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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"

25713 results found.

  1. GRB 250903A: Swift/UVOT detection
  2. GRB 250904A: Swift-XRT refined Analysis
  3. LIGO/Virgo/KAGRA S250904cv: Updated Sky localization
  4. LIGO/Virgo/KAGRA S250904br: Updated Sky localization
  5. EP detected a brightening of LMXB 1ES 1735-26.9
  6. GRB 250905A: KAIT optical upper limit
  7. GRB 250905A: Swift detection of a burst
  8. GRB 250904A: Enhanced Swift-XRT position
  9. IceCube-Cascade 250903A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 250904A: TRT optical counterpart detection
  11. EP250827a and EP250827b: Upper limit from Fermi-GBM Observations
  12. GRB 250904A: Swift detection of a burst
  13. LIGO/Virgo/KAGRA S250904ae: Updated Sky localization
  14. GRB 250902A: VZLUSAT-2 detection
  15. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  16. GRB 250903A: Swift-XRT observations
  17. EP250903a: Swift-XRT observations
  18. EP#01709201209: Swift-XRT observations
  19. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  20. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  21. GRB 250830C: VZLUSAT-2 detection
  22. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  23. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  25. GRB 250903A: EP-FXT counterpart detection
  26. GRB 250902A: GECAM-B detection
  27. GRB 250903A: LCO optical observation
  28. GRB 250903A: LCO optical afterglow detection
  29. GRB 250903A: SVOM/VT optical confirmation with VHF data
  30. EP250901a: Mondy, Assy and SAO RAS optical limits
  31. EP250903a: LCO candidate counterpart discovery
  32. GRB 250903A: TRT optical counterpart detection
  33. EP250903a: TRT optical observations
  34. EP250903a: Einstein Probe detection of an X-ray transient
  35. EP 250827B: Detection of supernova counterpart by LCO.
  36. GRB 250902B: SVOM/GRM observation
  37. EP250827b: SVOM/VT observation of AT 2025wkm
  38. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  39. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  40. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  41. GRB 250902A: Fermi GBM Detection
  42. GRB 250901A: Swift/UVOT Upper Limit
  43. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  44. GRB 250830B: Swift-XRT afterglow detection
  45. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  46. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  47. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  48. GRB 250902A: SVOM/GRM observation
  49. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  50. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  51. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  52. GRB 250901A: SVOM/VT optical afterglow with VHF data
  53. GRB 250901A: Swift-XRT afterglow detection
  54. EP250901a: Swift-XRT observations
  55. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  56. GRB 250901A: LCO optical upper limit
  57. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  58. EP250827b: Gemini Spectroscopy of AT 2025wkm
  59. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  60. EP250831a: NOT optical observations and tentative afterglow candidate
  61. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  62. GRB 250901A: SVOM detection of a burst
  63. EP250901a: Mephisto optical upper limits
  64. GRB 250830C: GECAM-B detection
  65. EP250901a: Einstein Probe detection of an X-ray transient
  66. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  67. EP250831a: Swift-XRT observations
  68. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  69. EP250831a: EP-WXT detection of a fast X-ray transient
  70. GRB 250831A: Swift-XRT counterpart detection
  71. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  72. GRB 250831A: SVOM/VT upper limit with VHF data
  73. GRB 250831A: SVOM detection of a soft burst
  74. GRB 250830B: Swift-XRT observations
  75. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  76. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  77. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  78. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  79. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  80. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  81. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  82. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  83. GRB 250830B: MAXI/GSC detection
  84. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  85. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  86. GRB 250828B: Swift-BAT refined analysis
  87. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  88. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  89. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  90. EP250828a: Optical counterpart detection with Kinder observations
  91. EP250828a: Liverpool Telescope upper limits
  92. EP250828a: Global MASTER-Net observations report
  93. EP-WXT trigger 01709200800 : KAIT optical observations
  94. EP250828a: KAIT optical upper limit
  95. EP250827a: Swift/UVOT Detection
  96. EP250828a: NOT optical counterpart confirmation
  97. EP250828a: SVOM/VT optical candidate
  98. EP250828a: Seimei/TriCCS optical counterpart detection
  99. EP250828a: Optical upper limit with Kinder observations
  100. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization

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