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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"

7398 results found.

  1. GRB 250728A: Swift ToO observations
  2. LIGO/Virgo/KAGRA S250727cl: Updated Sky localization
  3. GRB 250727A: EP-FXT counterpart detection
  4. GRB 250727A: Swift-XRT observations
  5. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  6. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  8. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  9. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  10. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  11. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  12. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  13. GRB 250725A: SVOM/VT optical candidate
  14. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate (duplicate submission)
  15. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  17. GRB 250725A: Swift detection of a burst
  18. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  19. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  20. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  21. GRB 250721A: Tiled Swift observations
  22. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  23. GRB 250717B: COLIBRÍ optical upper limit
  24. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  25. GRB 250717B: Swift ToO observations
  26. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  27. GRB 250716A: Swift ToO observations
  28. GRB 250716A: GOTO tentative optical counterpart candidate
  29. GRB 250713A: SVOM/VT optical upper limit
  30. GRB 250713A: SVOM/C-GFT upper limit
  31. GRB 250713A: EP-FXT counterpart detection
  32. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  33. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  34. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  35. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  36. EP250711a: NOT optical counterpart candidate
  37. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  38. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  40. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  41. IceCube-250708A: No Candidates from WINTER
  42. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  43. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  44. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  45. IceCube-250706A: No Candidates from WINTER
  46. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  47. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  48. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  49. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  50. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  51. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  52. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  53. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  54. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  55. GRB250706B: Swift-XRT counterpart detection
  56. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  57. GRB 250706B: SVOM/VT optical observation
  58. GRB 250706A: Swift detection of a burst
  59. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  60. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  62. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  63. EP250704a / GRB250704B: Swift-XRT counterpart detection
  64. EP250704a / GRB 250704B - REM observations
  65. EP250704a: COLIBRÍ optical counterpart candidate
  66. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  67. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  68. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  69. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  70. GRB 250702F: Swift detection of a burst with an optical counterpart
  71. LIGO/Virgo/KAGRA S250702n: Identification of a GW compact binary merger candidate
  72. LIGO/Virgo/KAGRA S250701bq: Identification of a GW compact binary merger candidate
  73. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  74. GRB 250628B: Swift-XRT observations
  75. LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
  76. LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
  77. LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
  78. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate (duplicate submission)
  79. LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S250628am: Updated Sky localization
  81. LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
  82. GRB 250628A: Swift detection of a burst
  83. GRB 250625A: Swift detection of a burst
  84. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  85. GRB 250617B: Swift detection of a burst with an optical counterpart
  86. EP#01709178975: Swift-XRT counterpart detection
  87. EP-WXT trigger 01709178975: GOTO optical upper limit
  88. GRB 250615A: Swift detection of a burst
  89. IceCube alert 141029_8144692 retraction
  90. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  91. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. sb25061218: Swift-XRT observations
  93. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  94. sb25061207: EP-FXT follow-up observation and afterglow candidate
  95. EP250612a: SVOM/VT optical candidate
  96. sb25061207: Swift-XRT observations
  97. sb25061207: SVOM/VT optical counterpart
  98. EP250610a: TNG NIR upper limit
  99. GRB 250610B: OHP/T120 optical counterpart candidate
  100. GRB 250610B : SVOM/GWAC-F60A and F50 observations

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