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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"

23094 results found.

  1. GRB 251205A: Swift-XRT refined Analysis
  2. Konus-Wind detection of GRB 251118A
  3. GRB 251205A: COLIBRÍ optical observations
  4. GRB 251205A: GOTO optical afterglow detection
  5. GRB 251205A: NOT optical observations
  6. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  7. GRB 251205A: Swift detection of a burst with an optical afterglow
  8. GRB 251203C: SVOM/ECLAIRs refined analysis
  9. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  10. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  11. GRB 251201B: SALT spectroscopic redshift z = 1.599
  12. GRB 251203C: J-band observations with WINTER
  13. GRB 251129B: Glowbug gamma-ray detection of a short burst
  14. GRB 251203A: AstroSat CZTI detection
  15. GRB 251203C: LCO optical afterglow confirmation
  16. GRB 251203C: SVOM/VT optical counterpart
  17. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  18. GRB 251203B: Swift-XRT observations
  19. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  20. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  21. GRB 251203C: LCO optical upper limits
  22. GRB 251203B: LCO optical upper limits
  23. GRB 251203C: SVOM detection of a burst
  24. GRB 251203B: SVOM detection of a burst
  25. EP251202a / GRB251202A: AstroSat CZTI detection
  26. GRB 251201B: Fermi GBM Observation
  27. EP251202a/GRB 251202A: KAIT optical observations
  28. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  29. GRB 251129B: AstroSat CZTI detection
  30. GRB 251202A: Swift/UVOT Detection
  31. GRB 251201B: Kilonova-Catcher optical afterglow detection
  32. GRB 251201B: Swift/UVOT Detection
  33. GRB 251130B: Glowbug gamma-ray detection
  34. GRB 251201B: GECAM-B observation of a long burst
  35. GRB 251202A: GOTO optical afterglow detection
  36. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  37. GRB 251202A: Swift-XRT afterglow detection
  38. EP251129a/GRB 251129A: NOWT Detection
  39. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  40. GRB 251201B: Swift-XRT refined Analysis
  41. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  42. Swift GRB 251201B: Global MASTER-Net observations report
  43. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  44. GRB 251130B: AstroSat CZTI detection
  45. GRB 251201B: Swift detection of a burst with an optical counterpart
  46. EP251130a: Optical detections with Kinder observations
  47. EP251130a: KAIT optical observations
  48. GRB 251201A: MAXI/GSC detection
  49. EP251130a: Swift-XRT counterpart detection
  50. EP251130a: COLIBRÍ optical counterpart candidate
  51. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  52. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  53. GRB 251128A: AstroSat CZTI detection
  54. GRB 251129A / EP251129a: SAO RAS optical observations
  55. Swift trigger 1418333 is not an astrophysical source
  56. GRB 251128A: Fermi GBM Observation
  57. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  58. GRB 251126A: Swift-BAT refined analysis
  59. GRB 251127A: Glowbug gamma-ray detection
  60. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  61. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  62. GRB 251126A NUTTelA-TAO Early Measurements
  63. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  64. EP251124a: Pan-STARRS ri-band imaging and photometry
  65. GRB 251126A: Swift-XRT refined Analysis
  66. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  67. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  68. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  69. GRB 251126A: Kilonova-Catcher optical afterglow detection
  70. GRB 251126A: Swift detection of a burst
  71. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  72. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  73. EP251124a: Swift-XRT observations
  74. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  75. EP251124a: Optical upper limit with Kinder observations
  76. EP251118A: 6 GHz VLA Detection
  77. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  78. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  79. GRB 251116C: Swift-XRT confirmation of fading
  80. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  81. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  82. GRB 251122A / EP251122a: SVOM detection of a long burst
  83. EP251118a: Continued Optical Detection with Kinder observations
  84. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  85. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  86. GRB 251115A: Fermi GBM Observation
  87. GRB 251118A: Swift/UVOT Detection
  88. EP251118a / GRB 251118C: SAO RAS optical observations
  89. GRB 251118A: Glowbug gamma-ray detection
  90. GRB 251118A: Swift-XRT afterglow detection
  91. EP251118a: Optical detection with Kinder observations
  92. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  93. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  94. GRB 251117A: Swift-XRT observations
  95. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  96. Konus-Wind detection of GRB 251118C (EP251118a)
  97. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  98. EP251118a: GOTO optical afterglow detection
  99. GRB 251118A: Fermi-LAT detection
  100. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations

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