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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"

45416 results found.

  1. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  3. GRB 250725A: Enhanced Swift-XRT position
  4. GRB 250725A: Swift detection of a burst
  5. Swift GRB 250725A: Global MASTER-Net OT detection
  6. GRB 250725A: Fermi GBM Final Real-time Localization
  7. Fermi GRB 250725A: Global MASTER-Net observations report
  8. Swift GRB 250725A: Global MASTER-Net observations report
  9. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  10. SVOM J195836+32283 is not a real source
  11. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  12. SVOM J195836+32283/sb25072103: Second VT observation
  13. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  14. GRB 250723B: Fermi GBM Final Real-time Localization
  15. GRB 250721A: Fermi GBM Observation
  16. GRB 250723A: Fermi GBM Final Real-time Localization
  17. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  18. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  19. Swift-BAT trigger 1334535 is not a GRB
  20. GRB 250721A: Swift-XRT observations
  21. GRB 250722A: Fermi GBM Final Real-time Localization
  22. GRB 250713A : SVOM/ECLAIRs refined analysis
  23. GRB 250717B: SVOM/GRM observation
  24. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  25. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  26. GRB 250721A: Tiled Swift observations
  27. GRB 250721A: MAXI/GSC detection
  28. GRB 250721A: Fermi GBM Final Localization
  29. GRB 250720B: Fermi GBM Final Localization Correction
  30. GRB 250720A: Fermi GBM Final Localization
  31. Fermi trigger No 774730635: Global MASTER-Net observations report
  32. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  33. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  34. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  35. GRB 250717B: COLIBRÍ optical upper limit
  36. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  37. GRB 250717B: Swift-XRT observations
  38. GRB 250718B: Fermi GBM Final Localization Correction
  39. GRB 250718B: Fermi GBM Final Real-time Localization
  40. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  41. Swift Trigger 1334535: a possible GRB 250718A
  42. Swift GRB250718.01: Global MASTER-Net observations report
  43. GRB 250717B: Swift ToO observations
  44. GRB 270713A: Kitab and AbAO Optical Observations
  45. GRB 250717B: Fermi GBM Observation
  46. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  47. Konus-Wind detection of GRB 250716A
  48. GRB 250716A: Swift-XRT afterglow detection
  49. GRB 250717B: Fermi GBM Final Real-time Localization
  50. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  51. GRB 250717A: Fermi GBM Final Real-time Localization
  52. GRB 250716A: Swift ToO observations
  53. GRB 250716A: GOTO tentative optical counterpart candidate
  54. GRB 250716A: Fermi GBM Observation
  55. GRB 250714A: SVOM/GRM observation
  56. Fermi GRB 250716A: Global MASTER-Net observations report
  57. GRB 250716A: Fermi GBM Final Real-time Localization
  58. Fermi GRB 250715A: Global MASTER-Net observations report
  59. GRB 250715A: Fermi GBM Final Real-time Localization
  60. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  61. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  62. GRB 250713A: Mephisto optical upper limits
  63. Fermi GRB 250714A: Global MASTER-Net observations report
  64. GRB 250713A: SVOM/VT optical upper limit
  65. GRB 250713A: NOT optical upper limits
  66. GRB 250713A: OHP/T193 upper limit
  67. GRB 250713A: SVOM/C-GFT upper limit
  68. GRB 250714A: Fermi GBM Final Real-time Localization
  69. GRB 250706B/C: 7DT Follow-up Observations
  70. GRB 250713A: Swift-XRT observations
  71. GRB 250713A: EP-FXT counterpart detection
  72. EP250711a: COLIBRÍ continuous optical observations
  73. GRB 250706A: Swift-BAT refined analysis
  74. GRB 250702F: Swift-BAT refined analysis
  75. GRB 250628A: Swift-BAT refined analysis
  76. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  77. GRB 250713A: JinShan optical upper limits
  78. GRB 250713A: SVOM detection of a long burst
  79. EP250711a: Global MASTER-Net observations report
  80. GRB 250711A: DDOTI Optical Upper Limit
  81. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  82. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  83. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  84. GRB 250711A: SVOM/GRM observation
  85. EP250711a: NOT optical counterpart candidate
  86. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  87. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  88. Fermi GRB 250711A: Global MASTER-Net observations report
  89. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  90. GRB 250704A: GRANDMA observations
  91. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  92. GRB 250711A: Fermi GBM Final Real-time Localization
  93. GRB 250704A: SVOM/ECLAIRs refined analysis
  94. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  95. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  96. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  97. GRB 250702B,D,E / EP250702a: ALMA detection
  98. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  99. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  100. IceCube-250708A: No Candidates from WINTER

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