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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"

24898 results found.

  1. GRB 251201A: SVOM/GRM observation of a burst
  2. GRB 251201B: SVOM/VT optical fading
  3. Swift GRB 251201B : MASTER optical counterpart detection
  4. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  5. GRB 251201B: Enhanced Swift-XRT position
  6. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  7. GRB 251130B: AstroSat CZTI detection
  8. GRB 251201B: Swift detection of a burst with an optical counterpart
  9. EP251130a: Mondy optical observations
  10. EP251130a: Optical detections with Kinder observations
  11. EP251130a: SAO RAS optical observations
  12. EP251130A: Optical observation from 1.3m DFOT
  13. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP251130a: JinShan optical observations
  15. GRB 251127A: SVOM/GRM observation
  16. EP251130a: Swift-XRT counterpart detection
  17. EP251130a: COLIBRÍ optical counterpart candidate
  18. EP251130a: Einstein Probe detection of an X-ray transient
  19. EP251129a/GRB 251129A: EP-FXT follow-up observations
  20. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  21. GRB 251128A: AstroSat CZTI detection
  22. GRB 251129A / EP251129a: SAO RAS optical observations
  23. GRB 251126A: SAO RAS optical observations
  24. GRB 251128A: GECAM-B detection
  25. GRB 251128A: SVOM/GRM observation of a long burst
  26. SVOM GRB 251129A : MASTER optical counterpart detection
  27. GRB 251129A: Swift-XRT afterglow detection
  28. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  29. GRB 251128A: Fermi GBM Observation
  30. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  31. GRB 251129A: SVOM detection of a burst
  32. GRB 251129A: SVOM detection of a burst
  33. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  34. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  35. GRB 251127A: Glowbug gamma-ray detection
  36. GRB 251126A: further SAO RAS optical observations
  37. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  38. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  39. GRB251126A: MAO/AZT-22 optical observations
  40. GRB251126A: Continued optical observation from 1.3m DFOT
  41. GRB 251126A: Swift/UVOT Detection
  42. GRB 251126A: Mondy and SAO RAS optical observations
  43. GRB 251126A: Swift-XRT refined Analysis
  44. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  45. GRB 251126A: 1.3m DFOT optical afterglow detection
  46. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  47. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  48. GRB 251125B: GECAM-B detection
  49. GRB 251126A: Enhanced Swift-XRT position
  50. GRB 251126A: Kilonova-Catcher optical afterglow detection
  51. GRB 251126A: Nanshan/HMT optical afterglow detection
  52. GRB 251121A: Fermi GBM Observation
  53. GRB 251126A: GIT discovery of the likely optical afterglow
  54. GRB 251126A: Swift detection of a burst
  55. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  56. EP251124b follow-up observation by EP-FXT
  57. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  58. EP251124b: NOT r- and z-band optical upper limits
  59. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  60. EP251124b: EP-WXT detection of a fast X-ray transient
  61. EP251124a: Xinglong GWAC-F60A optical observation
  62. EP251124a: NOT r- and z-band optical upper limits
  63. EP251124a: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  65. EP251124a: Optical upper limit with Kinder observations
  66. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  67. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  68. EP251124a: GROWTH-India Telescope optical upper limits
  69. EP251124a: Einstein Probe detection of an X-ray transient
  70. GRB 251116C: Swift-XRT confirmation of fading
  71. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  72. The EP-WXT trigger 01709248783 is likely a flaring star
  73. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  74. EP251118A: 3.6m DOT optical afterglow detection
  75. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  76. GRB 251122A / EP251122a: WFST optical observations
  77. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  78. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  79. GRB 251122A / EP251122a: LCO optical upper limits
  80. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  81. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  82. GRB 251122A / EP251122a: SVOM detection of a long burst
  83. EP251122a: Einstein Probe detection of an X-ray transient
  84. EP251118a: Continued Optical Detection with Kinder observations
  85. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  86. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  87. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  88. EP251118a: Xinglong-2.16m optical observation
  89. GRB 251115A: Fermi GBM Observation
  90. The EP-WXT trigger 01709248635 is likely a flaring star
  91. Fermi trigger No 785388351: Global MASTER-Net observations report
  92. EP251118A: 1.3m DFOT optical afterglow detection
  93. GRB 251118A: Swift/UVOT Detection
  94. EP251118a / GRB 251118C: SAO RAS optical observations
  95. GRB 251118A: Glowbug gamma-ray detection
  96. GRB 251118A: Fermi GBM Observation
  97. GRB 251118A: Swift-XRT afterglow detection
  98. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  99. EP251118a: Optical detection with Kinder observations
  100. GRB 251118A: GECAM-B detection

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