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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"

17479 results found.

  1. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  2. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  3. GRB 250702F: Enhanced Swift-XRT position
  4. GRB 250702F: NOT observations of the optical afterglow
  5. GRB 250702F: Swift detection of a burst with an optical counterpart
  6. Swift GRB 250702F: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  8. GRB 250628A: REM optical/NIR upper limits
  9. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  10. GRB 250628A: VLT/X-shooter upper limits
  11. GRB 250628A: Swift/UVOT Upper Limits
  12. GRB 250628A: Enhanced Swift-XRT position
  13. GRB 250628A: Swift detection of a burst
  14. GRB 250625A: Leavitt Observatory afterglow detection
  15. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  16. GRB 250625A: SVOM/C-GFT upper limit in early phase
  17. GRB 250625A: Swift/UVOT Upper Limits
  18. GRB 250625A: ABObservatory afterglow detection
  19. GRB 250625A: OHP/T193 optical detection
  20. GRB 250625A: COLIBRÍ optical observations
  21. GRB 250625A: JinShan optical observations
  22. GRB 250625A: SAO RAS possible optical afterglow
  23. GRB 250625A: Enhanced Swift-XRT position
  24. GRB 250625A: Swift detection of a burst
  25. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  26. GRB 250620A: AstroSat CZTI detection
  27. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  28. GRB 241018A: Maidanak optical observations
  29. IPN triangulation of GRB 250620С (long/bright)
  30. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  31. GRB 250620C: SVOM/GRM observation
  32. GRB 250620A: SVOM/GRM observation of a short burst
  33. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  34. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  35. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  36. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  37. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  38. GRB 250617B: Nickel telescope optical observations
  39. GRB 250615A: Kilonova-Catcher optical upper limits
  40. GRB 250617B: Assy AZT-20 Optical Observations
  41. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  42. GRB 250617B: Swift/UVOT Detection
  43. GRB 250617B: Kilonova-Catcher optical afterglow detection
  44. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  45. GRB 250617B: COLIBRÍ optical observations
  46. GRB 250617B: NOT NIR observations of the afterglow
  47. GRB 250617B: NUTTelA-TAO early time optical observations
  48. GRB 250617B: Enhanced Swift-XRT position
  49. The EP-WXT trigger 01709178990 is likely a flaring star
  50. GRB 250617B: SAO RAS optical observations
  51. GRB 250617B: Swift detection of a burst with an optical counterpart
  52. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  53. EP-WXT trigger 01709178975: GOTO optical upper limit
  54. GRB 250615A / EP250615a: AstroSat CZTI detection
  55. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  56. GRB 250615A: COLIBRÍ optical upper limit
  57. GRB 250615A: DDOTI Optical Upper Limit
  58. GRB 250615A: Swift/UVOT Upper Limits
  59. sb25061207/SVOM: T120 OHP optical upper limit
  60. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  61. GRB 250615A: Enhanced Swift-XRT position
  62. GRB 250615A: Swift detection of a burst
  63. sb25061207: Mephisto optical upper limits
  64. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  65. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  66. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  67. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  68. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  69. sb25061207: EP-FXT follow-up observation and afterglow candidate
  70. EP250612a: SVOM/VT optical candidate
  71. sb25061218: SVOM detection of a X-ray transient
  72. EP250612a/GRB 250612B: JinShan optical upper limit
  73. sb25061207: SVOM/VT optical counterpart
  74. GRB 250610B: Swift-XRT refined Analysis
  75. EP250612a: Einstein Probe detection of an X-ray transient
  76. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  77. sb25061207: SVOM detection of a X-ray transient
  78. GRB 250610B: Swift/UVOT Detection
  79. EP250610A: Swift/UVOT Upper limits
  80. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  81. EP250610a: TNG NIR upper limit
  82. GRB 250610B: REM optical/NIR observations
  83. EP250610a: Liverpool Telescope optical upper limits
  84. GRB 250610B: additional Liverpool Telescope optical observations
  85. GRB 250610B: SVOM/VT optical counterpart
  86. GRB 250610B: OHP/T120 optical counterpart candidate
  87. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  88. GRB 250610B: SVOM detection of a long burst
  89. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  90. EP250610a: SVOM/VT optical upper limit
  91. EP250610a: REM optical/NIR observations
  92. EP250610a: COLIBRÍ optical upper limit
  93. EP250610a: Einstein Probe detection of an X-ray transient
  94. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  95. GRB 250605A: Swift/UVOT Upper Limits
  96. GRB 250527C: CrAO Optical Upper Limit
  97. GRB 250607A: SVOM/GRM observation of a long burst
  98. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  99. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  100. The EP-WXT trigger 01709178069 is likely a flaring star

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