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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

19293 results found.

  1. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  2. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  3. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  4. GRB 260428A: AstroSat CZTI detection
  5. Fermi GRB 260428A: Global MASTER-Net observations report
  6. EP260416a: Mondy and Terskol optical upper limits
  7. GRB 260424B: Glowbug gamma-ray detection of a short burst
  8. GRB 260424B: COLIBRÍ optical upper limit
  9. GRB 260428A: Fermi GBM Final Real-time Localization
  10. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  11. GRB 260424C: Fermi GBM Final Localization
  12. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  13. GRB 260424B: SVOM/GRM detection of a short burst
  14. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  15. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  16. IceCube Alert 260425A: Global MASTER-Net observations report
  17. Fermi trigger No 798737427: Global MASTER-Net observations report
  18. GRB 260401A: cubesat Avion detection
  19. GRB 260424A: AstroSat CZTI detection of a long burst
  20. EP260321a: Upper limits from ATCA radio observations
  21. GRB 260421B: Insight-HXMT/HE detection
  22. The EP-WXT trigger 01709258652: Mondy optical observations
  23. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  24. EP260416a: Mondy optical observations
  25. GRB 260421B: SVOM/ECLAIRs refined analysis
  26. GRB 260421B: 3.6m DOT optical observation
  27. EP260416a: ZTSh R band observations
  28. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  29. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  30. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  31. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  32. GRB 260419A: AstroSat CZTI detection
  33. GRB 260421B: SVOM/GRM observation
  34. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  35. GRB 260421B: EP-FXT follow-up observation
  36. The EP-WXT trigger 01709260362 is likely a flaring star
  37. GOTO26djh/AT2026jpw: ATCA radio detection
  38. GRB 260421B: J-band upper limit with WINTER
  39. GRB 260421B: LCO optical counterpart detection
  40. GRB 260421B: Fermi GBM Observation
  41. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  42. GRB 260421A: AstroSat CZTI detection
  43. GOTO26djh/AT2026jpw: radio detection at 15GHz
  44. GRB 260412A: SVOM/ECLAIRs refined analysis
  45. GRB 260421B: SVOM/VT optical observations
  46. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  47. GRB 260310A: Late-time Chandra X-ray Detection
  48. GRB 260418A: Insight-HXMT/HE detection
  49. EP260416a: 1.3m DFOT optical observation
  50. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  51. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  52. Fermi GRB 260421C: Global MASTER-Net observations report
  53. GRB 260421C: Fermi GBM Final Real-time Localization
  54. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  55. Fermi GRB 260421B: Global MASTER-Net observations report
  56. GRB 260421B: BOOTES-7 early optical afterglow detection
  57. GRB 260421B: LCO optical afterglow confirmation
  58. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  59. GRB 260421B: SVOM detection of a long burst
  60. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  61. GRB 260421B: Fermi GBM Final Real-time Localization
  62. Fermi GRB 260421A: Global MASTER-Net observations report
  63. GRB 260421A: Fermi GBM Final Real-time Localization
  64. GRB 260412A: LCOGT Optical Upper Limits
  65. The EP-WXT trigger 01709260314 is likely a flaring star
  66. EP260416a: Optical follow-up observations with Kinder
  67. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  68. The EP-WXT trigger 01709260303 is likely a flaring star
  69. GRB 260417A: SVOM/GRM observation
  70. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  71. GRB 260419B: Fermi GBM Final Real-time Localization
  72. GRB 260419A: Fermi GBM Final Real-time Localization
  73. Fermi trigger No 798275385: Global MASTER-Net observations report
  74. EP260417a: GROWTH-India Telescope optical upper limit
  75. Fermi GRB 260417B: Global MASTER-Net observations report
  76. EP260417b: GROWTH-India Telescope optical upper limit
  77. EP260416a: Ondrejov D50 optical detection
  78. GRB 260418B: Fermi GBM Final Real-time Localization
  79. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  80. EP260417a: Global MASTER-Net observations report
  81. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  82. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  83. GRB 260418A: Fermi GBM Final Real-time Localization
  84. EP260416a: GMG Optical Observation
  85. Fermi GRB 260417A: Global MASTER-Net observations report
  86. GRB 260417B: Fermi GBM Final Real-time Localization
  87. GRB 260417A: AstroSat CZTI detection
  88. EP260416a: LCO observations confirm end of flaring phase
  89. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  90. EP260417a: Einstein Probe detection of an X-ray transient
  91. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  92. EP260417b: Einstein Probe detection of a fast X-ray transient
  93. GRB 260414A: Insight-HXMT/HE detection
  94. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  95. EP260416a: WFST optical observations and rebrightening
  96. GRB 260417A: Fermi GBM Final Real-time Localization
  97. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  98. EP260416a: SVOM/VT optical observation
  99. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  100. GRB 260415B: Glowbug gamma-ray detection

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