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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"

6788 results found.

  1. GRB 251214B: Swift-XRT refined Analysis
  2. EP251212a: EP-FXT follow-up observation
  3. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  4. GRB 251209A: Fermi GBM observation
  5. GRB 251208A: AstroSat CZTI detection
  6. GRB 251208B: Swift-XRT afterglow detection
  7. GRB 251208B: Fermi GBM Observation
  8. GRB 251208D: Swift-XRT observations
  9. GRB 251208B: Fermi-LAT detection
  10. GRB 251205A: FTW optical and NIR observations
  11. GRB 251205A: Swift-XRT refined Analysis
  12. GRB 251203C: Swift/UVOT Upper Limit
  13. GRB 251203A: Insight-HXMT/HE detection
  14. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  15. GRB 251203B: Swift-XRT observations
  16. GRB 251201B: Fermi GBM Observation
  17. GRB251129A/EP251129a: Swift UVOT detection
  18. GRB 251202A: Fermi GBM Observation
  19. EP251130a: continued NOT optical observations indicate steep fading phase
  20. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  21. GRB 251126A: SAO RAS optical marginal detection
  22. GRB 251202A: Swift-XRT afterglow detection
  23. EP251129a/GRB 251129A: NOWT Detection
  24. GRB 251201B: Swift-XRT refined Analysis
  25. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  26. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  27. EP251130a: Optical detections with Kinder observations
  28. EP251130a: SAO RAS optical observations
  29. EP251130A: Optical observation from 1.3m DFOT
  30. EP251130a: Swift-XRT counterpart detection
  31. GRB 251129A / EP251129a: SAO RAS optical observations
  32. GRB 251126A: SAO RAS optical observations
  33. GRB 251129A: Swift-XRT afterglow detection
  34. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  35. GRB 251128A: Fermi GBM Observation
  36. GRB 251126A: further SAO RAS optical observations
  37. GRB251126A: Continued optical observation from 1.3m DFOT
  38. GRB 251126A: Mondy and SAO RAS optical observations
  39. GRB 251126A: Swift-XRT refined Analysis
  40. GRB 251126A: 1.3m DFOT optical afterglow detection
  41. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  42. GRB 251121A: Fermi GBM Observation
  43. GRB 251126A: Prompt enhanced Swift-XRT position
  44. EP251124a: Swift-XRT observations
  45. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  46. EP251124a: Optical upper limit with Kinder observations
  47. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  48. EP251124a: GROWTH-India Telescope optical upper limits
  49. GRB 251116C: Swift-XRT confirmation of fading
  50. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  51. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  52. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  53. EP251118a: Continued Optical Detection with Kinder observations
  54. GRB 251115A: Fermi GBM Observation
  55. EP251118A: 1.3m DFOT optical afterglow detection
  56. GRB 251118A: Swift/UVOT Detection
  57. EP251118a / GRB 251118C: SAO RAS optical observations
  58. GRB 251118A: Fermi GBM Observation
  59. GRB 251118A: Swift-XRT afterglow detection
  60. EP251118a: Optical detection with Kinder observations
  61. GRB 251116C: NOT optical observations
  62. GRB 251117A: Swift-XRT observations
  63. GRB 251118A: Fermi-LAT detection
  64. GRB 251117A: Fermi GBM observation
  65. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  66. GRB 251115A: Swift-XRT observations
  67. GRB 251117A: Fermi-LAT detection
  68. GRB 251116C: Swift/BAT arcminute localization of a burst
  69. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  70. GRB 251116C: Swift-XRT observations
  71. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  72. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  73. GRB 251115A: Fermi-LAT detection
  74. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  75. Konus-Wind detection of GRB 251103A
  76. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  77. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  78. GRB251111A: 1.3m DFOT optical upper limit
  79. GRB 251111A: Swift-XRT afterglow detection
  80. GRB 251111A: Swift-XRT observations
  81. GRB 251013C: Chandra X-ray observations and jet break detection
  82. GRB 251111A: SVOM/VT optical observations with VHF data
  83. GRB 251106A: Swift/UVOT Upper Limits
  84. SVOM GRB251106.83: Global MASTER-Net observations report
  85. GRB 251106A: Swift-XRT afterglow detection
  86. GRB 251106A: MASTER optical observations
  87. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  88. GRB 251105A: Fermi GBM Observation
  89. GRB 251103B: Fermi GBM observation
  90. EP251102a: update of EP-FXT follow-up observation
  91. GRB 251103B: Swift-XRT refined Analysis
  92. GRB 251103B: Prompt enhanced Swift-XRT position
  93. GRB 251103A: Fermi GBM Observation
  94. GRB 251103A: Swift-XRT afterglow detection
  95. GRB 251031A: Fermi GBM Observation
  96. GRB 251028A: Fermi GBM Observation
  97. GRB 251022A: Swift-XRT confirmation of fading
  98. GRB 251026B: Fermi GBM Observation
  99. GRB 251026A/EP251026a: EP-FXT follow-up observation
  100. GRB 251028B: Fermi/GBM observation

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