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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"

14819 results found.

  1. GRB 251129A: Swift-XRT afterglow detection
  2. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  3. GRB 251129A: SVOM detection of a burst
  4. GRB 251129A: SVOM detection of a burst
  5. GRB 251127A: Glowbug gamma-ray detection
  6. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  7. GRB251126A: MAO/AZT-22 optical observations
  8. GRB 251128A: Fermi GBM Final Real-time Localization
  9. GRB251126A: Continued optical observation from 1.3m DFOT
  10. GRB 251126A: Swift/UVOT Detection
  11. EP251124a: Pan-STARRS ri-band imaging and photometry
  12. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  13. GRB 251126A: 1.3m DFOT optical afterglow detection
  14. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  15. GRB 251125B: GECAM-B detection
  16. GRB 251127A: Fermi GBM Final Real-time Localization
  17. GRB 251126A: Kilonova-Catcher optical afterglow detection
  18. GRB 251126A: Asiago i-band detection
  19. GRB 251126A: Nanshan/HMT optical afterglow detection
  20. GRB 251126A: Swift detection of a burst
  21. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  22. GRB 251125B: Fermi GBM Final Real-time Localization
  23. EP251124b: EP-WXT detection of a fast X-ray transient
  24. GRB 251125A: Fermi GBM Final Real-time Localization
  25. GRB 251124A: Fermi GBM Localization by automated pipeline
  26. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  27. GRB 251122B: Fermi GBM Final Localization
  28. EP251118A: 6 GHz VLA Detection
  29. GRB 251124a: Fermi GBM Final Localization
  30. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  31. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  32. EP251124a: Einstein Probe detection of an X-ray transient
  33. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  34. EP251118A: 3.6m DOT optical afterglow detection
  35. GRB 251122A / EP251122a: EP-FXT counterpart detection
  36. GRB 251122A / EP251122a: WFST optical observations
  37. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  38. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  39. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  40. GRB 251122A / EP251122a: SVOM detection of a long burst
  41. EP251122a: Einstein Probe detection of an X-ray transient
  42. EP251118a: Continued Optical Detection with Kinder observations
  43. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  44. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  45. EP251118a: Xinglong-2.16m optical observation
  46. GRB 251121A: Fermi GBM Final Real-time Localization
  47. EP251118A: 1.3m DFOT optical afterglow detection
  48. GRB 251118A: Swift/UVOT Detection
  49. GRB 251118A: Glowbug gamma-ray detection
  50. GRB 251118A: Swift-XRT afterglow detection
  51. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  52. EP251118a: Optical detection with Kinder observations
  53. GRB 251118A: GECAM-B detection
  54. GRB 251118A: NuSTAR detection of bright prompt emission
  55. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  56. GRB 251116C: NOT optical observations
  57. GRB 251118C: Glowbug gamma-ray detection of the fast X-ray transient EP251118A
  58. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  59. GRB 251018A: FRAM-Auger optical detection
  60. Konus-Wind detection of GRB 251118C (EP251118a)
  61. GRB 251117A: Insight-HXMT/HE detection
  62. EP251118a: GOTO optical afterglow detection
  63. GRB 251119A: SVOM detection of a possible burst
  64. EP251118a: NOT spectroscopic redshift of z = 1.216
  65. GRB 251118A: Fermi-LAT detection
  66. EP251118a: Einstein Probe detected of a fast X-ray transient
  67. GRB 251118B: Fermi GBM Final Real-time Localization
  68. GRB 251118A: Fermi GBM Final Real-time Localization
  69. GRB 251117A: AstroSat CZTI detection
  70. GRB 251114B: Insight-HXMT/HE detection
  71. GRB 251114B: GECAM-B detection of a short burst
  72. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  73. GRB 251116D: Insight-HXMT/HE detection
  74. GRB 251117A: Fermi-LAT detection
  75. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  76. GRB 251117A: Fermi GBM Final Localization Correction
  77. GRB 251116D: Glowbug gamma-ray detection
  78. GRB 251116D: AstroSat CZTI detection
  79. GRB 251116C: SVOM detection of a burst
  80. GRB 251116B: SVOM detection of a burst
  81. GRB 251116A: Fermi GBM Final Real-time Localization
  82. GRB 251115A: Fermi-LAT detection
  83. GRB 251115A: Fermi GBM Final Real-time Localization
  84. GRB 251113A: Glowbug gamma-ray detection
  85. GRB 251113A: AstroSat CZTI detection
  86. GRB 251114B: Fermi GBM Final Real-time Localization
  87. Konus-Wind detection of GRB 251108C
  88. Konus-Wind detection of GRB 251103A
  89. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  90. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  91. IPN triangulation of GRB 251108C
  92. GRB 251114A: Fermi GBM Final Real-time Localization
  93. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  94. GRB 251113A: Fermi GBM Final Real-time Localization
  95. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  96. GRB 251108C: AstroSat CZTI detection
  97. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  98. GRB 251112B: MAXI/GSC detection
  99. GRB 251108B: Glowbug gamma-ray detection
  100. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations

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