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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"

6466 results found.

  1. EP251129a/GRB 251129A: NOWT Detection
  2. GRB 251201B: Swift-XRT refined Analysis
  3. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  4. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  5. EP251130a: Optical detections with Kinder observations
  6. EP251130a: SAO RAS optical observations
  7. EP251130A: Optical observation from 1.3m DFOT
  8. EP251130a: Swift-XRT counterpart detection
  9. GRB 251129A / EP251129a: SAO RAS optical observations
  10. GRB 251126A: SAO RAS optical observations
  11. GRB 251129A: Swift-XRT afterglow detection
  12. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  13. GRB 251128A: Fermi GBM Observation
  14. GRB 251126A: further SAO RAS optical observations
  15. GRB251126A: Continued optical observation from 1.3m DFOT
  16. GRB 251126A: Mondy and SAO RAS optical observations
  17. GRB 251126A: Swift-XRT refined Analysis
  18. GRB 251126A: 1.3m DFOT optical afterglow detection
  19. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  20. GRB 251121A: Fermi GBM Observation
  21. GRB 251126A: Prompt enhanced Swift-XRT position
  22. EP251124a: Swift-XRT observations
  23. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  24. EP251124a: Optical upper limit with Kinder observations
  25. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  26. EP251124a: GROWTH-India Telescope optical upper limits
  27. GRB 251116C: Swift-XRT confirmation of fading
  28. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  29. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  30. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  31. EP251118a: Continued Optical Detection with Kinder observations
  32. GRB 251115A: Fermi GBM Observation
  33. EP251118A: 1.3m DFOT optical afterglow detection
  34. GRB 251118A: Swift/UVOT Detection
  35. EP251118a / GRB 251118C: SAO RAS optical observations
  36. GRB 251118A: Fermi GBM Observation
  37. GRB 251118A: Swift-XRT afterglow detection
  38. EP251118a: Optical detection with Kinder observations
  39. GRB 251116C: NOT optical observations
  40. GRB 251117A: Swift-XRT observations
  41. GRB 251118A: Fermi-LAT detection
  42. GRB 251117A: Fermi GBM observation
  43. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  44. GRB 251115A: Swift-XRT observations
  45. GRB 251117A: Fermi-LAT detection
  46. GRB 251116C: Swift/BAT arcminute localization of a burst
  47. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  48. GRB 251116C: Swift-XRT observations
  49. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  50. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  51. GRB 251115A: Fermi-LAT detection
  52. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  53. Konus-Wind detection of GRB 251103A
  54. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  55. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  56. GRB251111A: 1.3m DFOT optical upper limit
  57. GRB 251111A: Swift-XRT afterglow detection
  58. GRB 251111A: Swift-XRT observations
  59. GRB 251013C: Chandra X-ray observations and jet break detection
  60. GRB 251111A: SVOM/VT optical observations with VHF data
  61. GRB 251106A: Swift/UVOT Upper Limits
  62. SVOM GRB251106.83: Global MASTER-Net observations report
  63. GRB 251106A: Swift-XRT afterglow detection
  64. GRB 251106A: MASTER optical observations
  65. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  66. GRB 251105A: Fermi GBM Observation
  67. GRB 251103B: Fermi GBM observation
  68. EP251102a: update of EP-FXT follow-up observation
  69. GRB 251103B: Swift-XRT refined Analysis
  70. GRB 251103B: Prompt enhanced Swift-XRT position
  71. GRB 251103A: Fermi GBM Observation
  72. GRB 251103A: Swift-XRT afterglow detection
  73. GRB 251031A: Fermi GBM Observation
  74. GRB 251028A: Fermi GBM Observation
  75. GRB 251022A: Swift-XRT confirmation of fading
  76. GRB 251026B: Fermi GBM Observation
  77. GRB 251026A/EP251026a: EP-FXT follow-up observation
  78. GRB 251028B: Fermi/GBM observation
  79. GRB 251025B: Swift-XRT confirmation of fading
  80. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  81. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  82. GRB 251023B: Swift-UVOT Upper Limits
  83. GRB 251027A: Swift-XRT observations
  84. GRB 251026A: Swift-XRT observations
  85. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  86. GRB 251025B: Swift-XRT afterglow detection
  87. GRB 251024A: Swift-XRT refined Analysis
  88. GRB 251025B: SVOM/VT optical observations with VHF data
  89. GRB 251022A: Swift-XRT detection of GOTO25iym
  90. EP251023b: Global MASTER-Net observations report
  91. GRB 251022A: Fermi GBM Observation
  92. EP251023a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at Teide Observatory
  93. EP#01709247298: Swift-XRT counterpart detection
  94. GRB 251013C: further SAO RAS optical observations
  95. EP251023a: GSP Optical Counterpart Detection
  96. GRB 251022A: Fermi-LAT detection
  97. GRB 251016B: Fermi GBM Detection
  98. Fermi-LAT gamma-ray observations of IceCube-251018A
  99. GRB 251016A: Fermi GBM Observation
  100. GRB 251018A: Fermi GBM Observation

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