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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"

3115 results found.

  1. EP250108a / AT 2025kg: SAO RAS optical observations
  2. GRB 250101B: Fermi GBM Observation
  3. Fermi GRB 250107B: Global MASTER-Net observations report
  4. GRB 250103B: REM optical/NIR upper limits
  5. GRB 250101A: REM optical/NIR counterpart detection
  6. GRB 250106A: Swift-XRT observations
  7. GRB 250101A: Swift-BAT refined analysis
  8. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  9. GRB 241229B: SAO RAS optical upper limit
  10. GRB 241229A: SAO RAS optical observations
  11. GRB 240606B: 7DT Optical upper limits
  12. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  13. Fermi GRB 241228B: Global MASTER-Net observations report
  14. GRB 241228B: GOTO possible optical counterpart candidate
  15. GRB 241212A: VZLUSAT-2 detection
  16. GRB 241223A: Fermi GBM Detection
  17. Fermi trigger No 756678579: Global MASTER-Net observations report
  18. IceCube Alert 241224.30: Global MASTER-Net observations report
  19. GRB241113A: 7DT Optical upper limits
  20. GRB 241105A: JWST photometric observations of the host galaxy
  21. GRB 241223A: Fermi GBM Final Real-time Localization
  22. EP241217a : Leavitt Observatory optical upper limit
  23. EP241119a: 7DT Optical upper limits
  24. GRB 241213B: MAXI/GSC detection
  25. GRB 241209A: Chandra X-ray Detection
  26. Fermi GRB 241209E: Global MASTER-Net observations report
  27. Fermi GRB 241209A: Global MASTER-Net observations report
  28. GRB 241207C: MASTER optical observations
  29. Fermi trigger No 755225799: Global MASTER-Net observations report
  30. GRB 241207C: MAXI/GSC detection
  31. Fermi GRB 241207A: Global MASTER-Net observations report
  32. EP241206a: EP detection of a fast X-ray transient
  33. Fermi GRB 241204A: Global MASTER-Net observations report
  34. IceCube-241127A: No transient candidates from the Zwicky Transient Facility
  35. GRB 241130A: Fermi GBM Detection
  36. Fermi GRB 241201A: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S241125n: GRANDMA Optical Upper Limits
  38. GRB 241128A: AbAO optical upper limit
  39. EP241126a: WFST Observations
  40. Swift GRB241127.91: Global MASTER-Net observations report
  41. Fermi GRB 241118A: Global MASTER-Net observations report
  42. GRB 241117A: Fermi GBM Detection
  43. EP241113a: Swift XRT weak detection
  44. EP241115a: EP detection of a fast X-ray transient
  45. EP 241113a: LBT possible optical counterpart
  46. GRB 241113B: KAIT Optical Afterglow Candidate
  47. EP241113a: Global MASTER-Net observations report
  48. LIGO/Virgo/KAGRA S241114y: Identification of a GW compact binary merger candidate
  49. Fermi trigger No 753166198: Global MASTER-Net observations report
  50. EP241107a: EP-FXT follow-up observations
  51. Fermi trigger No 752990530: Global MASTER-Net observations report
  52. Fermi trigger No 752878030: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S241109bn: Global MASTER-Net observations report
  54. GRB 241108A: COLIBRÍ Upper Limits on the Optical Counterpart
  55. GRB 241030A: optical afterglow detection from the INAF Asiago Observatory
  56. Fermi GRB 241105A: Global MASTER-Net observations report
  57. Fermi GRB 241104A: Global MASTER-Net observations report
  58. EP241101a: Optical upper limits with Kinder observations
  59. S241102cy: Identification of a GW compact binary merger candidate
  60. LIGO/Virgo/KAGRA S241102br: Identification of a GW compact binary merger candidate
  61. GRB 241026A: SAO RAS optical observations
  62. Fermi trigger No 752006065: Global MASTER-Net observations report
  63. GRB 241030A: Keck/LRIS spectroscopic redshift z = 1.411
  64. GRB 241030A: ULL-ASTRO-MASTER detection of a bright optical counterpart with the LCOGT 40-cm telescope at McDonald Observatory
  65. GRB 241030A: Fermi GBM Final Real-time Localization
  66. GRB 241029A: Mephisto observations
  67. GRB 241026A: BTA and Zeiss-1000 optical observations
  68. EP241021a: further SAO RAS optical observations
  69. EP EP241026b: Global MASTER-Net observations report
  70. GRB 241026A: COLIBRÍ Detection of the Optical Counterpart
  71. GRB 241025A: Fermi GBM Observation
  72. IPN triangulation of GRB 241022A (short/hard)
  73. EP241021a: GTC OSIRIS+ spectroscopy of the optical counterpart
  74. GRB 241018A: EP-FXT afterglow detection
  75. GRB 240727A: VIRT Optical Upper Limit
  76. Fermi trigger No 750788395: Global MASTER-Net observations report
  77. Fermi GRB 241016A: Global MASTER-Net observations report
  78. Fermi trigger No 750211959: Global MASTER-Net observations report
  79. GRB 241010A: LCO optical observations
  80. Fermi GRB 241008A: Global MASTER-Net observations report
  81. IceCube-241006A: No candidates from the Zwicky Transient Facility
  82. IceCube Alert 241006.94: Global MASTER-Net observations report
  83. GRB 241006A: Swift detection of a burst
  84. EP trigger ID 01709065118: the X-ray transient is likely a stellar flare event
  85. Fermi trigger No 749693019: Global MASTER-Net observations report
  86. GRB 240929A: SAO RAS, Mondy, and CrAO optical observations
  87. GRB 241002A: 1.5m OSN optical upper limit
  88. IceCube-240929A: Upper limits from a search for additional neutrino events in IceCube
  89. Fermi GRB 240930B: Global MASTER-Net observations report
  90. GRB 240930B: Fermi GBM Final Real-time Localization
  91. Fermi GRB 240930A: Global MASTER-Net observations report
  92. Fermi GRB 240929A: Global MASTER-Net observations report
  93. Konus-Wind detection of GRB 240912A
  94. LIGO/Virgo/KAGRA S240921cw: Upper limits from Swift/BAT-GUANO
  95. EP trigger ID 01709059262: correction to the observation start time and source localization
  96. EP trigger ID 01709059262: the X-ray transient is likely a stellar flare event
  97. Fermi GBM Sub-Threshold Detection of GRB240919A / EP240919a
  98. GRB 240919A / EP240919a: SVOM/GRM observation
  99. EP240919a: NOT and Gemini optical observations
  100. EP240919a is likely a GRB event

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