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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"

5050 results found.

  1. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  2. GRB 250925A: Mondy and AbAO optical observations
  3. Fermi GRB 250926A: Global MASTER-Net observations report
  4. GRB 250924A: 1.6m Mephisto optical upper limits
  5. GRB 250924A: SAO RAS optical observations
  6. GRB 250924A: AstroSat CZTI detection
  7. GRB 250924A: Swift-XRT refined Analysis
  8. GRB 250924A: GROWTH-India Telescope Upper Limits
  9. GRB 250924A: Mondy optical observations, afterglow fading
  10. GRB 250924B: Fermi GBM Final Localization
  11. GRB 250924A: COLIBRÍ optical observations
  12. Swift GRB 250924A: Global MASTER-Net observations report
  13. GRB 250924A: DDOTI Detection of the Optical Counterpart
  14. Fermi trigger No 780156732: Global MASTER-Net observations report
  15. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  16. GRB 250920B: Swift-XRT refined Analysis
  17. GRB 250919A/EP250919a: SVOM/VT optical observation
  18. EP250916a: EP-FXT follow-up observation
  19. GRB 250917B: Fermi GBM Observation
  20. Fermi GRB 250917B: Global MASTER-Net observations report
  21. GRB 250916A: GOTO optical counterpart candidate
  22. GRB 250916A: AstroSat CZTI detection of a bright long burst
  23. GRB 250912A: SVOM detection of a burst
  24. GRB 250911A: Swift-XRT refined Analysis
  25. EP250911a: Optical detection with Kinder observations
  26. Fermi GRB 250910B: Global MASTER-Net observations report
  27. EP250910a: Global MASTER-Net observations report
  28. GRB 250903A: SVOM/ECLAIRs refined analysis
  29. EP250908C: GROND observation of the fading optical counterpart
  30. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  31. GRB 250905A: Swift-XRT refined Analysis
  32. IceCube Alert 250905.84: Global MASTER-Net observations report
  33. GRB 250904A: Swift-XRT refined Analysis
  34. GRB 250903A: Swift-XRT observations
  35. The EP-WXT trigger 01709201209 is likely a flaring star
  36. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  37. GRB 250903A: SVOM detection of a burst
  38. Fermi GRB 250902B: Global MASTER-Net observations report
  39. GRB 250901A: Swift-XRT afterglow detection
  40. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  41. EP250827b: FTW Observations of AT 2025wkm
  42. EP250831a: Swift-XRT observations
  43. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  44. GRB 250831A: Swift-XRT counterpart detection
  45. EP250830a: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  47. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  48. EP250828a: Optical counterpart detection with Kinder observations
  49. GRB 250828B: Swift detection of a burst
  50. GRID detection of GRB 250824A
  51. Fermi GRB 250827A: Global MASTER-Net observations report
  52. GRB 250826A: SVOM/GRM observation
  53. EP250827a: Global MASTER-Net observations report
  54. GRB 250826A: Fermi GBM Final Real-time Localization
  55. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  56. Fermi GRB 250824B: Global MASTER-Net observations report
  57. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  58. GRB 250823A: Swift-XRT refined Analysis
  59. EP triggers 01709200706 and 01709200707: GOTO confirmation of flaring stars
  60. GRB 250824B: Fermi GBM Final Real-time Localization
  61. GRB 250823A: COLIBRÍ optical observations
  62. GRB 250824A: Fermi GBM Final Real-time Localization
  63. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  64. GRB 250823A: Liverpool Telescope optical detection
  65. Swift GRB250823.84: Global MASTER-Net observations report
  66. Fermi GRB 250821B: Global MASTER-Net observations report
  67. GRB 250821A: Swift-XRT refined Analysis
  68. Swift GRB 250821A: Global MASTER-Net observations report
  69. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  70. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  71. IPN triangulation of GRB 250814C (short)
  72. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  73. Fermi trigger No 776849714: Global MASTER-Net observations report
  74. sb25081602: Swift-XRT observations
  75. SVOM/sb25081602: detection of a likely X-ray transient
  76. GRB 250814A: Swift-BAT refined analysis
  77. GRB 250814C: SVOM/GRM observation of a short burst
  78. GRB 250814A: Swift-XRT refined Analysis
  79. GRB 240814A: Fermi GBM Observation
  80. GRB 250814A: DDOTI Optical Upper Limit
  81. IceCube Alert 250813.14: Global MASTER-Net observations report
  82. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  83. Corrected Swift-XRT Refined Analysis of GRB 250809A
  84. GRB 250809A: Swift-XRT refined Analysis
  85. GRB 250807B: SVOM/VT optical observation
  86. Fermi GRB 250808A: Global MASTER-Net observations report
  87. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250807B: Swift-XRT refined Analysis
  89. EP 250807.979: GOTO optical upper limit
  90. IceCube Alert 250804.84: Global MASTER-Net observations report
  91. GRB 250806A: Swift-XRT counterpart detection
  92. EP250806a: COLIBRÍ optical upper limit
  93. GRB 250805A: SVOM/VT optical counterpart
  94. GRB 250805A: Swift-XRT refined Analysis
  95. GRB 250805A: Enhanced Swift-XRT position
  96. GRB 250805A: Swift-XRT observations
  97. GRB 250805A: Swift detection of a burst
  98. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  99. EP250711a: CrAO and Assy optical observations
  100. EP250730a: Global MASTER-Net observations report

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