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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"

20960 results found.

  1. GRB 250702B: SMA observations
  2. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  3. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  4. EP250711a: CrAO and Assy optical observations
  5. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  6. EP250730a: Global MASTER-Net observations report
  7. EP250730a: Einstein Probe detection of an X-ray transient
  8. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  9. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  10. GRB 250725A: PRIME near-infrared observations
  11. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  12. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  13. GRB 250728A: Swift-XRT observations
  14. GRB 250727A: SVOM/ECLAIRs refined analysis
  15. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  16. GRB 250728A: COLIBRÍ optical upper limit
  17. Fermi trigger No 775387550: Global MASTER-Net observations report
  18. GRB 250728A: Swift ToO observations
  19. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  20. GRB 250727A: AST3-2 Upper limit
  21. GRB250727A: SVOM/VT optical upper limit
  22. GRB 250727A: Swift-XRT observations
  23. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  24. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  25. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  26. GRB 250725A: Swift/UVOT Upper Limits
  27. Fermi GRB 250725A: Global MASTER-Net observations report
  28. Swift GRB 250725A: Global MASTER-Net observations report
  29. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  30. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  31. SVOM J195836+32283/sb25072103: Second VT observation
  32. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  33. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  34. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  35. GRB 250721A: Swift-XRT observations
  36. GRB 250713A : SVOM/ECLAIRs refined analysis
  37. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  38. GRB 250721A: Tiled Swift observations
  39. Fermi trigger No 774730635: Global MASTER-Net observations report
  40. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  41. GRB 250717B: Swift-XRT observations
  42. Swift GRB250718.01: Global MASTER-Net observations report
  43. GRB 250717B: Swift ToO observations
  44. GRB 270713A: Kitab and AbAO Optical Observations
  45. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  46. GRB 250716A: Swift-XRT afterglow detection
  47. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  48. GRB 250716A: Swift ToO observations
  49. GRB 250716A: GOTO tentative optical counterpart candidate
  50. Fermi GRB 250716A: Global MASTER-Net observations report
  51. Fermi GRB 250715A: Global MASTER-Net observations report
  52. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  53. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  54. GRB 250713A: Mephisto optical upper limits
  55. Fermi GRB 250714A: Global MASTER-Net observations report
  56. GRB 250713A: NOT optical upper limits
  57. GRB 250713A: OHP/T193 upper limit
  58. GRB 250713A: SVOM/C-GFT upper limit
  59. GRB 250706B/C: 7DT Follow-up Observations
  60. GRB 250713A: Swift-XRT observations
  61. EP250711a: COLIBRÍ continuous optical observations
  62. GRB 250713A: JinShan optical upper limits
  63. EP250711a: Global MASTER-Net observations report
  64. GRB 250711A: DDOTI Optical Upper Limit
  65. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  66. Fermi GRB 250711A: Global MASTER-Net observations report
  67. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  68. GRB 250704A: GRANDMA observations
  69. GRB 250704A: SVOM/ECLAIRs refined analysis
  70. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  71. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  72. GRB 250702B,D,E / EP250702a: ALMA detection
  73. IceCube-250708A: No Candidates from WINTER
  74. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  75. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  76. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  77. EP/WXT 01709181970: GOTO observations confirm stellar variability
  78. EP250704a/GRB 250704B: 10 GHz VLA detection
  79. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  80. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  81. IceCube-250706A: No Candidates from WINTER
  82. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  83. GRB 250704B / EP250704a: VLA radio detection
  84. Fermi GRB 250708A: Global MASTER-Net observations report
  85. IceCube-250708A: Global MASTER-Net observations report
  86. EP250704a/GRB250704B : HCT optical and NIR upper limits
  87. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  88. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  89. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  90. GRB 250702F: radio detection with the VLA
  91. IceCube-250706A: EP-FXT follow-up observations
  92. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  93. IceCube-250706A: Global MASTER-Net observations report
  94. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  95. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  96. GRB 250706B: Swift/UVOT Detection
  97. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  98. GRB 250702F: GRANDMA observations
  99. GRB 250706B: refined SVOM/MXT data analysis
  100. GRB 250706A: Swift/UVOT Upper Limits

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