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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"

25850 results found.

  1. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  2. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  3. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  4. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  5. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  6. GRB 250727A: EP-FXT follow-up observation
  7. GRB 250725A: PRIME near-infrared observations
  8. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  9. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  10. GRB 250728A: Swift-XRT observations
  11. GRB 250727A: SVOM/ECLAIRs refined analysis
  12. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  13. GRB 250728A: COLIBRÍ optical upper limit
  14. GRB 250728A: Fermi GBM Observation
  15. GRB 250727A: AST3-2 Upper limit
  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. The EP-WXT trigger 01709195487 is likely a flaring star
  24. Swift detection of the Soft Gamma Repeater PSR J1647-4552
  25. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  26. GRB 250725A: Swift-XRT refined Analysis
  27. GRB 250725A: Fermi GBM Observation
  28. GRB 250725A: Swift-BAT refined analysis
  29. Konus-Wind detection of GRB 250725A
  30. GRB 250725A: SVOM/GRM observation
  31. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  32. GRB 250725A: Swift/UVOT Upper Limits
  33. GRB 250725A: SVOM/VT optical candidate
  34. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  35. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  36. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  37. GRB 250725A: Enhanced Swift-XRT position
  38. GRB 250725A: Swift detection of a burst
  39. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  40. SVOM J195836+32283 is not a real source
  41. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  42. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  43. GRB 250721A: Fermi GBM Observation
  44. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  45. GRB 250721A: Swift-XRT observations
  46. GRB 250713A : SVOM/ECLAIRs refined analysis
  47. GRB 250717B: SVOM/GRM observation
  48. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  49. GRB 250717B: COLIBRÍ optical upper limit
  50. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO
  51. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  52. GRB 270713A: Kitab and AbAO Optical Observations
  53. GRB 250717B: Fermi GBM Observation
  54. GRB 250716A: Swift-XRT afterglow detection
  55. GRB 250716A: Fermi GBM Observation
  56. GRB 250714A: SVOM/GRM observation
  57. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  58. GRB 250713A: Mephisto optical upper limits
  59. GRB 250713A: SVOM/VT optical upper limit
  60. GRB 250713A: NOT optical upper limits
  61. GRB 250713A: OHP/T193 upper limit
  62. GRB 250713A: SVOM/C-GFT upper limit
  63. GRB 250706B/C: 7DT Follow-up Observations
  64. GRB 250713A: Swift-XRT observations
  65. GRB 250713A: EP-FXT counterpart detection
  66. EP250711a: COLIBRÍ continuous optical observations
  67. GRB 250706A: Swift-BAT refined analysis
  68. GRB 250713A: JinShan optical upper limits
  69. GRB 250713A: SVOM detection of a long burst
  70. GRB 250711A: DDOTI Optical Upper Limit
  71. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  72. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  73. GRB 250711A: SVOM/GRM observation
  74. EP250711a: NOT optical counterpart candidate
  75. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  76. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  77. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  78. GRB 250704A: GRANDMA observations
  79. GRB 250704A: SVOM/ECLAIRs refined analysis
  80. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  81. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  82. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  83. GRB 250702B,D,E / EP250702a: ALMA detection
  84. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  85. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  86. IceCube-250708A: No Candidates from WINTER
  87. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  88. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  89. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  90. EP250704a/GRB 250704B: 10 GHz VLA detection
  91. The EP-WXT trigger 01709181970 is likely a flaring star
  92. IceCube-250706A: No Candidates from WINTER
  93. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  94. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  95. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  96. EP250704a/GRB250704B : HCT optical and NIR upper limits
  97. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  98. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  99. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  100. GRB 250702F: radio detection with the VLA

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