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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. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  2. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  3. GRB 250717B: COLIBRÍ optical upper limit
  4. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  5. GRB 250717B: Swift-XRT observations
  6. GRB 250718B: Fermi GBM Final Localization Correction
  7. GRB 250718B: Fermi GBM Final Real-time Localization
  8. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  9. Swift Trigger 1334535: a possible GRB 250718A
  10. Swift GRB250718.01: Global MASTER-Net observations report
  11. GRB 250717B: Swift ToO observations
  12. GRB 270713A: Kitab and AbAO Optical Observations
  13. GRB 250717B: Fermi GBM Observation
  14. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  15. Konus-Wind detection of GRB 250716A
  16. GRB 250716A: Swift-XRT afterglow detection
  17. GRB 250717B: Fermi GBM Final Real-time Localization
  18. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  19. GRB 250717A: Fermi GBM Final Real-time Localization
  20. GRB 250716A: Swift ToO observations
  21. GRB 250716A: GOTO tentative optical counterpart candidate
  22. GRB 250716A: Fermi GBM Observation
  23. GRB 250714A: SVOM/GRM observation
  24. Fermi GRB 250716A: Global MASTER-Net observations report
  25. GRB 250716A: Fermi GBM Final Real-time Localization
  26. Fermi GRB 250715A: Global MASTER-Net observations report
  27. GRB 250715A: Fermi GBM Final Real-time Localization
  28. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  29. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  30. GRB 250713A: Mephisto optical upper limits
  31. Fermi GRB 250714A: Global MASTER-Net observations report
  32. GRB 250713A: SVOM/VT optical upper limit
  33. GRB 250713A: NOT optical upper limits
  34. GRB 250713A: OHP/T193 upper limit
  35. GRB 250713A: SVOM/C-GFT upper limit
  36. GRB 250714A: Fermi GBM Final Real-time Localization
  37. GRB 250706B/C: 7DT Follow-up Observations
  38. GRB 250713A: Swift-XRT observations
  39. GRB 250713A: EP-FXT counterpart detection
  40. EP250711a: COLIBRÍ continuous optical observations
  41. GRB 250706A: Swift-BAT refined analysis
  42. GRB 250702F: Swift-BAT refined analysis
  43. GRB 250628A: Swift-BAT refined analysis
  44. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  45. GRB 250713A: JinShan optical upper limits
  46. GRB 250713A: SVOM detection of a long burst
  47. EP250711a: Global MASTER-Net observations report
  48. GRB 250711A: DDOTI Optical Upper Limit
  49. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  50. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  51. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  52. GRB 250711A: SVOM/GRM observation
  53. EP250711a: NOT optical counterpart candidate
  54. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  55. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  56. Fermi GRB 250711A: Global MASTER-Net observations report
  57. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  58. GRB 250704A: GRANDMA observations
  59. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  60. GRB 250711A: Fermi GBM Final Real-time Localization
  61. GRB 250704A: SVOM/ECLAIRs refined analysis
  62. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  63. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  64. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  65. GRB 250702B,D,E / EP250702a: ALMA detection
  66. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  67. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  68. IceCube-250708A: No Candidates from WINTER
  69. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  70. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  71. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  72. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  73. GRB 250709A: Fermi GBM Final Localization
  74. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  75. GRB 250706B/C: Insight-HXMT detection
  76. EP/WXT 01709181970: GOTO observations confirm stellar variability
  77. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  78. EP250704a/GRB 250704B: 10 GHz VLA detection
  79. The EP-WXT trigger 01709181970 is likely a flaring star
  80. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  81. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  82. IceCube-250706A: No Candidates from WINTER
  83. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  84. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  85. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 250704B / EP250704a: VLA radio detection
  87. Fermi GRB 250708A: Global MASTER-Net observations report
  88. IceCube-250708A: Global MASTER-Net observations report
  89. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  90. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  91. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  92. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  93. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  94. EP250704a/GRB250704B : HCT optical and NIR upper limits
  95. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  96. GRB 250708A: Fermi GBM Final Real-time Localization
  97. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  98. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  99. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  100. GRB 250704B / EP250704a: Mondy and AbAO optical observations

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