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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"

20506 results found.

  1. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  2. GRB 251126A: SAO RAS optical marginal detection
  3. GRB 251202A: Swift-XRT afterglow detection
  4. EP251129a/GRB 251129A: NOWT Detection
  5. GRB 251126A: SVOM/VT optical observation
  6. EP251130a: SVOM/VT optical observation
  7. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  8. GRB 251201A: SVOM/GRM observation of a burst
  9. GRB 251201B: SVOM/VT optical fading
  10. Swift GRB 251201B : MASTER optical counterpart detection
  11. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  12. GRB 251201B: Enhanced Swift-XRT position
  13. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  14. GRB 251130B: AstroSat CZTI detection
  15. GRB 251201B: Swift detection of a burst with an optical counterpart
  16. EP251130a: Mondy optical observations
  17. EP251130a: Optical detections with Kinder observations
  18. EP251130a: SAO RAS optical observations
  19. EP251130A: Optical observation from 1.3m DFOT
  20. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  21. EP251130a: JinShan optical observations
  22. GRB 251127A: SVOM/GRM observation
  23. EP251130a: COLIBRÍ optical counterpart candidate
  24. EP251130a: Einstein Probe detection of an X-ray transient
  25. GRB 251128A: AstroSat CZTI detection
  26. GRB 251129A / EP251129a: SAO RAS optical observations
  27. GRB 251126A: SAO RAS optical observations
  28. GRB 251128A: SVOM/GRM observation of a long burst
  29. SVOM GRB 251129A : MASTER optical counterpart detection
  30. GRB 251129A: Swift-XRT afterglow detection
  31. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  32. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  33. GRB 251129A: SVOM detection of a burst
  34. GRB 251129A: SVOM detection of a burst
  35. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  36. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  37. GRB 251126A: further SAO RAS optical observations
  38. GRB 251126A NUTTelA-TAO Early Measurements
  39. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  40. GRB251126A: MAO/AZT-22 optical observations
  41. GRB251126A: Continued optical observation from 1.3m DFOT
  42. GRB 251126A: Swift/UVOT Detection
  43. GRB 251126A: Mondy and SAO RAS optical observations
  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 251126A: Enhanced Swift-XRT position
  49. GRB 251126A: Kilonova-Catcher optical afterglow detection
  50. GRB 251126A: Nanshan/HMT optical afterglow detection
  51. GRB 251121A: Fermi GBM Observation
  52. GRB 251126A: GIT discovery of the likely optical afterglow
  53. GRB 251126A: Swift detection of a burst
  54. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  55. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  56. EP251124b: NOT r- and z-band optical upper limits
  57. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  58. EP251124b: EP-WXT detection of a fast X-ray transient
  59. EP251124a: Xinglong GWAC-F60A optical observation
  60. EP251124a: NOT r- and z-band optical upper limits
  61. EP251124a: Swift-XRT observations
  62. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  63. EP251124a: Optical upper limit with Kinder observations
  64. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  65. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  66. EP251124a: GROWTH-India Telescope optical upper limits
  67. EP251124a: Einstein Probe detection of an X-ray transient
  68. GRB 251116C: Swift-XRT confirmation of fading
  69. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  70. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  71. EP251118A: 3.6m DOT optical afterglow detection
  72. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  73. GRB 251122A / EP251122a: WFST optical observations
  74. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  75. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  76. GRB 251122A / EP251122a: LCO optical upper limits
  77. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  78. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  79. GRB 251122A / EP251122a: SVOM detection of a long burst
  80. EP251122a: Einstein Probe detection of an X-ray transient
  81. EP251118a: Continued Optical Detection with Kinder observations
  82. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  83. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  84. EP251118a: Xinglong-2.16m optical observation
  85. EP251118A: 1.3m DFOT optical afterglow detection
  86. GRB 251118A: Swift/UVOT Detection
  87. EP251118a / GRB 251118C: SAO RAS optical observations
  88. GRB 251118A: Swift-XRT afterglow detection
  89. EP251118a: Optical detection with Kinder observations
  90. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  91. GRB 251118A: NuSTAR detection of bright prompt emission
  92. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  93. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  94. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  95. EP251118a: FTW optical and NIR observations
  96. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  97. EP251118a: VLT near-infrared observation
  98. GRB 251116D: SVOM/GRM observation of a long GRB
  99. GRB 251119A: SVOM detection of a possible burst
  100. EP251118a: NOT candidate optical counterpart

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