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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"

24766 results found.

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

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