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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"

18466 results found.

  1. GRB 250806A: EP-FXT observation
  2. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  3. EP250806a: SVOM /VT optical candidate
  4. GRB 250806A: J-band upper limit from WINTER
  5. GRB 250806A: KAIT optical upper limit
  6. EP250806a: COLIBRÍ optical upper limit
  7. GRB 250806A: Kilonova-Catcher optical upper limits
  8. EP250806a: Einstein Probe detection of an X-ray transient
  9. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. GRB 250806A: SVOM/VT optical upper limit
  11. GRB 250806A: SVOM detection of a soft burst
  12. GRB 250805A: SVOM/VT optical counterpart
  13. GRB 250805A: Enhanced Swift-XRT position
  14. GRB 250805A: TRT optical upper limits
  15. GRB 250805A: Swift-XRT observations
  16. GRB 250804B: SVOM/GRM observation of a short burst
  17. EP250802a: additional Liverpool Telescope upper limits
  18. EP250730a: SVOM/VT optical upper limit
  19. EP250802a: Liverpool Telescope optical upper limits
  20. EP250802a: GROWTH-India Telescope optical upper limit
  21. EP250802a: Einstein Probe detection of an X-ray transient
  22. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  23. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  24. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  25. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  26. EP250711a: CrAO and Assy optical observations
  27. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  28. EP250730a: COLIBRÍ optical upper limit
  29. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  30. EP250730a: Einstein Probe detection of an X-ray transient
  31. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  32. GRB 250725A: PRIME near-infrared observations
  33. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  34. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  35. GRB 250727A: SVOM/ECLAIRs refined analysis
  36. GRB 250728A: COLIBRÍ optical upper limit
  37. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  38. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  40. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  41. GRB 250725A: SVOM/GRM observation
  42. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  43. GRB 250725A: Swift/UVOT Upper Limits
  44. GRB 250725A: SVOM/VT optical candidate
  45. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  46. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  47. GRB 250725A: Enhanced Swift-XRT position
  48. GRB 250725A: Swift detection of a burst
  49. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  50. SVOM J195836+32283 is not a real source
  51. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  52. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  53. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  54. GRB 250721A: Swift-XRT observations
  55. GRB 250713A : SVOM/ECLAIRs refined analysis
  56. GRB 250717B: SVOM/GRM observation
  57. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  58. GRB 250717B: COLIBRÍ optical upper limit
  59. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  60. GRB 270713A: Kitab and AbAO Optical Observations
  61. Konus-Wind detection of GRB 250716A
  62. GRB 250716A: Swift-XRT afterglow detection
  63. GRB 250714A: SVOM/GRM observation
  64. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  65. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  66. GRB 250713A: Mephisto optical upper limits
  67. GRB 250713A: SVOM/VT optical upper limit
  68. GRB 250713A: NOT optical upper limits
  69. GRB 250713A: OHP/T193 upper limit
  70. GRB 250713A: SVOM/C-GFT upper limit
  71. GRB 250706B/C: 7DT Follow-up Observations
  72. GRB 250713A: EP-FXT counterpart detection
  73. EP250711a: COLIBRÍ continuous optical observations
  74. GRB 250713A: JinShan optical upper limits
  75. GRB 250713A: SVOM detection of a long burst
  76. GRB 250711A: DDOTI Optical Upper Limit
  77. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  78. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  79. GRB 250711A: SVOM/GRM observation
  80. EP250711a: NOT optical counterpart candidate
  81. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  82. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  83. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  84. GRB 250704A: GRANDMA observations
  85. GRB 250704A: SVOM/ECLAIRs refined analysis
  86. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  87. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  88. IceCube-250708A: No Candidates from WINTER
  89. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  90. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  91. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  92. EP250704a/GRB 250704B: 10 GHz VLA detection
  93. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  94. IceCube-250706A: No Candidates from WINTER
  95. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  96. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  97. EP250704a/GRB250704B : HCT optical and NIR upper limits
  98. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  99. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  100. GRB 250704B: CALET Gamma-Ray Burst Monitor detection

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