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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"

22101 results found.

  1. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  2. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  3. EP250711a: CrAO and Assy optical observations
  4. EP250730a: COLIBRÍ optical upper limit
  5. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  6. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  7. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  8. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  9. GRB 250727A: EP-FXT follow-up observation
  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 250728A: COLIBRÍ optical upper limit
  15. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  16. GRB 250727A: EP-FXT counterpart detection
  17. GRB250727A: SVOM/VT optical upper limit
  18. GRB 250727A: Swift-XRT observations
  19. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  20. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  21. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  22. GRB 250727A: SVOM detection of a burst
  23. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  24. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  25. GRB 250725A: Swift-XRT refined Analysis
  26. LIGO/Virgo/KAGRA S250725j: NED Galaxies in the 3-Initial Localization Volume
  27. GRB 250725A: SVOM/GRM observation
  28. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  29. GRB 250725A: Swift/UVOT Upper Limits
  30. GRB 250725A: SVOM/VT optical candidate
  31. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  33. GRB 250725A: Enhanced Swift-XRT position
  34. GRB 250725A: Swift detection of a burst
  35. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  36. SVOM J195836+32283 is not a real source
  37. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  38. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  39. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  40. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  41. GRB 250721A: Swift-XRT observations
  42. GRB 250717B: SVOM/GRM observation
  43. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  44. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  45. GRB 250717B: COLIBRÍ optical upper limit
  46. GRB 250717B: Swift-XRT observations
  47. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  48. Swift Trigger 1334535: a possible GRB 250718A
  49. GRB 270713A: Kitab and AbAO Optical Observations
  50. GRB 250717B: Swift/BAT-GUANO arcminute localization of a burst
  51. GRB 250716A: Swift-XRT afterglow detection
  52. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  53. GRB 250714A: SVOM/GRM observation
  54. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  55. GRB 250713A: Mephisto optical upper limits
  56. GRB 250713A: SVOM/VT optical upper limit
  57. GRB 250713A: NOT optical upper limits
  58. GRB 250713A: OHP/T193 upper limit
  59. GRB 250713A: SVOM/C-GFT upper limit
  60. GRB 250706B/C: 7DT Follow-up Observations
  61. GRB 250713A: Swift-XRT observations
  62. GRB 250713A: EP-FXT counterpart detection
  63. EP250711a: COLIBRÍ continuous optical observations
  64. GRB 250702F: Swift-BAT refined analysis
  65. GRB 250713A: JinShan optical upper limits
  66. GRB 250713A: SVOM detection of a long burst
  67. GRB 250711A: DDOTI Optical Upper Limit
  68. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  69. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  70. GRB 250711A: SVOM/GRM observation
  71. EP250711a: NOT optical counterpart candidate
  72. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  73. Fermi GRB 250711A: Global MASTER-Net observations report
  74. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  75. GRB 250704A: GRANDMA observations
  76. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  77. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  78. IceCube-250708A: No Candidates from WINTER
  79. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  80. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  81. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  82. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  83. EP250704a/GRB 250704B: 10 GHz VLA detection
  84. IceCube-250706A: No Candidates from WINTER
  85. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  86. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  87. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  88. EP250704a/GRB250704B : HCT optical and NIR upper limits
  89. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  90. GRB 250702F: radio detection with the VLA
  91. GRB 250706B/C: Fermi-LAT detection
  92. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  93. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  94. GRB 250706B: Swift/UVOT Detection
  95. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  96. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  97. GRB 250702F: GRANDMA observations
  98. GRB 250706B: refined SVOM/MXT data analysis
  99. GRB 250706A: Swift/UVOT Upper Limits
  100. GRB 250706B: REM optical observations

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