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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"

24931 results found.

  1. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  2. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  3. GRB 250727A: SVOM detection of a burst
  4. The EP-WXT trigger 01709195487 is likely a flaring star
  5. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  6. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  7. GRB 250725A: Swift-XRT refined Analysis
  8. GRB 250725A: Fermi GBM Observation
  9. GRB 250725A: Swift-BAT refined analysis
  10. Konus-Wind detection of GRB 250725A
  11. GRB 250725A: SVOM/GRM observation
  12. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  13. GRB 250725A: Swift/UVOT Upper Limits
  14. GRB 250725A: SVOM/VT optical candidate
  15. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  16. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  17. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  18. GRB 250725A: Enhanced Swift-XRT position
  19. GRB 250725A: Swift detection of a burst
  20. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  21. SVOM J195836+32283 is not a real source
  22. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  23. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  24. GRB 250721A: Fermi GBM Observation
  25. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  26. GRB 250721A: Swift-XRT observations
  27. GRB 250713A : SVOM/ECLAIRs refined analysis
  28. GRB 250717B: SVOM/GRM observation
  29. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  30. GRB 250717B: COLIBRÍ optical upper limit
  31. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  32. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  33. GRB 270713A: Kitab and AbAO Optical Observations
  34. GRB 250717B: Fermi GBM Observation
  35. GRB 250716A: Swift-XRT afterglow detection
  36. GRB 250716A: Fermi GBM Observation
  37. GRB 250714A: SVOM/GRM observation
  38. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  39. GRB 250713A: Mephisto optical upper limits
  40. GRB 250713A: SVOM/VT optical upper limit
  41. GRB 250713A: NOT optical upper limits
  42. GRB 250713A: OHP/T193 upper limit
  43. GRB 250713A: SVOM/C-GFT upper limit
  44. GRB 250706B/C: 7DT Follow-up Observations
  45. GRB 250713A: Swift-XRT observations
  46. GRB 250713A: EP-FXT counterpart detection
  47. EP250711a: COLIBRÍ continuous optical observations
  48. GRB 250706A: Swift-BAT refined analysis
  49. GRB 250713A: JinShan optical upper limits
  50. GRB 250713A: SVOM detection of a long burst
  51. GRB 250711A: DDOTI Optical Upper Limit
  52. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  53. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  54. GRB 250711A: SVOM/GRM observation
  55. EP250711a: NOT optical counterpart candidate
  56. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  57. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  58. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  59. GRB 250704A: GRANDMA observations
  60. GRB 250704A: SVOM/ECLAIRs refined analysis
  61. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  62. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  63. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  64. GRB 250702B,D,E / EP250702a: ALMA detection
  65. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  66. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  67. IceCube-250708A: No Candidates from WINTER
  68. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  69. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  70. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  71. EP250704a/GRB 250704B: 10 GHz VLA detection
  72. The EP-WXT trigger 01709181970 is likely a flaring star
  73. IceCube-250706A: No Candidates from WINTER
  74. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  75. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  76. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  77. EP250704a/GRB250704B : HCT optical and NIR upper limits
  78. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  79. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  80. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  81. GRB 250702F: radio detection with the VLA
  82. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  83. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  84. GRB 250706B/C: Fermi-LAT detection
  85. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  86. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  87. GRB 250706B: Swift/UVOT Detection
  88. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  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. GRB 250706A: JinShan optical upper limits
  100. GRB 250706A: SAO RAS optical observations

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