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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"

19189 results found.

  1. IPN triangulation of GRB 251129B (short/hard)
  2. GRB251129A/EP251129a: Swift UVOT detection
  3. GRB 251202A: Swift/UVOT Detection
  4. GRB 251201B: Kilonova-Catcher optical afterglow detection
  5. GRB 251201B: Swift/UVOT Detection
  6. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  7. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  8. GRB 251126A: SAO RAS optical marginal detection
  9. GRB 251202A: Swift-XRT afterglow detection
  10. EP251129a/GRB 251129A: NOWT Detection
  11. GRB 251126A: SVOM/VT optical observation
  12. EP251130a: SVOM/VT optical observation
  13. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  14. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  15. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 251201A: SVOM/GRM observation of a burst
  17. GRB 251201B: SVOM/VT optical fading
  18. Swift GRB 251201B : MASTER optical counterpart detection
  19. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  20. GRB 251201B: Enhanced Swift-XRT position
  21. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  22. GRB 251130B: AstroSat CZTI detection
  23. GRB 251201B: Swift detection of a burst with an optical counterpart
  24. EP251130a: Mondy optical observations
  25. EP251130a: Optical detections with Kinder observations
  26. EP251130a: SAO RAS optical observations
  27. EP251130A: Optical observation from 1.3m DFOT
  28. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  29. EP251130a: JinShan optical observations
  30. GRB 251127A: SVOM/GRM observation
  31. EP251130a: COLIBRÍ optical counterpart candidate
  32. EP251130a: Einstein Probe detection of an X-ray transient
  33. GRB 251129A / EP251129a: SAO RAS optical observations
  34. GRB 251126A: SAO RAS optical observations
  35. GRB 251128A: GECAM-B detection
  36. GRB 251128A: SVOM/GRM observation of a long burst
  37. SVOM GRB 251129A : MASTER optical counterpart detection
  38. GRB 251129A: Swift-XRT afterglow detection
  39. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  40. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  41. GRB 251129A: SVOM detection of a burst
  42. GRB 251129A: SVOM detection of a burst
  43. GRB 251126A: Swift-BAT refined analysis
  44. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  45. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  46. GRB 251126A: further SAO RAS optical observations
  47. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  48. GRB251126A: MAO/AZT-22 optical observations
  49. GRB251126A: Continued optical observation from 1.3m DFOT
  50. GRB 251126A: Swift/UVOT Detection
  51. EP251124a: Pan-STARRS ri-band imaging and photometry
  52. GRB 251126A: Mondy and SAO RAS optical observations
  53. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  54. GRB 251126A: 1.3m DFOT optical afterglow detection
  55. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  56. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  57. GRB 251126A: Enhanced Swift-XRT position
  58. GRB 251126A: Kilonova-Catcher optical afterglow detection
  59. GRB 251126A: Nanshan/HMT optical afterglow detection
  60. GRB 251126A: GIT discovery of the likely optical afterglow
  61. GRB 251126A: Swift detection of a burst
  62. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  63. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  64. EP251124b: NOT r- and z-band optical upper limits
  65. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  66. EP251124b: EP-WXT detection of a fast X-ray transient
  67. EP251124a: Xinglong GWAC-F60A optical observation
  68. EP251124a: NOT r- and z-band optical upper limits
  69. EP251124a: Swift-XRT observations
  70. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  71. EP251124a: Optical upper limit with Kinder observations
  72. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  73. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  74. EP251124a: GROWTH-India Telescope optical upper limits
  75. EP251124a: Einstein Probe detection of an X-ray transient
  76. GRB 251116C: Swift-XRT confirmation of fading
  77. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  78. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  79. EP251118A: 3.6m DOT optical afterglow detection
  80. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  81. GRB 251122A / EP251122a: WFST optical observations
  82. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  83. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  84. GRB 251122A / EP251122a: LCO optical upper limits
  85. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  86. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  87. GRB 251122A / EP251122a: SVOM detection of a long burst
  88. EP251122a: Einstein Probe detection of an X-ray transient
  89. EP251118a: Continued Optical Detection with Kinder observations
  90. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  91. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  92. EP251118a: Xinglong-2.16m optical observation
  93. EP251118A: 1.3m DFOT optical afterglow detection
  94. GRB 251118A: Swift/UVOT Detection
  95. EP251118a / GRB 251118C: SAO RAS optical observations
  96. GRB 251118A: Swift-XRT afterglow detection
  97. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  98. EP251118a: Optical detection with Kinder observations
  99. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  100. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO

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