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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"

25979 results found.

  1. EP 250827B: Detection of supernova counterpart by LCO.
  2. GRB 250902B: SVOM/GRM observation
  3. EP250827b: SVOM/VT observation of AT 2025wkm
  4. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  5. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  6. Fermi-LAT Gamma-ray Observations of IceCube-250831A
  7. GRB 250902A: Fermi GBM Detection
  8. GRB 250901A: Swift/UVOT Upper Limit
  9. IceCube-250831A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 250830B: Swift-XRT afterglow detection
  11. LIGO/Virgo/KAGRA S250902av: 1 counterpart neutrino candidate event from an IceCube neutrino search
  12. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  13. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  14. GRB 250902A: SVOM/GRM observation
  15. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  16. EP250901a: refined analysis of the EP-WXT and EP-FXT observations
  17. IceCube-Cascade 250828A: Upper limits from a search for additional neutrino events in IceCube
  18. GRB 250901A: SVOM/VT optical afterglow with VHF data
  19. GRB 250901A: Swift-XRT afterglow detection
  20. EP250901a: Swift-XRT observations
  21. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  22. GRB 250901A: LCO optical upper limit
  23. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  24. EP250827b: Gemini Spectroscopy of AT 2025wkm
  25. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  26. EP250831a: NOT optical observations and tentative afterglow candidate
  27. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  28. GRB 250901A: SVOM detection of a burst
  29. EP250901a: Mephisto optical upper limits
  30. GRB 250830C: GECAM-B detection
  31. EP250901a: Einstein Probe detection of an X-ray transient
  32. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  33. EP250831a: Swift-XRT observations
  34. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  35. EP250831a: EP-WXT detection of a fast X-ray transient
  36. GRB 250831A: Swift-XRT counterpart detection
  37. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. GRB 250831A: SVOM/VT upper limit with VHF data
  39. GRB 250831A: SVOM detection of a soft burst
  40. GRB 250830B: Swift-XRT observations
  41. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  42. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  43. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  44. LIGO/Virgo/KAGRA S250830bp: NED Galaxies in the 4-Update Localization Volume
  45. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  46. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  47. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  48. EP-WXT trigger 01709200994: confirmation of a stellar flare by BOOTES-6
  49. GRB 250830B: MAXI/GSC detection
  50. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  51. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  52. GRB 250828B: Swift-BAT refined analysis
  53. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  54. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  55. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  56. EP250828a: Optical counterpart detection with Kinder observations
  57. EP250828a: Liverpool Telescope upper limits
  58. EP250828a: Global MASTER-Net observations report
  59. EP-WXT trigger 01709200800 : KAIT optical observations
  60. EP250828a: KAIT optical upper limit
  61. EP250827a: Swift/UVOT Detection
  62. EP250828a: NOT optical counterpart confirmation
  63. EP250828a: SVOM/VT optical candidate
  64. EP250828a: Seimei/TriCCS optical counterpart detection
  65. EP250828a: Optical upper limit with Kinder observations
  66. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  67. EP250827a: LCO observations show fading optical counterpart
  68. EP250828a: Einstein Probe detection of an X-ray transient
  69. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  70. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  71. EP250827a: confirmation of optical rebrightening with LCO
  72. GRB 250826A: SVOM/GRM observation
  73. EP250827A: An optical rebrightening was detected by LCO.
  74. EP250827a: Swift-XRT counterpart detection
  75. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  76. EP250827a: TRT optical observations
  77. EP250827a: Gemini-South redshift z = 1.613
  78. EP250827a: Einstein Probe detection of an X-ray transient
  79. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  80. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  81. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  82. Fermi GRB 250824B: Global MASTER-Net observations report
  83. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  84. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  85. GRB 250823A: Swift-BAT refined analysis
  86. LIGO/Virgo/KAGRA S250818k: MASTER predicovery limits of the AT2025ulz/ZTF25abjmnps KN candidate
  87. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of SN 2025ulz as a type II supernova
  88. GRB 250823A: Swift-XRT refined Analysis
  89. EP250821a: MeerKAT radio counterpart
  90. GRB 250823A: COLIBRÍ optical observations
  91. GRB 250823A: SVOM/VT optical observation
  92. GRB 250823A: Swift/UVOT Detection
  93. LIGO/Virgo/KAGRA S250818k: COLIBRÍ confirmation of rebrightening of AT2025ulz
  94. GRB 250823A: Fermi GBM Observation
  95. GRB 250823A: Enhanced Swift-XRT position
  96. GRB 250823A: LCOGT Optical Detection
  97. GRB 250823A: Swift detection of a burst
  98. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  99. LIGO/Virgo/KAGRA S250818k: JinShan optical observations of AT2025ulz
  100. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Optical Detection of AT2025ulz

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