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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"

27297 results found.

  1. GRB 251129A: SVOM detection of a burst
  2. GRB 251129A: SVOM detection of a burst
  3. GRB 251126A: Swift-BAT refined analysis
  4. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  5. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  6. GRB 251127A: Glowbug gamma-ray detection
  7. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  8. GRB 251126A: further SAO RAS optical observations
  9. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  10. GRB 251126A NUTTelA-TAO Early Measurements
  11. GRB251126A: MAO/AZT-22 optical observations
  12. GRB 251128A: Fermi GBM Final Real-time Localization
  13. GRB251126A: Continued optical observation from 1.3m DFOT
  14. GRB 251126A: Swift/UVOT Detection
  15. EP251124a: Pan-STARRS ri-band imaging and photometry
  16. GRB 251126A: Mondy and SAO RAS optical observations
  17. GRB 251126A: Swift-XRT refined Analysis
  18. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  19. GRB 251126A: NOT optical observations
  20. GRB 251126A: 1.3m DFOT optical afterglow detection
  21. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  22. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  23. GRB 251125B: GECAM-B detection
  24. GRB 251127A: Fermi GBM Final Real-time Localization
  25. GRB 251126A: Enhanced Swift-XRT position
  26. GRB 251126A: Kilonova-Catcher optical afterglow detection
  27. GRB 251126A: Asiago i-band detection
  28. GRB 251126A: Nanshan/HMT optical afterglow detection
  29. Swift GRB 251126A: Global MASTER-Net observations report
  30. GRB 251121A: Fermi GBM Observation
  31. GRB 251126A: Prompt enhanced Swift-XRT position
  32. GRB 251126A: GIT discovery of the likely optical afterglow
  33. GRB 251126A: Swift detection of a burst
  34. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  35. GRB 251125B: Fermi GBM Final Real-time Localization
  36. EP251124b: EP-WXT detection of a fast X-ray transient
  37. EP251124a: Xinglong GWAC-F60A optical observation
  38. GRB 251125A: Fermi GBM Final Real-time Localization
  39. EP251124a: NOT r- and z-band optical upper limits
  40. EP251124a: Swift-XRT observations
  41. GRB 251124A: Fermi GBM Localization by automated pipeline
  42. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  43. GRB 251122B: Fermi GBM Final Localization
  44. EP251118A: 6 GHz VLA Detection
  45. GRB 251124a: Fermi GBM Final Localization
  46. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  47. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  48. EP251124a: Einstein Probe detection of an X-ray transient
  49. GRB 251116C: Swift-XRT confirmation of fading
  50. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  51. EP251118A: 3.6m DOT optical afterglow detection
  52. GRB 251122A / EP251122a: EP-FXT counterpart detection
  53. GRB 251122A / EP251122a: WFST optical observations
  54. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  55. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  56. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  57. GRB 251122A / EP251122a: SVOM detection of a long burst
  58. EP251122a: Einstein Probe detection of an X-ray transient
  59. EP251118a: Continued Optical Detection with Kinder observations
  60. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  61. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  62. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  63. GRB 251121A: Fermi GBM Final Real-time Localization
  64. EP251118A: 1.3m DFOT optical afterglow detection
  65. GRB 251118A: Swift/UVOT Detection
  66. GRB 251118A: Glowbug gamma-ray detection
  67. GRB 251118A: Fermi GBM Observation
  68. GRB 251118A: Swift-XRT afterglow detection
  69. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  70. EP251118a: Optical detection with Kinder observations
  71. GRB 251118A: GECAM-B detection
  72. GRB 251118A: NuSTAR detection of bright prompt emission
  73. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  74. GRB 251116C: NOT optical observations
  75. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  76. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  77. GRB 251018A: FRAM-Auger optical detection
  78. GRB 251117A: Swift-XRT observations
  79. Konus-Wind detection of GRB 251118C (EP251118a)
  80. GRB 251117A: Insight-HXMT/HE detection
  81. EP251118a: GOTO optical afterglow detection
  82. GRB 251119A: SVOM detection of a possible burst
  83. GRB 251118A: Fermi-LAT detection
  84. GRB 251118A: Swift ToO observations
  85. EP251118a: Einstein Probe detected of a fast X-ray transient
  86. GRB 251118B: Fermi GBM Final Real-time Localization
  87. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  88. GRB 251118A: Fermi GBM Final Real-time Localization
  89. GRB 251116C: SVOM/ECLAIRs refined analysis
  90. GRB 251117A: AstroSat CZTI detection
  91. GRB 251114B: Insight-HXMT/HE detection
  92. GRB 251114B: GECAM-B detection of a short burst
  93. GRB 251117A: Fermi GBM observation
  94. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  95. GRB 251116D: Insight-HXMT/HE detection
  96. GRB 251115A: Swift-XRT observations
  97. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  98. GRB 251117A: Tiled Swift observations
  99. GRB 251117A: Fermi-LAT detection
  100. GRB 251116C: Swift/BAT arcminute localization of a burst

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