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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"

3028 results found.

  1. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  2. EP trigger 01709131361 (possible EP250207a): NOT optical observations and flaring star
  3. IPN triangulation of GRB 250201A
  4. GRB 250202B: Fermi GBM Detection
  5. The EP-WXT trigger 01709131153 is not a real source
  6. GRB 250128B: VLA radio upper limit
  7. GRB 250129A: REM optical/NIR afterglow detection
  8. GRB 250129A: GOTO optical observations show brightening afterglow
  9. Fermi GRB 250128B: Global MASTER-Net observations report
  10. GRB 250129A: Swift detection of a burst with an optical counterpart
  11. GRB 250117A: Fermi GBM Observation
  12. Fermi GRB 250127B: Global MASTER-Net observations report
  13. IPN triangulation of GRB 250119C
  14. GECAM-A detection of a bright burst from SGR 1E1841-045
  15. EP250125a: Optical upper limit with Kinder observations
  16. Konus-Wind detection of a bright burst from SGR 1E1841-045 on 2025 January 23
  17. IPN triangulation of a bright burst from SGR 1E1841-045
  18. GRB 250119B: Fermi GBM Observation
  19. GRB 250118A: Fermi GBM Final Real-time Localization
  20. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  21. Integral GRB250114.55: Global MASTER-Net observations report
  22. EP250108a / AT 2025kg: SAO RAS optical observations
  23. GRB 250101B: Fermi GBM Observation
  24. Fermi GRB 250107B: Global MASTER-Net observations report
  25. GRB 250103B: REM optical/NIR upper limits
  26. GRB 250101A: REM optical/NIR counterpart detection
  27. GRB 250106A: Swift-XRT observations
  28. GRB 250101A: Swift-BAT refined analysis
  29. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  30. GRB 241229B: SAO RAS optical upper limit
  31. GRB 241229A: SAO RAS optical observations
  32. GRB 240606B: 7DT Optical upper limits
  33. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  34. Fermi GRB 241228B: Global MASTER-Net observations report
  35. GRB 241228B: GOTO possible optical counterpart candidate
  36. GRB 241212A: VZLUSAT-2 detection
  37. GRB 241223A: Fermi GBM Detection
  38. Fermi trigger No 756678579: Global MASTER-Net observations report
  39. IceCube Alert 241224.30: Global MASTER-Net observations report
  40. GRB241113A: 7DT Optical upper limits
  41. GRB 241105A: JWST photometric observations of the host galaxy
  42. GRB 241223A: Fermi GBM Final Real-time Localization
  43. EP241217a : Leavitt Observatory optical upper limit
  44. EP241119a: 7DT Optical upper limits
  45. GRB 241213B: MAXI/GSC detection
  46. GRB 241209A: Chandra X-ray Detection
  47. Fermi GRB 241209E: Global MASTER-Net observations report
  48. Fermi GRB 241209A: Global MASTER-Net observations report
  49. GRB 241207C: MASTER optical observations
  50. Fermi trigger No 755225799: Global MASTER-Net observations report
  51. GRB 241207C: MAXI/GSC detection
  52. Fermi GRB 241207A: Global MASTER-Net observations report
  53. EP241206a: EP detection of a fast X-ray transient
  54. Fermi GRB 241204A: Global MASTER-Net observations report
  55. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  56. GRB 241130A: Fermi GBM Detection
  57. Fermi GRB 241201A: Global MASTER-Net observations report
  58. LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
  59. GRB 241128A: AbAO optical upper limit
  60. EP241126a: WFST Observations
  61. Swift GRB241127.91: Global MASTER-Net observations report
  62. Fermi GRB 241118A: Global MASTER-Net observations report
  63. GRB 241117A: Fermi GBM Detection
  64. EP241113a: Swift XRT weak detection
  65. EP241115a: EP detection of a fast X-ray transient
  66. EP 241113a: LBT possible optical counterpart
  67. GRB 241113B: KAIT Optical Afterglow Candidate
  68. EP241113a: Global MASTER-Net observations report
  69. LIGO/Virgo/KAGRA S241114y: Identification of a GW compact binary merger candidate
  70. Fermi trigger No 753166198: Global MASTER-Net observations report
  71. EP241107a: EP-FXT follow-up observations
  72. Fermi trigger No 752990530: Global MASTER-Net observations report
  73. Fermi trigger No 752878030: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S241109bn: Global MASTER-Net observations report
  75. GRB 241108A: COLIBRÍ Upper Limits on the Optical Counterpart
  76. GRB 241030A: optical afterglow detection from the INAF Asiago Observatory
  77. Fermi GRB 241105A: Global MASTER-Net observations report
  78. Fermi GRB 241104A: Global MASTER-Net observations report
  79. EP241101a: Optical upper limits with Kinder observations
  80. S241102cy: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S241102br: Identification of a GW compact binary merger candidate
  82. GRB 241026A: SAO RAS optical observations
  83. Fermi trigger No 752006065: Global MASTER-Net observations report
  84. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  85. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  86. GRB 241030A: Fermi GBM Final Real-time Localization
  87. GRB 241029A: Mephisto observations
  88. GRB 241026A: BTA and Zeiss-1000 optical observations
  89. EP241021a: further SAO RAS optical observations
  90. EP EP241026b: Global MASTER-Net observations report
  91. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  92. GRB 241025A: Fermi GBM Observation
  93. IPN triangulation of GRB 241022A (short/hard)
  94. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  95. GRB 241018A: EP-FXT afterglow detection
  96. GRB 240727A: VIRT Optical Upper Limit
  97. Fermi trigger No 750788395: Global MASTER-Net observations report
  98. Fermi GRB 241016A: Global MASTER-Net observations report
  99. Fermi trigger No 750211959: Global MASTER-Net observations report
  100. GRB 241010A: LCO optical observations

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