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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"

22063 results found.

  1. GRB 240502C: GOTO possible optical counterpart candidates
  2. Fermi GRB 240502B: Global MASTER-Net observations report
  3. Fermi GRB 240502A: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  5. Integral GRB240502.23: Global MASTER-Net observations report
  6. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  7. Fermi GRB 240501A: Global MASTER-Net observations report
  8. Fermi trigger No 736197684: Global MASTER-Net observations report
  9. MeerKAT Discovery of a Probable Radio Counterpart to EP240414a
  10. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  11. Additional DECam GW-MMADS Candidates from three nights of observations
  12. Fermi-LAT gamma-ray observations of IceCube-240424A
  13. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  14. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  15. LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
  16. Fermi GRB 240428A: Global MASTER-Net observations report
  17. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  18. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  19. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  20. LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  21. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  22. EP240426b: EP-WXT detection of a new fast X-ray transient
  23. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  24. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  25. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  26. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  27. GRB 240414A: NOEMA detection
  28. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  29. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  30. LVK S240422ed: Further Swift-XRT followup of three sources
  31. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  32. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  33. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  34. S240422ed: BlackGEM/MeerLICHT transient detection AT2024hgl/MLTJ080628.10-250116.4
  35. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  36. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  37. S240422ed: MeerLICHT/BlackGEM photometry on AT2024hfx and archival ZTF detection
  38. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  39. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  40. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  41. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  42. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  43. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  44. LIGO/Virgo/KAGRA S240422ed: ANU 2.3m followup of candidate counterparts
  45. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  46. Fermi trigger No 735697285: Global MASTER-Net observations report
  47. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  48. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  49. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  50. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  51. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  52. LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
  53. LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
  54. LIGO/Virgo/KAGRA S240422ed: MOSFIRE imaging of the DECam GW-MMADS candidate AT 2024hdm
  55. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  56. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  57. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  58. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  59. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  60. LIGO/Virgo/KAGRA S240422ed: DECam GW-MMADS Candidates
  61. LIGO/Virgo/KAGRA S240422ed: Potential Magellan candidates from GCN 36263 are unrelated.
  62. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  63. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  64. IceCube Alert 240424.08: Global MASTER-Net observations report
  65. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  66. LIGO/Virgo/KAGRA S240422ed: SAGUARO upper limits from CSS
  67. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  68. LIGO/Virgo/KAGRA S240422ed: LAST optical observations
  69. LIGO/Virgo/KAGRA S240422ed: Potential Candidates from Magellan galaxy-based search
  70. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61
  71. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from Pan-STARRS observations of the skymap
  72. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search
  73. LIGO/Virgo/KAGRA S240422ed: No Counterparts in DDOTI/OAN Optical Observations
  74. LXT240402A/GRB240402B: Chandra X-ray detection
  75. LIGO/Virgo/KAGRA S240422ed: no candidate counterparts from ATLAS observations
  76. GRB 240419A: Possible ATCA radio detection
  77. GRB 240421B: ATCA radio observations
  78. LIGO/Virgo/KAGRA S240422ed: WINTER near-infrared J-band observations
  79. LIGO/Virgo S240422ed: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  80. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility observations and candidates
  81. LIGO/Virgo/KAGRA S240422ed: GW-MMADS DECam observations
  82. LIGO/Virgo/KAGRA S240422ed: Magellan Observations
  83. LIGO/Virgo/KAGRA S240422ed: Updated NED Galaxies in the Localization Volume
  84. LIGO/Virgo/KAGRA S240422ed: Upper limits from Fermi-GBM Observations
  85. LIGO/Virgo/KAGRA S240421ar: Upper limits from Swift/BAT-GUANO
  86. LIGO/Virgo/KAGRA S240422ed: Coverage and upper limits from MAXI/GSC observations
  87. LIGO/Virgo/KAGRA S240422ed: MeerLICHT and BlackGEM observations report
  88. LIGO/Virgo/Kagra S240422ed: NED Galaxies in the Localization Volume
  89. LIGO/Virgo/KAGRA S240422ed: Global MASTER-Net observations report
  90. Fermi trigger No 735470374: Global MASTER-Net observations report
  91. GRB 240414A: radio detection with the VLA
  92. Fermi-LAT gamma-ray observations of IceCube-240419A
  93. GRB 240414A: AMI-LA radio observations
  94. GRB 240414A: LBT optical detection
  95. GRB 240415B: Swift-XRT observations
  96. Fermi GRB 240422A: Global MASTER-Net observations report
  97. GRB240421B: Zadko Observations
  98. Fermi GRB 240421B: Global MASTER-Net observations report
  99. Swift GRB 240421B: Global MASTER-Net observations report
  100. GRB 240421B: J-band upper limits from WINTER

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