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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"

24767 results found.

  1. GRB 250302A: Fermi GBM Observation
  2. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  3. GRB 250312A: Swift detection of a burst
  4. GRB 241213A: VIRT Optical Upper Limit
  5. GRB 241228A: VIRT Optical Upper Limit
  6. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  7. GRB 250311A: Swift-XRT observations
  8. GRB 230509B: 1.3m DFOT Optical observations
  9. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  11. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  12. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  13. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  14. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  15. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  16. GRB 250309B: PRIME near-infrared detection
  17. GRB 250225B: Swift-BAT refined analysis
  18. GRB 250311A/EP250311a: TRT optical upper limit
  19. EP250311a/GRB 250311A: EP-WXT detection
  20. GRB 250311B: SVOM detection of a burst
  21. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  22. GRB 250309B / AT2025dws: further SAO RAS optical observations
  23. EP250308a: 1.6m Mephisto optical upper limits
  24. Konus-Wind detection of GRB 250309B
  25. IPN triangulation of GRB 250308A (short)
  26. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  27. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  28. GRB 250309B: Swift-XRT refined Analysis
  29. GRB 250309B / IceCube-250309A: GECAM-B observations
  30. GRB 250309B / AT2025dws: SAO RAS optical observations
  31. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  32. GRB 250309B: Fermi GBM Observation
  33. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  34. IceCube-250309A: No candidates from the Zwicky Transient Facility
  35. Fermi-LAT gamma-ray observations of IceCube-250309A
  36. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  38. EP250308a: GSP optical upper limit
  39. EP250308a: Einstein Probe detection of an X-ray transient
  40. EP250308a: NOT optical upper limit
  41. GRB 250306A: EIRSAT-1 GMOD detection
  42. GRB 250306A: Swift-BAT refined analysis
  43. GRB 250306A: NuSTAR detection of the prompt emission
  44. EP250304a: MeerKAT detection of a possible radio counterpart
  45. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  46. GRB 250305A: AstroSat CZTI detection
  47. EP250302a:Xinglong optical observations
  48. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  49. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  50. GRB250101A: Radio upper limits from VLA observations
  51. GRB 250305A: SVOM/GRM observation of a burst
  52. The EP-WXT trigger 01709132323 is likely a flaring star
  53. EP250304A: Upper limits from Fermi-GBM Observations
  54. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  55. EP250302a: Optical Observations at CrAO and SAO RAS
  56. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  57. EP 250304A: Optical counterpart detection by LCO
  58. EP250302A: 1.3m DFOT optical afterglow detection
  59. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  60. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  61. EP250304a: REM NIR upper limits
  62. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  63. EP250302a: Mondy Continued Optical Observations
  64. EP250304a: Swift-XRT detection of a fading X-ray source
  65. EP250304a: TRT optical counterpart detection
  66. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  67. EP250304a: Einstein Probe detection of an X-ray transient
  68. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: Swift/UVOT Upper Limits
  69. EP250302a: SAO RAS optical observations
  70. EP250302a : GIT optical follow-up
  71. EP250225a: the candidate optical counterpart is an AGN
  72. EP250302a: Kinder optical follow-up observations
  73. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  74. EP250302a: Swift/UVOT detection
  75. EP250302a: optical observation from the INAF Asiago Observatory
  76. EP250302a: REM NIR upper limits
  77. IceCube-241113A: MASTER flaring blazar 5BZB J1311+0853 with Zhirkov effect
  78. EP250302a: Mondy Observations and Optical Light Curve
  79. EP250302a: VLT/MUSE optical redshift z = 1.131
  80. EP250302A: VLT near-infrared observations
  81. EP250302A: VLT/X-shooter tentative redshift
  82. EP250302a: OHP/T193 optical and spectroscopic observations
  83. EP250302a: Swift-XRT observations of a fading X-ray source
  84. EP250302a: Einstein Probe detection of an X-ray transient
  85. EP250302a: SVOM/C-GFT optical observations
  86. GRB 250226A: GRANDMA Optical Observations
  87. EP250302a: Montarrenti Observatory optical detection
  88. EP250302a: Nanshan/HMT optical counterpart detection
  89. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  90. GRB 250225B: VLT near-infrared afterglow confirmation
  91. EP250228a: Optical observations with Kinder and Swift/UVOT
  92. Konus-Wind detection of GRB 250226A
  93. GRB 250225B: EIRSAT-1 GMOD Detection
  94. GRB 250226A: KAO Optical Upper Limit
  95. GRB 250226A: AbAO AS-32 Optical Upper Limit
  96. EP250227a: Global MASTER-Net observations report
  97. EP250223A: Upper limits from Fermi-GBM Observations
  98. EP250227a: TRT optical upper limit
  99. GRB 250225B: VLT/HAWKI near-infrared observations
  100. EP250227a: Optical upper limits with Kinder observations

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