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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"

20504 results found.

  1. GRB 251202A: Swift-XRT afterglow detection
  2. EP251129a/GRB 251129A: NOWT Detection
  3. GRB 251126A: SVOM/VT optical observation
  4. EP251130a: SVOM/VT optical observation
  5. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  6. GRB 251201A: SVOM/GRM observation of a burst
  7. GRB 251201B: SVOM/VT optical fading
  8. Swift GRB 251201B : MASTER optical counterpart detection
  9. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  10. GRB 251201B: Enhanced Swift-XRT position
  11. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  12. GRB 251130B: AstroSat CZTI detection
  13. GRB 251201B: Swift detection of a burst with an optical counterpart
  14. EP251130a: Mondy optical observations
  15. EP251130a: Optical detections with Kinder observations
  16. EP251130a: SAO RAS optical observations
  17. EP251130A: Optical observation from 1.3m DFOT
  18. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  19. EP251130a: JinShan optical observations
  20. GRB 251127A: SVOM/GRM observation
  21. EP251130a: COLIBRÍ optical counterpart candidate
  22. EP251130a: Einstein Probe detection of an X-ray transient
  23. GRB 251128A: AstroSat CZTI detection
  24. GRB 251129A / EP251129a: SAO RAS optical observations
  25. GRB 251126A: SAO RAS optical observations
  26. GRB 251128A: SVOM/GRM observation of a long burst
  27. SVOM GRB 251129A : MASTER optical counterpart detection
  28. GRB 251129A: Swift-XRT afterglow detection
  29. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  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 251126A: further SAO RAS optical observations
  36. GRB 251126A NUTTelA-TAO Early Measurements
  37. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  38. GRB251126A: MAO/AZT-22 optical observations
  39. GRB251126A: Continued optical observation from 1.3m DFOT
  40. GRB 251126A: Swift/UVOT Detection
  41. GRB 251126A: Mondy and SAO RAS optical observations
  42. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  43. GRB 251126A: 1.3m DFOT optical afterglow detection
  44. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  45. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  46. GRB 251126A: Enhanced Swift-XRT position
  47. GRB 251126A: Kilonova-Catcher optical afterglow detection
  48. GRB 251126A: Nanshan/HMT optical afterglow detection
  49. GRB 251121A: Fermi GBM Observation
  50. GRB 251126A: GIT discovery of the likely optical afterglow
  51. GRB 251126A: Swift detection of a burst
  52. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  53. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  54. EP251124b: NOT r- and z-band optical upper limits
  55. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  56. EP251124b: EP-WXT detection of a fast X-ray transient
  57. EP251124a: Xinglong GWAC-F60A optical observation
  58. EP251124a: NOT r- and z-band optical upper limits
  59. EP251124a: Swift-XRT observations
  60. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  61. EP251124a: Optical upper limit with Kinder observations
  62. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  63. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  64. EP251124a: GROWTH-India Telescope optical upper limits
  65. EP251124a: Einstein Probe detection of an X-ray transient
  66. GRB 251116C: Swift-XRT confirmation of fading
  67. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  68. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  69. EP251118A: 3.6m DOT optical afterglow detection
  70. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  71. GRB 251122A / EP251122a: WFST optical observations
  72. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  73. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  74. GRB 251122A / EP251122a: LCO optical upper limits
  75. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  76. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  77. GRB 251122A / EP251122a: SVOM detection of a long burst
  78. EP251122a: Einstein Probe detection of an X-ray transient
  79. EP251118a: Continued Optical Detection with Kinder observations
  80. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  81. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  82. EP251118a: Xinglong-2.16m optical observation
  83. EP251118A: 1.3m DFOT optical afterglow detection
  84. GRB 251118A: Swift/UVOT Detection
  85. EP251118a / GRB 251118C: SAO RAS optical observations
  86. GRB 251118A: Swift-XRT afterglow detection
  87. EP251118a: Optical detection with Kinder observations
  88. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  89. GRB 251118A: NuSTAR detection of bright prompt emission
  90. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  91. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  92. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  93. EP251118a: FTW optical and NIR observations
  94. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  95. EP251118a: VLT near-infrared observation
  96. GRB 251116D: SVOM/GRM observation of a long GRB
  97. GRB 251119A: SVOM detection of a possible burst
  98. EP251118a: NOT candidate optical counterpart
  99. EP251118a: Einstein Probe detected of a fast X-ray transient
  100. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations

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