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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"

16753 results found.

  1. EP250901a: Mondy, Assy and SAO RAS optical limits
  2. GRB 250903A: TRT optical counterpart detection
  3. EP250903a: TRT optical observations
  4. EP250903a: Einstein Probe detection of an X-ray transient
  5. EP 250827B: Detection of supernova counterpart by LCO.
  6. GRB 250902B: SVOM/GRM observation
  7. EP250827b: SVOM/VT observation of AT 2025wkm
  8. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  9. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  10. GRB 250901A: Swift/UVOT Upper Limit
  11. GRB 250830B: Swift-XRT afterglow detection
  12. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  13. GRB 250902A: SVOM/GRM observation
  14. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  15. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  16. GRB 250901A: EP-FXT follow-up observation
  17. GRB 250901A: SVOM/VT optical afterglow with VHF data
  18. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  19. GRB 250901A: LCO optical upper limit
  20. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  21. EP250831a: NOT optical observations and tentative afterglow candidate
  22. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  23. GRB 250901A: SVOM detection of a burst
  24. EP250901a: Mephisto optical upper limits
  25. GRB 250830C: AstroSat CZTI detection of a long burst
  26. EP250901a: Einstein Probe detection of an X-ray transient
  27. EP250831a: EP-FXT follow-up observation
  28. EP250831a: EP-WXT detection of a fast X-ray transient
  29. GRB 250831A: Swift-XRT counterpart detection
  30. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. GRB 250831A: SVOM/VT upper limit with VHF data
  32. GRB 250831A: SVOM detection of a soft burst
  33. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  34. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  35. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  36. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  37. The EP-WXT trigger 01709200994 is likely a flaring star
  38. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  39. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  40. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  41. EP250828a: Optical counterpart detection with Kinder observations
  42. EP250828a: Liverpool Telescope upper limits
  43. EP-WXT trigger 01709200800 : KAIT optical observations
  44. EP250828a: KAIT optical upper limit
  45. EP250827a: Swift/UVOT Detection
  46. EP250828a: NOT optical counterpart confirmation
  47. EP250828a: SVOM/VT optical candidate
  48. EP250828a: Seimei/TriCCS optical counterpart detection
  49. EP250828a: Optical upper limit with Kinder observations
  50. EP250828a: Einstein Probe detection of an X-ray transient
  51. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  52. EP250827a: confirmation of optical rebrightening with LCO
  53. GRB 250826A: SVOM/GRM observation
  54. EP250827A: An optical rebrightening was detected by LCO.
  55. The EP-WXT trigger 01709200800 is likely a flaring star
  56. EP250827a: TRT optical observations
  57. EP250827a: Einstein Probe detection of an X-ray transient
  58. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  59. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  60. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  61. GRB 250821B: AstroSat CZTI detection
  62. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  63. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  64. EP250821a: MeerKAT radio counterpart
  65. The EP-WXT trigger 01709200707 is likely a flaring star
  66. GRB 250823A: COLIBRÍ optical observations
  67. The EP-WXT trigger 01709200706 is likely a flaring star
  68. GRB 250823A: SVOM/VT optical observation
  69. GRB 250823A: Swift/UVOT Detection
  70. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  71. GRB 250823A: Enhanced Swift-XRT position
  72. GRB 250823A: LCOGT Optical Detection
  73. GRB 250823A: Swift detection of a burst
  74. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  75. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz
  76. LIGO/Virgo/KAGRA S250818k: 3 GHz MeerKAT observations of AT2025ulz
  77. GRB 250821A: Kilonova-Catcher optical upper limits
  78. GRB 250821A: VLT/FORS2 Optical Observation
  79. GRB 250821B: SVOM/GRM observation
  80. EP250821a: SVOM/VT optical observation
  81. GRB 250821A: NOT z-band upper limit
  82. GRB 250821A: KAIT optical upper limit
  83. GRB 250821A: Enhanced Swift-XRT position
  84. GRB 250821A: Swift/UVOT Upper Limits
  85. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  86. GRB 250821A: LCOGT Optical Upper Limits
  87. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  88. GRB 250821A: Swift detection of a burst
  89. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  90. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  91. EP250821a: Einstein Probe detection of an X-ray transient
  92. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  93. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  94. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  95. GRB 250814A: Swift/UVOT Upper Limits
  96. GRB 250813B: Swift/UVOT Upper Limit
  97. IPN triangulation of GRB 250816A (short)
  98. IPN triangulation of GRB 250814C (short)
  99. IPN triangulation of GRB 250804B (short)
  100. GRB 250818B: Kilonova-Catcher optical afterglow detection

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