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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"

32510 results found.

  1. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  2. GRB 250717B: Swift ToO observations
  3. GRB 270713A: Kitab and AbAO Optical Observations
  4. GRB 250717B: Fermi GBM Observation
  5. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  6. Konus-Wind detection of GRB 250716A
  7. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  8. GRB 250716A: Swift ToO observations
  9. GRB 250714A: SVOM/GRM observation
  10. Fermi GRB 250716A: Global MASTER-Net observations report
  11. Fermi GRB 250715A: Global MASTER-Net observations report
  12. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  13. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  14. GRB 250713A: Mephisto optical upper limits
  15. Fermi GRB 250714A: Global MASTER-Net observations report
  16. GRB 250713A: SVOM/VT optical upper limit
  17. GRB 250713A: NOT optical upper limits
  18. GRB 250713A: OHP/T193 upper limit
  19. GRB 250713A: SVOM/C-GFT upper limit
  20. GRB 250706B/C: 7DT Follow-up Observations
  21. GRB 250713A: EP-FXT counterpart detection
  22. EP250711a: COLIBRÍ continuous optical observations
  23. GRB 250706A: Swift-BAT refined analysis
  24. GRB 250702F: Swift-BAT refined analysis
  25. GRB 250628A: Swift-BAT refined analysis
  26. LIGO/Virgo/KAGRA S250712cd: Updated Sky localization
  27. GRB 250713A: JinShan optical upper limits
  28. EP250711a: Global MASTER-Net observations report
  29. GRB 250711A: DDOTI Optical Upper Limit
  30. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  31. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  32. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  33. GRB 250711A: SVOM/GRM observation
  34. EP250711a: NOT optical counterpart candidate
  35. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  36. Fermi GRB 250711A: Global MASTER-Net observations report
  37. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  38. GRB 250704A: GRANDMA observations
  39. GRB 250704A: SVOM/ECLAIRs refined analysis
  40. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  41. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  42. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  43. GRB 250702B,D,E / EP250702a: ALMA detection
  44. IceCube-250708A: No Candidates from WINTER
  45. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  46. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  47. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  48. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  49. GRB 250706B/C: Insight-HXMT detection
  50. EP/WXT 01709181970: GOTO observations confirm stellar variability
  51. EP250704a/GRB 250704B: 10 GHz VLA detection
  52. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  53. IceCube-250706A: No Candidates from WINTER
  54. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  55. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  56. GRB 250704B / EP250704a: VLA radio detection
  57. Fermi GRB 250708A: Global MASTER-Net observations report
  58. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  59. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  60. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  61. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  62. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  63. EP250704a/GRB250704B : HCT optical and NIR upper limits
  64. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  65. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  66. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  67. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  68. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  69. GRB 250702F: radio detection with the VLA
  70. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  71. IceCube-250706A: EP-FXT follow-up observations
  72. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  73. GRB 250706B/C: Fermi-LAT detection
  74. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  76. GRB 250706B: Swift/UVOT Detection
  77. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  78. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  79. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  80. GRB 250702F: GRANDMA observations
  81. GRB 250706B: refined SVOM/MXT data analysis
  82. GRB 250706A: Swift/UVOT Upper Limits
  83. GRB 250706B: REM optical observations
  84. GRB 250706A: REM optical/NIR observations
  85. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  86. IceCube-250416A: DDOTI Optical Upper Limit
  87. IceCube-250706A: COLIBRÍ optical upper limits
  88. Swift GRB 250706A: Global MASTER-Net observations report
  89. GRB 250706A: JinShan optical upper limits
  90. GRB 250706A: SAO RAS optical observations
  91. EP250704A: NOWT Detection
  92. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  93. GRB250706B: Swift-XRT counterpart detection
  94. GRB 250706B: iTelescope optical observations
  95. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  96. GRB 250706B: SVOM/VT optical observation
  97. GRB 250706B: TRT bright optical counterpart detection
  98. GRB 250706A: GROWTH-India Telescope optical upper limit
  99. GRBs 250702B,C,D,E / EP250702a: J band upper limit by SYSU 80cm infrared telescope
  100. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart

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