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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"

15252 results found.

  1. Swift Trigger 1439093: is probably not GRB 260113A
  2. GRB 260111A: GECAM-B observation of a burst
  3. GRB 260111A: Fermi GBM Observation
  4. GRB 260111A: Swift ToO observations
  5. GRB 251230A: Mondy Optical Observations
  6. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  7. EP260110a: SVOM/VT optical upper limits
  8. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  9. EP260110a: KAIT optical upper limit
  10. EP 260110a: COLIBRÍ optical observations
  11. EP260110a: BOOTES-5/JGU optical upper limit
  12. GRB 260102A: Swift-XRT afterglow detection
  13. GRB 260105B: Fermi GBM Detection
  14. GRB 260105A: SVOM/GRM observation
  15. GRB 260105B: SVOM/GRM observation
  16. EP260105a: SVOM/VT optical upperlimit
  17. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  18. EP260105a: LCO Optical Upper limit
  19. EP260104a: Einstein Probe detection of a fast X-ray transient
  20. GRB 260103A: Insight-HXMT/HE detection
  21. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  22. GRB 260103A: GECAM-B observation of a burst
  23. GRB 260103A: SVOM/GRM observation of a possible GRB
  24. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  25. GRB 260102A: EP-FXT follow-up observation
  26. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  27. GRB 251230A / EP251230a: GECAM-B detection
  28. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  29. GRB 260102A: Swift ToO observations
  30. GRB 260101A: Fermi GBM Observation
  31. GRB 260102A: SVOM detection of a burst
  32. GRB 260101A: GECAM-B detection
  33. GRB 260101A: NOT spectroscopic observations
  34. GRB 260101A: SVOM/GRM observation
  35. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  36. GRB 251230A: GRANDMA/TAROT Early Detection
  37. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  38. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  39. EP251229a: BOOTES-2 early optical upper limit
  40. GRB 251230A: Early optical counterpart detection by LCO.
  41. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  42. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  43. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  44. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  45. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  46. GRB 251226A: SVOM/GRM observation
  47. GRB 251226A: GECAM-B detection
  48. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  49. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 251222A: NUTTelA-TAO Early Measurements
  51. GRB 251222A/EP251222b: Optical detection with Kinder observations
  52. GRB 251205A: Kilonova-Catcher optical afterglow detection
  53. GRB 251222A: AbAO optical observations
  54. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  55. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  56. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  57. GRB 251222A: Fermi GBM Observation
  58. EP251220a: CrAO ZTSh optical observations
  59. GRB 251222A / EP251222b: GECAM-B observation
  60. Konus-Wind detection of GRB 251222A / EP251222b
  61. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  62. EP251222a: NTT/ULTRACAM optical observations
  63. GRB 251222A / EP251222b: LCO optical observations
  64. EP251222b/GRB 251222A: SVOM/GRM observation
  65. GRB 251222A: PRIME near-infrared detection
  66. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  67. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  68. GRB 251222A: Swift ToO observations
  69. GRB 251222A: SVOM detection of a long burst
  70. EP251220a: PRIME upper limit
  71. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  72. GRB 251221A: PRIME near-infrared observation
  73. GRB 251221A: UAFO and Mondy optical upper limit
  74. GRB 251221A: Fermi GBM Observation
  75. GRB 251220B: SVOM/GRM observation of a short burst
  76. GRB 251221A: COLIBRÍ detection of the optical counterpart
  77. GRB 251219A: SVOM/GRM observation of a short burst
  78. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  79. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  80. GRB 251215A: Swift-XRT afterglow detection
  81. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  82. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  83. GRB 251214B: VIRT Optical Upper Limit
  84. GRB 251202A/EP251202a: Koshka optical upper limit
  85. GRB 251214B: Mondy optical upper limit
  86. GRB 251215A: COLIBRÍ optical upper limit
  87. EP251214b: KAIT optical upper limit
  88. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  89. GRB 251215A: Glowbug gamma-ray detection
  90. GRB 251214B: UAFO optical upper limit
  91. GRB 251213A: GRID-10B observation
  92. GRB 251214B: AbAO optical observations
  93. GRB 251209A: GECAM-B observation of a long burst
  94. GRB 251214D: GECAM-B observation of a long burst
  95. GRB 251214B: Fermi GBM Observation
  96. GRB 251209A: Insight-HXMT/HE detection
  97. GRB 251215A: Swift ToO observations
  98. GRID detection of GRB 251213A
  99. GRB 251203B: AbAO optical observations
  100. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst

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