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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"

18478 results found.

  1. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  2. GRB 251201A: SVOM/GRM observation of a burst
  3. GRB 251201B: SVOM/VT optical fading
  4. Swift GRB 251201B : MASTER optical counterpart detection
  5. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  6. GRB 251201B: Enhanced Swift-XRT position
  7. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  8. GRB 251130B: AstroSat CZTI detection
  9. GRB 251201B: Swift detection of a burst with an optical counterpart
  10. EP251130a: Mondy optical observations
  11. EP251130a: Optical detections with Kinder observations
  12. EP251130a: SAO RAS optical observations
  13. EP251130A: Optical observation from 1.3m DFOT
  14. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  15. EP251130a: JinShan optical observations
  16. GRB 251127A: SVOM/GRM observation
  17. EP251130a: COLIBRÍ optical counterpart candidate
  18. EP251130a: Einstein Probe detection of an X-ray transient
  19. GRB 251129A / EP251129a: SAO RAS optical observations
  20. GRB 251126A: SAO RAS optical observations
  21. GRB 251128A: SVOM/GRM observation of a long burst
  22. SVOM GRB 251129A : MASTER optical counterpart detection
  23. GRB 251129A: Swift-XRT afterglow detection
  24. GRB 251129A: Swift ToO observations
  25. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  26. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  27. GRB 251129A: SVOM detection of a burst
  28. GRB 251129A: SVOM detection of a burst
  29. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  30. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  31. GRB 251126A: further SAO RAS optical observations
  32. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  33. GRB251126A: MAO/AZT-22 optical observations
  34. GRB251126A: Continued optical observation from 1.3m DFOT
  35. GRB 251126A: Swift/UVOT Detection
  36. GRB 251126A: Mondy and SAO RAS optical observations
  37. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  38. GRB 251126A: 1.3m DFOT optical afterglow detection
  39. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  40. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  41. GRB 251126A: Enhanced Swift-XRT position
  42. GRB 251126A: Kilonova-Catcher optical afterglow detection
  43. GRB 251126A: Nanshan/HMT optical afterglow detection
  44. GRB 251126A: GIT discovery of the likely optical afterglow
  45. GRB 251126A: Swift detection of a burst
  46. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  47. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  48. EP251124b: NOT r- and z-band optical upper limits
  49. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  50. EP251124b: EP-WXT detection of a fast X-ray transient
  51. EP251124a: Xinglong GWAC-F60A optical observation
  52. EP251124a: NOT r- and z-band optical upper limits
  53. EP251124a: Swift-XRT observations
  54. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  55. EP251124a: Optical upper limit with Kinder observations
  56. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  57. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  58. EP251124a: GROWTH-India Telescope optical upper limits
  59. EP251124a: Einstein Probe detection of an X-ray transient
  60. GRB 251116C: Swift-XRT confirmation of fading
  61. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  62. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  63. EP251118A: 3.6m DOT optical afterglow detection
  64. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 251122A / EP251122a: WFST optical observations
  66. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  67. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  68. GRB 251122A / EP251122a: LCO optical upper limits
  69. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  70. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  71. GRB 251122A / EP251122a: SVOM detection of a long burst
  72. EP251122a: Einstein Probe detection of an X-ray transient
  73. EP251118a: Continued Optical Detection with Kinder observations
  74. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  75. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  76. EP251118a: Xinglong-2.16m optical observation
  77. Fermi trigger No 785388351: Global MASTER-Net observations report
  78. EP251118A: 1.3m DFOT optical afterglow detection
  79. GRB 251118A: Swift/UVOT Detection
  80. EP251118a / GRB 251118C: SAO RAS optical observations
  81. GRB 251118A: Swift-XRT afterglow detection
  82. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  83. EP251118a: Optical detection with Kinder observations
  84. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  85. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  86. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  87. GRB 251117A: Swift-XRT observations
  88. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  89. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  90. EP251118a: VLT near-infrared observation
  91. GRB 251116D: SVOM/GRM observation of a long GRB
  92. GRB 251119A: SVOM detection of a possible burst
  93. EP251118a: NOT candidate optical counterpart
  94. GRB 251118A: Swift ToO observations
  95. EP251118a: Einstein Probe detected of a fast X-ray transient
  96. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray 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. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate

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