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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 GRB 250716A: Global MASTER-Net observations report
  2. GRB 250716A: Fermi GBM Final Real-time Localization
  3. Fermi GRB 250715A: Global MASTER-Net observations report
  4. GRB 250715A: Fermi GBM Final Real-time Localization
  5. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  6. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  7. GRB 250713A: Mephisto optical upper limits
  8. Fermi GRB 250714A: Global MASTER-Net observations report
  9. GRB 250713A: SVOM/VT optical upper limit
  10. GRB 250713A: NOT optical upper limits
  11. GRB 250713A: OHP/T193 upper limit
  12. GRB 250713A: SVOM/C-GFT upper limit
  13. GRB 250714A: Fermi GBM Final Real-time Localization
  14. GRB 250706B/C: 7DT Follow-up Observations
  15. GRB 250713A: Swift-XRT observations
  16. GRB 250713A: EP-FXT counterpart detection
  17. EP250711a: COLIBRÍ continuous optical observations
  18. GRB 250706A: Swift-BAT refined analysis
  19. GRB 250702F: Swift-BAT refined analysis
  20. GRB 250628A: Swift-BAT refined analysis
  21. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  22. GRB 250713A: JinShan optical upper limits
  23. GRB 250713A: SVOM detection of a long burst
  24. EP250711a: Global MASTER-Net observations report
  25. GRB 250711A: DDOTI Optical Upper Limit
  26. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  27. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  28. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  29. GRB 250711A: SVOM/GRM observation
  30. EP250711a: NOT optical counterpart candidate
  31. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  32. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  33. Fermi GRB 250711A: Global MASTER-Net observations report
  34. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  35. GRB 250704A: GRANDMA observations
  36. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  37. GRB 250711A: Fermi GBM Final Real-time Localization
  38. GRB 250704A: SVOM/ECLAIRs refined analysis
  39. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  40. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  41. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  42. GRB 250702B,D,E / EP250702a: ALMA detection
  43. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  44. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  45. IceCube-250708A: No Candidates from WINTER
  46. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  47. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  48. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  49. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  50. GRB 250709A: Fermi GBM Final Localization
  51. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  52. GRB 250706B/C: Insight-HXMT detection
  53. EP/WXT 01709181970: GOTO observations confirm stellar variability
  54. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  55. EP250704a/GRB 250704B: 10 GHz VLA detection
  56. The EP-WXT trigger 01709181970 is likely a flaring star
  57. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  58. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  59. IceCube-250706A: No Candidates from WINTER
  60. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  61. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  62. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  63. GRB 250704B / EP250704a: VLA radio detection
  64. Fermi GRB 250708A: Global MASTER-Net observations report
  65. IceCube-250708A: Global MASTER-Net observations report
  66. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  67. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  68. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  69. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  70. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  71. EP250704a/GRB250704B : HCT optical and NIR upper limits
  72. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  73. GRB 250708A: Fermi GBM Final Real-time Localization
  74. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  75. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  76. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  77. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  78. GRB 250702F: radio detection with the VLA
  79. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  80. IceCube-250706A: EP-FXT follow-up observations
  81. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  82. GRB 250706B/C: Fermi-LAT detection
  83. IceCube-250706A: Global MASTER-Net observations report
  84. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  85. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  86. GRB 250706B: Swift/UVOT Detection
  87. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  88. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  89. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  90. GRB 250702F: GRANDMA observations
  91. GRB 250706A: Swift-XRT refined Analysis
  92. GRB 250706B: refined SVOM/MXT data analysis
  93. GRB 250706A: Swift/UVOT Upper Limits
  94. GRB 250706B: REM optical observations
  95. GRB 250706A: REM optical/NIR observations
  96. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  97. IceCube-250416A: DDOTI Optical Upper Limit
  98. IceCube-250706A: COLIBRÍ optical upper limits
  99. Swift GRB 250706A: Global MASTER-Net observations report
  100. GRB 250706A: JinShan optical upper limits

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