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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

18498 results found.

  1. GRB 250910A: SVOM/VT optical upper limit
  2. GRB 250910A: LCO optical upper limit
  3. EP250908b/EP#01709240653: Swift/UVOT Detection
  4. The EP-WXT trigger 01709240674 is triggered by the known source SS Cyg
  5. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  6. EP250908c: SVOM/VT optical observation
  7. EP250908c: VLT/FORS2 optical counterpart identification
  8. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  9. EP250908b: SVOM/VT optical candidate
  10. EP250908c: Einstein Probe detection of an X-ray transient
  11. GRB 250909A: Fermi GBM Final Real-time Localization
  12. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  13. GRB 250903A: Swift-XRT afterglow detection
  14. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  15. EP250905a: Liverpool Telescope i-band upper limits
  16. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  17. EP250905b: EP-FXT follow-up observation
  18. EP250905a: Liverpool Telescope observations
  19. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  20. EP250905b: EP-WXT detection of a fast X-ray transient
  21. EP250905a: JinShan likely optical counterpart detection
  22. GRB 250905A: Swift/UVOT Upper Limits
  23. EP250905a: Einstein Probe detection of an X-ray transient
  24. GRB250904A: Liverpool Telescope upper limits
  25. GRB 250905A: Enhanced Swift-XRT position
  26. GRB 250904A: Swift/UVOT Detection
  27. GRB 250903A: Swift/UVOT detection
  28. GRB 250904A: Swift-XRT refined Analysis
  29. EP detected a brightening of LMXB 1ES 1735-26.9
  30. GRB 250905A: KAIT optical upper limit
  31. GRB 250905A: Swift detection of a burst
  32. GRB 250904A: Enhanced Swift-XRT position
  33. GRB 250904A: TRT optical counterpart detection
  34. GRB 250904A: Swift detection of a burst
  35. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  36. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  37. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  38. GRB 250830C: VZLUSAT-2 detection
  39. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  40. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  41. The EP-WXT trigger 01709201209 is likely a flaring star
  42. GRB 250903A: EP-FXT counterpart detection
  43. GRB 250903A: LCO optical observation
  44. GRB 250903A: LCO optical afterglow detection
  45. GRB 250903A: SVOM/VT optical confirmation with VHF data
  46. EP250901a: Mondy, Assy and SAO RAS optical limits
  47. GRB 250903A: TRT optical counterpart detection
  48. EP250903a: TRT optical observations
  49. EP250903a: Einstein Probe detection of an X-ray transient
  50. EP 250827B: Detection of supernova counterpart by LCO.
  51. GRB 250902B: SVOM/GRM observation
  52. EP250827b: SVOM/VT observation of AT 2025wkm
  53. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  54. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  55. GRB 250901A: Swift/UVOT Upper Limit
  56. GRB 250830B: Swift-XRT afterglow detection
  57. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  58. GRB 250902A: SVOM/GRM observation
  59. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  60. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  61. GRB 250901A: EP-FXT follow-up observation
  62. GRB 250901A: SVOM/VT optical afterglow with VHF data
  63. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  64. GRB 250901A: LCO optical upper limit
  65. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  66. EP250831a: NOT optical observations and tentative afterglow candidate
  67. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  68. GRB 250901A: SVOM detection of a burst
  69. EP250901a: Mephisto optical upper limits
  70. GRB 250830C: AstroSat CZTI detection of a long burst
  71. EP250901a: Einstein Probe detection of an X-ray transient
  72. EP250831a: EP-FXT follow-up observation
  73. EP250831a: EP-WXT detection of a fast X-ray transient
  74. GRB 250831A: Swift-XRT counterpart detection
  75. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  76. GRB 250831A: SVOM/VT upper limit with VHF data
  77. GRB 250831A: SVOM detection of a soft burst
  78. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  79. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  80. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  81. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  82. The EP-WXT trigger 01709200994 is likely a flaring star
  83. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  84. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  85. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP250828a: Optical counterpart detection with Kinder observations
  87. EP250828a: Liverpool Telescope upper limits
  88. EP-WXT trigger 01709200800 : KAIT optical observations
  89. EP250828a: KAIT optical upper limit
  90. EP250827a: Swift/UVOT Detection
  91. EP250828a: NOT optical counterpart confirmation
  92. EP250828a: SVOM/VT optical candidate
  93. EP250828a: Seimei/TriCCS optical counterpart detection
  94. EP250828a: Optical upper limit with Kinder observations
  95. EP250828a: Einstein Probe detection of an X-ray transient
  96. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  97. EP250827a: confirmation of optical rebrightening with LCO
  98. GRB 250826A: SVOM/GRM observation
  99. EP250827A: An optical rebrightening was detected by LCO.
  100. The EP-WXT trigger 01709200800 is likely a flaring star

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