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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"

32693 results found.

  1. EP260502a: BOOTES-7: early optical upper limit
  2. EP260502a: Las Cumbres upper limit
  3. GRB 260429A: SVOM/GRM observation of a short burst
  4. EP260429a: Global MASTER-Net observations report
  5. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  6. GRB 260424B: AstroSat CZTI detection
  7. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  8. EP260429a: LCO optical upper limits
  9. EP260430a: LCO optical upper limits
  10. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  11. Fermi GRB 260429A: Global MASTER-Net observations report
  12. EP260430a: Global MASTER-Net observations report
  13. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  14. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  15. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 260428A: AstroSat CZTI detection
  17. Fermi GRB 260428A: Global MASTER-Net observations report
  18. EP260416a: Mondy and Terskol optical upper limits
  19. GRB 260424B: Glowbug gamma-ray detection of a short burst
  20. GRB 260424B: COLIBRÍ optical upper limit
  21. Konus-Wind detection of GRB 260424B
  22. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  23. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  24. IPN triangulation of GRB 260424B (short)
  25. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  26. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  27. GRB 260401A: cubesat Avion detection
  28. EP260321a: Upper limits from ATCA radio observations
  29. GRB 260421B: Kilonova-Catcher optical afterglow detection
  30. GRB 260421B: Insight-HXMT/HE detection
  31. The EP-WXT trigger 01709258652: Mondy optical observations
  32. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  33. EP260416a: Mondy optical observations
  34. GRB 260421B: SVOM/ECLAIRs refined analysis
  35. GRB 260421B: 3.6m DOT optical observation
  36. EP260416a: ZTSh R band observations
  37. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  38. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  39. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  40. GRB 260419A: AstroSat CZTI detection
  41. GRB 260421B: SVOM/GRM observation
  42. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  43. GRB 260421B: EP-FXT follow-up observation
  44. GOTO26djh/AT2026jpw: ATCA radio detection
  45. GRB 260421B: J-band upper limit with WINTER
  46. GRB 260421B: LCO optical counterpart detection
  47. GRB 260421B: Fermi GBM Observation
  48. GRB 260421A: AstroSat CZTI detection
  49. GOTO26djh/AT2026jpw: radio detection at 15GHz
  50. GRB 260412A: SVOM/ECLAIRs refined analysis
  51. GRB 260421B: SVOM/VT optical observations
  52. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  53. GRB 260310A: Late-time Chandra X-ray Detection
  54. GRB 260418A: Insight-HXMT/HE detection
  55. EP260416a: 1.3m DFOT optical observation
  56. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  57. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  58. Fermi GRB 260421C: Global MASTER-Net observations report
  59. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  60. Fermi GRB 260421B: Global MASTER-Net observations report
  61. GRB 260421B: BOOTES-7 early optical afterglow detection
  62. GRB 260421B: LCO optical afterglow confirmation
  63. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  64. GRB 260421B: TRT optical counterpart detection
  65. GRB 260421B: SVOM detection of a long burst
  66. Fermi GRB 260421A: Global MASTER-Net observations report
  67. EP260321a: VLA radio follow-up
  68. GRB 260412A: LCOGT Optical Upper Limits
  69. EP260416a: Optical follow-up observations with Kinder
  70. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  71. EP-WXT trigger 01709260303: KAIT optical observations
  72. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  73. GRB 260417A: SVOM/GRM observation
  74. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  75. EP260417a: GROWTH-India Telescope optical upper limit
  76. Fermi GRB 260417B: Global MASTER-Net observations report
  77. EP260417b: GROWTH-India Telescope optical upper limit
  78. EP260416a: Ondrejov D50 optical detection
  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. EP260416a: GMG Optical Observation
  84. Fermi GRB 260417A: Global MASTER-Net observations report
  85. Konus-Wind detection of GRB 260411B
  86. GRB 260417A: AstroSat CZTI detection
  87. IPN triangulation of GRB 260411B
  88. EP260416a: LCO observations confirm end of flaring phase
  89. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  90. EP260417a: TRT optical counterpart detection
  91. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  92. EP-WXT trigger 01709259586: KAIT optical observations
  93. EP260416a: KAIT optical upper limit
  94. GRB 260414A: Insight-HXMT/HE detection
  95. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  96. EP260416a: WFST optical observations and rebrightening
  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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