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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"

20502 results found.

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

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