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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"

3758 results found.

  1. GRB 250228A: Fermi GBM Final Localization
  2. Konus-Wind detection of GRB 250226A
  3. GRB 250226A: KAO Optical Upper Limit
  4. GRB 250226A: AbAO AS-32 Optical Upper Limit
  5. EP250227a: Global MASTER-Net observations report
  6. EP250227a: TRT optical upper limit
  7. GRB 250225B: VLT/HAWKI near-infrared observations
  8. EP250227a: Optical upper limits with Kinder observations
  9. EP250228a: Swift/XRT localisation
  10. EP250228a: Global MASTER-Net observations report
  11. GRB 250226A / EP250226a: LCO detection of the afterglow
  12. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  13. GRB 250225B: Fermi GBM Observation
  14. GRB 250225B: VLT/FORS2 candidate optical afterglow
  15. EP250226a: Global MASTER-Net observations report
  16. Fermi GRB 250225A: Global MASTER-Net observations report
  17. EP250223a: LCO detection of the afterglow
  18. Fermi trigger No 762020305: Global MASTER-Net observations report
  19. Fermi GRB 250217A: Global MASTER-Net observations report
  20. GRB 250215A: Fermi GBM Observation
  21. EP250215a: Global MASTER-Net observations report
  22. GRB 250205A: Leavitt Observatory optical upper limit
  23. Integral GRB250211.89: Global MASTER-Net observations report
  24. EP250207b: Global MASTER-Net observations report
  25. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  26. IceCube Alert 250207.09: Global MASTER-Net observations report
  27. GRB 250204A: GRBAlpha detection
  28. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  29. GRB 250129A: Continued AbAO and Mondy optical observations
  30. EP250205a/GRB 250205A: Einstein Probe observation
  31. IPN triangulation of GRB 250204B (short/hard)
  32. GRB 250204A: Fermi GBM Final Real-time Localization
  33. Ep250125A: 1.3m DFOT optical upper limit
  34. GRB 250127A: CrAO and Terskol optical upper limits
  35. Fermi GRB 250128B: Global MASTER-Net observations report
  36. GRB 250128B: Fermi GBM Observation
  37. GRB 250128B: GOTO optical upper limit
  38. Swift GRB 250128B: Global MASTER-Net observations report
  39. GRB 250128B: LCO optical observations
  40. GRB 250128B: Fermi GBM Final Real-time Localization
  41. GRB 250127B: DDOTI Upper Limit on the Afterglow
  42. Fermi GRB 250128A: Global MASTER-Net observations report
  43. GRB 250128A: Fermi GBM Final Real-time Localization
  44. Fermi GRB 250127B: Global MASTER-Net observations report
  45. IPN triangulation of GRB 250119C
  46. GRB 250126A: MAXI/GSC detection
  47. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  48. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  49. Fermi trigger No 758442826: Global MASTER-Net observations report
  50. EP250111a: NOT likely optical counterpart
  51. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  52. EP250109a: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  54. GRB 241228B: Fermi-LAT detection
  55. Fermi GRB 250107B: Global MASTER-Net observations report
  56. Fermi trigger No 757753930: Global MASTER-Net observations report
  57. GRB 250103A: Swift-XRT observations
  58. GRB 250103A: Montarrenti Observatory optical detection
  59. GRB 250103A: Fermi GBM Observation
  60. GRB 250103A: Xinglong 2.16m Optical Candidate
  61. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  62. GRB 250103A: SVOM detection of a long burst
  63. GRB 250101A: Swift/UVOT Detection
  64. GRB 250101A: AKO Optical Afterglow Detection
  65. GRB 250101A : GIT optical detection
  66. GRB 250101A: GMG Optical Observation
  67. GRB 250101A: Swift detection of a burst with an optical counterpart
  68. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  69. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 241228B: Fermi GBM Observation
  71. GRB 241228A: Mondy optical afterglow observations
  72. Swift GRB 241229B: Global MASTER-Net observations report
  73. GRB 241229A: GOTO optical upper limits
  74. GRB 241228A: NOT optical upper limits
  75. GRB 241228B: LCO optical observation
  76. Fermi GRB 241228B: Global MASTER-Net observations report
  77. GRB 241228A: Fermi GBM Observation
  78. GRB241228B: GROWTH-India Telescope optical observations
  79. Swift GRB 241228A: Global MASTER-Net observations report
  80. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  81. GRB 241228B: GOTO24jmz optical follow-up observations
  82. GRB 241228B: TRT optical counterpart confirmation
  83. GRB 241228B: GOTO possible optical counterpart candidate
  84. GRB 241228B: Fermi GBM Final Real-time Localization
  85. Fermi GRB 241226A: Global MASTER-Net observations report
  86. LIGO/Virgo/KAGRA S241225v: Identification of a GW compact binary merger candidate
  87. Fermi trigger No 756678579: Global MASTER-Net observations report
  88. IceCube Alert 241224.30: Global MASTER-Net observations report
  89. GRB 241223A: GOTO optical observations summary
  90. Fermi trigger No 756447119: Global MASTER-Net observations report
  91. Fermi GRB 241221A: Global MASTER-Net observations report
  92. EP241217a: 1.6m Mephisto multi-band optical observations
  93. GRB 241217A/EP241217b: REM optical/NIR upper limits
  94. EP241217b: Global MASTER-Net observations report
  95. EP241217a: Global MASTER-Net observations report
  96. GRB 241209A: BOOTES-7 and 2.2m CAHA early optical upper limits
  97. Fermi GRB 241209A: Global MASTER-Net observations report
  98. Fermi trigger No 755277791: Global MASTER-Net observations report
  99. Fermi GRB 241207A: Global MASTER-Net observations report
  100. Fermi GRB 241204A: Global MASTER-Net observations report

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