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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"

7396 results found.

  1. GRB 251005C: Swift detection of a burst
  2. LIGO/Virgo/KAGRA S251003at: Retraction of GW compact binary merger candidate
  3. GRB 251002A: Swift-XRT afterglow detection
  4. GRB 251003A: 1.5m OSN afterglow candidate
  5. GRB 251003A: Swift detection of a burst
  6. GRB 251002A: SVOM/VT optical observation
  7. GRB 251001B: Swift detection of a burst
  8. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  9. LIGO/Virgo/KAGRA S250929c: Updated Sky localization
  10. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  11. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  12. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  13. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  15. IceCube-250926A - IceCube observation of a high-energy neutrino candidate track-like event
  16. GRB250925A: Liverpool Telescope optical observations
  17. GRB 250925A: NOT optical afterglow candidate
  18. GRB 250925A: Leavitt Observatory optical upper limit
  19. GRB 250924A: 1.6m Mephisto optical upper limits
  20. GRB 250924A: Swift detection of a burst with an optical counterpart
  21. GRB 250920C: COLIBRÍ optical observations
  22. GRB 250920B: NIR observations with WINTER
  23. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  24. GRB250920C: LCOGT Optical Detection
  25. GRB 250920C: GOTO optical counterpart candidate
  26. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  27. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  28. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  29. GRB 250916A: NuSTAR detection of the prompt emission
  30. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  31. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  32. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  33. GRB 250916A: Swift ToO observations
  34. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  35. GRB 250917B: Swift detection of a short burst
  36. GRB 250916A: GOTO optical counterpart candidate
  37. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  38. GRB 250912A: VLT observations
  39. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  40. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  41. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  42. LIGO/Virgo/KAGRA S250912f: Updated Sky localization
  43. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  44. EP250911a: Optical detection with Kinder observations
  45. LIGO/Virgo/KAGRA S250911ac: Updated Sky localization and Source Classification
  46. LIGO/Virgo/KAGRA S250908y: Updated Sky localization
  47. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  48. GRB 250911A: COLIBRÍ optical counterpart candidate
  49. LIGO/Virgo/KAGRA S250906ca: Updated Sky localization
  50. GRB 250910A: SVOM/VT optical upper limit
  51. EP250908C: GROND observation of the fading optical counterpart
  52. LIGO/Virgo/KAGRA S250910b: Retraction of GW compact binary merger candidate
  53. EP#01709240653: Swift-XRT observations
  54. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  55. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  56. EP250908b: SVOM/VT optical candidate
  57. LIGO/Virgo/KAGRA S250908y: Identification of a GW compact binary merger candidate
  58. LIGO/Virgo/KAGRA S250906ca: Identification of a GW compact binary merger candidate
  59. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  60. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  61. IceCube-250905A - IceCube observation of a high-energy neutrino candidate track-like event
  62. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  63. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  64. EP detected a brightening of LMXB 1ES 1735-26.9
  65. GRB 250905A: KAIT optical upper limit
  66. GRB 250905A: Swift detection of a burst
  67. GRB 250904A: Swift detection of a burst
  68. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  69. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  70. GRB 250903A: Swift-XRT observations
  71. EP250903a: Swift-XRT observations
  72. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  73. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  75. EP250903a: LCO candidate counterpart discovery
  76. EP/WXT01709201159: GOTO optical follow-up
  77. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  78. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  79. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  80. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  81. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  82. EP250831a: NOT optical observations and tentative afterglow candidate
  83. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  84. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  85. IceCube-250831A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 250831A: Swift-XRT counterpart detection
  87. GRB 250831A: SVOM/VT upper limit with VHF data
  88. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  89. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  90. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  91. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  92. GRB 250830B: Swift ToO observations
  93. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  94. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  95. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  96. EP250828a: Optical counterpart detection with Kinder observations
  97. EP250828a: Liverpool Telescope upper limits
  98. EP250828a: NOT optical counterpart confirmation
  99. EP250828a: SVOM/VT optical candidate
  100. EP250828a: Optical upper limit with Kinder observations

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