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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"

20503 results found.

  1. EP250905a: JinShan likely optical counterpart detection
  2. GRB 250905A: Swift/UVOT Upper Limits
  3. GRB 250901A - SVOM/ECLAIRs refined analysis
  4. EP250905a: Einstein Probe detection of an X-ray transient
  5. GRB250904A: Liverpool Telescope upper limits
  6. GRB 250905A: Enhanced Swift-XRT position
  7. GRB 250904A: Swift/UVOT Detection
  8. GRB 250903A: Swift/UVOT detection
  9. EP detected a brightening of LMXB 1ES 1735-26.9
  10. GRB 250905A: KAIT optical upper limit
  11. GRB 250905A: Swift detection of a burst
  12. GRB 250904A: Enhanced Swift-XRT position
  13. GRB 250904A: TRT optical counterpart detection
  14. GRB 250904A: Swift detection of a burst
  15. GRB 250902A: VZLUSAT-2 detection
  16. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  17. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  18. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  19. GRB 250830C: VZLUSAT-2 detection
  20. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  21. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  22. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  23. GRB 250903A: LCO optical observation
  24. GRB 250903A: LCO optical afterglow detection
  25. GRB 250903A: SVOM/VT optical confirmation with VHF data
  26. EP250901a: Mondy, Assy and SAO RAS optical limits
  27. GRB 250903A: TRT optical counterpart detection
  28. GRB 250902B: AstroSat CZTI detection
  29. GRB 250903A: SVOM detection of a burst
  30. EP250903a: TRT optical observations
  31. EP250903a: Einstein Probe detection of an X-ray transient
  32. EP 250827B: Detection of supernova counterpart by LCO.
  33. GRB 250902B: SVOM/GRM observation
  34. EP250827b: SVOM/VT observation of AT 2025wkm
  35. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  36. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  37. GRB 250901A: Swift/UVOT Upper Limit
  38. GRB 250830B: Swift-XRT afterglow detection
  39. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  40. GRB 250902A: SVOM/GRM observation
  41. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  42. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  43. GRB 250901A: EP-FXT follow-up observation
  44. GRB 250901A: SVOM/VT optical afterglow with VHF data
  45. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  46. GRB 250901A: LCO optical upper limit
  47. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  48. EP250831a: NOT optical observations and tentative afterglow candidate
  49. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  50. GRB 250901A: SVOM detection of a burst
  51. EP250901a: Mephisto optical upper limits
  52. GRB 250830C: AstroSat CZTI detection of a long burst
  53. EP250901a: Einstein Probe detection of an X-ray transient
  54. IceCube Alert 250831.75: Global MASTER-Net observations report
  55. EP250831a: EP-WXT detection of a fast X-ray transient
  56. GRB 250831A: Swift-XRT counterpart detection
  57. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. GRB 250831A: SVOM/VT upper limit with VHF data
  59. GRB 250831A: SVOM detection of a soft burst
  60. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  61. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  62. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  63. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  64. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  65. GRB 250828B: Swift-BAT refined analysis
  66. EP250821a: SOAR observations
  67. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  68. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  69. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  70. GRB 250808B: SVOM detection of a burst through offline search
  71. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP250828a: Optical counterpart detection with Kinder observations
  73. EP250828a: Liverpool Telescope upper limits
  74. EP-WXT trigger 01709200800 : KAIT optical observations
  75. EP250828a: KAIT optical upper limit
  76. EP250827a: Swift/UVOT Detection
  77. EP250828a: NOT optical counterpart confirmation
  78. EP250828a: SVOM/VT optical candidate
  79. EP250828a: Seimei/TriCCS optical counterpart detection
  80. EP250828a: Optical upper limit with Kinder observations
  81. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  82. EP250828a: Einstein Probe detection of an X-ray transient
  83. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  84. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  85. EP250827a: confirmation of optical rebrightening with LCO
  86. EP250827a: GOTO observation of the optical afterglow
  87. GRB 250826A: SVOM/GRM observation
  88. EP250827A: An optical rebrightening was detected by LCO.
  89. EP250827a: TRT optical observations
  90. EP250827a: BOOTES-7 early optical dectection
  91. EP250827a: Las Cumbres independent detection of the optical counterpart
  92. EP250827a: Einstein Probe detection of an X-ray transient
  93. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  94. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  95. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  96. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  97. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  98. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  99. EP250821a: MeerKAT radio counterpart
  100. GRB 250823A: COLIBRÍ optical observations

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