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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"

6506 results found.

  1. GRB 251222A/EP251222b: Optical detection with Kinder observations
  2. EP251222a: Optical upper limit with Kinder observations
  3. GRB 251222A: Fermi GBM Observation
  4. Konus-Wind detection of GRB 251222A / EP251222b
  5. GRB 251222A: Swift-XRT afterglow detection
  6. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  7. EP251222a: GSP Optical Counterpart Detection
  8. GRB 251221A: Swift-XRT refined Analysis
  9. GRB 251221A: Fermi GBM Observation
  10. EP251220a: EP-FXT follow-up observation
  11. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  12. GRB 251215A: Swift-XRT afterglow detection
  13. GRB 251215A: Swift/UVOT Upper LImits
  14. GRB 251215A: Fermi GBM Observation
  15. GRB 251215A: Swift-XRT observations
  16. EP251214a: Optical upper limit with Kinder observations
  17. GRB 251214B: Fermi GBM Observation
  18. GRB 251209A: Insight-HXMT/HE detection
  19. GRB 251214B: Swift-XRT refined Analysis
  20. EP251212a: EP-FXT follow-up observation
  21. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  22. GRB 251209A: Fermi GBM observation
  23. GRB 251208A: AstroSat CZTI detection
  24. GRB 251208B: Swift-XRT afterglow detection
  25. GRB 251208B: Fermi GBM Observation
  26. GRB 251208D: Swift-XRT observations
  27. GRB 251208B: Fermi-LAT detection
  28. GRB 251205A: FTW optical and NIR observations
  29. GRB 251205A: Swift-XRT refined Analysis
  30. GRB 251203C: Swift/UVOT Upper Limit
  31. GRB 251203A: Insight-HXMT/HE detection
  32. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  33. GRB 251203B: Swift-XRT observations
  34. GRB 251201B: Fermi GBM Observation
  35. GRB251129A/EP251129a: Swift UVOT detection
  36. GRB 251202A: Fermi GBM Observation
  37. EP251130a: continued NOT optical observations indicate steep fading phase
  38. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  39. GRB 251126A: SAO RAS optical marginal detection
  40. GRB 251202A: Swift-XRT afterglow detection
  41. EP251129a/GRB 251129A: NOWT Detection
  42. GRB 251201B: Swift-XRT refined Analysis
  43. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  44. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  45. EP251130a: Optical detections with Kinder observations
  46. EP251130a: SAO RAS optical observations
  47. EP251130A: Optical observation from 1.3m DFOT
  48. EP251130a: Swift-XRT counterpart detection
  49. GRB 251129A / EP251129a: SAO RAS optical observations
  50. GRB 251126A: SAO RAS optical observations
  51. GRB 251129A: Swift-XRT afterglow detection
  52. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  53. GRB 251128A: Fermi GBM Observation
  54. GRB 251126A: further SAO RAS optical observations
  55. GRB251126A: Continued optical observation from 1.3m DFOT
  56. GRB 251126A: Mondy and SAO RAS optical observations
  57. GRB 251126A: Swift-XRT refined Analysis
  58. GRB 251126A: 1.3m DFOT optical afterglow detection
  59. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  60. GRB 251121A: Fermi GBM Observation
  61. GRB 251126A: Prompt enhanced Swift-XRT position
  62. EP251124a: Swift-XRT observations
  63. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  64. EP251124a: Optical upper limit with Kinder observations
  65. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  66. EP251124a: GROWTH-India Telescope optical upper limits
  67. GRB 251116C: Swift-XRT confirmation of fading
  68. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  69. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  70. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  71. EP251118a: Continued Optical Detection with Kinder observations
  72. GRB 251115A: Fermi GBM Observation
  73. EP251118A: 1.3m DFOT optical afterglow detection
  74. GRB 251118A: Swift/UVOT Detection
  75. EP251118a / GRB 251118C: SAO RAS optical observations
  76. GRB 251118A: Fermi GBM Observation
  77. GRB 251118A: Swift-XRT afterglow detection
  78. EP251118a: Optical detection with Kinder observations
  79. GRB 251116C: NOT optical observations
  80. GRB 251117A: Swift-XRT observations
  81. GRB 251118A: Fermi-LAT detection
  82. GRB 251117A: Fermi GBM observation
  83. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  84. GRB 251115A: Swift-XRT observations
  85. GRB 251117A: Fermi-LAT detection
  86. GRB 251116C: Swift/BAT arcminute localization of a burst
  87. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  88. GRB 251116C: Swift-XRT observations
  89. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  90. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  91. GRB 251115A: Fermi-LAT detection
  92. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  93. Konus-Wind detection of GRB 251103A
  94. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  95. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  96. GRB251111A: 1.3m DFOT optical upper limit
  97. GRB 251111A: Swift-XRT afterglow detection
  98. GRB 251111A: Swift-XRT observations
  99. GRB 251013C: Chandra X-ray observations and jet break detection
  100. GRB 251111A: SVOM/VT optical observations with VHF data

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