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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"

3674 results found.

  1. GRB 250309B / AT2025dws: OSIRIS+/GTC spectroscopy z=1.898
  2. GRB 250309B / AT2025dws: SAO RAS optical observations
  3. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  4. IceCube Alert 250309.32: Global MASTER-Net observations report
  5. EP250308a: FTW optical and NIR upper limits
  6. GRB 250305A: AstroSat CZTI detection
  7. EP250302a:Xinglong optical observations
  8. Fermi trigger No 762963055: Global MASTER-Net observations report
  9. GRB 250305A: SVOM/GRM observation of a burst
  10. GRB 250305A: Fermi GBM Final Real-time Localization
  11. EP250302a: Mondy Continued Optical Observations
  12. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  13. EP250304a: Global MASTER-Net observations report
  14. GRB 250226A: GRANDMA Optical Observations
  15. Fermi GRB 250302A: Global MASTER-Net observations report
  16. EP250302a: FTW optical and NIR detection
  17. GRB 250228A: Fermi GBM Final Localization
  18. Konus-Wind detection of GRB 250226A
  19. GRB 250226A: KAO Optical Upper Limit
  20. GRB 250226A: AbAO AS-32 Optical Upper Limit
  21. EP250227a: Global MASTER-Net observations report
  22. EP250227a: TRT optical upper limit
  23. GRB 250225B: VLT/HAWKI near-infrared observations
  24. EP250227a: Optical upper limits with Kinder observations
  25. EP250228a: Swift/XRT localisation
  26. EP250228a: Global MASTER-Net observations report
  27. GRB 250226A / EP250226a: LCO detection of the afterglow
  28. LIGO/Virgo/KAGRA S250226dl: Identification of a GW compact binary merger candidate
  29. GRB 250225B: Fermi GBM Observation
  30. GRB 250225B: VLT/FORS2 candidate optical afterglow
  31. EP250226a: Global MASTER-Net observations report
  32. Fermi GRB 250225A: Global MASTER-Net observations report
  33. EP250223a: LCO detection of the afterglow
  34. Fermi trigger No 762020305: Global MASTER-Net observations report
  35. Fermi GRB 250217A: Global MASTER-Net observations report
  36. GRB 250215A: Fermi GBM Observation
  37. EP250215a: Global MASTER-Net observations report
  38. GRB 250205A: Leavitt Observatory optical upper limit
  39. Integral GRB250211.89: Global MASTER-Net observations report
  40. EP250207b: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  42. IceCube Alert 250207.09: Global MASTER-Net observations report
  43. GRB 250204A: GRBAlpha detection
  44. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  45. GRB 250129A: Continued AbAO and Mondy optical observations
  46. EP250205a/GRB 250205A: Einstein Probe observation
  47. IPN triangulation of GRB 250204B (short/hard)
  48. GRB 250204A: Fermi GBM Final Real-time Localization
  49. Ep250125A: 1.3m DFOT optical upper limit
  50. GRB 250127A: CrAO and Terskol optical upper limits
  51. Fermi GRB 250128B: Global MASTER-Net observations report
  52. GRB 250128B: Fermi GBM Observation
  53. GRB 250128B: GOTO optical upper limit
  54. Swift GRB 250128B: Global MASTER-Net observations report
  55. GRB 250128B: LCO optical observations
  56. GRB 250128B: Fermi GBM Final Real-time Localization
  57. GRB 250127B: DDOTI Upper Limit on the Afterglow
  58. Fermi GRB 250128A: Global MASTER-Net observations report
  59. GRB 250128A: Fermi GBM Final Real-time Localization
  60. Fermi GRB 250127B: Global MASTER-Net observations report
  61. IPN triangulation of GRB 250119C
  62. GRB 250126A: MAXI/GSC detection
  63. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  64. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  65. Fermi trigger No 758442826: Global MASTER-Net observations report
  66. EP250111a: NOT likely optical counterpart
  67. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  68. EP250109a: Global MASTER-Net observations report
  69. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  70. GRB 241228B: Fermi-LAT detection
  71. Fermi GRB 250107B: Global MASTER-Net observations report
  72. Fermi trigger No 757753930: Global MASTER-Net observations report
  73. GRB 250103A: Swift-XRT observations
  74. GRB 250103A: Montarrenti Observatory optical detection
  75. GRB 250103A: Fermi GBM Observation
  76. GRB 250103A: Xinglong 2.16m Optical Candidate
  77. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  78. GRB 250103A: SVOM detection of a long burst
  79. GRB 250101A: Swift/UVOT Detection
  80. GRB 250101A: AKO Optical Afterglow Detection
  81. GRB 250101A : GIT optical detection
  82. GRB 250101A: GMG Optical Observation
  83. GRB 250101A: Swift detection of a burst with an optical counterpart
  84. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  85. IceCube-Cascade 241228A: Upper limits from a search for additional neutrino events in IceCube
  86. GRB 241228B: Fermi GBM Observation
  87. GRB 241228A: Mondy optical afterglow observations
  88. Swift GRB 241229B: Global MASTER-Net observations report
  89. GRB 241229A: GOTO optical upper limits
  90. GRB 241228A: NOT optical upper limits
  91. GRB 241228B: LCO optical observation
  92. Fermi GRB 241228B: Global MASTER-Net observations report
  93. GRB 241228A: Fermi GBM Observation
  94. GRB241228B: GROWTH-India Telescope optical observations
  95. Swift GRB 241228A: Global MASTER-Net observations report
  96. GRB 241228B: LCOGT photometry of the likely optical counterpart GOTO24jmz
  97. GRB 241228B: GOTO24jmz optical follow-up observations
  98. GRB 241228B: TRT optical counterpart confirmation
  99. GRB 241228B: GOTO possible optical counterpart candidate
  100. GRB 241228B: Fermi GBM Final Real-time Localization

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