G111.7-2.1  Cassiopeia A, 3C461

Right Ascension: 23 23 26
Declination: +58 48
Size (/arcmin): 5
Type: S
Flux density at 1 GHz (/Jy): 2300
Spectral Index: 0.77
  
Notes: Presumably the remnant of a late 17th century SN.

Radio: Bright shell with compact knots and extended plateau of emission;
  shows secular decline.
Optical: Fast knots and quasi-stationary flocculli, with many filaments
  at large radii, and NE `jet'.
X-ray: Incomplete shell, with hard spectral component.
Point sources: Central compact X-ray source.
Distance: Optical expansion gives 3.3 kpc.
  
References:

Anderson & Rudnick 1995, ApJ, 441, 307. VLA at 1.4 GHz and 4.8 GHz,
  for proper motion studies.
Kassim et al. 1995, ApJ, 455, L59. VLA at 74 (25") and 332 MHz (6"),
  including spectral index comparisons.
Anderson & Rudnick 1996, ApJ, 456, 234. VLA for spectral index comparisons.
Schwarz et al. 1997, A&AS, 123, 43. WSRT at 1.4 GHz (30") for HI absorption.
O'Sullivan & Green 1999, MNRAS, 303, 575. Flux density changes at 13.5,
  15.5 and 16.5 GHz.
Agueros & Green 1999, MNRAS, 305, 957. 151 MHz observations for bulk
  expansion studies.
Gotthelf et al. 2001, ApJ, 552, L39. Chandra observations, showing
  outer shock.
Hwang et al. 2001, ApJ, 560, L175. Chandra observations of Doppler
  shifted lines.
Fesen et al. 2001, AJ, 122, 2644. HST observations.
Reynoso & Goss 2002, ApJ, 575, 871. VLA at 5 GHz (6."0 x 6."4) for H2CO
  absorption studies.
Krause et al. 2005, Science, 308, 1604. Spitzer light echoes from
  surroundings.
Ennis et al. 2006, ApJ, 652, 376. Spitzer observations.
Kang & Koo 2007, ApJS, 173, 85. SGPS of high velocity HI.
Rho et al. 2008, ApJ, 673, 271. Spitzer observations.
Rest et al. 2008, ApJ, 681, L81. SN light echo.
Krause et al. 2008, Science, 320, 1195. SN light echo spectrum.
Helmboldt & Kassim 2009, AJ, 138, 838. Low radio frequency temporal
  variations.
Barlow et al. 2010, A&A, 518, L138. Herschel observations.
Sibthorpe et al. 2010, ApJ, 719, 1553. Akari and sub-mm observations
  of region.
DeLaney et al. 2010, ApJ, 725, 2038. Spitzer and Chandra observations
  for 3-D structure.
Patnaude et al. 2011, ApJ, 729, L28. Chandra observations of fading.
Rest et al. 2011, ApJ, 732, 3. SN light echo observations.
Fesen et al. 2011, ApJ, 736, 109. HST variability studies.
Besel & Krause 2012, A&A, 541, L3. IR light echoes.
Vogt et al. 2012, ApJ, 750, 155. Spitzer light echoes.
Asgekar et al. 2013, A&A, 551, L11. LOFAR of carbon recombination lines.
Yang et al. 2013, ApJ, 766, 44. Suzaku spectroscopy.
Rutherford et al. 2013, ApJ, 769, 64. Chandra spectroscopy.
Milisavljevic & Fesen 2013, ApJ, 772, 134. Optical spectroscopy for
  3-D structure.
Koo et al. 2013, Science, 342, 1346. IR spectroscopy.
DeLaney et al. 2014, ApJ, 785, 7. VLA plus Pie Town at 74 MHz (9") and
  comparison with higher frequencies.
Arendt et al. 2014, ApJ, 786, 55. Spitzer and Herschel IR observations.
Patnaude & Fesen 2014, ApJ, 789, 138. Multi-epoch optical and X-ray
  observations.
Lee et al. 2014, ApJ, 789, 7. Spitzer and CO observations.
Vinyaikin 2014, ARep, 58, 626. Time evolution of radio emission.
Alarie et al. 2014, MNRAS, 441, 2996. Optical imaging/spectroscopy,
  including distance from expansion.
Grefenstette et al. 2014, Nature, 506, 339. NuSTAR 44Ti observations.
Grefenstette et al. 2015, ApJ, 802, 15. NuSTAR observations.
Lee et al. 2015, ApJ, 808, 98. WISE, Spitzer and other IR observations.
Milisavljevic & Fesen 2015, Science, 347, 526. Near-IR observations.
Planck Collaboration: Arnaud et al. 2016, A&A, 586, A134. Planck flux
  densities at 7 frequencies between 30 and 353 GHz.
Kilpatrick et al. 2016, ApJ, 816, 1. CO observations, including broad lines.
Fesen & Milisavljevic 2016, ApJ, 818, 17. HST [SIII] and [SII] observations.
Koo et al. 2016, ApJ, 821, 20. Spitzer and Herschel flux densities (and
  comparison with X-ray properties).
Wang & Li 2016, ApJ, 825, 102. INTEGRAL observations.
Acero et al. 2016, ApJS, 224, 8. Fermi observations.
Oonk et al. 2017, MNRAS, 465, 1066. LOFAR observations, including H and
  C lines, 33 to 78 MHz, including 69 MHz (9."8 x 11."2).
De Looze et al. 2017, MNRAS, 465, 3309. Spitzer and Herschel observations.
Trotter et al. 2017, MNRAS, 469, 1299. Time evolution of radio emission.
Grefenstette et al. 2017, ApJ, 834, 19. NuSTAR observations.
Sato et al. 2017, ApJ, 836, 225. Multi-epoch Chandra observations.
Lee et al. 2017, ApJ, 837, 118. IR observations.
Arias et al. 2018, A&A, 612, A110. LOFAR at 30 to 77 MHz (7" x 17").
Salas et al. 2018, MNRAS, 475, 2496. LOFAR C recombination lines as 43,
  54, 148 and 340 MHz (70").
Sato et al. 2018, ApJ, 853, 46. Chandra and NuSTAR observations.
Zhou et al. 2018, ApJ, 865, 6. CO observations.
Raymond et al. 2018, ApJ, 866, 128. IR observations.
Koo et al. 2018, ApJ, 866, 139. IR observations.
  also see: Koo et al. 2020, ApJ, 896, 177. Erratum.
Chowdhury & Chengalur 2019, MNRAS, 486, 42. GMRT at 410 to 460 MHz for
  C recombination lines.
Weinberger et al. 2020, A&A, 638, A83. INTEGRAL observations.
Koo et al. 2020, NatAs, 4, 584. Near IR spectroscopy of surroundings.
Weil et al. 2020, ApJ, 891, 116. Deep Halpha of surroundings.
Mayer & Becker 2021, A&A, 651, A40. Multi-epoch Chandra observations for
  proper motion of compact source.
Domcek et al. 2021, MNRAS, 502, 1026. Radio to IR spectral study.
  
Last updated: 16 Dec 2022