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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"

23627 results found.

  1. GRB 250727A: SVOM detection of a burst
  2. LIGO/Virgo/KAGRA S250725l: Updated Sky localization
  3. LIGO/Virgo/KAGRA S250726ak: Updated Sky localization
  4. The EP-WXT trigger 01709195487 is likely a flaring star
  5. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  6. GRB 250725A: Fermi GBM Observation
  7. LIGO/Virgo/KAGRA S250725j: Updated Sky localization
  8. GRB 250725A: Swift-BAT refined analysis
  9. Konus-Wind detection of GRB 250725A
  10. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  11. GRB 250725A: SVOM/GRM observation
  12. GRB 250725A: Fermi-LAT detection
  13. GRB 250725A: BOOTES-7 early optical detection
  14. GRB 250725A: SVOM/VT optical candidate
  15. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  16. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  17. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  18. Swift GRB 250725A: Global MASTER-Net OT detection
  19. GRB 250725A: Fermi GBM Final Real-time Localization
  20. Fermi GRB 250725A: Global MASTER-Net observations report
  21. Swift GRB 250725A: Global MASTER-Net observations report
  22. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  23. SVOM J195836+32283 is not a real source
  24. SVOM J195836+32283/sb25072103: Second VT observation
  25. GRB 250723B: Fermi GBM Final Real-time Localization
  26. GRB 250721A: Fermi GBM Observation
  27. GRB 250723A: Fermi GBM Final Real-time Localization
  28. GRB 250721A: Swift-XRT observations
  29. GRB 250722A: Fermi GBM Final Real-time Localization
  30. GRB 250713A : SVOM/ECLAIRs refined analysis
  31. GRB 250717B: SVOM/GRM observation
  32. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  33. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  34. GRB 250721A: Fermi GBM Final Localization
  35. GRB 250720B: Fermi GBM Final Localization Correction
  36. GRB 250720A: Fermi GBM Final Localization
  37. Fermi trigger No 774730635: Global MASTER-Net observations report
  38. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  39. GRB 250717B: COLIBRÍ optical upper limit
  40. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  41. GRB 250717B: Swift-XRT observations
  42. GRB 250718B: Fermi GBM Final Localization Correction
  43. GRB 250718B: Fermi GBM Final Real-time Localization
  44. Swift GRB250718.01: Global MASTER-Net observations report
  45. GRB 270713A: Kitab and AbAO Optical Observations
  46. GRB 250717B: Fermi GBM Observation
  47. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  48. Konus-Wind detection of GRB 250716A
  49. GRB 250717B: Fermi GBM Final Real-time Localization
  50. GRB 250717A: Fermi GBM Final Real-time Localization
  51. GRB 250716A: GOTO tentative optical counterpart candidate
  52. GRB 250716A: Fermi GBM Observation
  53. Fermi GRB 250716A: Global MASTER-Net observations report
  54. GRB 250716A: Fermi GBM Final Real-time Localization
  55. Fermi GRB 250715A: Global MASTER-Net observations report
  56. GRB 250715A: Fermi GBM Final Real-time Localization
  57. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  58. GRB 250713A: Mephisto optical upper limits
  59. Fermi GRB 250714A: Global MASTER-Net observations report
  60. GRB 250713A: SVOM/VT optical upper limit
  61. GRB 250713A: SVOM/C-GFT upper limit
  62. GRB 250714A: Fermi GBM Final Real-time Localization
  63. GRB 250713A: EP-FXT counterpart detection
  64. GRB 250706A: Swift-BAT refined analysis
  65. GRB 250702F: Swift-BAT refined analysis
  66. GRB 250628A: Swift-BAT refined analysis
  67. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  68. GRB 250713A: SVOM detection of a long burst
  69. EP250711a: Global MASTER-Net observations report
  70. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  71. GRB 250711A: SVOM/GRM observation
  72. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  73. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  74. Fermi GRB 250711A: Global MASTER-Net observations report
  75. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  76. GRB 250711A: Fermi GBM Final Real-time Localization
  77. GRB 250704A: SVOM/ECLAIRs refined analysis
  78. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  79. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  80. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  81. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  82. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  83. IceCube-250708A: No Candidates from WINTER
  84. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  85. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  86. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 250709A: Fermi GBM Final Localization
  88. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  89. EP/WXT 01709181970: GOTO observations confirm stellar variability
  90. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  91. EP250704a/GRB 250704B: 10 GHz VLA detection
  92. The EP-WXT trigger 01709181970 is likely a flaring star
  93. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  94. IceCube-250706A: No Candidates from WINTER
  95. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  96. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  97. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  98. GRB 250704B / EP250704a: VLA radio detection
  99. Fermi GRB 250708A: Global MASTER-Net observations report
  100. IceCube-250708A: Global MASTER-Net observations report

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