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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"

18846 results found.

  1. GRB 251013C: Asiago optical observations
  2. GRB 251013C: ABObservatory optical observations
  3. GRB 251014A: SAO RAS optical upper limit
  4. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  5. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  6. GRB 251013C: DDOTI detection of the optical afterglow
  7. GRB 251013C: SAO RAS optical observations
  8. GRB 251013C: LCO optical afterglow detection
  9. GRB 251013C: NOT spectroscopic redshift z = 0.572
  10. GRB 251013C: LAST detection of optical counterpart
  11. GRB 251013C: SVOM/VT optical observation
  12. GRB 251013C: SVOM detection of a burst
  13. GRB 251013B: SVOM/GRM observation
  14. GRB 251013A: SVOM/GRM observation
  15. GRB 251003A: Mondy optical upper limit
  16. MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
  17. LIGO/Virgo/KAGRA S251013x: Identification of a GW compact binary merger candidate
  18. GRB 251011B inspection: MASTER orphan GRB detection
  19. GRB 251011B: Swift/UVOT Upper Limits
  20. GRB 251011B: SVOM/GRM observation
  21. GRB 251011B : MASTER optical observations
  22. GRB 251011B: Enhanced Swift-XRT position
  23. GRB 251010A: AstroSat CZTI detection
  24. GRB 251011B: Swift detection of a burst
  25. GRB 251007B: Swift/UVOT Upper Limits
  26. GRB251007A: Swift/UVOT Detection
  27. GRB 251007A: SVOM/GRM observation
  28. GRB 251007B - SVOM/ECLAIRs refined analysis
  29. SVOM/sb25101004: SVOM detection of a stellar flare
  30. GRB 251002A - SVOM/ECLAIRs refined analysis
  31. GRB 251007B: COLIBRÍ optical upper limit
  32. GRB 251007A: AstroSat CZTI detection
  33. GRB 250917B: iTelescope T-26 upper limit
  34. GRB 251007A: Enhanced Swift-XRT position
  35. GRB 251007B: Enhanced Swift-XRT position
  36. GRB 251007A: AKO Optical Upper Limit
  37. GRB 251007A: SVOM/C-GFT optical observations
  38. GRB 251005C: PRIME J-band upper limit
  39. GRB 251007B: SVOM/C-GFT upper limit
  40. GRB 251007B: Swift detection of a burst
  41. GRB 251007A: Swift detection of a burst with an optical counterpart
  42. GRB 250702B/EP250702a: JWST/NIRCam Observations
  43. GRB 251006A: Swift/BAT-GUANO subthreshold detection of a short burst
  44. GRB 251006B: SVOM/GRM observation
  45. GRB 251006B: COLIBRÍ optical upper limit
  46. GRB 251006B/EP251006a: EP-WXT detection
  47. GRB 251005C: SVOM/VT optical fading
  48. GRB 251005C: SVOM/GRM observation of a likely short GRB
  49. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  50. GRB 251005C: COLIBRÍ optical observations
  51. Fermi GRB 251006A: Global MASTER-Net observations report
  52. GRB 251005C: VLT/X-shooter Imaging
  53. GRB 251003A: LAST optical observations
  54. GRB 251002A: LAST optical observations
  55. GRB 251005​C: Swift/UVOT Upper Limits
  56. GRB 251005C: Swift-XRT refined Analysis
  57. GRB 251005C: Enhanced Swift-XRT position
  58. GRB 251005C: Swift detection of a burst
  59. GRB 251002A: Mondy/AZT-33IK optical observations
  60. EP251003a: Einstein Probe detection of an X-ray transient
  61. GRB 251003A: J-band detection with WINTER
  62. GRB 251002A: NIR observations with WINTER
  63. GRB 251001B: NIR observations with WINTER
  64. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  65. GRB 251003A: Swift/UVOT Upper Limits
  66. GRB 251002A: Swift/UVOT detection
  67. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  68. GRB 251002A: GOTO detection of optical counterpart
  69. GRB 251001C: SVOM/GRM observation
  70. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  71. GRB 251003A: Enhanced Swift-XRT position
  72. GRB 251002A: AKO Early Optical Afterglow Detection
  73. GRB 251003A: Kilonova-Catcher optical afterglow detection
  74. GRB 251002A: Swift-XRT afterglow detection
  75. GRB 251001B: AbAO optical upper limit
  76. GRB 251002A: Kilonova-Catcher optical afterglow detection
  77. GRB 251002A: AbAO optical observations
  78. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  80. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  81. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  82. GRB 251003A: LCOGT Optical Detection
  83. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  84. GRB 251003A: Swift detection of a burst
  85. GRB 251002A: SAO RAS optical observations
  86. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  87. GRB 251002A: LCO optical observation
  88. GRB 251002A: SVOM/VT optical observation
  89. GRB 251002A: SVOM detection of a burst
  90. GRB 251001A: SVOM/GRM observation
  91. GRB 251001B: Swift/UVOT Detection
  92. GRB 251001B: COLIBRÍ optical observations
  93. GRB 251001B: Swift-XRT refined Analysis
  94. GRB 251001B: SVOM/VT optical observation
  95. GRB 251001B: NOT optical observations
  96. GRB 251001B: Enhanced Swift-XRT position
  97. GRB 251001B: LCOGT Optical Observations
  98. GRB 250930A: SVOM/GRM observation
  99. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  100. GRB 251001B: Swift detection of a burst

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