenly much brighter middle equal to 10th magnitude star". Initially thought to be about 30 million light-years distant, a 2001 Hubble Space Telescope survey of the galaxy's Cepheid variables determined its distance to be approximately 14.1 megaparsecs or 46 million light-years. The optical size of the galaxy is 8.1′ × 3.5′.

<span class="mw-page-title-main">SN 1994D</span> Type Ia supernova

SN 1994D was a Type Ia supernova event in the outskirts of galaxy NGC 4526. It was offset by 9.0″ west and 7.8″ south of the galaxy center and positioned near a prominent dust lane. It was caused by the explosion of a white dwarf star composed of carbon and oxygen. This event was discovered on March 7, 1994 by R. R. Treffers and associates using the automated 30-inch telescope at Leuschner Observatory. It reached peak visual brightness two weeks later on March 22. Modelling of the light curve indicates the explosion would have been visible around March 3-4. A possible detection of helium in the spectrum was made by W. P. S. Meikle and associates in 1996. A mass of 0.014 to 0.03 M_☉ in helium would be needed to produce this feature.

NGC 4639 is a barred spiral galaxy located in the equatorial constellation of Virgo. It was discovered by German-born astronomer William Herschel on 12 April 1784. John L. E. Dreyer described it as "pretty bright, small, extended, mottled but not resolved, 12th magnitude star 1 arcmin to southeast". This is a relatively nearby galaxy, lying approximately 72 million light-years away from the Milky Way. It is a companion to NGC 4654, and the two appear to have interacted roughly 500 million years ago. NGC 4639 is a member of the Virgo Cluster.

<span class="mw-page-title-main">SN 2003gd</span> Supernova in the constellation Pisces

SN 2003gd was a Type II-P supernova explosion in the Phantom Galaxy, located in the constellation Pisces. SN 2003gd was discovered on 12 June 2003 by Robert Evans, using a 0.31m reflector, and its discovery was confirmed on 13 June 2003 by R. H. McNaught using the 1.0m telescope at the Siding Spring Observatory.

<span class="mw-page-title-main">NGC 7424</span> Galaxy in the constellation Grus

NGC 7424 is a barred spiral galaxy located 37.5 million light-years away in the southern constellation Grus. Its size makes it similar to our own galaxy, the Milky Way. It is called a "grand design" galaxy because of its well defined spiral arms. Two supernovae and two ultraluminous X-ray sources have been discovered in NGC 7424.

NGC 4666 is a spiral galaxy in the equatorial constellation of Virgo, located at a distance of approximately 55 megalight-years from the Milky Way. It was discovered by the German-born astronomer William Herschel on February 22, 1784. It is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. John L. E. Dreyer described it as "bright, very large, much extended 45°±, pretty suddenly brighter middle". It is a member of an interacting system with NGC 4668 and a dwarf galaxy, and belongs to a small group that also includes NGC 4632.

SN 1998aq is a nearby supernova located in the intermediate spiral galaxy NGC 3982, offset 18″ west and 7″ of the galactic nucleus. It was discovered April 13, 1998 by amateur astronomer Mark Armstrong and was confirmed by fellow British amateur Ron Arbour; both members of the U.K. Supernova/Nova Patrol. The event was not visible on a prior check by Armstrong made April 7. It reached peak brightness on April 27, and 15 days later had declined by 1.14 magnitudes in the B (blue) band.

NGC 5806 is an intermediate spiral galaxy in the constellation Virgo. It was discovered on February 24, 1786, by the astronomer John Herschel. It is located about 70 million light-years away from the Milky Way. It is a member of the NGC 5846 Group.

NGC 3938 is an unbarred spiral galaxy in the Ursa Major constellation. It was discovered on 6 February 1788 by William Herschel. It is one of the brightest spiral galaxies in the Ursa Major South galaxy group and is roughly 67,000 light years in diameter. It is approximately 43 million light years away from Earth. NGC 3938 is classified as type Sc under the Hubble sequence, a loosely wound spiral galaxy with a smaller and dimmer bulge. The spiral arms of the galaxy contain many areas of ionized atomic hydrogen gas, more so towards the center.

NGC 1084 is an unbarred spiral galaxy in the constellation Eridanus. It is located at a distance of about 63 million light-years away from the Milky Way. The galaxy was discovered by William Herschel on 10 January 1785. It has multiple spiral arms, which are not well defined. It belongs in the same galaxy group with NGC 988, NGC 991, NGC 1022, NGC 1035, NGC 1042, NGC 1047, NGC 1052 and NGC 1110. This group is in turn associated with the Messier 77 group.

NGC 3367 is a barred spiral galaxy located in the constellation Leo. It is located at a distance of about 120 million light years from Earth, which, given its apparent dimensions, means that NGC 3367 is about 85,000 light years across. It was discovered by William Herschel on March 19, 1784.

NGC 6951 is a barred spiral galaxy located in the constellation Cepheus. It is located at a distance of about 75 million light-years from Earth, which, given its apparent dimensions, means that NGC 6951 is about 100,000 light-years across. It was discovered by Jérôme Eugène Coggia in 1877 and independently by Lewis Swift in 1878.

NGC 3786 is an spiral galaxy located 107.5 million light-years away in the northern constellation of Ursa Major. It was discovered by English astronomer John Herschel on April 10, 1831. This object appears to form a close pair with its peculiar neighbor to the north, NGC 3788. They show some indications of interaction, such as minor distortion of the disk or tidal features.

References

1 2 Leonard, Douglas C.; et al. (September 2003), "The Cepheid Distance to NGC 1637: A Direct Test of the Expanding Photosphere Method Distance to SN 1999em", The Astrophysical Journal, 594 (1): 247–278, arXiv: astro-ph/0305259 , Bibcode:2003ApJ...594..247L, doi:10.1086/376831.
1 2 3 4 Elmhamdi, Abouazza; et al. (February 2003), "Photometry and spectroscopy of the Type IIP SN 1999em from outburst to dust formation", Monthly Notice of the Royal Astronomical Society, 338 (4): 939–956, arXiv: astro-ph/0209623 , Bibcode:2003MNRAS.338..939E, doi: 10.1046/j.1365-8711.2003.06150.x .
↑ "SN 1999em", SIMBAD , Centre de données astronomiques de Strasbourg , retrieved 2025-01-05.
1 2 Li, W. D. (October 1999), Green, D. W. E. (ed.), "Supernova 1999em in NGC 1637", IAU Circular, 7294: 1, Bibcode:1999IAUC.7294....1L.
↑ Dessart, L.; Hillier, D. J. (February 2006), "Quantitative spectroscopic analysis of and distance to SN1999em", Astronomy and Astrophysics, 447 (2): 691–707, arXiv: astro-ph/0510526 , Bibcode:2006A&A...447..691D, doi:10.1051/0004-6361:20054044.
↑ Galbany, Lluís; Hamuy, Mario; Phillips, Mark M.; Suntzeff, Nicholas B.; Maza, José; de Jaeger, Thomas; Moraga, Tania; González-Gaitán, Santiago; Krisciunas, Kevin; Morrell, Nidia I.; homas-Osip, Joanna; Krzeminski, Wojtek; González, Luis; Antezana, Roberto; Wishnjewski, Marina; McCarthy, Patrick; Galaz, Gaspar; Green, Elisabeth M.; Impey, Chris; Kim, Yong-Cheol; Kirhakos, Soﬁa; Malkan, Mathew A.; Mulchaey, John S.; Phillips, Andrew C.; Pizzella, Alessandro; Prosser, Charles F.; Schmidt, Brian P.; Schommer, Robert A.; Sherry, William; Strolger, Louis-Gregory; Wells, Lisa A.; Williger, Gerard M. (February 2016). "UBVRIz Light Curves of 51 Type II Supernovae". The Astronomical Journal. 151 (2): 33. arXiv: 1511.08402 . Bibcode:2016AJ....151...33G. doi: 10.3847/0004-6256/151/2/33 .
↑ Jha, S.; et al. (October 1999), Green, D. W. E. (ed.), "Supernova 1999em in NGC 1637", IAU Circular, 7296: 2, Bibcode:1999IAUC.7296....2J.
↑ Fox, D. W.; Lewin, W. H. G. (November 1999), Marsden, B. G. (ed.), "Supernova 1999em in NGC 1637", IAU Circular, 7318: 1, Bibcode:1999IAUC.7318....1F.
1 2 Lacey, C. K.; et al. (December 1999), Green, D. W. E. (ed.), "Supernova 1999em in NGC 1637", IAU Circular, 7336: 2, Bibcode:1999IAUC.7336....2L.
1 2 Pooley, David; et al. (June 2002), "X-Ray, Optical, and Radio Observations of the Type II Supernovae 1999em and 1998S", The Astrophysical Journal, 572 (2): 932–943, Bibcode:2002ApJ...572..932P, doi:10.1086/340346.
1 2 3 4 Leonard, Douglas C.; et al. (June 2001), "Is It Round? Spectropolarimetry of the Type II-p Supernova 1999EM", The Astrophysical Journal, 553 (2): 861–885, arXiv: astro-ph/0009285 , Bibcode:2001ApJ...553..861L, doi:10.1086/320959.
↑ Wang, L.; et al. (February 2000), Green, D. W. E. (ed.), "Supernova 1999em in NGC 1637", IAU Circular, 7355: 1, Bibcode:2000IAUC.7355....1W.
↑ Hamuy, Mario; et al. (September 2001), "The Distance to SN 1999em from the Expanding Photosphere Method", The Astrophysical Journal, 558 (2): 615–642, arXiv: astro-ph/0105006 , Bibcode:2001ApJ...558..615H, doi:10.1086/322450.
↑ Smartt, Stephen J.; et al. (February 2002), "The Nature of the Progenitor of the Type II-P Supernova 1999em", The Astrophysical Journal, 565 (2): 1089–1100, arXiv: astro-ph/0107499 , Bibcode:2002ApJ...565.1089S, doi:10.1086/324690.
1 2 You, Kai-An; et al. (August 2024), "Modeling the Progenitor Stars of Observed Type IIP Supernovae", The Astrophysical Journal, 970 (2), id. 145, arXiv: 2402.19260 , Bibcode:2024ApJ...970..145Y, doi: 10.3847/1538-4357/ad50c6 .

SN 1999em

Contents

Observations

Related Research Articles

References

Further reading