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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"
  1. LIGO/Virgo/KAGRA S250711q: Updated Sky localization
  2. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  3. GRB 250721A: Tiled Swift observations
  4. GRB 250721A: MAXI/GSC detection
  5. GRB 250721A: Fermi GBM Final Localization
  6. GRB 250720B: Fermi GBM Final Localization Correction
  7. GRB 250720A: Fermi GBM Final Localization
  8. Fermi trigger No 774730635: Global MASTER-Net observations report
  9. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  10. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  11. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  12. GRB 250717B: COLIBRÍ optical upper limit
  13. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  14. GRB 250717B: Swift-XRT observations
  15. GRB 250718B: Fermi GBM Final Localization Correction
  16. GRB 250718B: Fermi GBM Final Real-time Localization
  17. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  18. Swift Trigger 1334535: a possible GRB 250718A
  19. Swift GRB250718.01: Global MASTER-Net observations report
  20. GRB 250717B: Swift ToO observations
  21. GRB 270713A: Kitab and AbAO Optical Observations
  22. GRB 250717B: Fermi GBM Observation
  23. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  24. Konus-Wind detection of GRB 250716A
  25. GRB 250716A: Swift-XRT afterglow detection
  26. GRB 250717B: Fermi GBM Final Real-time Localization
  27. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  28. GRB 250717A: Fermi GBM Final Real-time Localization
  29. GRB 250716A: Swift ToO observations
  30. GRB 250716A: GOTO tentative optical counterpart candidate
  31. GRB 250716A: Fermi GBM Observation
  32. GRB 250714A: SVOM/GRM observation
  33. Fermi GRB 250716A: Global MASTER-Net observations report
  34. GRB 250716A: Fermi GBM Final Real-time Localization
  35. Fermi GRB 250715A: Global MASTER-Net observations report
  36. GRB 250715A: Fermi GBM Final Real-time Localization
  37. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  38. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  39. GRB 250713A: Mephisto optical upper limits
  40. Fermi GRB 250714A: Global MASTER-Net observations report
  41. GRB 250713A: SVOM/VT optical upper limit
  42. GRB 250713A: NOT optical upper limits
  43. GRB 250713A: OHP/T193 upper limit
  44. GRB 250713A: SVOM/C-GFT upper limit
  45. GRB 250714A: Fermi GBM Final Real-time Localization
  46. GRB 250706B/C: 7DT Follow-up Observations
  47. GRB 250713A: Swift-XRT observations
  48. GRB 250713A: EP-FXT counterpart detection
  49. EP250711a: COLIBRÍ continuous optical observations
  50. GRB 250706A: Swift-BAT refined analysis
  51. GRB 250702F: Swift-BAT refined analysis
  52. GRB 250628A: Swift-BAT refined analysis
  53. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  54. GRB 250713A: JinShan optical upper limits
  55. GRB 250713A: SVOM detection of a long burst
  56. EP250711a: Global MASTER-Net observations report
  57. GRB 250711A: DDOTI Optical Upper Limit
  58. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  59. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  60. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  61. GRB 250711A: SVOM/GRM observation
  62. EP250711a: NOT optical counterpart candidate
  63. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  64. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  65. Fermi GRB 250711A: Global MASTER-Net observations report
  66. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  67. GRB 250704A: GRANDMA observations
  68. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  69. GRB 250711A: Fermi GBM Final Real-time Localization
  70. GRB 250704A: SVOM/ECLAIRs refined analysis
  71. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  72. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  73. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  74. GRB 250702B,D,E / EP250702a: ALMA detection
  75. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  76. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  77. IceCube-250708A: No Candidates from WINTER
  78. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  79. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  80. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  81. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  82. GRB 250709A: Fermi GBM Final Localization
  83. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  84. GRB 250706B/C: Insight-HXMT detection
  85. EP/WXT 01709181970: GOTO observations confirm stellar variability
  86. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  87. EP250704a/GRB 250704B: 10 GHz VLA detection
  88. The EP-WXT trigger 01709181970 is likely a flaring star
  89. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  90. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  91. IceCube-250706A: No Candidates from WINTER
  92. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  93. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  94. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  95. GRB 250704B / EP250704a: VLA radio detection
  96. Fermi GRB 250708A: Global MASTER-Net observations report
  97. IceCube-250708A: Global MASTER-Net observations report
  98. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  99. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  100. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification

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