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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"

5152 results found.

  1. GRB 251001B: Swift-XRT refined Analysis
  2. GRB 250930A: SVOM/GRM observation
  3. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  4. GRB 250925A: Mondy and AbAO optical observations
  5. Fermi GRB 250926A: Global MASTER-Net observations report
  6. GRB 250924A: 1.6m Mephisto optical upper limits
  7. GRB 250924A: SAO RAS optical observations
  8. GRB 250924A: AstroSat CZTI detection
  9. GRB 250924A: Swift-XRT refined Analysis
  10. GRB 250924A: GROWTH-India Telescope Upper Limits
  11. GRB 250924A: Mondy optical observations, afterglow fading
  12. GRB 250924B: Fermi GBM Final Localization
  13. GRB 250924A: COLIBRÍ optical observations
  14. Swift GRB 250924A: Global MASTER-Net observations report
  15. GRB 250924A: DDOTI Detection of the Optical Counterpart
  16. Fermi trigger No 780156732: Global MASTER-Net observations report
  17. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  18. GRB 250920B: Swift-XRT refined Analysis
  19. GRB 250919A/EP250919a: SVOM/VT optical observation
  20. EP250916a: EP-FXT follow-up observation
  21. GRB 250917B: Fermi GBM Observation
  22. Fermi GRB 250917B: Global MASTER-Net observations report
  23. GRB 250916A: GOTO optical counterpart candidate
  24. GRB 250916A: AstroSat CZTI detection of a bright long burst
  25. GRB 250912A: SVOM detection of a burst
  26. GRB 250911A: Swift-XRT refined Analysis
  27. EP250911a: Optical detection with Kinder observations
  28. Fermi GRB 250910B: Global MASTER-Net observations report
  29. EP250910a: Global MASTER-Net observations report
  30. GRB 250903A: SVOM/ECLAIRs refined analysis
  31. EP250908C: GROND observation of the fading optical counterpart
  32. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  33. GRB 250905A: Swift-XRT refined Analysis
  34. IceCube Alert 250905.84: Global MASTER-Net observations report
  35. GRB 250904A: Swift-XRT refined Analysis
  36. GRB 250903A: Swift-XRT observations
  37. The EP-WXT trigger 01709201209 is likely a flaring star
  38. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  39. GRB 250903A: SVOM detection of a burst
  40. Fermi GRB 250902B: Global MASTER-Net observations report
  41. GRB 250901A: Swift-XRT afterglow detection
  42. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  43. EP250827b: FTW Observations of AT 2025wkm
  44. EP250831a: Swift-XRT observations
  45. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  46. GRB 250831A: Swift-XRT counterpart detection
  47. EP250830a: Global MASTER-Net observations report
  48. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  49. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  50. EP250828a: Optical counterpart detection with Kinder observations
  51. GRB 250828B: Swift detection of a burst
  52. GRID detection of GRB 250824A
  53. Fermi GRB 250827A: Global MASTER-Net observations report
  54. GRB 250826A: SVOM/GRM observation
  55. EP250827a: Global MASTER-Net observations report
  56. GRB 250826A: Fermi GBM Final Real-time Localization
  57. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  58. Fermi GRB 250824B: Global MASTER-Net observations report
  59. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  60. GRB 250823A: Swift-XRT refined Analysis
  61. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  62. GRB 250824B: Fermi GBM Final Real-time Localization
  63. GRB 250823A: COLIBRÍ optical observations
  64. GRB 250824A: Fermi GBM Final Real-time Localization
  65. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  66. GRB 250823A: Liverpool Telescope optical detection
  67. Swift GRB250823.84: Global MASTER-Net observations report
  68. Fermi GRB 250821B: Global MASTER-Net observations report
  69. GRB 250821A: Swift-XRT refined Analysis
  70. Swift GRB 250821A: Global MASTER-Net observations report
  71. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  72. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  73. IPN triangulation of GRB 250814C (short)
  74. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  75. Fermi trigger No 776849714: Global MASTER-Net observations report
  76. sb25081602: Swift-XRT observations
  77. SVOM/sb25081602: detection of a likely X-ray transient
  78. GRB 250814A: Swift-BAT refined analysis
  79. GRB 250814C: SVOM/GRM observation of a short burst
  80. GRB 250814A: Swift-XRT refined Analysis
  81. GRB 240814A: Fermi GBM Observation
  82. GRB 250814A: DDOTI Optical Upper Limit
  83. IceCube Alert 250813.14: Global MASTER-Net observations report
  84. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  85. Corrected Swift-XRT Refined Analysis of GRB 250809A
  86. GRB 250809A: Swift-XRT refined Analysis
  87. GRB 250807B: SVOM/VT optical observation
  88. Fermi GRB 250808A: Global MASTER-Net observations report
  89. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  90. GRB 250807B: Swift-XRT refined Analysis
  91. EP 250807.979: GOTO optical upper limit
  92. IceCube Alert 250804.84: Global MASTER-Net observations report
  93. GRB 250806A: Swift-XRT counterpart detection
  94. EP250806a: COLIBRÍ optical upper limit
  95. GRB 250805A: SVOM/VT optical counterpart
  96. GRB 250805A: Swift-XRT refined Analysis
  97. GRB 250805A: Enhanced Swift-XRT position
  98. GRB 250805A: Swift-XRT observations
  99. GRB 250805A: Swift detection of a burst
  100. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate

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