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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"

19549 results found.

  1. EP250908c: VLT/FORS2 optical counterpart identification
  2. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  3. EP250908b: SVOM/VT optical candidate
  4. EP250908c: Einstein Probe detection of an X-ray transient
  5. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  6. GRB 250903A: Swift-XRT afterglow detection
  7. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  8. EP250905a: Liverpool Telescope i-band upper limits
  9. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  10. EP250905a: Liverpool Telescope observations
  11. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  12. EP250905b: EP-WXT detection of a fast X-ray transient
  13. EP250905a: JinShan likely optical counterpart detection
  14. GRB 250905A: Swift/UVOT Upper Limits
  15. GRB 250901A - SVOM/ECLAIRs refined analysis
  16. EP250905a: Einstein Probe detection of an X-ray transient
  17. GRB250904A: Liverpool Telescope upper limits
  18. GRB 250905A: Enhanced Swift-XRT position
  19. GRB 250904A: Swift/UVOT Detection
  20. GRB 250903A: Swift/UVOT detection
  21. EP detected a brightening of LMXB 1ES 1735-26.9
  22. GRB 250905A: KAIT optical upper limit
  23. GRB 250905A: Swift detection of a burst
  24. GRB 250904A: Enhanced Swift-XRT position
  25. GRB 250904A: TRT optical counterpart detection
  26. GRB 250904A: Swift detection of a burst
  27. GRB 250902A: VZLUSAT-2 detection
  28. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  29. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  30. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  31. GRB 250830C: VZLUSAT-2 detection
  32. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  33. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  35. GRB 250903A: LCO optical observation
  36. GRB 250903A: LCO optical afterglow detection
  37. GRB 250903A: SVOM/VT optical confirmation with VHF data
  38. EP250901a: Mondy, Assy and SAO RAS optical limits
  39. GRB 250903A: TRT optical counterpart detection
  40. EP250903a: TRT optical observations
  41. EP250903a: Einstein Probe detection of an X-ray transient
  42. EP 250827B: Detection of supernova counterpart by LCO.
  43. GRB 250902B: SVOM/GRM observation
  44. EP250827b: SVOM/VT observation of AT 2025wkm
  45. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  46. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  47. GRB 250901A: Swift/UVOT Upper Limit
  48. GRB 250830B: Swift-XRT afterglow detection
  49. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  50. GRB 250902A: SVOM/GRM observation
  51. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  52. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  53. GRB 250901A: SVOM/VT optical afterglow with VHF data
  54. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  55. GRB 250901A: LCO optical upper limit
  56. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  57. EP250831a: NOT optical observations and tentative afterglow candidate
  58. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  59. GRB 250901A: SVOM detection of a burst
  60. EP250901a: Mephisto optical upper limits
  61. EP250901a: Einstein Probe detection of an X-ray transient
  62. EP250831a: EP-WXT detection of a fast X-ray transient
  63. GRB 250831A: Swift-XRT counterpart detection
  64. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 250831A: SVOM/VT upper limit with VHF data
  66. GRB 250831A: SVOM detection of a soft burst
  67. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  68. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  69. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  70. GRB 250830B: Swift ToO observations
  71. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  72. EP250821a: SOAR observations
  73. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  74. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  75. GRB 250808B: SVOM detection of a burst through offline search
  76. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  77. EP250828a: Optical counterpart detection with Kinder observations
  78. EP250828a: Liverpool Telescope upper limits
  79. EP-WXT trigger 01709200800 : KAIT optical observations
  80. EP250828a: KAIT optical upper limit
  81. EP250827a: Swift/UVOT Detection
  82. EP250828a: NOT optical counterpart confirmation
  83. EP250828a: SVOM/VT optical candidate
  84. EP250828a: Seimei/TriCCS optical counterpart detection
  85. GRB 250828B: Swift detection of a burst
  86. EP250828a: Optical upper limit with Kinder observations
  87. EP250828a: Einstein Probe detection of an X-ray transient
  88. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  89. EP250827a: confirmation of optical rebrightening with LCO
  90. GRB 250826A: SVOM/GRM observation
  91. EP250827A: An optical rebrightening was detected by LCO.
  92. EP250827a: TRT optical observations
  93. EP250827a: Einstein Probe detection of an X-ray transient
  94. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  95. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  96. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  97. Fermi GRB 250824B: Global MASTER-Net observations report
  98. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  99. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  100. EP250821a: MeerKAT radio counterpart

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