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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"

37518 results found.

  1. GRB 260424A: AstroSat CZTI detection of a long burst
  2. GRB 260421B: Kilonova-Catcher optical afterglow detection
  3. GRB 260421B: Insight-HXMT/HE detection
  4. The EP-WXT trigger 01709258652: Mondy optical observations
  5. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  6. EP260416a: Mondy optical observations
  7. GRB 260421B: SVOM/ECLAIRs refined analysis
  8. GRB 260421B: 3.6m DOT optical observation
  9. EP260416a: ZTSh R band observations
  10. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  11. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  12. GRB 260419A: AstroSat CZTI detection
  13. GRB 260421B: SVOM/GRM observation
  14. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  15. GRB 260421B: EP-FXT follow-up observation
  16. GRB 260421B: J-band upper limit with WINTER
  17. GRB 260421B: LCO optical counterpart detection
  18. GRB 260421B: Fermi GBM Observation
  19. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  20. GRB 260421A: AstroSat CZTI detection
  21. GRB 260412A: SVOM/ECLAIRs refined analysis
  22. GRB 260421B: SVOM/VT optical observations
  23. GRB 260310A: Late-time Chandra X-ray Detection
  24. GRB 260418A: Insight-HXMT/HE detection
  25. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  26. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  27. Fermi GRB 260421C: Global MASTER-Net observations report
  28. GRB 260421C: Fermi GBM Final Real-time Localization
  29. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  30. Fermi GRB 260421B: Global MASTER-Net observations report
  31. GRB 260421B: BOOTES-7 early optical afterglow detection
  32. GRB 260421B: LCO optical afterglow confirmation
  33. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  34. GRB 260421B: TRT optical counterpart detection
  35. GRB 260421B: SVOM detection of a long burst
  36. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  37. GRB 260421B: Fermi GBM Final Real-time Localization
  38. Fermi GRB 260421A: Global MASTER-Net observations report
  39. GRB 260421A: Fermi GBM Final Real-time Localization
  40. GRB 260412A: LCOGT Optical Upper Limits
  41. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  42. EP-WXT trigger 01709260303: KAIT optical observations
  43. GRB 260417A: SVOM/GRM observation
  44. GRB 260419B: Fermi GBM Final Real-time Localization
  45. GRB 260419A: Fermi GBM Final Real-time Localization
  46. Fermi trigger No 798275385: Global MASTER-Net observations report
  47. Fermi GRB 260417B: Global MASTER-Net observations report
  48. GRB 260418B: Fermi GBM Final Real-time Localization
  49. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  50. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  51. GRB 260418A: Fermi GBM Final Real-time Localization
  52. Fermi GRB 260417A: Global MASTER-Net observations report
  53. Konus-Wind detection of GRB 260411B
  54. GRB 260417B: Fermi GBM Final Real-time Localization
  55. GRB 260417A: AstroSat CZTI detection
  56. IPN triangulation of GRB 260411B
  57. EP-WXT trigger 01709259586: KAIT optical observations
  58. EP260416a: KAIT optical upper limit
  59. GRB 260414A: Insight-HXMT/HE detection
  60. GRB 260417A: Fermi GBM Final Real-time Localization
  61. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  62. GRB 260415B: Glowbug gamma-ray detection
  63. GRB 260411B: Glowbug gamma-ray detection
  64. GRB 260415A: Insight-HXMT/HE detection
  65. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  66. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  67. GRB 260415B: NuSTAR detection of long prompt emission
  68. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  69. GRB 260415B: Fermi GBM Final Localization
  70. GRB 260415A: Fermi GBM Final Real-time Localization
  71. Fermi trigger No 797912738: Global MASTER-Net observations report
  72. GRB 260414A: Glowbug gamma-ray detection
  73. EP260321a: CMO SAI J,K observations
  74. GRB 260412A: Insight-HXMT/HE detection
  75. GRB 260414A: Fermi GBM Final Real-time Localization
  76. Fermi GRB 260413A: Global MASTER-Net observations report
  77. GRB 260410A: Glowbug gamma-ray detection of a short burst
  78. GRB 260413A: Fermi GBM Final Real-time Localization
  79. GRB 260410B: Insight-HXMT/HE detection
  80. GRB 260410A: Insight-HXMT/HE detection
  81. Konus-Wind detection of GRB 260410A (short/hard)
  82. GRB 260411B: GECAM-B observation of a long burst
  83. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  84. GRB 260412A: GECAM-B observation of a long burst
  85. Fermi GRB 260412A: Global MASTER-Net observations report
  86. GRB 260412A: Fermi GBM Observation
  87. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  88. GRB 260411B: Fermi-LAT detection
  89. GRB 260412A: SVOM detection of a long burst
  90. GRB 260412A: Fermi GBM Final Real-time Localization
  91. GRB 260411B: COLIBRÍ optical observations
  92. GRB 260410B: Fermi GBM Observation
  93. GRB 260411B: Ondrejov D50 optical afterglow detection
  94. GRB260411B: 3.6m DOT optical observation
  95. GRB 260411A: SVOM/GRM observation
  96. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  97. GRB 260411B: SVOM/GRM observation of a long burst
  98. GRB 260409A: Insight-HXMT/HE detection
  99. GRB 260411B: Fermi GBM Detection
  100. GRB 260411B: GOTO optical counterpart candidate

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