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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"

5843 results found.

  1. EP250903a: LCO candidate counterpart discovery
  2. GRB 250903A: TRT optical counterpart detection
  3. GRB 250902B: AstroSat CZTI detection
  4. GRB 250903A: SVOM detection of a burst
  5. EP250903a: Global MASTER-Net observations report
  6. EP250903a: TRT optical observations
  7. EP250903a: Einstein Probe detection of an X-ray transient
  8. EP 250827B: Detection of supernova counterpart by LCO.
  9. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  10. EP250827b: continued Liverpool Telescope observations
  11. GRB 250902B: SVOM/GRM observation
  12. EP250827b: SVOM/VT observation of AT 2025wkm
  13. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  14. Fermi GRB 250902B: Global MASTER-Net observations report
  15. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  16. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  17. EP250827b: Liverpool Telescope observations
  18. GRB 250902A: SVOM/GRM observation
  19. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 250901A: EP-FXT follow-up observation
  21. GRB 250901A: SVOM/VT optical afterglow with VHF data
  22. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  23. GRB 250901A: LCO optical upper limit
  24. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  25. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  26. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  27. GRB 250901A: SVOM detection of a burst
  28. GRB 250831B: SVOM/GRM observation
  29. EP250901a: Mephisto optical upper limits
  30. EP250901a: Global MASTER-Net observations report
  31. EP250901a: Einstein Probe detection of an X-ray transient
  32. IceCube Alert 250831.75: Global MASTER-Net observations report
  33. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  34. Swift GRB 250828B: Global MASTER-Net observations report
  35. EP250828a: Global MASTER-Net observations report
  36. EP250828a: KAIT optical upper limit
  37. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  38. Fermi GRB 250827A: Global MASTER-Net observations report
  39. EP250827a: Global MASTER-Net observations report
  40. Fermi trigger No 777883624: Global MASTER-Net observations report
  41. Fermi GRB 250824B: Global MASTER-Net observations report
  42. Fermi GRB 250821B: Global MASTER-Net observations report
  43. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  44. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  45. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  46. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  47. GRB 250818B: GOTO optical counterpart candidate
  48. GRB 250818B: SVOM detection of a short burst
  49. sb25081602: Swift-XRT observations
  50. SVOM/sb25081602: detection of a likely X-ray transient
  51. GRB 250814A: Possible afterglow candidate from P200/WIRC
  52. Fermi trigger No 776818276: Global MASTER-Net observations report
  53. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  54. GRB 250814A: DDOTI Optical Upper Limit
  55. GRB 250814A: Fermi GBM Final Real-time Localization
  56. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  57. GRB 250812A: Swift/UVOT Detection
  58. EP250812a: SVOM/VT optical counterpart
  59. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  60. IceCube Alert 250813.14: Global MASTER-Net observations report
  61. EP250812a: Einstein Probe detection of an X-ray transient
  62. GRB 250812A: Swift-XRT afterglow detection
  63. GRB 250812A: TRT likely optical counterpart detection
  64. IceCube-Cascade 250809A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 250702B: Chandra X-ray Detection
  66. Fermi GRB 250808A: Global MASTER-Net observations report
  67. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  68. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. Swift GRB250807.45: Global MASTER-Net observations report
  70. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  71. EP250806a: SVOM /VT optical candidate
  72. GRB 250805A: ESO/VLT observations
  73. GRB 250805A: Swift detection of a burst
  74. Swift GRB250805.26: Global MASTER-Net observations report
  75. EP250730a: SVOM/VT optical upper limit
  76. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  77. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  78. EP250730a: Global MASTER-Net observations report
  79. EP250730a: Einstein Probe detection of an X-ray transient
  80. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  81. GRB 250728A: Fermi GBM Observation
  82. GRB 250727A: AST3-2 Upper limit
  83. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  84. GRB 250721A: Fermi GBM Observation
  85. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  86. GRB 250722A: Fermi GBM Final Real-time Localization
  87. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  88. GRB 250721A: MAXI/GSC detection
  89. GRB 250721A: Fermi GBM Final Localization
  90. Fermi trigger No 774730635: Global MASTER-Net observations report
  91. GRB 250717B: COLIBRÍ optical upper limit
  92. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  93. GRB 250713A: SVOM/VT optical upper limit
  94. GRB 250713A: SVOM/C-GFT upper limit
  95. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  96. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  97. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  98. GRB 250702B,D,E / EP250702a: ALMA detection
  99. IceCube-250708A: No Candidates from WINTER
  100. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility

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