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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"

23654 results found.

  1. Fermi GRB 250711A: Global MASTER-Net observations report
  2. GRB 250711A: BALROG localization (Fermi Trigger 773937617 / GRB 250711611)
  3. GRB 250711A: Fermi GBM Final Real-time Localization
  4. GRB 250704A: SVOM/ECLAIRs refined analysis
  5. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  6. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  7. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  8. LIGO/Virgo/KAGRA S250629bs: Upper limits from Swift/BAT-GUANO
  9. LIGO/Virgo/KAGRA S250629ae: Upper limits from Swift/BAT-GUANO
  10. IceCube-250708A: No Candidates from WINTER
  11. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  12. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  13. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  14. GRB 250709A: Fermi GBM Final Localization
  15. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  16. EP/WXT 01709181970: GOTO observations confirm stellar variability
  17. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  18. EP250704a/GRB 250704B: 10 GHz VLA detection
  19. The EP-WXT trigger 01709181970 is likely a flaring star
  20. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  21. IceCube-250706A: No Candidates from WINTER
  22. IPN triangulation of GRB 250706C (consistent with the GRB 250706B)
  23. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  24. IceCube-250708A - IceCube observation of a high-energy neutrino candidate track-like event
  25. GRB 250704B / EP250704a: VLA radio detection
  26. Fermi GRB 250708A: Global MASTER-Net observations report
  27. IceCube-250708A: Global MASTER-Net observations report
  28. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  29. LIGO/Virgo/KAGRA S250705cb: Updated Sky localization
  30. LIGO/Virgo/KAGRA S250704ab: Updated Sky localization and EM Bright Classification
  31. LIGO/Virgo/KAGRA S250702n: Updated Sky localization
  32. LIGO/Virgo/KAGRA S250701bq: Updated Sky localization
  33. EP250704a/GRB250704B : HCT optical and NIR upper limits
  34. LIGO/Virgo/KAGRA S250701bp: Updated Sky localization
  35. GRB 250708A: Fermi GBM Final Real-time Localization
  36. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  37. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  38. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  39. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  40. IceCube-250706A: EP-FXT follow-up observations
  41. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  42. GRB 250706B/C: Fermi-LAT detection
  43. IceCube-250706A: Global MASTER-Net observations report
  44. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  45. GRB 250706C: Konus-Wind detection of a very bright GRB ~1200 s before GRB 250706B
  46. GRB 250704A: Swift/BAT-GUANO localization skymap of a burst
  47. GRB 250706B: refined SVOM/MXT data analysis
  48. GRB 250706B: REM optical observations
  49. GRB 250706A: REM optical/NIR observations
  50. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  51. Swift GRB 250706A: Global MASTER-Net observations report
  52. GRB 250706A: SVOM/C-GFT upper limit in eary phase
  53. The EP-WXT trigger 01709181580 is likely a flaring star
  54. GRB 250706B: iTelescope optical observations
  55. IceCube-250706A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 250706B: SVOM/VT optical observation
  57. GRB 250706A: GROWTH-India Telescope optical upper limit
  58. GRB 250706B: SVOM detection of a long burst
  59. EP250702a/GRB250702 B,E,D: MeerKAT radio counterpart
  60. GRB 250703A: EIRSAT-1 GMOD Detection
  61. LIGO/Virgo/KAGRA S250705cb: Identification of a GW compact binary merger candidate
  62. Konus-Wind detection of GRB 250703A
  63. IPN triangulation of GRB 250703A
  64. EP250704a/GRB 250704B: FTW optical and NIR observations of the counterpart
  65. GRB 250702F: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  66. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  67. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  68. EP250704a / GRB 250704B: JinShan optical observations
  69. GRB 250704A: SVOM/VT optical observation
  70. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  71. GRBs 250702B,D,E / EP250702a: fast fading, extremely red counterpart
  72. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 3-Initial Localization Volume
  73. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  74. LIGO/Virgo/KAGRA S250704ab: Upper limits from Fermi-GBM Observations
  75. GRB 250704A: VLT/X-shooter afterglow discovery and spectroscopic redshift z = 1.091
  76. GRB 250702B / EP2050702a: FTW optical and NIR observations
  77. Konus-Wind detection of GRB 250702F
  78. EP250704a / GRB 250704B - REM observations
  79. GRB 250702F: GROWTH-India Telescope optical observations
  80. GRB 250704A: REM retraction of optical afterglow detection and updated limit
  81. GRB 250704B: SVOM/GRM observation of a short burst
  82. GRB 250704A: REM detection of the optical afterglow
  83. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  84. GRB 250702F: SVOM/VT optical observation
  85. LIGO/Virgo/KAGRA S250704ab: Identification of a GW compact binary merger candidate
  86. GRB 250704A: SVOM detection of a burst
  87. GRB 250702A: CALET Gamma-Ray Burst Monitor detection
  88. Fermi GBM Analysis of GRB 250702B (formerly B,D,E); dissociation of C burst
  89. Fermi GRB 250703A: Global MASTER-Net observations report
  90. GRBs 250702B,C,D,E / EP250702a: 2.2m CAHA optical upper limit
  91. GRB 250702F: Swift-XRT refined Analysis
  92. GRB 250702F: Fermi GBM Observation
  93. GRBs 250702B,C,D,E / EP250702a: VLT/HAWK-I NIR candidate
  94. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  95. GRB 250702A: GECAM-B detection
  96. GRBs 250702B/C/D/E / EP250702a: Swift XRT localization
  97. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  98. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  99. GRB 250702F: REM optical afterglow detection
  100. EP250702a: Global MASTER-Net observations report

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