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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"

32501 results found.

  1. GRB 250902B: SVOM/GRM observation
  2. EP250827b: SVOM/VT observation of AT 2025wkm
  3. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data
  4. GRB 250831A (SVOM trigger sb25083102): KAIT confirmation of stellar flare
  5. Fermi GRB 250902B: Global MASTER-Net observations report
  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. LIGO/Virgo/KAGRA S250901cb: Updated Sky localization
  11. EP250827b: Liverpool Telescope observations
  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: NOT optical observations
  18. GRB 250901A: SVOM/VT optical afterglow with VHF data
  19. LIGO/Virgo/KAGRA S250830bp: DECam GW-MMADS candidates
  20. GRB 250901A: LCO optical upper limit
  21. EP250827b: Swift observations of AT 2025wkm
  22. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  23. EP250827b: Gemini Spectroscopy of AT 2025wkm
  24. LIGO/Virgo/KAGRA S250901cb: Identification of a GW compact binary merger candidate
  25. EP250831a: NOT optical observations and tentative afterglow candidate
  26. EP250827b: FTW Observations of AT 2025wkm
  27. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  28. GRB 250830C: Insight-HXMT detection
  29. EP250901a: Mephisto optical upper limits
  30. EP250901a: Global MASTER-Net observations report
  31. LIGO/Virgo/KAGRA S250830m: Updated Sky localization
  32. EP250831a: EP-FXT follow-up observation
  33. EP250831a: Swift-XRT observations
  34. EP250831a: Global MASTER-Net observations report
  35. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  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. EP250830a: Global MASTER-Net observations report
  40. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  41. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  42. LIGO/Virgo/KAGRA S250830bp GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  43. LIGO/Virgo/KAGRA S250830bp: Updated Sky localization, EM Bright Classification, and Source Classification
  44. LIGO/Virgo/KAGRA S250830bp: Identification of a GW compact binary merger candidate
  45. EP-WXT trigger 01709200994: Liverpool Telescope upper limits
  46. GRB 250830B: Swift ToO observations
  47. LIGO/Virgo/KAGRA S250830m: Identification of a GW compact binary merger candidate
  48. GRB 250828B: Swift-BAT refined analysis
  49. EP250821a: SOAR observations
  50. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  51. LIGO/Virgo/KAGRA S250725j: Observations with the NSF-DOE Vera C. Rubin Observatory
  52. LIGO/Virgo/KAGRA S250818k: MeerKAT detection of an increase in radio flux from AT2025ulz
  53. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  54. EP250828a: Optical counterpart detection with Kinder observations
  55. EP250828a: Liverpool Telescope upper limits
  56. Swift GRB 250828B: Global MASTER-Net observations report
  57. EP250828a: Global MASTER-Net observations report
  58. EP-WXT trigger 01709200800 : KAIT optical observations
  59. EP250828a: KAIT optical upper limit
  60. EP250827a: Swift/UVOT Detection
  61. EP250828a: NOT optical counterpart confirmation
  62. EP250828a: SVOM/VT optical candidate
  63. EP250828a: Seimei/TriCCS optical counterpart detection
  64. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  65. EP250828a: Optical upper limit with Kinder observations
  66. LIGO/Virgo/KAGRA S250827fo: Updated Sky localization
  67. LIGO/Virgo/KAGRA S250818k: uGMRT 1.3 GHz observations of AT2025ulz
  68. EP250827a: LCO observations show fading optical counterpart
  69. EP250827a: Preliminary analysis of the EP-WXT and EP-FXT observations
  70. GRID detection of GRB 250824A
  71. LIGO/Virgo/KAGRA S250827fo: Identification of a GW compact binary merger candidate
  72. EP250827A: VLT/X-shooter redshift confirmation
  73. Fermi GRB 250827A: Global MASTER-Net observations report
  74. EP250827a: confirmation of optical rebrightening with LCO
  75. EP250827a: GOTO observation of the optical afterglow
  76. GRB 250826A: SVOM/GRM observation
  77. EP250827A: An optical rebrightening was detected by LCO.
  78. EP250827a: Swift-XRT counterpart detection
  79. LIGO/Virgo/KAGRA S250827l: Updated Sky localization
  80. EP250827a: TRT optical observations
  81. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  82. EP250827a: Gemini-South redshift z = 1.613
  83. EP250827a: Global MASTER-Net observations report
  84. EP250827a: Las Cumbres independent detection of the optical counterpart
  85. EP250827a: Gemini-South optical counterpart detection
  86. LIGO/Virgo/KAGRA S250827l: Identification of a GW compact binary merger candidate
  87. Fermi GRB 250826A: Global MASTER-Net observations report
  88. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  89. EP250821a: Gemini GMOS Redshift Confirmation
  90. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  91. LIGO/Virgo/KAGRA S250818k: GTC/OSIRIS Confirmation of Rebrightening of AT2025ulz
  92. Fermi GRB 250824B: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S250818k: VLA upper limits on AT2025ulz
  94. LIGO/Virgo/KAGRA S250818k: nature of the AT2025ulz/ZTF25abjmnnps OT
  95. LIGO/Virgo/KAGRA S250818k: Pan-STARRS imaging confirms re-brightening of SN2025ulz
  96. GRB 250823A: Swift-BAT refined analysis
  97. LIGO/Virgo/KAGRA S250818k: Continued Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  98. GRB 250821B: AstroSat CZTI detection
  99. GRB 250819A: AstroSat CZTI detection
  100. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz

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