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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"

27774 results found.

  1. GRB 251127A: Fermi GBM Final Real-time Localization
  2. GRB 251126A: Enhanced Swift-XRT position
  3. GRB 251126A: Kilonova-Catcher optical afterglow detection
  4. GRB 251126A: Asiago i-band detection
  5. GRB 251126A: Nanshan/HMT optical afterglow detection
  6. Swift GRB 251126A: Global MASTER-Net observations report
  7. GRB 251121A: Fermi GBM Observation
  8. GRB 251126A: Prompt enhanced Swift-XRT position
  9. GRB 251126A: GIT discovery of the likely optical afterglow
  10. GRB 251126A: Swift detection of a burst
  11. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  12. GRB 251125B: Fermi GBM Final Real-time Localization
  13. EP251124b: EP-WXT detection of a fast X-ray transient
  14. EP251124a: Xinglong GWAC-F60A optical observation
  15. GRB 251125A: Fermi GBM Final Real-time Localization
  16. EP251124a: NOT r- and z-band optical upper limits
  17. EP251124a: Swift-XRT observations
  18. GRB 251124A: Fermi GBM Localization by automated pipeline
  19. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  20. GRB 251122B: Fermi GBM Final Localization
  21. EP251118A: 6 GHz VLA Detection
  22. GRB 251124a: Fermi GBM Final Localization
  23. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  24. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  25. EP251124a: Einstein Probe detection of an X-ray transient
  26. GRB 251116C: Swift-XRT confirmation of fading
  27. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  28. EP251118A: 3.6m DOT optical afterglow detection
  29. GRB 251122A / EP251122a: EP-FXT counterpart detection
  30. GRB 251122A / EP251122a: WFST optical observations
  31. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  32. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  33. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  34. GRB 251122A / EP251122a: SVOM detection of a long burst
  35. EP251122a: Einstein Probe detection of an X-ray transient
  36. EP251118a: Continued Optical Detection with Kinder observations
  37. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  38. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  39. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  40. GRB 251121A: Fermi GBM Final Real-time Localization
  41. EP251118A: 1.3m DFOT optical afterglow detection
  42. GRB 251118A: Swift/UVOT Detection
  43. GRB 251118A: Glowbug gamma-ray detection
  44. GRB 251118A: Fermi GBM Observation
  45. GRB 251118A: Swift-XRT afterglow detection
  46. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  47. EP251118a: Optical detection with Kinder observations
  48. GRB 251118A: GECAM-B detection
  49. GRB 251118A: NuSTAR detection of bright prompt emission
  50. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  51. GRB 251116C: NOT optical observations
  52. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  53. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  54. GRB 251018A: FRAM-Auger optical detection
  55. GRB 251117A: Swift-XRT observations
  56. Konus-Wind detection of GRB 251118C (EP251118a)
  57. GRB 251117A: Insight-HXMT/HE detection
  58. EP251118a: GOTO optical afterglow detection
  59. GRB 251119A: SVOM detection of a possible burst
  60. GRB 251118A: Fermi-LAT detection
  61. GRB 251118A: Swift ToO observations
  62. EP251118a: Einstein Probe detected of a fast X-ray transient
  63. GRB 251118B: Fermi GBM Final Real-time Localization
  64. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  65. GRB 251118A: Fermi GBM Final Real-time Localization
  66. GRB 251116C: SVOM/ECLAIRs refined analysis
  67. GRB 251117A: AstroSat CZTI detection
  68. GRB 251114B: Insight-HXMT/HE detection
  69. GRB 251114B: GECAM-B detection of a short burst
  70. GRB 251117A: Fermi GBM observation
  71. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  72. GRB 251116D: Insight-HXMT/HE detection
  73. GRB 251115A: Swift-XRT observations
  74. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  75. GRB 251117A: Tiled Swift observations
  76. GRB 251117A: Fermi-LAT detection
  77. GRB 251116C: Swift/BAT arcminute localization of a burst
  78. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  79. GRB 251116C: Swift-XRT observations
  80. GRB 251117A: Fermi GBM Final Localization Correction
  81. GRB 251116D: Glowbug gamma-ray detection
  82. GRB 251116D: AstroSat CZTI detection
  83. GRB 251116C: SVOM/VT optical upper limit
  84. GRB 251116C: SVOM detection of a burst
  85. GRB 251116B: SVOM detection of a burst
  86. GRB 251116A: Fermi GBM Final Real-time Localization
  87. GRB 251115A: Tiled Swift observations
  88. GRB 251115A: Fermi-LAT detection
  89. GRB 251115A: Fermi GBM Final Real-time Localization
  90. GRB 251113A: Glowbug gamma-ray detection
  91. GRB 251113A: AstroSat CZTI detection
  92. GRB 251114B: Fermi GBM Final Real-time Localization
  93. GRB 251112A: Swift-BAT refined analysis
  94. Konus-Wind detection of GRB 251108C
  95. Konus-Wind detection of GRB 251103A
  96. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  97. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  98. IPN triangulation of GRB 251108C
  99. GRB 251114A: Fermi GBM Final Real-time Localization
  100. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates

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