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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"

35259 results found.

  1. GRB 251126A: further SAO RAS optical observations
  2. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  3. GRB 251126A NUTTelA-TAO Early Measurements
  4. GRB251126A: MAO/AZT-22 optical observations
  5. GRB 251128A: Fermi GBM Final Real-time Localization
  6. GRB251126A: Continued optical observation from 1.3m DFOT
  7. GRB 251126A: Swift/UVOT Detection
  8. GRB 251126A: Mondy and SAO RAS optical observations
  9. GRB 251126A: Swift-XRT refined Analysis
  10. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  11. GRB 251126A: NOT optical observations
  12. GRB 251126A: 1.3m DFOT optical afterglow detection
  13. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  14. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  15. GRB 251125B: GECAM-B detection
  16. Fermi GRB 251127A: Global MASTER-Net observations report
  17. GRB 251127A: Fermi GBM Final Real-time Localization
  18. GRB 251126A: Enhanced Swift-XRT position
  19. GRB 251126A: Kilonova-Catcher optical afterglow detection
  20. GRB 251126A: Asiago i-band detection
  21. GRB 251126A: Nanshan/HMT optical afterglow detection
  22. Swift GRB 251126A: Global MASTER-Net observations report
  23. GRB 251121A: Fermi GBM Observation
  24. GRB 251126A: Prompt enhanced Swift-XRT position
  25. GRB 251126A: GIT discovery of the likely optical afterglow
  26. GRB 251126A: Swift detection of a burst
  27. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  28. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  29. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  30. Fermi GRB 251125B: Global MASTER-Net observations report
  31. GRB 251125B: Fermi GBM Final Real-time Localization
  32. Fermi GRB 251125A: Global MASTER-Net observations report
  33. GRB 251125A: Fermi GBM Final Real-time Localization
  34. GRB 251124A: Fermi GBM Localization by automated pipeline
  35. GRB 251122B: Fermi GBM Final Localization
  36. Fermi GRB 251124a: Global MASTER-Net observations report
  37. GRB 251124a: Fermi GBM Final Localization
  38. GRB 251116C: Swift-XRT confirmation of fading
  39. GRB 251122A/EP251122a: FTW optical and NIR observations
  40. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  41. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  42. GRB 251122A / EP251122a: EP-FXT counterpart detection
  43. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  44. GRB 251122A / EP251122a: WFST optical observations
  45. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  46. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  47. GRB 251122A / EP251122a: LCO optical upper limits
  48. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  49. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  50. GRB 251122A / EP251122a: SVOM detection of a long burst
  51. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  52. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  53. EP251118a: Xinglong-2.16m optical observation
  54. GRB 251115A: Fermi GBM Observation
  55. GRB 251121A: Fermi GBM Final Real-time Localization
  56. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  57. GRB 251118A: Swift/UVOT Detection
  58. EP251118a / GRB 251118C: SAO RAS optical observations
  59. GRB 251118A: Glowbug gamma-ray detection
  60. GRB 251118A: Fermi GBM Observation
  61. GRB 251118A: Swift-XRT afterglow detection
  62. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  63. GRB 251118A: GECAM-B detection
  64. EP251118a / GRB 251118C: SVOM/VT optical observation
  65. GRB 251118A: NuSTAR detection of bright prompt emission
  66. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  67. GRB 251116C: NOT optical observations
  68. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  69. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  70. GRB 251018A: FRAM-Auger optical detection
  71. GRB 251117A: Swift-XRT observations
  72. EP251118A / GRB 251118C : MASTER optical counterpart observations
  73. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  74. Konus-Wind detection of GRB 251118C (EP251118a)
  75. GRB 251117A: Insight-HXMT/HE detection
  76. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  77. GRB 251116D: SVOM/GRM observation of a long GRB
  78. GRB 251119A: SVOM detection of a possible burst
  79. EP251118a: NOT spectroscopic redshift of z = 1.216
  80. GRB 251118A: Fermi-LAT detection
  81. GRB 251118A: Swift ToO observations
  82. Fermi GRB 251118B: Global MASTER-Net observations report
  83. GRB 251118B: Fermi GBM Final Real-time Localization
  84. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  85. GRB 251118A: BALROG localization (Fermi Trigger 785190695 / GRB 251118855)
  86. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  87. GRB 251118A: Fermi GBM Final Real-time Localization
  88. GRB 251116C: SVOM/ECLAIRs refined analysis
  89. GRB 251116B: 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: SVOM/GRM observation of a short burst
  99. GRB 251117A: Tiled Swift observations
  100. GRB 251117A: Fermi-LAT detection

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