Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! See news and announcements

GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

32490 results found.

  1. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  2. EP260416a: Global MASTER-Net observations report
  3. GOTO26djh/AT2026jpw : MASTER OT observation
  4. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  5. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  6. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  7. GRB 260415B: NuSTAR detection of long prompt emission
  8. GRB 260414A: Glowbug gamma-ray detection
  9. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  10. EP260321a: CMO SAI J,K observations
  11. GRB 260412A: Insight-HXMT/HE detection
  12. Fermi GRB 260413A: Global MASTER-Net observations report
  13. GRB 260410A: Glowbug gamma-ray detection of a short burst
  14. GRB 260410B: Insight-HXMT/HE detection
  15. GRB 260410A: Insight-HXMT/HE detection
  16. Konus-Wind detection of GRB 260410A (short/hard)
  17. GRB 260411B: GECAM-B observation of a long burst
  18. EP260321a: SVOM/VT optical observations and color changes around peak
  19. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 260412A: GECAM-B observation of a long burst
  21. Fermi GRB 260412A: Global MASTER-Net observations report
  22. GRB 260412A: Fermi GBM Observation
  23. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  24. GRB 260411B: Fermi-LAT detection
  25. GRB 260412A: SVOM detection of a long burst
  26. GRB 260411B: COLIBRÍ optical observations
  27. GRB 260410B: Fermi GBM Observation
  28. GRB 260411B: Ondrejov D50 optical afterglow detection
  29. GRB260411B: 3.6m DOT optical observation
  30. GRB 260411A: SVOM/GRM observation
  31. GRB 260411B: SVOM/GRM observation of a long burst
  32. GRB 260409A: Insight-HXMT/HE detection
  33. GRB 260411B: Fermi GBM Detection
  34. GRB 260411B: GOTO optical counterpart candidate
  35. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  36. GRB 260410A: COLIBRÍ optical upper limit
  37. EP-WXT01709259790: Optical Upper limits with kinder observations
  38. GRB 260410A: Fermi GBM Observation
  39. GRB 260410B: SVOM/GRM detection of a short faint burst
  40. GRB 260410A: Fermi-LAT detection
  41. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  42. EP260321a: Chandra X-ray Non-detection
  43. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  44. GRB 260407A: GECAM-A detection
  45. GRB 260407A: Insight-HXMT/HE detection
  46. EP260409a: SVOM/VT optical upper limits
  47. EP260409a: COLIBRÍ optical upper limits
  48. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  49. EP260409a: Global MASTER-Net observations report
  50. EP260321a: VLA radio detection
  51. GRB 260407A: Glowbug gamma-ray detection
  52. GRB 260402A: SVOM/ECLAIRs refined analysis
  53. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  54. GRB 260310A / AT2026fgk: X-ray rebrightening
  55. EP260402a / GRB 260402A: Mephisto optical upper limits
  56. EP-WXT01709259586: Xinglong optical upper limit
  57. EP260403a: Mephisto optical upper limits
  58. EP260402a/GRB 260402A: Xinglong optical upper limit
  59. EP260321a: Upper limits from VLA radio observations
  60. GRID detection of GRB 260401A
  61. EP260321a: uGMRT observations
  62. EP260405a: GMOS-N optical upper limits
  63. EP260405a: SVOM/VT optical upper limits
  64. EP260405a: Global MASTER-Net observations report
  65. EP260405a: Einstein Probe detection of a fast X-ray transient
  66. GRB 260403A: GECAM-B observation of a long burst
  67. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  68. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 260330B: SVOM/VT further optical observation
  70. GRB 260330B: SVOM/ECLAIRs refined analysis
  71. EP260403a: LCO optical observations of the counterpart
  72. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  73. EP260403a: LCO optical counterpart detection
  74. EP260403a: COLIBRÍ optical counterpart candidate
  75. GRB 260330B: SVOM/VT optical candidate
  76. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  77. GRB 260403A: AstroSat CZTI detection
  78. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  79. GRB 260402B: GECAM-B observation
  80. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  81. GRB 260402C: NuSTAR detection of prompt emission
  82. EP260324A / AT 2026hir: COLIBRÍ optical observations
  83. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  84. GRB 260402A: WINTER J-band upper limit
  85. GRB260402A: GROWTH-India Telescope optical upper limit
  86. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  87. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  88. GRB 260401A: SVOM/GRM observation
  89. GRB 260401A: GECAM-B observation
  90. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  91. GRB 260402A: Kilonova-Catcher optical upper limit
  92. GRB 260402A: MASTER optical observations
  93. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  95. Fermi GRB 260401A: Global MASTER-Net observations report
  96. GRB 260401A: Fermi GBM Observation
  97. GRB 260401A: NuSTAR detection of prompt emission
  98. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  99. GRB 260401A: MAXI/GSC detection
  100. EP260329b: Mondy and Assy-Turgen optical upper limits

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov