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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"

6533 results found.

  1. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  2. GRB 260114A: Swift-XRT refined Analysis
  3. GRB 260114A: NOT optical observations
  4. GRB 260114A: Fermi GBM observation
  5. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  6. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  7. Konus-Wind detection of GRB 260101A
  8. GRB 260111A: Swift-XRT observations
  9. Swift Trigger 1439093: is probably not GRB 260113A
  10. GRB 260111A: Fermi GBM Observation
  11. IceCube Alert 260111A: Global MASTER-Net observations report
  12. Swift Trigger 1434591: possible GRB 260109C
  13. GRB 260102A: Swift-XRT afterglow detection
  14. GRB 260105B: Fermi GBM Detection
  15. GRB 260104A: Swift-XRT refined Analysis
  16. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  17. GRB 260102A: Swift-XRT observations
  18. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  19. GRB 260101A: Fermi GBM Observation
  20. GRB 260101A: Swift-XRT refined Analysis
  21. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  22. EP251229a: Optical upper limit with Kinder observations
  23. GRB 251230A: Swift-XRT refined Analysis
  24. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  25. GRB 251230A: Early optical counterpart detection by LCO.
  26. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  27. GRB 251222A: NUTTelA-TAO Early Measurements
  28. GRB 251222A/EP251222b: Optical detection with Kinder observations
  29. EP251222a: Optical upper limit with Kinder observations
  30. GRB 251222A: Fermi GBM Observation
  31. Konus-Wind detection of GRB 251222A / EP251222b
  32. GRB 251222A: Swift-XRT afterglow detection
  33. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  34. EP251222a: GSP Optical Counterpart Detection
  35. GRB 251221A: Swift-XRT refined Analysis
  36. GRB 251221A: Fermi GBM Observation
  37. EP251220a: EP-FXT follow-up observation
  38. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  39. GRB 251215A: Swift-XRT afterglow detection
  40. GRB 251215A: Swift/UVOT Upper LImits
  41. GRB 251215A: Fermi GBM Observation
  42. GRB 251215A: Swift-XRT observations
  43. EP251214a: Optical upper limit with Kinder observations
  44. GRB 251214B: Fermi GBM Observation
  45. GRB 251209A: Insight-HXMT/HE detection
  46. GRB 251214B: Swift-XRT refined Analysis
  47. EP251212a: EP-FXT follow-up observation
  48. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  49. GRB 251209A: Fermi GBM observation
  50. GRB 251208A: AstroSat CZTI detection
  51. GRB 251208B: Swift-XRT afterglow detection
  52. GRB 251208B: Fermi GBM Observation
  53. GRB 251208D: Swift-XRT observations
  54. GRB 251208B: Fermi-LAT detection
  55. GRB 251205A: FTW optical and NIR observations
  56. GRB 251205A: Swift-XRT refined Analysis
  57. GRB 251203C: Swift/UVOT Upper Limit
  58. GRB 251203A: Insight-HXMT/HE detection
  59. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  60. GRB 251203B: Swift-XRT observations
  61. GRB 251201B: Fermi GBM Observation
  62. GRB251129A/EP251129a: Swift UVOT detection
  63. GRB 251202A: Fermi GBM Observation
  64. EP251130a: continued NOT optical observations indicate steep fading phase
  65. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  66. GRB 251126A: SAO RAS optical marginal detection
  67. GRB 251202A: Swift-XRT afterglow detection
  68. EP251129a/GRB 251129A: NOWT Detection
  69. GRB 251201B: Swift-XRT refined Analysis
  70. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  71. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  72. EP251130a: Optical detections with Kinder observations
  73. EP251130a: SAO RAS optical observations
  74. EP251130A: Optical observation from 1.3m DFOT
  75. EP251130a: Swift-XRT counterpart detection
  76. GRB 251129A / EP251129a: SAO RAS optical observations
  77. GRB 251126A: SAO RAS optical observations
  78. GRB 251129A: Swift-XRT afterglow detection
  79. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  80. GRB 251128A: Fermi GBM Observation
  81. GRB 251126A: further SAO RAS optical observations
  82. GRB251126A: Continued optical observation from 1.3m DFOT
  83. GRB 251126A: Mondy and SAO RAS optical observations
  84. GRB 251126A: Swift-XRT refined Analysis
  85. GRB 251126A: 1.3m DFOT optical afterglow detection
  86. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  87. GRB 251121A: Fermi GBM Observation
  88. GRB 251126A: Prompt enhanced Swift-XRT position
  89. EP251124a: Swift-XRT observations
  90. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  91. EP251124a: Optical upper limit with Kinder observations
  92. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  93. EP251124a: GROWTH-India Telescope optical upper limits
  94. GRB 251116C: Swift-XRT confirmation of fading
  95. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  96. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  97. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  98. EP251118a: Continued Optical Detection with Kinder observations
  99. GRB 251115A: Fermi GBM Observation
  100. EP251118A: 1.3m DFOT optical afterglow detection

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