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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"

28089 results found.

  1. EP260214b: EP-FXT follow-up observation
  2. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  3. EP260214b: DDOTI Optical Detection
  4. EP260214b: GROWTH-India Telescope optical upper limit
  5. EP260214a: VLT near-infrared observation
  6. EP260214a: NOT optical upper limits
  7. EP260214a: COLIBRÍ optical upper limits
  8. EP260214b: OHP/T120 optical observations
  9. EP260214a: refined analysis of the EP-FXT observation
  10. EP260214b: LCO optical counterpart detection
  11. GRB 260211A: SVOM/VT optical counterpart
  12. EP260214b: COLIBRÍ optical observations
  13. EP260214b: NOT optical counterpart detection
  14. EP260214b: Einstein Probe detection of a fast X-ray transient
  15. EP260214a: Global MASTER-Net observations report
  16. EP260214a: Einstein Probe detection of an X-ray transient
  17. GRB 260212A: AstroSat CZTI detection
  18. GRB 260212A: Fermi GBM Observation
  19. EP260213a: Liverpool Telescope optical upper limits
  20. EP260213a: Global MASTER-Net observations report
  21. EP260213a: COLIBRÍ optical upper limits
  22. EP260213a: Optical upper limits with Kinder observations
  23. EP260213a: Mondy R-band optical upper limit
  24. EP260213a: SVOM/C-GFT upper limit
  25. EP260213a: refined analysis of the EP-FXT observation
  26. EP260213a: Einstein Probe detection of a fast X-ray transient
  27. EP/WXT 01709258378: NOT optical upper limits
  28. GRB 260212A: SVOM/GRM observation of a long burst
  29. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  30. GRB 260211A: EP-FXT follow-up observation
  31. GRB 260211A: SVOM/VT optical observation
  32. GRB 260212A: Glowbug gamma-ray detection
  33. Fermi GRB 260212A: Global MASTER-Net observations report
  34. GRB 260211A: LAST optical upper limit
  35. GRB 260210A: SVOM/GRM observation
  36. Fermi GBM Sub-Threshold Detection of GRB 260211A
  37. GRID detection of GRB 260207B
  38. GRB 260211A: LCO optical upper limits
  39. GRB260131A/B: 3.6m DOT Optical Observations
  40. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  41. Fermi trigger No 792537871: Global MASTER-Net observations report
  42. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  43. EP260209a: COLIBRÍ optical upper limit
  44. Fermi GRB 260210C: Global MASTER-Net observations report
  45. EP260209a: LCO optical upper limits
  46. EP260210a: Global MASTER-Net observations report
  47. EP260210a: refined analysis of the EP-FXT observation
  48. EP260209a: Global MASTER-Net observations report
  49. GRB 260208A: LCO detection of the optical counterpart
  50. EP260209a: Einstein Probe detection of a fast X-ray transient
  51. EP260210a: Optical upper limits with Kinder observations
  52. GRB 260210A: Glowbug gamma-ray detection
  53. GRB 260208C: AstroSat CZTI detection
  54. EP260210a: COLIBRÍ optical upper limit
  55. EP260210a: SVOM/C-GFT upper limit
  56. EP260210a: Einstein Probe detection of an X-ray transient
  57. GRB 260207B: AstroSat CZTI detection
  58. GRB 260208C: SVOM/GRM observation
  59. GRB 260204A: Swift-XRT afterglow detection
  60. GRB 260208B: AstroSat CZTI detection of a bright long burst
  61. GRB260208A: Liverpool Telescope optical follow-up observations
  62. GRB 260208A: Glowbug gamma-ray detection
  63. GRB 260208A: NuSTAR detection of prompt emission
  64. GRB 260208A: Fermi GBM Observation
  65. Fermi GRB 260209A: Global MASTER-Net observations report
  66. GRB 260208B: Swift-XRT observations
  67. GRB 260131A/B: continued Mondy optical observations
  68. GRB 260204A: Swift/UVOT Upper Limits
  69. GRB 260208B: COLIBRÍ optical observations
  70. GRB 260208A: Mondy optical observations
  71. GRB 260208A: 1.3m DFOT optical detection
  72. GRB 260208A: COLIBRÍ optical observations
  73. GRB 260208B: EP-FXT observation
  74. Fermi GRB 260208C: Global MASTER-Net observations report
  75. GRB 260208B: SVOM/VT optical candidate
  76. GRB 260208A: GECAM-B observation of a bright burst
  77. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  78. GRB 260208A: SVOM/VT optical observation
  79. Fermi GRB 260208D: Global MASTER-Net observations report
  80. GRB 260208A: Swift-XRT observations
  81. GRB 260208B: SVOM/GRM observation of a bright burst
  82. GRB 260208B: Fermi GBM Detection
  83. LAT GRB 260208B: Global MASTER-Net observations report
  84. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  85. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  86. Fermi GRB 260208A: Global MASTER-Net observations report
  87. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  88. GRB 260131A/B: Mondy and Terskol optical observations
  89. Fermi GRB 260207B: Global MASTER-Net observations report
  90. GRB 260206A: Swift-XRT observations
  91. Fermi trigger No 792135758: Global MASTER-Net observations report
  92. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  93. GRB 260204A: Swift-XRT observations
  94. GRB 260204A: SVOM/VT optical candidate
  95. GRB 260204A : MASTER Global robotic net optical observations
  96. Fermi GBM Sub-Threshold Detection of GRB 260204A
  97. GRB 260204A: LCO optical upper limits
  98. EP260110a: Late GTC/EMIR near-infrared observations
  99. GRB 260121A: 239Alferov CubeSat detection
  100. GRB 260131A: KAIT optical observations

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